Handbook on Sourdough Biotechnology
Abstract
In the last few decades, many efforts have been made to exploit sourdough's potential for making baked goods. Through the biotechnology of this traditional baking method, many sensory, rheological, nutritional, and shelf-life properties have been discovered and/or rediscovered. Bakery industries are greatly attracted by the potentials that sourdough presents, and new industrial protocols are being developed. To the best of our knowledge, there has been no single book dedicated to sourdough biotechnology, and which clearly demonstrate its potential. This book aims at defining and highlighting the microbiological, technological, nutritional, and chemical aspects of sourdough biotechnology. The book will be the first reference guide on this topic for the worldwide scientific, teaching and students communities, also opening a way of communication and transferring the main results to a more productive industrial application. © Springer Science+Business Media New York 2013. All rights reserved.
Chapters (12)
This chapter provides clear evidence of how the manufacture and consumption of bread is closely linked to human subsistence and intimately connected to tradition, the various practices of civil society and to religion. The common language of the world still retains expressions that recall the close bond between life and bread. Throughout time, the eating of bread, especially sourdough bread, was very often a choice of civilization. Information on the documented manufacture and consumption of sourdough bread over the centuries is presented herein. In particular, the history and social aspects of sourdough use in France, Italy and Germany are described.
With an annual production of more than two billion tons cereals are amongst the most important commodities in the world. Thus, products made from cereals are staple foods that contribute considerably to the energy and nutrient intake of mankind. The major cereals are corn, wheat, rice, barley, sorghum, millet, oats, and rye. Their constituents affect the nutritional and technological properties of cereals. Carbohydrates are the main constituents with starch providing energy and texture. However, although nonstarch polysaccharides are minor constituents they represent dietary fiber and exhibit positive health effects, in particular for whole grain products. Cereal proteins are quantitatively less important than carbohydrates, but they are of major importance for the functional properties, in particular for the bread-making performance of wheat and rye or for the quality of tortillas made from corn. The protein composition of different cereals varies considerably, but they have in common that lysine and methionine contents are low. Thus, cereal proteins are of poor nutritional value. Lipids are a minor constituent of cereals, but particularly in wheat flour polar lipids positively affect dough properties and enable the production of bread with good texture and quality. Whole grain cereals are important sources of minerals and B-vitamins.
The chapter describes the main ingredients (wheat flour, water, salt, sugar, and fats) and the different steps of the chain used for making baked goods, from milling to the baking process (mixing, leavening, proofing, dough makeup and baking operations). An overview of the main analytical methods used to determine the quality of baked goods (e.g. fundamental rheology, descriptive empirical measurements, and innovative approaches) is also included.
Sourdough technology is widespread throughout the world and is considered as the best practice to prepare bread and other baked goods with distinctive characters and prolonged shelf life. Sourdough applications and performances mainly rely on the composition and stability of its microbiota, which is in turn influenced by many exogenous and endogenous factors. Different type of sourdoughs exist for many applications, both at artisan and industrial level, and a variety of baked goods are considered here as an example of sourdough-based product diversity. Moreover, the chapter covers relevant aspects of the evaluation of sourdough characteristics, both from a physico-chemical and microbiological point of view. This latter point is addressed by reporting routine as well as innovative approaches to microbe identification, typing and monitoring based both on phenotypic and genetic systems. Finally, novel types of stabilized sourdough, recently developed with the main aim of improving the flavour of leavened baked products without using traditional protocols of manufacture, are described and challenges related to the selection and use of starter cultures are discussed.
This chapter describes the taxonomy and biodiversity of yeasts and lactic acid bacteria (LAB) isolated from sourdoughs collected around the world. The phylogenetic position of yeast and LAB species found in sourdoughs is discussed, and important problems in taxonomic nomenclature of typical sourdough-associated species are highlighted. An overview is given of factors that may influence the taxonomic composition of sourdough ecosystems, such as geographical location, type of cereals and other raw materials, and technological process parameters. A brief history is provided of the most commonly used approaches to isolate yeast and LAB strains from sourdough samples. Finally, the main techniques for identification of sourdough yeasts and LAB are discussed, emphasizing both on conventional culture-based methods as well as on culture-independent molecular approaches.
Cereal dough is a dynamic system that is characterised by continuous changes in nutrient availability and changes in physico-chemical conditions. Depending on the type of flour and bread-making technology, starvation conditions can also be envisaged. The imbalance between yeast consumption and starch hydrolysis might lead to the rapid depletion of soluble carbohydrates. Overall, microbial starvation induces a quiescent state whose length is controlled by the presence of limiting factors. Yeast responds to a changing environment not with a small adjustment to key control points but with the coherent transcriptional regulation of large sets of genes. During the fermentation of sourdough yeast cells may encounter different environmental states. Co-fermentation with lactic acid bacteria and yeasts determines environmental fluctuations not only in terms of availability of nutrients, but also organic acid concentration, pH decrease and changes in the texture profile. Maintaining optimal functionality in the presence of such external variability is a central evolutionary constraint. The exposure of microbial cells to stressful and fluctuating conditions during fermentation involves a broad transcriptional response with many induced or repressed genes. The selective pressure exerted by the environmental conditions encountered by yeast cells during sourdough fermentation, accounts for the consolidated dominance of selected yeast species, such as in particular C. milleri and S. cerevisiae. The microbial ecology of sourdough is likely modulated by two factors, nutrient availability or limitation. However, within the sourdough ecosystem there are numerous mechanisms whereby one species may influence the growth of another species. This chapter describes the stress response, of those species, to nutrient availability (starvation), DY, pH (acid stress), the presence of sugars, salts and polysaccharides (osmotic stress), oxygen (oxidative stress), temperature fluctuations (heat shock and cold stress) and interactions between lactic acid bacteria and yeasts (e.g. S. cerevisiae, C. milleri and L. sanfranciscensis), and between yeasts (e.g. S. cerevisiae and C. milleri). Moreover, both environmental process parameters and the interaction with lactic acid bacteria affect the metabolism of yeast in terms of fusel alcohols and specifically branched-chain amino acid metabolites, carbonyl compounds and unsaturated fatty acid oxidation products, and also induce the production of inter-species signalling molecules. An overview of the use of baker’s yeast in the bread-making industry is also included.
In the past decades, studies on the physiology and biochemistry of sourdough lactic acid bacteria provided insight into the microbial ecology of sourdough as well as the effect of the metabolic activity of lactic acid bacteria on flavor, texture, shelf-life, and nutritional properties of leavened baked goods. Lactic acid bacteria are the dominant microorganisms of sourdough. Their metabolic versatility favors adaptation to the various processing conditions and the metabolic interactions with autochthonous yeasts determine mechanisms of proto-cooperation during sourdough fermentation [1–3]. Lactobacillus species are most frequently found in sourdough fermentations although species belonging to the genera Pediococcus, Enterococcus, Lactococcus, Weissella and Leuconostoc were also identified ([4–6], see Chap. 5). A large number of Lactobacillus species were first identified from sourdoughs or fermentation processes of cereals [5]. This chapter gives an overview of the general growth and stress parameters, carbohydrate and amino acid metabolism, synthesis of exopolysaccharides and antimicrobial compounds, and the conversion of phenolic compounds and lipids of lactic acid bacteria during sourdough fermentation.
The quality of bread is characterized by its flavor, nutritional value, texture, and shelf life [1]. In the baking industry, these characteristics are improved by addition of bread improvers or enzymes. Alternatively, the addition of sourdough influences all aspects of bread quality and thus meets consumer demands for a reduced use of additives. Since sourdough is an intermediate but not an end product the microbiological activity has to be determined on the bases of their impact on bread quality. Biochemical changes during sourdough fermentation occur in protein and carbohydrate components of the flour. The rate and extent of these changes greatly influence the properties of the sourdough and consequently the quality of the bread dough and bread structure. The effects are associated with the metabolites produced by lactic acid bacteria (LAB) and yeast during fermentation, including organic acids, exopolysaccharides (EPS), enzymes, and CO2. The following chapter presents the impact of sourdough fermentation on structure-forming components of bread, and bread texture.
Sourdough fermentation is best known and most studied for its effects on the sensory quality and shelf life of baked goods. Acidification, activation of enzymes and their effects on the cereal matrix as well as production of microbial metabolites all produce changes in the dough and bread matrix that also influence the nutritional quality of the products. The nutritional quality is formed through the chemical composition and structure of the fermented foods, i.e. content and bioavailability of nutrients and non-nutrients. Sourdough fermentation can change all of these, as previously reviewed by Poutanen et al. [1] and Katina et al. [2].
Over the last years, sourdough has received increasing interest as an alternative, natural and low-cost tool for improving the quality of gluten-free (GF) bread. The textural, nutritional and sensory benefits deriving from the use of sourdough in bread arise from the metabolic activities of the sourdough-resident lactic acid bacteria and yeasts. A deep understanding of the microbiological complexity and its influence on the technological properties of GF materials is a pre-requisite for setting guidelines for the successful application of GF sourdough in GF bread. This chapter will give a comprehensive review of the latest outcomes on the characterization of the microbial diversity of GF fermentations and on the applications of GF sourdough in GF breads.
Cereal-based fermented beverages are traditionally used as staple foods and consumed in certain geographical regions. One of the main advantages of the fermented products is the increased mineral availability due to the phytate elimination during fermentations. Further development of the traditional beverage fermentations at an industrial scale could improve the nutritional quality of the products as well as their sensory properties. This chapter focuses on traditional cereal-based non-alcoholic fermented beverages and introduces products that differ in their manufacturing concepts. The microbial composition and manufacturing processes of the beverages as well as their functions are presented in a concise manner. The chapter deals with the following beverages: boza, togwa, mahewu, bushera, pozol, chicha, kishk, kvass, sourish shchi, and hulu-mur. The cereal raw materials for these include: sorghum, finger millet, millet, wheat, maize, rice, rye, oat, and malts.
This chapter reviews the principal aspects described in this book and highlights some of the main perspectives in the short and medium term. Critical considerations and new perspectives, based on the point of view of the editors, are reviewed for the main aspects of sourdough such as microbial ecology, product quality, nutrition, and industrial and artisanal uses.
... Hazardous bacteria's ability to cling to the host cell membrane can be prevented by plant extracts. It thus lessens the likelihood of bacteria Table 3. Microbial fermentation preservation approach for increasing bread shelf life (Stefan et al., 2013 adhering to host cell surface membranes, which occasionally makes it a possible anti-adhesive agent (Wei et al., 2009). The presence of numerous significant antifungal chemicals in plants, including pyroxylins, cyanogenic Glycosides, phenolic compounds, and alkaloids, has led to a great deal of research on plant extracts as bio-preservatives (Axel et al., 2017). ...
... Significant microorganisms that cause microbiological bread deterioration(Stefan et al., 2013). ...
... Plant essential oils preserve bread(Stefan et al., 2013). ...
Bread is one of the most convenient foods available, yet it is highly susceptible to microbial attacks. It loses its organoleptic freshness after storage due to a variety of changes. Bread spoilage results in significant financial losses for both manufacturers and consumers. The bread industry has long sought an affordable approach to increase the shelf life and guarantee the safety of their bread. One such treatment is the replacement of hazardous chemical preservatives. Nonetheless, recent research has explored some previously uncharted ground. Other techniques for preserving bread have shown promise, including active packaging, modified atmospheric packaging, and bio-preservation. Furthermore, certain plant extracts and essential oils have shown positive effects in reducing the growth of fungi on bread and other baked items. This study summarizes the results of many experiments on biopreservation of bread and offers suggestions for possible uses of these methods.
... The majority of GF breads, such as those made from rice flour, are often described as having an inferior mouthfeel, dry crumb, and quicker loss of freshness and lack typical flavor notes commonly present in conventional bakery items. Hence, studies in this field are focusing on quality enhancement of GF bread products [3,4]. In this context, alternative techniques and new ingredients are being employed to enhance the quality of GF bakery products [5][6][7]. ...
... Table 3. Analysis of variance and significance (p-values) of the general linear model main effects for the loaf specific volume and crust color parameters of gluten-free control and sourdough-containing breads fortified with chickpea flour and made with different levels of added water in the respective batters. 2 The main effects of the tested factors are significant at p < 0.05. 3 Mean values for each specified color parameter or specific volume at a certain level of one factor were calculated using all levels of the other factors. Values followed by the same letter in the same column and for the same factor are not significantly different (p > 0.05); comparison of means was made by Tukey's test. ...
... 2 The main effects of the tested factors are significant at p < 0.05. 3 Mean values of each specified parameter at a certain level of one factor were calculated using all levels of the other factors. Values followed by the same letter in the same column and for the same factor are not significantly different (p > 0.05); comparison of means was made by Tukey's test. ...
This study aimed to develop a novel gluten-free bread using a rice/chickpea flour-based sourdough, fermented by a commercial starter culture, to improve the quality characteristics and shelf life of this product. The effects of sourdough incorporation, chickpea flour content (6.5 and 10.0%), and added water level (80–110%) on batter rheology and bread quality were investigated; bread textural characteristics upon storage (0–2 days) were also monitored. The level of added water was the primary factor influencing batter rheology, as evaluated by the back extrusion test. Sourdough incorporation decreased the pH and increased the acidity of batters and breads. The inclusion of sourdough, the water level, and the storage time affected the moisture and texture parameters of the bread crumb. Sourdough incorporation into bread formulations decreased crumb hardness and staling rate and increased loaf specific volume. Moreover, intermediate water (90 and 100%) and high chickpea (10%) levels in the batters increased loaf specific volumes and crust redness, respectively. Sensory analysis revealed that sourdough-enriched breads were preferred by the assessors concerning general appearance and crumb texture. Overall, bread formulations with the incorporation of sourdough, at a 90% level of added water in the batter mixtures, exhibited the most desirable characteristics according to both instrumental and sensory analyses.
... The religious traditions associated with bread stem back to biblical times, a common phrase, such as Luke 11:3, are recited during communion. The connection between bread and religion is symbolized through the body of Christ for Christians, 3 in Jewish culture bread is "cultivated from raw ingredients gifted to the Jewish people by God'', 4 and in some regional Islamic beliefs throwing away bread is "religiously wrong because bread is na'amat Allah, God's grace or blessing". 5 Another example of this bond is shown through the form of communion loaves at weddings ( Figure 1) which symbolizes the covenant between the couple and God. ...
... 9 As the bread-making knowledge traveled to Greece, women began making bread primarily for the wealthy. 3 The recipes at this point ranged from sweet to savory breads. Shortly after, the Romans learned bread making from the Greeks and began spreading it to the rest of Europe. ...
... In San Francisco, the microclimate provided a place for L. sanfranciscensis, a lactic acid bacterium that provides the distinct taste to sourdough bread, to thrive due to its adaptation to more acidic environments. 3 As the miners traveled, they carried their starters with them since sourdough required minimal ingredients and provided nutritional sustenance. The word "sourdough" came as a result of this naturally fermented bread. ...
Throughout history, bread has been a representation of food (in)security. From being a symbol of wealth to being the staple of the poor, bread has served as the centerpiece of meals all around the world. Breaking bread is an act of community that captivates culture and tradition. By documenting the narratives of sourdough bakers, we want to reconnect people with the bakers as sourdough bread provides a narrative that goes beyond a meal. Through interviews, in-person observations, and bench work, this research highlights the complexities of our food system and challenges the views of locality and sustainability. Taking on the idea of farm-to-table, we follow the journey of grain to bread. With a staple like bread, the stories told shape cultures and narratives. These narratives highlight the importance of shopping locally and preserving the rich history around food. As a vessel for learning, food education connects people back to the environment and it also symbolizes the community bakers bring together through bread.
... and 0.72-0.90% (lactic acid) respectively, in sourdough fermentation [18]. Torrieri and coauthors [6] determined that the pH and TA values of sourdough samples were ranged from 4.00-4.02 ...
... The increase in the number of yeast did not occur due to the predominance of LAB in the following days and the effect of the acid formed. Gobbetti and Gänzle [18] stated that the number of LAB in sourdough varied from 7 to 9 log10 cfu/g. ...
Abstract This study aimed to isolate sourdough starters and use them in the production of dephytinized wheat bran enriched bread. Four different sourdoughs, used separately in bread production, which were spontaneous sourdough (SS), Type II sourdough produced with Lactobacillus fermentum, isolated from SS, as a starter (LFS), local produced sourdough (Vakfıkebir, Trabzon, Türkiye) (VS), and Type II sourdough produced with Lactococcus lactis, isolated from VS, as a starter (LCS). The dephytinization process effectively reduced the phytic acid level of bran at the rate of 95.21 g/100 g. The highest specific volume was determined in the control bread produced with the local sourdough sample (3.27 mL/g). The lowest specific volume was determined in the sample of bread containing 15% dephytinized wheat bran produced with Lactococcus lactis fermented sourdough (1.82 mL/g). As expected, increasing bran level caused decreased L* value of bread samples and increased a* and b* values. The high rates of bran had deleterious effects on the texture of bread. Additionally, the changes in texture profile were more intense in bread samples containing dephytinized wheat bran during storage. According to the sensory analysis results, it was determined that the scores of bread samples produced with Lactobacillus fermentum sourdough and including 5% wheat bran were higher.
... and 0.72-0.90% (lactic acid), respectively (Gobbetti and Gänzle, 2012). When the pH and TA values of the sourdough sample are examined at the end of the 5 th day, it is seen that it is compatible with data in the literature. ...
... The pH decrease occurred rapidly in the sourdough sample, the increase in the number of yeast did not occur due to the predominance of lactic acid bacteria in the following days and the effect of the acid formed. Gobbetti and Gänzle (2012) stated that the number of lactic acid bacteria in sourdough varied from 7 to 9 log10 cfu/g. In this study, it is seen that the number of lactic acid bacteria in the spontaneous sourdough sample reached 8.77 log10 cfu/g and was within the range given in the literature. ...
In this study, the rheological properties of flours containing wheat bran or dephytinized wheat bran at different rates (0, 5, 10, 15%) and some physicochemical and microbiological properties of bread doughs produced with sourdough by using these flour mixes were investigated. Four different sourdoughs, which were spontaneous (SS), Vakfıkebir (VS), containing Lactobacillus fermentum as a starter (LFS) and containing Lactococcus lactis as a starter (LCS), were used. The water absorption, softening degree, resistance to extension values of dough increased while the stability, energy and extensibility values decreased as the rate of bran increased for both bran types. The pH and total acidity (TA) values of the bread dough samples generally increased with the addition of bran. The lowest moisture content, TA and LAB count, and the highest pH and yeast count were obtained in VS. The lowest pH and the highest TA values belonged to the bread dough samples containing SS. The number of LAB and yeast counts in bread dough samples increased with addition of bran compared to control sample.
... The addition of probiotics to bakery products not only provides beneficial effects, but also improves their nutritional quality. According to several reports, the dough of probiotic bakery products contains more digestible protein, starch digestibility is improved, which reduces the glycemic index of the product, soluble dietary fiber and vitamin content are increased, and mineral bioavailability is increased (Gobbetti & Gänzle, 2013). As for anti-nutrients, phytic acid decreases due to its degradation by microbial phytases. ...
Currently, the search to improve lifestyle through the consumption of foods with nutritional properties has been increasing, which has led the food industry to develop foods with greater benefits for the consumer’s health. Incorporating functional components is a challenge faced by the food industry for the nutritional improvement of products. One of these industries is the bakery, which seeks to implement functional compounds in its products to promote health. However, incorporation of functional ingredients can modify the nutritional, sensory, and technological properties. This review provides a perspective on the development of bakery products with functional properties and their nutritional potential, based on the incorporation of different compounds such as probiotics, polyunsaturated fatty acids, polyphenols, and microalgae. On the other hand, the impact of the use of flours from sprouts and different pseudocereals in the formulation of bakery products is addressed. Stipulating that bakery products enriched with functional compounds are nutritionally superior to products such as cookies and cakes.
... This statement can be reinforced by an observation made by Guinotte et al. [35], indicating that the lower gastric pH, the better solubilization of calcium (in the form of calcium carbonate CaCO 3 ) that can be achieved, and gastric acid secretion is a prerequisite for CaCO 3 , solubilization. Moreover, credible characterization of Lba as a strong calcium and other divalent cations chelator has been reported by Gobbetti and Gänzle [36], thus supporting the facts mentioned above. The higher assimilation of calcium by hens due to Lba may account for the initial pale color of egg yolks from the EXP group at the beginning of the dietary intervention. ...
Simple Summary
Lactobionic acid (Lba) has been found to have a range of health-promoting benefits and practical applications across various fields, including agriculture. However, the impact of Lba on the chemical composition and nutritional quality of eggs from early laying hens has been largely overlooked. The incorporation of Lba into the diet has been observed to elevate the content of monounsaturated fatty acids (MUFAs), specifically palmitoleic and vaccenic acids. In summary, as a functional product, Lba has the potential to improve the productivity of laying hens and enhance the nutritional value of eggs during the early laying period.
Abstract
Lactobionic acid (Lba), an oligosaccharide aldonic acid, has demonstrated various health-promoting benefits and applications in diverse areas. Lba has been recognized for its multifunctional properties, such as metal ion chelation and calcium sequestration. This study aimed to evaluate the effects of supplementing the diet of early-laying hens with Lba (EXP group) on their performance and the physical–chemical properties, and nutritional quality of eggs. The 12-week study involved 700 Sonja breed hens per group, with the EXP group’s diet enriched with 2% of biotechnologically produced Lba, while the control group (CON) received no Lba supplementation. Lba supplementation influenced both the hen’s performance and egg quality, particularly in terms of egg production and fatty acid accumulation. Performance in the EXP group was significantly improved (p < 0.05), showing a 4.6–8.9% increase compared to the CON group at all experiment stages. Lba also promoted an increase in monounsaturated fatty acid (MUFA) content, particularly palmitoleic and vaccenic acids. Overall, Lba supplementation enhanced both the productivity of laying hens and the nutritional value of eggs during the early laying period.
... At the same time, the breadcrumb also became dryer and more elastic (Man et al., 2011). At a temperature of 140 -150 o C, reducing sugars and amino acids will participate in the Maillard reaction to give the bread a characteristic color and odor (Hoi et al., 2009;Gobbetti & Gänzle, 2013). ...
Oat (Avena Sativa L.) is characterized by a high content of protein with a favorable amino acid composition, β-glucans, and unsaturated fatty acids. This study aimed to determine the factors affecting the physical properties and sensory value of bread made of wheat combined with oats. The research was to investigate the effects of (i) the proportion of added oat flour (15, 20, 30%); (ii) the fermentation time (60, 75, 90, 105 min); and (iii) baking temperature (200, 210, 220oC) for baking time (10, 15, 20 min) to bread quality with added oat flour. The quality assessment criteria include hardness, moisture content, specific volume, color, and sensory value of the product. According to the results, the most acceptable proportion of oat flour supplement in all of the criteria of bread was found to be 20%. The fermentation time of 90 minutes provided the best texture and highest sensory value for the bread. Oat-wheat bread was baked at 210oC for 20 minutes to obtain a good taste, helping the bread to have a crispy texture, smooth surface, and an attractive yellow-brown color.
... TA B L E 2 Major microbial metabolites in sourdough and their effects on dough and bread quality (summarized from Gänzle & Gobbetti, 2013). Type I sourdough is usually a firm dough (DY 150∼160), which is incubated at an ambient temperature range of 20∼30 • C and initiated by the naturally present strains in the starting dough mixture. ...
Deterioration of bread quality, characterized by the staling of bread crumb, the softening of bread crust and the loss of aroma, has caused a huge food waste and economic loss, which is a bottleneck restriction to the development of the breadmaking industry. Various bread improvers have been widely used to alleviate the issue. However, it is noteworthy that the sourdough technology has emerged as a pivotal factor in this regard. In sourdough, the metabolic breakdown of carbohydrates, proteins, and lipids leads to the production of exopolysaccharides, organic acids, aroma compounds, or prebiotics, which contributes to the preeminent ability of sourdough to enhance bread attributes. Moreover, sourdough exhibits a “green‐label” feature, which satisfies the consumers’ increasing demand for additive‐free food products. In the past two decades, there has been a significant focus on sourdough with in situ produced dextran due to its exceptional performance. In this review, the behaviors of bread crucial compositions (i.e., starch and gluten) during dough mixing, proofing, baking and bread storing, as well as alterations induced by the acidic environment and the presence of dextran are systemically summarized. From the viewpoint of starch and gluten, results obtained confirm the synergistic amelioration on bread quality by the coadministration of acidity and dextran, and also highlight the central role of acidification. This review contributes to establishing a theoretical foundation for more effectively enhancing the quality of wheat breads through the application of in situ produced dextran.
... Even if, acetic acid was found only in common wheat and einkorn bread, it might be possible that part of the acetate formed during metabolic pathways remained bound in esters like acetic acid, hexyl ester, and acetic acid, butyl ester, as the results for VOCs showed (Table S2) and contributing to the bread aroma profile. On the other hand, when lactobacilli have low amounts of fermentable carbohydrates available, the production of lactate is shifted to transforming citrate (Gobbetti & Gänzle, 2013). Sometimes citrate is used as an energy supplier (Teleky, Martȃu, Ranga, Chețan, & Vodnar, 2020). ...
This study aimed to investigate the effect of ancient wheat flour type and sourdough fermentation time on the nutritional, textural and sensorial properties of fiber-rich sourdough bread. The proximate composition, minerals, carbohydrates, organic acids, volatiles, total phenolic content, simulated gastrointestinal digestion, textural and sensorial characteristics were investigated. Bread's minerals, total phenolics, cellulose contents and radical scavenging activity variations clearly indicates an increasing trend with sourdoughs fermentation time. Compared to maltose and glucose, fructose was predominant in all bread samples. Sourdough fermentation time and wheat type had non-significant influence on fructose content from digested fraction. Excepting emmer bread, fermentation time increased in vitro digestibility values for tested samples. The crumb textural parameters (hardness, gumminess, chewiness, cohesiveness and springiness index) were positively influenced by fermentation time. The specific clustering of the analysed characteristics distinguished emmer bread from other samples in terms of volatile compounds, textural and overall acceptability, being preferred by panellists.
... A gelatinized, viscous mass termed a starch paste was formed in the scalded and saccharified flour ( Figure 2A4). When heated above the crystallization temperature, the crystallites inside the starch granules begin to melt, amylose leaches [38], and irreversibly swells when absorbing water. Mainly, starch amylose dissolves in water, forming an amylose matrix. ...
In wholemeal bread production, scalding and fermentation contribute to the improvement of the structural characteristics of the dough and bread. The influence of fermented scald on rye and barley dough and bread structure formation was specified in this study. The microstructural analysis performed using a scanning electron microscope revealed the separation of phases during the fermentation of scalds. According to the storage G′ and loss G″ moduli, both scalds exhibited elastic character over viscous. The fermentation of barley scald increased both moduli and complex viscosity, while no substantial changes were observed in the fermented rye scald. The addition of fermented scald containing partially hydrolyzed starch and a fraction of water-soluble compounds contributed positively to the formation of a well-organized structure of dough fermented for 4 h. Fermentation substantially reduced the dough’s complex viscosity and moduli values, confirming the partial structure alteration leading to the viscous portion increase. The dough with fermented scald showed a significantly lower loss factor than the dough without fermented scald, indicating enhanced mechanical process ability. The most substantial weakening of the structure was observed for dough without scald. The addition of rye scald to the rye dough promoted the formation of fewer pores with relatively smaller specific volumes.
... Pasta is a popular food item among consumers largely due to its nutritional properties, ease of preparation and cheap price (Foschia et al., 2015). Pasta is prepared from wheat or semolina flour which in turn is known to be low in amino acids lysine and methionine (Gobbetti and Ganzle, 2013). Therefore, it becomes necessary to fortify pasta with proteins from sources rich in essential amino acids (Nogueira and Steel, 2018). ...
Demand for healthier food products is increasing all over the world, and cereal food industry has attempted to enhance
the nutritional content of products by the addition of protein and lipid-rich ingredients. Incorporation of fish proteins rich in amino acids, specially lysine and methionine, through partial substitution of semolina flour is expected to improve the nutritional value of pasta. The present study is focused on the effect of such incorporations on the physical properties like texture profile, colour, cooking properties, water absorption and swelling index. Surimi powder (SP) prepared from tilapia (Oreochromis mossambicus) was used for the study. Four replacement levels were tested T5 (5%), T10 (10%), T15 (15%) and T20 (20%) together with a control pasta, T0 (100% semolina flour). The results demonstrated an increase in cooking yield (158.18±0.82% in T5 to 175.31±3.31% in T20) and cooking loss (3.98±0.12% in T5 to 5.26±0.17% in T20) and all pasta samples were in the acceptable range (8 g/100 g) for cooking loss. The addition of SP resulted in significantly (p<0.05) decreased swelling index and water absorption, with an increase in hardness from 73.13±34.11 g (T5) to 128.21±8.88 g (T20). Instrumental colour parameters indicated that T10 to T20 had better yellowness than T0 and T5. Thus, pasta can be fortified using surimi powder, characterized with increased hardness and fracturability. The fortification levels above 5% i.e., treatment T10 to T20 will be preferred more due to better yellowness.
... Specific volume (SV) is a parameter that reflects gluten network quality and the bread matrix's capability to retain gas produced during the fermentation process. As the bran fraction in flour limits gluten hydration [133] and negatively interferes with the bonds required for gluten formation [134], a high volume in whole-grain bread is difficult to achieve [135][136][137]. With the addition of SDs, SV was reduced (by 13% in SB-RYE106, 18% in SB-FST1.7, and 21% in SD-R3) when compared to RB, with higher acid contents causing more pronounced effects (Table 3). ...
FODMAPs are fermentable oligo-, di-, monosaccharides, and polyols. The application of homofermentative lactic acid bacteria (LAB) has been investigated as a promising approach for producing low-FODMAP whole-wheat bread. The low-FODMAP diet is recommended to treat irritable bowel syndrome (IBS). Wheat flour is staple to many diets and is a significant source of fructans, which are considered FODMAPs. The reduction of fructans via sourdough fermentation, generally associated with heterofermentative lactic acid bacteria (LAB), often leads to the accumulation of other FODMAPs. A collection of 244 wild-type LAB strains was isolated from different environments and their specific FODMAP utilisation profiles established. Three homofermentative strains were selected for production of whole-wheat sourdough bread. These were Lactiplantibacillus plantarum FST1.7 (FST1.7), Lacticaseibacillus paracasei R3 (R3), and Pediococcus pentosaceus RYE106 (RYE106). Carbohydrate levels in flour, sourdoughs (before and after 48 h fermentation), and resulting breads were analysed via HPAEC-PAD and compared with whole-wheat bread leavened with baker’s yeast. While strain R3 was the most efficient in FODMAP reduction, breads produced with all three test strains had FODMAP content below cut-off levels that would trigger IBS symptoms. Results of this study highlighted the potential of homofermentative LAB in producing low-FODMAP whole-wheat bread.
... During the fermentation of sourdough, the lactic acid bacteria can, using sucrose, synthesize glucan and fructan-type exopolysaccharides [25,26]. These polymers act as hydrocolloids, and their impact in dough and bread is based on the water-binding capacity in the dough preparation stage and the mutual interaction with other components of dough, like starch and proteins [27]. In addition to biochemical interactions, there are also chemical transformation in nutrients during sourdough and dough fermentation. ...
The complex of polysaccharides of the grain transforms during processing and modifies the physical and chemical characteristics of bread. The aim of the research was to characterize the changes of glucans, mannans and fructans in hull-less barley and wholegrain wheat breads fermented with spontaneous hull-less barley sourdough, germinated hull-less barley sourdough and yeast, as well as to analyze the impact of polysaccharides on the physical parameters of bread. By using the barley sourdoughs for wholegrain wheat bread dough fermentation, the specific volume and porosity was reduced; the hardness was not significantly increased, but the content of β-glucans was doubled. Principal component analysis indicates a higher content of β-glucans and a lower content of starch, total glucans, fructans and mannans for hull-less barley breads, but wholegrain wheat breads fermented with sourdoughs have a higher amount of starch, total glucans, fructans and mannans, and a lower content of β-glucans. The composition of polysaccharides was affected by the type of flour and fermentation method used.
... To improve the quality of wholemeal products, sourdough fermentation is considered one of the most effective methods (Gobbetti & Gänzle, 2012). Firstly, the fermentation of sourdough produces a variety of organic acids that lower the pH in the fermentation system and activate some enzymes (Gong et al., 2020); secondly, the macromolecules in whole wheat flour are hydrolyzed or modified by the combination of the acidic environment and enzymes; such as bran proteins, non-starch polysaccharides and cell wall polysaccharides (Gong et al., 2020;Montemurro et al., 2019); whole wheat products will benefit significantly from this improvement in textural properties as well as processing quality (Heiniö et al., 2016;Pei et al., 2020). ...
This investigation used the sourdough fermentation technique to ferment dough at different WBDF addition levels (0%, 3%, 6%, 9% & 12%) and to evaluate the quality of the finished steamed breads. The results show that WBDF addition promotes the hydrolytic behaviour of both GMP and SDS soluble proteins; especially for high molecular weight protein subunits (Mw = 120-80 kDa). MRI images clearly showed the water migration and escape behaviour in the fermented dough at different WBDF levels. Further, it was found that the specific volume of steamed breads increased from 3.75 mL/g to 6.97 mL/g (p < 0.05); the DPPH· scavenging capacity of steamed breads increased from 4.46% to 9.68% (p < 0.05). Finally, the GC-MS results demonstrated that the addition of WBDF significantly increased the 2-pentylfuran content in the steamed breads from 0.9 to 182.9 (p < 0.05, in terms of relative peak area).
... Sourdough fermentation technology is considered a promising way to improve wholemeal product quality; it is considered a "gold standard" fermentation technique and an effective way to meet future food challenges (5,6). However, the use of sourdough in industrial fermentation processes is challenging as microorganism complexity in sourdough is significantly influenced by the environment (7). ...
The effect of synergistic fermentation of Lactobacillus plantarum and Saccharomyces cerevisiae on the structural properties and aggregation behavior of gluten containing different wheat bran dietary fiber (WBDF) levels (0, 3, 6, 9, and 12%) was investigated. The results showed that WBDF addition affected the aggregation behavior of gluten at the molecular level, while WBDF significantly induced depolymerization behaviors in large aggregated gluten proteins (Molecular weight > 130 kDa) under reducing conditions (p < 0.05). In terms of secondary structure, WBDF significantly reduced glutamine side chain levels and reduced antiparallel β-sheet structures from 28.57 to 24.53% (p < 0.05). In addition, WBDF thermal properties and its water holding capacity were the main factors causing changes in thermal properties in the overall gluten system. This study provides new data for the improved production of sourdough whole grain and/or high fiber flour products.
The aim of this study was to characterize in vitro digestion of wheat breads baked with sourdough or the postponed baking method without and with arabinoxylan (AX) of different molar mass. The influence of the AX share on the rate of starch digestion, the molar mass of resistant starch (RS) and the pasting characteristics of crumb suspensions of breads baked by the sourdough and postponed baking methods were investigated. Sourdough wheat breads were characterized by contents of very slowly digestible starch (DS) of 1.3% and RS of 1% higher in the crumb, compared to breads baked by the postponed baking method. In the crumb of sourdough breads, after storage for 1 and 3 days, in all variants of the samples (especially with the 2% share of high molar mass AXs), the content of the rapidly digested starch (RDS) fraction decreased, the content of the slowly digestible (SDS) and DS fractions did not change significantly, while the content of the RS fraction increased. In addition, the RS fraction present in the crumb of sourdough breads was generally characterized by a lower molar mass than the RS isolated from the crumb of breads baked by the postponed baking method. The crumb of wheat breads baked using sourdough was characterized by higher viscosity, compared to those baked by the postponed baking method.
Fungal growth is a major cause of bread spoilage. Commercial bread formulas thus often contain one or several preservatives. The use of sourdough, addition of antifungal plant ingredients or a reduction of the aW may provide alternatives to chemical preservation. This study explored the use of 10% sourdough fermented with Fructilactobacillus sanfranciscensis in bread formulations with an aW of 0.96 and 0.92 in presence and absence of propionic acid. Breads were challenged with Aspergillus clavatus FUA5004, Penicillium roqueforti 3969 and P. roqueforti 6130. Sourdough addition alone did not extend the mould-free shelf life when compared to chemically acidified bread. Sourdough in combination with aW 0.92 and addition of propionate extended the mold-free shelf life to up to 9 d. A low aW also increased crumb hardness and decreased the specific volume of bread. Challenge of bread with single spores documented that the use of sourdough, propionate and low aW independently influenced the proportion of germinating spores and the time to germination in a strain-specific manner. In conclusion, the use of sourdough alone is not sufficient to achieve a mould-free shelf life of more than 10 d but sourdough can be an effective complement in preservative systems that achieve a longer shelf life.
Hemp seed flour (Cannabis sativa) is a non-traditional matrix alternative to wheat for baked goods production. The aim of this study was to investigate the microbiota of two liquid sourdoughs (SLs) based on hemp or a wheat–hemp mixture, before and after spontaneous or piloted fermentation (Lactiplantibacillus plantarum ITM21B or Weissella cibaria C43-11 used as starters). Culture-dependent and -independent (high-throughput sequencing of bacterial phylogenetic V3-V4 regions of the 16S rRNA gene) methods, were used to evaluate the microbial community. The effect of fermentation on the content of bioactive molecules (polyphenols, organic acids, proteins, and amino acids) was also investigated. Results indicated that the microbial community of all SLs was mainly (99.7 ÷ 100%) composed of Firmicutes and Proteobacteria, and the latter was the unique phylum before fermentation in formulations produced exclusively with hemp flour. Two PCoA plots (Test adonis with pseudo-F ratio, p > 0.05) showed no significance difference between the microbial communities of the formulations. However, the relative abundance variation at the family level in the wheat–hemp-based mixture SLs showed a significant enrichment of the Lactobacillaceae family (Kruskal–Wallis test, p = 0.04). Moreover, results confirmed hemp seed flour as a suitable fermentation substrate to obtain microbial consortia allowing for an increase in organic acids, especially lactic acid (9.12 ± 1.22 and 7.45 ± 0.75 mmol/kg with Lpb. plantarum and W. cibaria, respectively), in both piloted fermentations, and in polyphenols by 21% and amino acids by 158% in SL fermented by the C43-11 strain.
Very high gravity (VHG) starch to ethanol fermentation with whole and debranned triticale grains using the conventional (warm) and cold (raw starch) conversion methods were compared, with regards to fermentation performance and the quality of the distillers’ dried grains with solubles (DDGS). For both the warm and cold process configurations, debranning increased final ethanol concentration, yield (as % of theoretical maximum) and productivity. Furthermore, debranning decreased the required enzyme dosage of the cold process by 20.7%. The improvements by debranning were achieved by nutrient-recycling from the protease-treated bran and germ hydrolysate to the fermentation slurries of these processes. DDGS produced by the cold debranned process configuration had the highest protein content of 44%, while the neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents of 17.8% and 13.8%, respectively, were lower than DDGS from the whole grain, making it the more favourable animal feed ingredient, particularly for monogastric animals.
In this work, the type of fermentation and baking technology used to make hemp bread was investigated. The physicochemical composition of flour and bread, the protein nutritional quality, fatty acids profile, texture, consumer acceptance, analysis of volatile compounds using an electronic nose and chemical compounds using an electronic tongue were determined. Differences in protein and total dietary fiber content were observed in the obtained breads. The use of sourdoughs had a minor effect on the physical properties of the bread tested (the volume and mass of the loaves, color, or crumb texture). There was no clear effect of the tested sourdoughs on the parameters of the crumb texture and its moisture, assessed physically, both on the day of baking and during storage. In this bread, the limiting amino acid was lysine (amino acid score from 56.22% to 57.63%), but the breads did not differ significantly in the value of this indicator. The n-6/n-3 ratio in breads containing hemp flour (from 3.73 to 4.48) may have a beneficial effect on human health. The best-rated bread was the HB4 with a score of 6.09. The acceptance of remaining breads were in the range from 3.91 for HB1 to 4.91 for HB2.
Determining the bioactive compounds during the production of artisanal breads will allow us to identify healthy food alternatives that replace ultra-processed products, which cause health risks. Five formulations were prepared: wheat flour+water (WF), whole wheat flour+water (WWF), whole wheat flour+water+beer (WWFB), whole wheat flour+water+beer+habanero chili (WWFBH) and whole wheat flour+water+beer+serrano chili (WWFBS). The WWFB bread was the fluffiest, and the WF and WWF breads were the most acidic. During the bread-making process, the total phenol content was higher in the WWFBS sourdough (33.74 ± 0.03 mg GAE/100 g), while the WF bread had the highest total flavonoid content (13.32 ± 0.06 mg QE/100g). Artisanal bread fermented with wheat flour without a starter culture and vegetable substrate can be considered a functional food with a higher content of bioactive compounds that benefits human health.
The baking industry’s enduring relationship with microbes and the integration of biotechnological advancements have transformed the production of bakery products. The symbiotic interaction between microbes and baking has been instrumental in creating a vast range of bakery products throughout history. This chapter delves into the historical and contemporary importance of both microbes and biotechnology in various baking processes, demonstrating their role in modern bakery product applications. The discovery of yeast leavening in ancient Egypt revolutionized bread-making and led to the development of various bread types with distinct flavors and textures. Modern times have integrated Biotechnological techniques into the baking industry, leading to innovative techniques and applications. Biotechnological advancements have led to the development of genetically engineered, yeast and bacteria which have enhanced their fermentation capabilities, resulting in improved leavening, texture, and flavor development. Biotechnological techniques have facilitated the use of enzymes in baking, enabling precise control over dough conditioning and product quality. The integration of probiotics and prebiotics through biotechnology has resulted in the production of healthy baked goods. The combined impact of microbes and biotechnology in the baking industry has transformed the production of bakery products, enhancing their quality, diversity, and sustainability.
This study aims to investigate sensory attributes that play a significant role in determining consumer preferences in the food sector. The research explores the impact of three different yeast types used in bread preparation, assessed through sensory analysis methods, on the perceived taste and overall acceptability of the products. The study employs an experimental design and conducts product testing in real sales environments. A panel of 22 participants was requested to evaluate breads prepared with three visually similar but content-wise different yeast types. Following a tasting session, participants provided data based on sensory analysis criteria, including "appearance," "flavor," "texture," "odor," and "general acceptability," using a designed survey method. The collected data were analyzed using statistical software packages, specifically through Friedman's and Wilcoxon Signed-Rank tests. The research findings indicate variations in consumer preferences regarding taste, texture, odor, and overall acceptability. Panelists expressed a higher preference for breads obtained with sourdough yeast.
The increasing popularity of home brewing and the fast evolution of craft beer companies have fuelled the interest in novel yeasts as the main actors diversifying the beer portfolio. Here, we have characterized the thermal tolerance and brewing-related features of two sourdough (SD) isolates of Saccharomyces cerevisiae, SDy01 and SDy02, at different temperatures, 20 and 37 °C, comparing them with commercial brew strains, AaB and kNB. The SD strains exhibited tolerance to the main brewing-related stress conditions and increased growth rates and lower lag phases than the reference beer strains at both temperatures. Consistent with this, SDy01 and SDy02 displayed higher fermentative activity in terms of sugar rate depletion and the release of metabolic by-products. Moreover, SDy01 and SDy02 brewing at 20 °C increased their total amount of volatile compounds (VOCs), in particular, their esters and carboxyl compounds, as compared to the reference AaB strain. In contrast, fermentation at 37 °C resulted in a drastic reduction in the number of VOCs in wort fermented with SD yeast, especially in its level of esters. In conclusion, our results stress the high fermentative performance of SD strains in beer wort and their ability to provide a complex and specific aromatic profile at a wide range of temperatures.
Highly valued for their nutritional benefits, sprouts are characterized by high water content, which promotes microbial proliferation, potentially leading to toxicity and a reduced shelf life. To address this challenge, the present study explores the application of a novel drying–texturizing approach, named IVDV (Intensification of Vaporization by Decompression to the Vacuum), to sprouts. This technique would enable faster drying of the sprouts and better preservation of their nutritional content, compared to traditional hot-air drying. Using Response Surface Methodology, optimal IVDV parameters (saturated steam pressure P, processing time t, and water content W) for wheat sprouts were defined, with a focus on preserving vitamins, proteins, and lipids, and optimizing the expansion ratio. This optimization process identified optimal experimental conditions at 5.5 bars, a duration of 15 s, and 8.8% d.b. water content. Under these conditions, the use of IVDV endowed the expanded sprouts with a crunchier and more friable texture. In addition, it significantly improved the preservation of vitamins B6 and E by 412% and 42%, respectively, compared to traditional mild hot-air drying, without significantly affecting vitamin B2, proteins, and lipids. When combined with conventional hot-air drying, IVDV not only enhanced the preservation of the sprouts’ nutritional content but also reduced drying time and energy consumption. This marks a significant advancement in sprouts preservation techniques, paving the way for novel potential applications.
Sourdough bread is a traditional product made using lactic acid bacteria (LAB) and yeast. The influence of rye arabinoxylans (AXs) of different molar masses on sourdough wheat bread has not been studied to date. The aim of this study was to research the influence of arabinoxylans of different molar masses on the properties of sourdough wheat bread. The breads were baked using the sourdough method with wheat flour without and with 1% or 2% rye AX with different molar masses, which were unmodified, partially enzymatically hydrolyzed and cross-linked. The addition of all the AX preparations significantly increased the water absorption of the wheat flour. In particular, the addition of the preparation of cross-linked arabinoxylans at an amount of 2% caused the highest increase (by 9.8%) in the addition of water to the wheat flour dough. It was shown that a 2% addition of partially hydrolyzed AXs, with a low molar mass (190,440 g/mol), had the highest influence on increasing (by 23.7%) the volume of the bread and decreasing (by 41%) the crumb hardness of the sourdough bread, determined on the day of baking. The addition of the cross-linked AXs at an amount of 2% had the strongest influence on increasing the moisture content of the crumbs on the day of baking, both in the central (by 2.6%) and peripheral (by 5.1%) parts of the bread compared to the bread without the addition of AXs. The breads with all the AX preparations after the first and third days of storage had a higher crumb moisture content compared to the bread without the AXs.
Debido a los problemas de salud producidos por el alto consumo de alimentos ultraprocesados, es necesario determinar el contenido de compuestos fenólicos durante la elaboración de panes artesanales fermentados con dos tipos de harina, un cultivo iniciador y dos sustratos vegetales. Se prepararon cinco formulaciones, harina de trigo+agua (HT), harina de trigo integral+agua (HTI), harina de trigo integral+agua+cerveza (HTIC), harina de trigo integral+agua+cerveza+chile habanero (HTICH) y harina de trigo integral+agua+cerveza+chile serrano (HTICS). El pan HTIC fue el más esponjoso y los panes HT y HTI fueron los más ácidos. En las diferentes etapas del proceso de elaboración de pan, la cantidad de fenoles totales fue mayor en la masa madre HTICS (33.74±0.03 mg EAG/100 g), mientras que el pan HT tuvo el mayor contenido de flavonoides totales (13.32±0.06 mg EQ/100 g). Los panes artesanales pueden considerarse como un alimento funcional para mejorar la salud del ser humano.
This study focused on evaluating the potential of the natural fermentation of pea flour to improve the release of antioxidant compounds. Preliminary fermentations of 36.4% w/w flour dispersions were performed in tubes under different conditions (24 and 48 h, 30 and 37 °C). Finally, fermented flours (FFs) were obtained in a bioreactor under two conditions: 1: 36.4% w/w, 24 h, 30 °C (FF1); 2: 14.3% w/w, 24 h, 37 °C (FF2). The pH values decreased to 4.4–4.7, with a predominance of lactic acid bacteria. As in the fermentations in tubes, an increment in the proteolysis degree (TNBS method) (greater for FF2), polypeptide aggregation and a decrease in their solubility, an increase in <2 kDa peptides, and an increase in the Oxygen Radical Absorption Capacity (ORAC) potency of PBS-soluble fractions after fermentation were demonstrated. Also, fermentation increased the proteolysis degree after simulated gastrointestinal digestion (SGID, COST-INFOGEST) with respect to the non-fermented flour digests, with some differences in the molecular composition of the different digests. ORAC and Hydroxyl Radical Averting Capacity (HORAC) potencies increased in all cases. The digest of FF2 (FF2D) presented the greater ORAC value, with higher activities for >4 kDa, as well as for some fractions in the ranges 2–0.3 kDa and <0.10 kDa. Fermentation also increased the 60%-ethanol-extracted phenolic compounds, mainly flavonoids, and the ORAC activity. After SGID, the flavan-3-ols disappeared, but some phenolic acids increased with respect to the flour. Fermentation in condition 2 was considered the most appropriate to obtain a functional antioxidant ingredient.
Pasta, prepared from wheat or semolina flour, has gained worldwide popularity due to its ease of preparation, affordability and nutritional benefits. However, it often lacks specific amino acids, namely lysine and methionine, as these components are limited in the cereal proteins present in wheat. Therefore, enhancing the nutritional profile of pasta may necessitate the inclusion of proteins from alternative sources that are abundant in essential amino acids. Fish, known for its richness in lysine, methionine, omega-3 fatty acids, as well as vitamins such as A, D, B6, and B12, along with minerals like iron, zinc, iodine, selenium, potassium and sodium, emerges as a promising option. Dried surimi powders, derived from fish, can be conveniently utilized to fortify the protein content of carbohydrate-rich pasta made from cereals. As the conventional method for preparing and storing fish protein-enriched pasta faces limitations, the aim of this study was to establish a standardized drying temperature and duration for 10% Tilapia surimi powder fortified pasta. The nutritionally enriched, low-carb, low calorie raw pasta was dried at different temperatures (60°C, 70°C and 80°C) to standardize the time and temperature for drying before storage in ambient temperature. Moisture content (11.54±0.47%) was achieved after 64 minutes of drying at 70°C followed by 'best' overall acceptability (4.10±0.42) by 30 expert sensory panellist members. Therefore, based on highest protein content (21.68±0.38%) and significantly (p<0.05) lowest carbohydrate content (60.53±0.45%) followed by sensory evaluation, 10% Tilapia surimi powder fortified pasta dried at 70°C for 64 minutes was chosen to be the optimum drying temperature and time.
Non-conventional yeasts (NCYs) (i.e., non-Saccharomyces) are used as alternative starters to promote aroma complexity of fermented foods (e.g., bakery products). A total of 66 yeasts isolated from artisanal food matrices (bread and pizza sourdoughs and milk whey) from different geographical areas of the Campania region (Italy) were screened for physiological and technological characteristics such as leavening ability, resistance to NaCl and pH, exopolysaccharide and phytase activity production, and carbohydrate assimilation. Selected and isolated microorganisms were also used to study the leavening kinetics in experimental doughs as mixed inocula of two different strains. Volatile organic compounds (VOCs) of the inoculated doughs were analyzed with solid-phase microextraction/gas chromatography–mass spectrometry (SPME/GC-MS). Most of the strains belonged to non-Saccharomyces species (Pichia kudriavzevii, Kluyveromyces marxianus) and Saccharomyces (S. cerevisiae). Several strains produced exopolysaccharides (EPSs), that are important for dough rheological properties. Moreover, yeasts isolated from whey showed extracellular phytase activity. The mixed starter culture of the S. cerevisiae and NCY strains showed a synergic effect that enhanced the doughs’ aroma complexity. The use of non-conventional yeasts mixed with S. cerevisiae strains can be advantageous in the bakery industry because they improve the bread aroma profiles and nutritional properties by bioactive molecule production.
Bread is the oldest and most essential food consumed by humans, with its consumption exceeding nutritional needs and becoming part of cultural habits. Fermentation is an important step in the bread-making process, giving it its rheological, organoleptic, aromatic, and nutritional properties. Lactic acid bacteria and yeasts are both responsible for the fermentation step and part of the natural flour microbiota. In this study, we aimed to characterize LAB in three types of flour, namely, wheat, oat, and rice flour, using conventional phenotypic and biochemical assays and to carry out molecular-biology-based characterization via studying the rrn Operon using RFLP of the ITS region and via PCR using species-specific primers. Additionally, the effect of LAB diversity among the three types of flour and their influence on dough characteristics were assessed. Also, we evaluated the antagonistic effects of LAB on two bacterial (E. coli and S. aureus) and two fungal (Botrytis and Fusarium) pathogens. This study showed that LAB are not the predominant species in rice flour, while they were predominant in wheat and oat flour. Additionally, Lactobacillus sanfranciscencis was found to be the predominant species in wheat flour, while its presence in oat flour was minor. Finally, through their production of soluble substances, LAB exerted antagonistic effects on the four types of pathogenic microorganisms.
In this study, sourdough powder was used as a natural additive to enhance functional properties and reduce glycemic index of corn flakes. Lactobacillus fermentum, Lactococcus lactis, previously isolated from sourdough samples, and Saccharomyces cerevisiae were used as starter cultures to produce sourdough powder from wheat flour. To produce corn flakes sourdough powder was replaced by maize flour in amounts of 15 and 30%, while the control sample contained no sourdough powder. The total phenolic content, 2,2-di-phenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP) of the samples were 421.58 mg GAE/kg, 333.90 µM TE/g, 62.53 mg/kg for control sample, 482.41 mg GAE/kg, 350.60 µM TE/g, 82.22 mg/kg for corn flakes with 15% sourdough, and 531.10 mg GAE/kg, 368.14 µM TE/g, 117.42 mg/kg for corn flakes with 30% sourdough, respectively. Total dietary fibre content, the starch hydrolysis rate, and rapidly digestible starch (RDS) values of corn flakes samples decreased with the addition of 30% sourdough powder (P < 0.05). The estimated glycemic index (eGI), which was 95.76 for the control sample, decreased to 83.41 for the sample with 30% sourdough. The addition of sourdough had no negative effect on the sensorial properties (P > 0.05).
The seeds of Mahuad (Lepisanthes rubiginosa (Roxb.) Leenh (LRL) were analyzed for proximate composition and the contents of phenolic acids, flavonoids, and sugars/oligosaccharides. The LRL seeds contained approximately 29% moisture, 10% protein, 2% fat, 16% fiber, 2% ash, and 42% carbohydrate. The major phenolic acids were vanillic acid and p-hydroxybenzoic acid, accounting for 30% and 26% of total phenolic content, respectively. The predominant flavonoids were quercetin (62% of total flavonoid content) followed by myricetin (22%). Proline, methionine, and arginine were the dominant amino acids, constituting 35%, 19%, and 13% of total amino acid content, respectively. Prebiotic fructooligosaccharide (5.3 mg/g) and stachyose (4.2 mg/g) were also found in the LRL seeds. The major fatty acids were palmitic acid (C 16:0, 41%), oleic acid (C 18:1n9, 27%), and linoleic acid (C 18:2n6, 19%). This information reveals useful information about LRL seeds as a potential source of bioactive compounds for future use in various aspects including food, feeds, pharmaceuticals, and cosmetics.
Tartary buckwheat contains more valuable nutrients than common buckwheat, but it also contains allergenic proteins that induce allergic reactions through an IgE-mediated response. Our study demonstrated that fermentation by Pediococcus pentosaceus degrades allergenic proteins in Tartary buckwheat, as confirmed by HPLC-MS/MS analysis of polypeptides. Our results showed significant degradation of the protein after 16 h of Pediococcus pentosaceus fermentation (PP16), leading to a reduction in IgE-binding activity. Comparison with unfermented Tartary buckwheat (UTB) peptides yielded 2042 fragments, of which 756 fragments associated with allergenic proteins were upregulated. Among them, the expression of 213 fragments was reduced by 71.83%. By performing bioactivity prediction on potential allergenic peptide fragments, we identified six peptide fragments derived from Fagt 1, potentially contributing to the residual allergenicity in PP16. These suggest that Pediococcus pentosaceus fermentation can effectively destroy allergen epitopes and mitigate the allergenicity of Tartary buckwheat.
The continuous development of bakery products as well as the increased demands from consumers transform ancient grains into alternatives with high nutritional potential for modern wheat species. The present study, therefore, follows the changes that occur in the sourdough obtained from these vegetable matrices fermented by Lactiplantibacillus plantarum ATCC 8014 during a 24 h. period. The samples were analyzed in terms of cell growth dynamics, carbohydrate content, crude cellulose, minerals, organic acids, volatile compounds, and rheological properties. The results revealed significant microbial growth in all samples, with an average value of 9 log cfu/g but also a high accumulation of organic acids with the increase in the fermentation period. Lactic acid content ranged from 2.89 to 6.65 mg/g, while acetic acid recorded values between 0.51 and 1.1 mg/g. Regarding the content of simple sugars, maltose was converted into glucose, and fructose was used as an electron acceptor or carbon source. Cellulose content decreased as a result of the solubilization of soluble fibers into insoluble fibers under enzymatic action, with percentages of 3.8 to 9.5%. All sourdough samples had a high content of minerals; the highest of which—Ca (246 mg/kg), Zn (36 mg/kg), Mn (46 mg/kg), and Fe (19 mg/kg)—were recorded in the einkorn sourdough.
Cereals and their derivative products such as starch and cyclodextrin are significant natural materials for sustainable textile processing (e.g., sizing, dispersing, etc.). However, the contamination of cereals with polychlorinated biphenyls (PCBs) is often neglected, which has led to increasing concerns due to the adverse effects on end users. Therefore, monitoring PCBs in cereals is of great importance in preventing health risks. However, high starch, protein, and fat contents make cereals a complicated matrix and can challenge the analysis of PCBs in cereals. This work describes a facile and rapid strategy for quantifying 18 PCBs in cereals that included corn, wheat, and rice through dispersive solid-phase extraction and gas chromatography with mass spectrometry. Importantly, this was the first time that carboxyl-modified, multi-walled carbon nanotubes were incorporated in the detection of PCBs in cereals. The influences of several parameters on the extraction and clean-up efficiency were investigated; these included the type and volume of extraction solvent, sonication time, and the type and dosage of the adsorbent. The matrix effects on quantification were also evaluated. This approach exhibited a better clean-up performance. All the analytes showed weak matrix effects, and thus a solvent standard plot could be prepared for their quantification. Spiking experiments in the selected matrices at three concentration levels from 0.5 to 10 μg/kg resulted in satisfactory recoveries that ranged from 79.2% to 110.5% with relative standard deviations (RSDs; n = 6) less than 10.3%. The limits of detection (LODs) and quantification (LOQs) ranged from 0.04 to 0.1 μg/kg and 0.1 to 0.4 μg/kg, respectively. The practical application of this method was investigated by analyzing actual cereal samples, which demonstrated that the proposed approach was a facile and efficient strategy for PCB determination and provided a reference for the safety evaluation of sustainable textiles. The method also could be generalized to other troublesome samples for testing of multiple PCBs.
Dough rheology, mainly enabled by gluten in the traditional dough, determines the end-products’ quality, particularly by affecting gas production and retention capacities during proofing. Gluten-free dough has quite different rheological performance compared with gluten-containing dough. To deepen the understanding of gluten-free dough, variations of rheology and moisture distribution of corn starch-hydroxypropylmethylcellulose (CS–HPMC) gluten-free dough in the process of proofing were studied. Significant differences were found in terms of soluble carbohydrate composition, moisture distribution, and rheology. Arabinose, glucose, fructose, and mannose were the main composition of soluble carbohydrates in CS–HPMC dough, out of which glucose was preferentially utilized during proofing. Non-freezable water content and third relaxation time decreased from 44.24% and 2171.12 ms to 41.39% and 766.4 ms, respectively, whereas the amplitudes of T23 increased from 0.03% to 0.19%, indicating reduced bounded water proportion and improved water mobility with proofing time. Frequency dependence and the maximum creep compliance increased, whereas zero shear viscosity reduced, suggesting decreased molecular interactions and flowability, but improved dough rigidity. In conclusion, the reduced soluble carbohydrates and improved water mobility decreased molecular entanglements and hydrogen bonding. Furthermore, yeast growth restricted a large amount of water, resulting in declined flowability and increased rigidity.
Sourdough fermentation is an ancient technique to ferment cereal flour that improves bread quality, bringing nutritional and health benefits. The fermented dough has a complex microbiome composed mainly of lactic acid bacteria and yeasts. During fermentation, the production of metabolites and chemical reactions occur, giving the product unique characteristics and a high sensory quality. Mastery of fermentation allows adjustment of gluten levels, delaying starch digestibility, and increasing the bio-accessibility of vitamins and minerals. This review focuses on the main steps of sourdough fermentation, the microorganisms involved, and advances in bread production with functional properties. The impact of probiotics on human health, the metabolites produced, and the main microbial enzymes used in the bakery industry are also discussed.
The use of sourdough for bread production involves fermentation, which is dominated by lactic acid bacteria (LAB) and yeast. Sourdough can be inoculated with a starter culture or through a food matrix containing microorganisms to initiate sourdough fermentation. Sourdough is used as leavening agent for bread making, and metabolites produced by LAB and yeast confer a specific aroma and flavor profile to bread, thus improving its sensory attributes. However, few publications report the effect of microorganisms from different food products and by-products on sourdough fermentation. This review focuses on using different starter cultures from various food sources, from wheat flour to starter cultures. Additionally, included are the types of sourdough, the sourdough fermentation process, and the biochemical transformations that take place during the sourdough fermentation process.
Bread is one of the most discarded foods in the world. In this study, we aimed to create sustainable, carbonated, non-alcoholic drinks by using leftover bread. For that purpose, we used leftover bread (non-treated, and pre-treated with Aspergillus oryzae) from the Michelin 3-star Azurmendi restaurant. The drinks were obtained by fermentation, via three different microorganisms (Saccharomyces bayanus, kombucha symbiotic culture of bacteria and yeast “SCOBY”, and water kefir grains). We investigated (i) the optimal fermentation processes, (ii) the physicochemical properties of the obtained drinks, and (iii) consumer liking by a sensory study. The drink elaborated by S. bayanus was preferred by consumers in the liking test.
The aim of this work was to investigate the effect of refreshments on the growth of endogenous microorganisms during liquid sourdough preparation by using an Italian and Mexican wheat flours and its effects on the physico-chemical properties (pH, total titratable acidity, water activity, moisture content and reducing sugars). The liquid sourdoughs were prepared (DY 200) and incubated for 6 days at 20°C. The sourdoughs were refreshed every day and compared with the not-refreshed ones. Preliminary results showed that in the early stages of the microbial growth process, their population was greater in the sourdough made from the Mexican wheat flour than that of the Italian one. However, after 6 days, the microbial population was not significantly different in refreshed or not-refreshed samples for both sourdoughs (Italian and Mexican). Similarly, physicochemical properties did not show significant differences.
Pulses and whole grains are considered staple foods that provide a significant amount of calories, fibre and protein, making them key food sources in a nutritionally balanced diet. Additionally, pulses and whole grains contain many bioactive compounds such as dietary fibre, resistant starch, phenolic compounds and mono- and polyunsaturated fatty acids that are known to combat chronic disease. Notably, recent research has demonstrated that protein derived from pulse and whole grain sources contains bioactive peptides that also possess disease-fighting properties. Mechanisms of action include inhibition or alteration of enzyme activities, vasodilatation, modulation of lipid metabolism and gut microbiome and oxidative stress reduction. Consumer demand for plant-based proteins has skyrocketed primarily based on the perceived health benefits and lower carbon footprint of consuming foods from plant sources versus animal. Therefore, more research should be invested in discovering the health-promoting effects that pulse and whole grain proteins have to offer.
Nghiên cứu được thực hiện nhằm xác định thông số tối ưu của quy trình tạo sourdough từ nước khóm lên men cũng như thông số tối ưu của quy trình chế biến bánh mì từ sourdough để bánh mì có chất lượng tốt nhất. Nội dung nghiên cứu bao gồm: (i) xác định thời gian lên men sourdough tối ưu, là thời gian phối trộn bột mì với nước khóm lên men (5, 6 và 7 ngày); (ii) xác định tỷ lệ levain tối ưu (10%, 20% và 30%) cùng thời gian ủ bánh mì lần thứ nhất tối ưu (1 giờ, 2 giờ và 3 giờ); và (iii) xác định nhiệt độ nướng tối ưu (220oC, 230oC, 240oC) trong quy trình chế biến bánh mì. Kết quả nghiên cứu cho thấy bánh mì đạt chất lượng cao nhất khi sử dụng sourdough được lên men trong 6 ngày, tỷ lệ levain 20%, thời gian ủ lần thứ nhất là 2 giờ và nhiệt độ nướng 230oC.
The aim of the present study was to assess the antimold capacity of three Wickerhamomyces anomalus strains, both in vitro and in situ, and to identify the responsible volatile organic compounds. For that purpose, two substrates were applied; the former included brain heart infusion broth, adjusted to six initial pH values (3.5, 4.0, 4.5, 5.0, 5.5, 6.0) and supplemented with six different NaCl concentrations (0.0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%), while the latter was a liquid dough, fortified with the six aforementioned NaCl concentrations. After a 24 h incubation at 30 °C, the maximum antimold activity was quantified for all strains at 5120 AU/mL, obtained under different combinations of initial pH value and NaCl concentration. A total of twelve volatile compounds were detected; ethanol, ethyl acetate, isoamyl alcohol and isoamyl acetate were produced by all strains. On the contrary, butanoic acid-ethyl ester, acetic acid-butyl ester, ethyl caprylate, 3-methyl-butanoic acid, 2,4-di-tert-butyl-phenol, benzaldehyde, nonanal and octanal were occasionally produced. All compounds exhibited antimold activity; the lower MIC was observed for 2,4-di-tert-butyl-phenol and benzaldehyde (0.04 and 0.06 μL/mL of headspace, respectively), while the higher MIC was observed for butanoic acid-ethyl ester and ethyl caprylate (5.14 and 6.24 μL/mL of headspace, respectively). The experimental breads made with W. anomalus strains LQC 10353, 10346 and 10360 gained an additional period of 9, 10 and 30 days of mold-free shelf life, compared to the control made by commercially available baker’s yeast. Co-culture of the W. anomalus strains with baker’s yeast did not alter the shelf-life extension, indicating the suitability of these strains as adjunct cultures.
Two hydrocolloids, acacia gum and cactus gum, were tested in the current study to see if they could improve the quality of the dough or have an effect on the shelf life of pan bread and sponge cake. Both gums considerably (p < 0.05) enhanced the dough development time, softness, and mixing tolerance index while decreasing the water absorption. Although the dough was more stable with the addition of acacia gum than with cactus gum, the control sample had the highest peak, final, breakdown, and setback viscosities. Acacia gum, on the other hand, resulted in a higher wheat-flour-slurry pasting temperature (84.07 °C) than cactus gum (68.53 °C). The inclusion of both gums, particularly 3%, reduces the gel’s textural hardness, gumminess, chewiness, springiness, and adhesiveness. Lightness (L*) and yellowness (b*) were both increased by the addition of acacia gum to bread and cake, whereas the addition of cactus gum increased both color parameters for cakes. The use of acacia gum increased the bread and cake’s volume. Cactus gum, on the other hand, caused a decrease in bread hardness after 24 h and 96 h. The cake containing acacia gum, on the other hand, was the least stiff after both storage times. Similarly, sensory attributes such as the crumb color and overall acceptability of the bread and cake were improved by 3% with acacia gum. For these and other reasons, the addition of cactus and acacia gums to bread and cake increased their organoleptic qualities, controlled staining, and made them softer.
Интерес к ржаному хлебу на заквасках активно проявляют российские производители, в основном владельцы хлебопекарных мини-производств. Для изготовления данных хлебобулочных изделий используются закваски из ржаной муки, в основном обдирной ввиду ее большей доступности. Мука ржаная цельнозерновая имеет более высокую пищевую ценность, поскольку в её составе содержатся все компоненты перемолотого зерна. Для исследования была использована технология выведения густой шестидневной ржаной закваски, состоящая из следующих стадий: 1) соединение ржаной муки и воды в соотношении 1:1, время брожения ‒ 24 часа, температура ферментации 30‒31 ºС; 2) соотношение стартера, муки и воды 0,25:1:1. При равных условиях брожения закваска из обдирной муки созревает быстрее, может перекисать и иметь уксусный запах и более кислый вкус. Закваска на цельнозерновой муке имеет более активное брожение, но в то же время процесс усвоения питательных веществ происходит медленнее, эта закваска не перекисает, не разжижается, ее пористость выше. Исследования показателей готовых изделий показали, что хлеб из цельнозерновой муки на закваске обладает большей влажностью (49 %), кислотность составила 9,0 градусов. Хлеб из обдирной муки на закваске имеет кислотность ниже, чем кислотность ржаного цельнозернового хлеба (8,0 градусов), имеет меньшие показатели влажности (48 %). По органолептическим показателям и по пищевой ценности образцы хлеба не имеют значительных отличий. Таким образом, использование цельнозерновой муки и закваски для хлеба из данной муки влияет незначительно как на органолептические, так и физико-химические показатели, и пищевую ценность ржаного хлеба на заквасках.
Background : Currently, the increase in the nutritional value of food constitutes a
major challenge in global nutrition, which is mainly aimed at preventing malnutrition
and related diseases. Among the foods that are subject to this challenge, wheat bread,
the traditional staple food of many populations worldwide, is often denigrated because
of its low nutritional value due to the poor manufacturing practices that use baker’s
yeast. Methods : Research was conducted on a wide range of databases (MEDLINE
via PubMed, SpringerLink, Scopus, and Science Direct), over the period from 1970 to
2020, using the keywords : Wheat bread, sourdough, Lactic acid bacteria, yeasts,
quality characteristics, nutritional value. Results : All reviewed publications proposed
the use of sourdough during bread-making as an alternative to baker’s yeast. Its
effectiveness has been proven through its capacity to improve the nutritional
composition of wheat bread, which remains capable to satisfy the daily nutritional
requirements in macronutrients and micronutrients, along with its sensory
characteristics in terms of taste, flavor, volume, texture, and shelf life. Interestingly, the
consumption of sourdough bread as a staple food prevents diabetes, gluten intolerance,
and mineral deficiency, which are major global public health problems. Conclusion :
The use of sourdough in the bread production industry may become a future innovative
technology, considering the changes in the human diet, caused by the increase in the
production of processed foods, rapid urbanization, and changing lifestyles.
Cereal Chem. 81(1):87–93 Bakeries use sourdoughs to improve bread properties such as flavor and shelf life. The degradation of gluten proteins during fermentation may, however, crucially alter the gluten network formation. We observed changes that occurred in the HMW glutenins during wheat sourdough fermentations. As fermentation starters, we used either rye sourdough or pure cultures of lactobacilli and yeast. In addition, we incubated wheat flour (WF) in the presence of antibiotics under different pH conditions. The proteolytic activities of cereal and sourdough-derived proteinases were studied with edestin and casein. During sourdough fermentations, most of the highly polymerized HMW glutenins degraded. A new area of alcohol-soluble proteins (30.000 MW) appeared as a result of the proteolytic breakdown of gluten proteins. Very similar changes were observable as WF was incubated in the presence of antibiotics at pH 3.7. Cereal and sourdough-derived proteinases hydrolyzed edestin at pH 3.5 but showed no activity at pH 5.5. An aspartic proteinase inhibitor (pepstatin A) arrested 88–100% of the activities of sourdough enzymes. According to these results, the most active proteinases in wheat sourdoughs were the cereal aspartic proteinases. Acidic conditions present in sourdoughs create an ideal environment for cereal aspartic proteinases to be active against gluten proteins.
Proteolysis in dairy lactic acid bacteria has been studied in great detail by genetic, biochemical and ultrastructural methods. From these studies the picture emerges that the proteolytic systems of lactococci and lactobacilli are remarkably similar in their components and mode of action. The proteolytic system consists of an extracellularly located serine-proteinase, transport systems specific for di-tripeptides and oligopeptides (> 3 residues), and a multitude of intracellular peptidases. This review describes the properties and regulation of individual components as well as studies that have led to identification of their cellular localization. Targeted mutational techniques developed in recent years have made it possible to investigate the role of individual and combinations of enzymes in vivo. Based on these results as well as in vitro studies of the enzymes and transporters, a model for the proteolytic pathway is proposed. The main features are: (i) proteinases have a broad specificity and are capable of releasing a large number of different oligopeptides, of which a large fraction falls in the range of 4 to 8 amino acid residues; (ii) oligopeptide transport is the main route for nitrogen entry into the cell; (iii) all peptidases are located intracellularly and concerted action of peptidases is required for complete degradation of accumulated peptides.
The aim of this study was to assess the mode of carbohydrate catabolism by lactic acid bacteria isolated from traditional
sourdoughs, as well as to study their effect on the metabolites produced. For this purpose, single cultures of the heterofermentative
lactic acid bacteria Lactobacillus sanfranciscensis, Lactobacillus brevis, Weissella cibaria, and the homofermentative Lactobacillus paralimentarius and Pediococcus pentosaceus were grown in liquid media containing glucose, fructose, maltose and sucrose, either as a single carbon source or in combination
with glucose. Carbon catabolism and the production of metabolites were determined by HPLC analysis. W.cibaria could ferment all carbon sources, L.sanfranciscensis, L.paralimentarius and P.pentosaceus could not ferment sucrose, while L.brevis could only ferment maltose. The presence of glucose did not influence the utilization of fructose and maltose by L.sanfranciscensis, while it repressed the fermentation of fructose, maltose and sucrose by W.cibaria, and fructose and maltose by L.paralimentarius and P.pentosaceus. Moreover, L. sanfranciscensis and L. brevis could obtain extra ATP through the reduction of fructose to mannitol, which favored the production of acetic acid against
ethanol. The utilization of fructose as an electron acceptor has a decisive effect on the prevailing of L.sanfranciscensis and L.brevis in spontaneously fermented sourdough and in the scarce appearance of the other lactic acid bacteria studied.
From a total of four thousand presumed lactic acid bacteria, obtained from raw, unmalted sorghum and barley, 308 isolates were shown to exhibit inhibitory activity against the indicator strain Listeria innocua 4202. Six of these inhibitor-producing isolates were selected for further study on the basis of their relatively wide antimicrobial spectrum, which showed that these producers inhibited several Gram-positive bacteria, including a range of beer spoiling bacteria. The proteinaceous nature, anti-microbial activity against closely related species, heat resistance and pH stability of the inhibitory substances produced by these six bacteria identified these compounds as bacteriocins. All six isolates were shown to secrete the inhibitory compounds into the cell free supernatants. Bacteriocins produced by five of the six producers were purified to homogeneity. Further analytic data was obtained for three of the inhibitory compounds by means of mass spectroscopy and/or N-terminal amino acid sequencing.
Sourdough bread is a traditional product with great potential. This can only be achieved if the interactions between the lactic acid bacteria and yeasts that populate the sourdough are understood. The trophic and non-trophic interactions between sourdough lactic acid bacteria and yeasts are reviewed with particular emphasis on the metabolism of the carbohydrates and nitrogen compounds, the production of CO2 and other volatile compounds, and antimicrobial activity.
The effect of redox reactions catalysed by lactobacilli on properties of wheat gluten was followed during sourdough fermentations. Thiol levels in doughs remained high in doughs fermented with Lactobacillus sanfranciscensis or in chemically acidified doughs to which 10 μmol g–1 glutathione were added. In chemically acidified doughs or sourdoughs fermented with L. sakei or L. perolens, the thiol levels decreased during fermentation. Thiol-groups in gluten proteins were estimated by RP-HPLC separation of DAC-maleimide-labeled, propanol-soluble proteins extracted from wheat doughs. An increase of the SH groups in gluten proteins was observed in protein fractions from sourdoughs fermented with L. sanfranciscensis but not from chemically acidified doughs. A glutathione-reductase was expressed in L. sanfranciscensis and during its growth in sourdough resulted in the reduction of extracellular GSSG to GSH. It was concluded that in addition to the pH-dependent activity of cereal proteases, redox reactions catalysed by lactobacilli determine gluten quality during sourdough fermentations. The formation of thiols by L. sanfranciscensis interferes with gluten polymerisation. Due to differences in their central carbon metabolism, homo- or facultative hetero-fermentative lactobacilli have opposite effects on redox-reactions in wheat doughs.
This study aimed at investigating the antifungal activity of sourdough fermented (Lactobacillus plantarum LB1 and Lactobacillus rossiae LB5) wheat germ (SFWG). Preliminarily, methanol and water/salt-soluble extracts from SFWG were assayed by agar diffusion towards Penicillium roqueforti DPPMAF1. As shown by hyphal radial growth rate, the water/salt-soluble extract showed the inhibition of various fungi isolated from bakeries. The antifungal activity was attributed to a mixture of organic acids and peptides which were synthesized during fermentation. Formic (24.7 mM) acid showed the highest antifungal activity. Four peptides, having similarities with well known antifungal sequences, were identified and chemically synthesized. The minimal inhibitory concentration was 2.5–15.2 mg/ml. Slices of bread made by addition of 4% (wt/wt) of freeze dried SFWG were packed in polyethylene bags and stored at room temperature. Slices did not show contamination by fungi until at least 28 days of storage and behaved as the calcium propionate (0.3%, wt/wt).
An X-prolyl dipeptidyl aminopeptidase (PepX) from Lactobacillus sanfranciscensis CB1, a key sourdough lactic acid bacterium, was partially purified by five chromatographic steps. As estimated by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration, the enzyme appeared to be a 49.2–56 kDa monomer. Optimal activity occurred at pH 6.0 and 30 °C, with Km of 0.6 mM and Vmax of 99.6 nmol mg−1 min−1. The D value, calculated at 45 °C, was ∼5.46 s. The enzyme hydrolyzed (almost exclusively) substrates with a X-Pro N-terminal sequence. It did not possess prolidase, aminopeptidase or endopeptidase activities. No hydrolysis of the Pro-rich 33-mer epitope (a potent inducer of gut-derived human T-cell lines in celiac patients) was found when it was treated with PepX alone. When the general aminopeptidase type N was combined with PepX, the hydrolysis of 33-mer peptide (0.2 mM) was complete after 24 h of incubation at 30 °C. Leucine and glutamine residues were liberated from the Pro-rich 33-mer peptide by aminopeptidase type N, thus favouring the subsequent PepX activity. PepX was inactivated by p-chloromercuribenzoate, 3,4-dichloroisocoumarin and phenanthroline which exerted a competitive mode of inhibition. Among divalent cations, only Zn2+, Hg2+ and Mn2+ markedly decreased the enzyme activity. Quadratic response surface methodology was used to study the individual and interactive effects of temperature, pH and NaCl on the PepX activity. The enzyme maintained considerable activity under the environmental conditions which characterize the sourdough fermentation.
Gluten-free breads, which are composed of gluten-free flours, starch, and hydrocolloids, differ from wheat and rye breads in relation to texture, volume, and crumb structure. Moreover, the dietary fiber content is lower compared with wheat or rye breads. Cereal isolates of lactic acid bacteria frequently produce oligo- and homopolysaccharides from sucrose, which can improve the nutritional and technological properties of gluten-free breads as prebiotic carbohydrates and hydrocolloids, respectively. Sorghum sourdough was fermented with Lactobacillus reuteri LTH5448 or Weissella cibaria 10M, which synthesize fructooligosaccharides (FOS) and levan, and isomaltooligosaccharides and dextran, respectively. The gluten-free bread was produced with 14% sourdough addition. L. reuteri LTH5448 formed FOS and 1.5 g of levan/kg DM in quinoa sourdoughs. FOS were digested by the baker's yeast during proofing, and the levan could be qualitatively detected in the bread. W. ciburia 10M produced >60 g of isomaltooligosaccharides/kg DM and 0.6 g of dextran/kg DM, which could still be detected in the bread. Breads prepared with W. cibariu 10M were less firm compared with breads prepared with L. reuteri LTH5448 or a FOS and levan-negative mutant of L. reuteri LTH5448. The addition of sourdoughs fermented with oligo- and polysaccharide forming starter cultures can increase the content of prebiotic oligosaccharides in gluten-free breads.
The ability of selected lactic acid bacteria to inhibit the growth of rope-forming Bacillus strains in laboratory experiments and in wheat bread was investigated. Growth of Bacillus subtilis and Bacillus licheniformis was inhibited by Lactobacillus plantarum VTT E-78076 and Pediococcus pentosaceus VTT E-90390 in an automated turbidometry assay and in test bakings. Rope spoilage of wheat bread was inhibited by adding 20–30 g of sourdough/100 g of wheat dough if the sourdough was fermented with Lactobacillus plantarum VTT E-78076,Pediococcus pentosaceus VTT E-90390 or Lactobacillus brevis (commercial starter culture) and the pH values of sourdoughs were adjusted below 4.0 and the amount of total titratable acidity value was >12. Addition of lactic acid alone in concentrations comparable with those formed in sourdoughs did not prevent rope spoilage.
One hundred and seventy strains of sourdough lactobacilli were screened for their capacity to grow optimally by using pentoses. Lb. alimentarius M106 and M137, Lb. hilgardii S32, Lb. brevis AM11, Lb. fermentum I4 and Lb. brevis AM8 had a higher cell yield, growth rate and acetic acid production on a mix of arabinose, xylose or ribose and maltose than on maltose as carbon sources. In the cofermentation process, pentoses were preferentially consumed instead of maltose. Pentosan extract was treated with α-L-arabinofuranosidase from Aspergillus niger or endo-xylanase from Bacillus subtilis to produce hydrolysates respectively each of arabinose and xylose. Depending on the type of pentose and other unidentified compounds, hydrolysates specifically substantiated the growth and acetic acid production of sourdough lactobacilli. Sourdough fermentation by Lb. hilgardii S32 with addition of pentosans and endo-xylanase enzyme increased the acidification rate, titratable acidity, acetic acid content and cell yield number. In addition to the well known role in retarding bread staling, pentosans may also be used as sources of pentoses which favour the performances of selected sourdough lactobacilli.
Bakery industry has known a revolution over the past 150 years. The small artisan bakeries, which were present in every village, made place for high technological bakery industry. Industrial mono-production took over from the high variety bakeries as bread could be produced in a more efficient way. Productivity became the key of success. Different baking technologies were developed to answer better to new market demands. The main consequence of this evolution was a decreased interest for bread flavour through long fermentation processes. A trend has been observed for an increased demand for tastier bread as some artisan bakeries are still producing nowadays or for specialty breads from all over the world. A new business has been created through that demand for companies specialised in the production of stabilised sourdough products. Bakery industry was enabled to provide an answer to the market demand without investment in time, equipment, or extra labour cost.
Amino acid metabolism by one strain each of Lactobacillus casei and Lactobacillus paracasei subsp. paracasei in resting cell suspensions was studied. The experiment was performed under cheese like conditions in terms of pH, salt concentration, temperature and carbohydrate starvation using a mixture of l-amino acids as substrate. The effect of supplementing the amino acids mixture with α-ketoglutarate was estimated. Asparagine, serine and glutamine were utilised in the suspension with only amino acids. In the suspension with both amino acids and α-ketoglutarate, the degradation of leucine and lysine was observed. Production of metabolites that could be important for cheese flavour such as carbon dioxide, ammonia, organic acids and volatiles was measured. The suspensions with amino acids were characterised by high production of acetoin and ammonia and both increased even more when α-ketoglutarate was added. Carbon dioxide was produced in high amounts in the suspension with both amino acids and α-ketoglutaric acid.
The utilisation of glucose and maltose was investigated with Lactobacillus strains isolated from sourdough starters. These preparations have been in continuous use for a long period to produce sourdough from rye, wheat and sorghum. The major metabolic products formed by resting cells from glucose or maltose were lactate, ethanol and acetate. Upon fermentation of maltose, resting cells of Lactobacillus sanfrancisco, L. reuteri, L. fermentum and Lactobacillus ep. released up to 13.8 mM glucose after 8 h. The ratio of released glucose per mol of utilised maltose was up to 1:1. Glucose formation was high when starved cells of L. sanfrancisco and Lactobacillus sp. were used. This is consistent with maltose utilisation via maltose phosphorylase which phosphorylates maltose without the expenditure of ATP and thus allows the cell to waste glucose in the presence of abundant maltose. The glucose formed may be utilised by the lactobacilli or other microorganisms, e.g. yeasts. However, the release of glucose into the medium by sourdough lactobacilli prevents competitors from utilising the abundant maltose by glucose repression. In strains of L. sanfrancisco, maltose utilisation was very effective and not subject to glucose repression. Therefore, they overgrow other microorganisms sharing this habitat. Wild isolates of L. sanfrancisco were initially unable to grow on glucose. Upon growth on maltose such strains required adaptation times of up to 150 h to grow on glucose. After subsequent transfer of glucose-grown cells to fresh medium the strains resumed growth both on glucose or maltose. They readily lost their ability to grow on glucose upon exposure to maltose. L. sanfrancisco exhibited biphasic growth characteristics on media containing glucose, maltose or both carbon sources. Evidence is provided that biphasic growth and metabolite formation are dependent on the redox potential.
Lactobacillus reuteri TMW 1.106, a dominant type II sourdough bacterium, produces glucan from sucrose in vitro and in situ. Exopolysaccharides positively affect the texture and mouth feel of foods and their in situ production in fermented foods could be an alternative to the addition of hydrocolloids from plants or non-GRAS microorganisms. The aim of this study was to elucidate a probable function of the EPS for the bacterium. Lb. reuteri TMW 1.106 harbors two glucosyltransferases, Gtf106A and Gtf106B and produces a dextran. Gtf106B exhibited hydrolysis but no transferase activity. Enzymatic production of dextran with the heterologously expressed, N-terminally truncated ΔN Gtf106A was highest at a pH of 4.0, whereas dextran formation in pH static fermentations was optimal between pH 4.7 and 5.4. The dextran synthesised at these pH values had the highest molecular mass (1.2 × 10) and 15% α–(1–4) linkages. A protective effect of this EPS on Lb. reuteri TMW 1.106 against low pH, explaining the low pH-production maximum, could be demonstrated through the delay of cell death.
Growth, substrates and end-product formation of the maltose and citrate co-metabolization byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain were initially studied in synthetic medium. Compared to maltose (19 g/l) fermentation, the co-metabolization of maltose (10 g/l) plus citrate (9 g/l) caused faster cell growth, increased the concentrations of lactic acid and especially of acetic acid (from 0.7 g/l to 2.9 g/l), produced succinic acid (0.5 g/l) and reduced ethanol synthesis. Highest activities of acetate kinase, the same of lactate dehydrogenase and a reduced alcohol dehydrogenase activity were detected in cytoplasmic extracts of cells growing on maltose plus citrate. The breakdown of citrate depended upon the continuous presence of maltose in the growth medium. Upon depletion of citrate, the cells continued through the normal maltose fermentation, having a diauxic metabolic curve as shown by impedance measurements. Concentrations of citrate from 3 g/l to 15 g/l led to increases of acetic acid from 1.25 g/l to 5.55 g/l. Since maltose was naturally present during sourdough fermentation, the addition of 9 g citrate per kg wheat dough enabled the co-metabolization of maltose and citrate byL. brevis subsp.lindneri CB1. Compared with traditional sourdough fermentation, faster cell growth, a higher acetic acid concentration and a reduced quotient of fermentation were obtained by co-metabolism.
The amino acid release was determined in wheat doughs supplied with salt, acid, dithiothreitol, or starter cultures to evaluate the relevance of the amino acid concentration on bread flavor. Wheat flour proteinases almost linearly released amino acids and the highest activity of wheat flour proteinases was found in acidified and reduced doughs. The effects of starter cultures on amino acid concentrations depended on their composition. Yeasts exhibited a high demand for amino acids, however, the total amino acid concentrations were not markedly affected by lactic acid bacteria. The individual amino acid contents were determined by the pH during fermentation and microbial metabolism. The formation of proline was favored by values higher than pH 5.5, whereas release of phenylalaaine, leucine and cysteine mainly occurred at lower pH. Ornithine was found only in doughs fermented with Lactobacillus pontis. To determine effects of the amino acid concentration on bread aroma, fermented doughs were evaluated in baking experiments. An increased intensity of bread flavor was obtained by preferments prepared with lactic acid bacteria. The roasty note of wheat bread crust could be markedly enhanced by L pontis. This results support the assumption that flavor of wheat bread is enhanced by increasing the concentration of free amino acids and especially ornithine in dough.
Prevention of growth in wheat bread for more than 6 d of approximately 106 rope-producing Bacillus subtilis spores per gram of dough was achieved by addition of propionic or acetic acids at levels of 0·10% v/w (based on flour weight), or by addition of 15% sour dough fermented with Lactobacillus plantarum C11, Lact. brevis L62, Lact. plantarum (‘vege-start 60’), Lact. plantarum (ch 20), Lact. maltaromicus (ch 15), or the commercial sour dough starter culture, Lact. sanfrancisco L99. These cultures resulted in an amount of total titratable acids above 10 in the sour dough and a pH value below 4·8 in the final bread. Bacteriocin-producing lactic acid bacteria added as starter cultures in wheat dough and nisin (Nisaplin) at levels up to 100 p.p.m. g−1 flour had no effect against B. subtilis and B. licheniformis strains, despite the fact that nisin-producing strains of Lactococcus lactis ssp. lactis among 186 strains of lactic acid bacteria had demonstrated inhibitory activity against B. subtilis and B. licheniformis in an agar spot assay.
Eighty-seven strains (15 species) of sourdough lactic acid bacteria (homo- and hetero-fermentative) and yeasts were characterized and statistically discriminated on the basis of volatile compounds produced during sourdough fermentation. The species differed and, in general, the strains differed within the species. Heterofermentative LAB mainly produced ethylacetate with some alcohols and aldehydes, and homofermentative LAB synthetized diacetyl and other carbonyls, while iso-alcohols were produced by yeast fermentation.Lactobacillus brevissubsp.lindneriandLactobacillus plantarumwere the LAB with the most complete profiles. Sourdoughs started with bacterial associations were characterized by a more complete profile (integrations of hetero- and homo-fermentative volatile compounds) and by a decrease of the percentage amounts of the main products individually synthetized. In association with yeasts (with the exception ofL. plantarumDC400 -Saccharomyces exiguusM14 association) both hetero- and homo-fermentative LAB enhanced the formation of the yeast volatile compounds. Mixed sourdough starters (L. brevissubsp.lindneriCB1,L. plantarumDC400 andSaccharomyces cerevisiae141 orS. exiguusM14) were selected to produce sourdoughs with different volatile compound profiles.
Biosynthesis of gelatinase, a virulence factor of Enterococcus faecalis, was found to be regulated in a cell density-dependent fashion in which its production is active in late log to early stationary phase. Addition of early stationary phase culture filtrate to medium shifted the onset of gelatinase production to that of mid-log phase, suggesting that E. faecalis secretes a gelatinase biosynthesis-activating pheromone (GBAP). GBAP was isolated from culture supernatant of E. faecalis OG1S-P. Structural analysis suggested GBAP to be an 11-residue cyclic peptide containing a lactone structure, in which the α-carboxyl group of the C-terminal amino acid is linked to a hydroxyl group of the serine of the third residue. A synthetic peptide possessing the deduced structure showed GBAP activity at nanomolar concentrations as did natural GBAP. Database searches revealed that GBAP corresponds to a C-terminal part of a 242-residue FsrB protein. Northern analysis showed that GBAP slowly induces the transcription of two operons, fsrB-fsrC encoding FsrB and a putative histidine kinase FsrC and gelE-sprE encoding gelatinase GelE and serine protease SprE. Strains with an insertion mutation in either fsrC or a putative response regulator gene fsrA failed to respond to GBAP, suggesting that the GBAP signal is transduced by a two-component regulatory system.
Dough quality and baking performance of wheat dough are significantly affected by the qualitative and quantitative composition
of the gluten. Therefore, the degradation was studied of specific fractions of gluten proteins in sourdough as affected by
starter cultures. Doughs were fermented for 0, 5, and 24h at 30°C after addition of Lactobacillus sakei, L. plantarum, L. sanfranciscensis or Enterococcus faecalis. Chemically acidified doughs were used as controls. All doughs were analyzed quantitatively for their content of albumins,
globulins, gliadins, glutenins, and glutenin macropolymer by means of a combined extraction/HPLC procedure. Protein degradation
during sourdough fermentation was primarily due to acidic proteases present in flour. While L. sakei, L. plantarum and L. sanfranciscensis were mostly non-proteolytic, E. faecalis clearly contributed to gluten proteolysis. Single gluten protein types were clearly different in their resistance to proteolytic
activities of the dough system and E. faecalis, and, in contrast to total glutenins, the amounts of gluten macropolymer were significantly reduced already after 5h of
incubation. When longer fermentation times were applied, gluten was substantially degraded. The strongest decrease was found
for the glutenin fraction leading to an increase of alcohol soluble oligomeric proteins in the gliadin fraction. The extent
of the decrease of monomeric gliadins was strongest for the γ-type followed by the α- and the ω-types. This indicates that
dough properties residing in specific types of gluten fractions can be influenced by the duration of fermentation and the
application of proteolytic strains.
The metabolism of maltose and the use of electron acceptors has been investigated in strains of lactobacilli which are known to be stable elements in sourdoughs, which, traditionally, have been used for a long time. The metabolic features ofLactobacillus sanfrancisco have been described by us in a previous communication. Similar principles have been detected for the competitiveness ofL. pontis, L. reuteri, L. fermentum andL. amylovorus, as well as species-specific characteristics. Based on these findings the metabolic key reactions have been identified and the use of electron acceptors present in sourdough are presented in a schematic overview. In contrast toL. sanfrancisco, these species can not use oxygen as an electron acceptor, and the length of their lag phase was not affected by agitation. Malate and fumarate were reduced to succinate, and fructose was used, depending on the species, as an electron acceptor, carbon source or both. All heterofermentative sourdough lactobacilli efficiently split maltose using maltose phosphorylase. Glucose was excreted, which induced glucose repression in competing indigenous micro-organisms, without affecting the maltose metabolism of sourdough lactobacilli. Lactobacilli generate additional adenosine 5-triphosphate (ATP) from acetyl phosphate in the presence of electron acceptors. These special features are suggested to represent a general principle which accounts for the prevalence of specific heterofermentative lactobacilli which are propagated over long periods present in sourdough fermentations.
The content and composition of dietary fibre (DF), phenolic acids and ferulic acid dehydrodimers as well as the activity of endogenous enzymes were measured in freeze-dried samples of rye wholemeal, dough and bread during the rye bread-making process. Activities of !-amylase, #-xylosidase, !-arabinofuranosidase, and cinnamoyl esterase(s) were found in extracts of wholemeal and in dough after mixing and proofing, whereas activity of endo-xylanase was only found in the wholemeal. As a result of dough mixing, the content of total DF decreased by 21%, which was caused by a decrease in the amount of water-unextractable (WUE) DF. The content of water-extractable (WE) DF was unchanged during the bread-making process, but the relative content of WE DF increased. The content of total ester-bound phenolic acids and ferulic acid dehydrodimers decreased from 1575 g/g in the wholemeal to 1472 g/g in rye bread. The most pronounced effect occurred in an imitated sour dough (acidified with lactic and acetic acid instead of by lactic acid bacteria). The observed changes in content and solubility of DF in the dough could be explained by the activity of endogenous enzymes and mechanical disaggregation, whereas the changes observed in the imitated sour dough indicated that some acid hydrolysis might also have taken place.
In this study, the yields of exopolysaccharides (EPS) produced in situ during sourdough fermentations with Lactobacillus reuteri TMW 1.106 synthesizing glucan from sucrose were investigated under variation of the fermentation parameters dough yield (DY),
pH, sucrose content and fermentation substrate. The obtained amounts of EPS after 1day of fermentation were higher in softer
(DY 500) than in firmer (DY 220) doughs. With the regulation of the pH to a constant value of 4.7, the optimum for EPS synthesis
in liquid medium, the EPS production in dough also increased. The EPS yield could further be improved by additional sucrose
fed-batch during fermentation. Fermentations with wheat flours, a rye-wheat mixture and rye bran with 10% sucrose as fermentation
substrate showed, that the use of rye bran is a promising tool to get high dextran formation through L. reuteri even in the first 8h of fermentation. Further, alternative production of oligosaccharides and organic acids from sucrose
was investigated. Lactobacillus reuteri synthesized high amounts of acetic acid leading to low fermentation quotient values. In wheat doughs, the formation of maltooligosaccharides
was observed. Confirmatory experiments with fructan producing Lactobacillus sanfranciscensis TMW 1.392 revealed the same trends with a few distinct differences, indicating that this approach is transferable to other
EPS types and producers.
The performance of Lactobacillus sanfranciscensis TMW 1.392 and its levansucrase deletion mutant TMW 1.392Δlev in wheat dough was compared. The effects of both strains on
dough and bread characteristics were determined in order to find benchmarks for in situ production of exopolysaccharides (EPS).
Growth and acidification were lower in doughs prepared with the Δlev mutant than in those employing the wild type. Extensogram
resistance of the dough was reduced and extensibility increased with the addition of L.sanfranciscensis levan. Added EPS positively influenced water absorption, bread volume and firming of the crumb. In situ production of EPS
was not sufficient to achieve the same positive effects of EPS, as they partially overlapped with effects resulting from enhanced
acidification. Control doughs were made to separate effects of predough, EPS and different metabolism/acidification. High
acetic acid levels decreased extensibility and volume. High lactic acid levels negatively influenced crumb hardness and firming
kinetics. The use of knock out mutants proved helpful to judge overall performance of a strain, although the interpretation
of specific effects must consider all changes in its metabolism.
Lactobacillus sanfranciscensis CB1 uses cellobiose and other β-glucosides (methyl-β-glucoside, arbutin, amygdalin and salicin) as carbon sources. A hexameric ca. 288 kDa β-glucosidase was purified to homogeneity from Lact. sanfranciscensis CB1 by four chromatographic steps. The enzyme was optimally active at pH 7.5 and 40°C. It had a pI of ca. 4.38 and a D55°C value of ca. 27 sec. Almost total inhibition was found with sulfhydryl-modifying agents and divalent cations such as Cu2+, Co2+, Hg2+, Ni2+ and Fe2+ at a concentration of 2 mM. The enzyme was active towards β-(1→4) substrates such as p-nitrophenyl-β-D-glucoside, -D-galactoside and -L-rhamnoside, and cellobiose. The sequencing of four internal peptides showed an elevated identity with other bacterial β-glucosides of family 3. A PCR strategy with primers designed on the basis of conserved sequences was used to partially identify the gene. The deduced amino acid sequence showed 53, 48 and 45% identity with GHF3 from Ruminococcus albus, Clostridium thermocellum and Bifidobacteriam longum, respectively.
(E)-2-Nonenal and (E,E)-2,4-decadienal are key aroma compounds in wheat bread crumb. The fate of these unsaturated aldehydes in sourdoughs fermented with homo- and heterofermentative lactobacilli or baker's yeast was investigated, and the metabolic pathways in these microorganisms identified. Clear differences were observed between homofermentative lactobacilli, heterofermentative lactobacilli and Saccharomyces cerevisiae. Heterofermentative strains rapidly reduced the concentrations of these aldehydes in dough, whereas S. cerevisiae displayed a lower activity. Lactobacillus sanfranciscensis reduced the aldehydes to the corresponding unsaturated alcohols, whereas S. cerevisiae reduced both the aldehyde moiety and the double bond, resulting in the formation of the corresponding saturated alcohols. S. cerevisiae first reduced the aldehyde moiety and then the double bond. In L. sanfranciscensis, the reduction of aldehydes is coupled to the oxidation of NADH to NAD+, which enables this heterofermentative strain to produce additional ATP from glucose. L. sakei, a strain that produces only lactic acid during sourdough fermentation, did not metabolise the unsaturated aldehydes at all. Both L. sakei and S. cerevisiae appeared to enhance aldehyde formation during the first hours of dough fermentation, probably due to the hydrogen peroxide production by these two strains.
Over the last years, the production of exopolysaccharides (EPS) by lactic acid bacteria (LAB) has been extensively studied. These EPS play an important role in the rheology and texture of fermented food products. Significant progress in the understanding of EPS biosynthetic pathways, genetics, kinetic models, and physics has been made. This knowledge can now be applied to rationally design metabolic engineering studies to modify EPS production and composition. This mini review will discuss the potential engineering strategies of sugar catabolism for the production of EPS by lactic acid bacteria (LAB).
Lactobacillus plantarum FST 1.7 was screened for in vitro antimicrobial activity and was shown to be active against spoilage moulds and bacteria. Isolation of antimicrobial compounds from cell-free supernatant identified lactic acid, phenyllactic acid and the two cyclic dipeptides cyclo (l-Leu-l-Pro) and cyclo (l-Phe-l-Pro) as the major components responsible for this activity. L. plantarum FST 1.7 was tested for the ability to produce the antifungal compounds during sourdough fermentation and to produce bread of good quality and increased shelf-life. A rheofermentometer was used to examine the gaseous release and development characteristics of the dough. A range of parameters was determined including pH, TTA and specific loaf volume. The results were compared with those obtained using Lactobacillus sanfranciscensis, a chemically acidified and a non-acidified dough. The quality of sourdough and bread produced using L. plantarum FST 1.7 was comparable to that obtained using common sourdough starters, e.g. L. sanfranciscensis. Sourdoughs and breads were evaluated for the ability to retard growth of Fusarium culmorum and Fusarium graminearum two fungi found on breads. Sourdough and bread produced with strain FST 1.7 showed consistent ability to retard the growth of both Fusarium species, thus indicating that L. plantarum FST 1.7 has also the potential to improve the shelf-life of wheat bread.
Microbial exopolysaccharides (EPS) occur as capsules or as secreted slime. They represent a small fraction of today's biopolymer market with factors limiting their use being mainly associated with economical production. Efficient production and reduction in recovery costs requires knowledge of biosynthesis and adoption of appropriate bioprocess technology. EPS from generally recognized as safe food grade microorganisms, particularly lactic acid bacteria (LAB), have potential as food additives or as functional food ingredients with both health and economic benefits. Many different heteropolysaccharides (HePS) are secreted by LAB regarding sugar composition and molecular size but they show few common structural features, which raises questions about the relationship between structure and texture.HePS are made by polymerizing repeating units formed in the cytoplasm. These are assembled at the membrane by specific glycosyltransferases (GTF) through the sequential addition of sugar nucleotides. The latter are delivered as building blocks and attached to the growing repeating unit that is anchored on a lipid carrier. After completion, the repeating unit is externalized and polymerized. The enzymes and proteins involved in biosynthesis and secretion are not necessarily unique to HePS formation. These processes involve a genetic organization that includes specific eps genes and “housekeeping” genes involved in sugar nucleotide biosynthesis.The intentional and controlled use of HePS from LAB or use of strains producing HePS in situ is important in the food industry. However, instability in production and variability of HePS yields are well documented. Therefore, a well understood optimized carbon flux and supply of sugar nucleotides, knowledge of the GTF, and the functional expression of combinations of genes from different origin into stable, industrial strains open interesting ways to polysaccharide engineering.
The production of sourdough bread can be traced back to ancient times. Sourdough is a mixture of flour and water that is fermented with lactic acid bacteria (LAB). Sourdough is an intermediate product and contains metabolically active yeast and LAB strains. The LAB that develop in the dough may originate from selected natural contaminants in the flour or from a starter culture containing one or more known species of LAB. Sourdough can be produced in bakeries or obtained from commercial suppliers. The microbial ecology of the sourdough fermentation is determined by ecological factors. Microbiological studies have revealed that more than 50 species of LAB, mostly species of the genus Lactobacillus, and more than 20 species of yeasts, especially species of the genera Saccharomyces and Candida, occur in this ecological niche. The sourdough microflora is composed of stable associations of lactobacilli and yeasts, in particular due to metabolic interactions. As shown for certain industrial sourdough processes, such microbial associations may endure for years, although the fermentation process runs under non-aseptic conditions. A reproducible and controlled composition and activity of the sourdough microflora is indispensable to achieve a constant quality of sourdough bread.
The biochemistry and physiology of sourdough lactic acid bacteria (LAB) have received extensive attention during the last decade for giving an explanation of the microbial colonisation of the natural sourdough environment, which affects the rheology, flavour and nutritional properties of baked goods. Carbohydrate and nitrogen metabolisms deserved the major interest but other biochemical mechanisms have also been considered. A striking property of many sourdough LAB is their enormous flexibility and potential with respect not only to catabolic substrates and anabolic products but also with respect to the continuous changes in the surrounding environment.
Sorghum is a good source of phenolic compounds with a variety of genetically dependent types and levels including phenolic acids, flavonoids, and condensed tannins. Most sorghums do not contain condensed tannins, but all contain phenolic acids. Pigmented sorghums contain unique anthocyanins that could be potential food colorants. Some sorghums have a prominent pigmented testa that contains condensed tannins composed of flavan-3-ols with variable length. Flavan-3-ols of up to 8–10 units have been separated and quantitatively analyzed. These tannin sorghums are excellent antioxidants, which slow hydrolysis in foods, produce naturally dark-colored products and increase the dietary fiber levels of food products. Sorghums have high concentration of 3-deoxyanthocyanins (i.e. luteolinidin and apigenidin) that give stable pigments at high pH. Pigmented and tannin sorghum varieties have high antioxidant levels that are comparable to fruits and vegetables. Finger millet has tannins in some varieties that contain a red testa. There are limited data on the phenolic compounds in millets; only phenolic acids and flavones have been identified.
The ability of lactic acid bacteria (LAB) to inhibit Aspergillus, Fusarium, and Penicillium, the main contaminants in bread, was evaluated. Only four strains (Lactobacillus plantarum CRL 778, Lactobacillus reuteri CRL 1100, and Lactobacillus brevis CRL 772 and CRL 796) from 95 strains tested displayed antifungal activity. The major antifungal compounds were acetic and phenyllactic acids. The fermentation quotient (FQ = 2.0) and the leaven volume (80 cm3) of doughs with LB and yeasts were higher than doughs without LB. The inclusion of antifungal LAB strains in the starter culture allowed a reduction in the concentration of calcium propionate by 50% while still attaining a shelf life similar to that of traditional bread containing 0.4% CP.
The deamination of glutamine is a crucial step in the production of enzymatically hydrolyzed plant proteins to reach high glutamic acid yields. The required glutaminase activity usually is provided by addition of technical enzymes or by in situ generation from fungi, yeast or bacteria (i.e. Aspergillus oryzae in soy sauce production). We screened food-grade Lactobacilli for potential glutaminase activity and selected the enzyme found in Lactobacillus rhamnosus for further characterization. Glutaminase from L. rhamnosus was induced by growing the microorganism on hydrolyzed wheat gluten, a glutamine-rich protein source. Glutamine deaminating activity (glutaminase, EC 3.5.1.2) was found to be membrane-bound and lost its activity gradually upon solubilization. Functional studies of the glutaminase showed an optimal working pH of 7.0 and maximum activity at 50 °C. High salt-tolerance of the enzyme was observed, i.e. the presence of 5% (w/v) salt increased glutaminase activity almost two-fold and 90% of the initial activity still remained at 15% (w/v) salt. The glutaminase activity showed typical Michaelis–Menten behavior with an affinity constant Km of 4.8±0.4 mM for glutamine and a Vmax of 101±2 U/l.
Sorghum and millets have considerable potential in foods and beverages. As they are gluten-free they are suitable for coeliacs. Sorghum is also a potentially important source of nutraceuticals such antioxidant phenolics and cholesterol-lowering waxes. Cakes, cookies, pasta, a parboiled rice-like product and snack foods have been successfully produced from sorghum and, in some cases, millets. Wheat-free sorghum or millet bread remains the main challenge. Additives such as native and pre-gelatinised starches, hydrocolloids, fat, egg and rye pentosans improve bread quality. However, specific volumes are lower than those for wheat bread or gluten-free breads based on pure starches, and in many cases, breads tend to stale faster. Lager and stout beers with sorghum are brewed commercially. Sorghum's high-starch gelatinisation temperature and low beta-amylase activity remain problems with regard to complete substitution of barley malt with sorghum malt . The role of the sorghum endosperm matrix protein and cell wall components in limiting extract is a research focus. Brewing with millets is still at an experimental stage. Sorghum could be important for bioethanol and other bio-industrial products. Bioethanol research has focused on improving the economics of the process through cultivar selection, method development for low-quality grain and pre-processing to recover valuable by-products. Potential by-products such as the kafirin prolamin proteins and the pericarp wax have potential as bioplastic films and coatings for foods, primarily due to their hydrophobicity.
In the dairy industry, microbial exopolysaccharides (EPSs) produced by lactic acid bacteria (LAB) in situ are used to improve the texture of fermented dairy products such as yoghurt or cheese. In addition, it has been suggested that EPSs produced by LAB may confer health benefits. Over the past few years, several studies have been initiated to further understand the genetics and biochemistry of microbial EPS biosynthesis. Eps clusters from different strains of LAB have been identified. In this study, we present the homologies shared by the genes present in the eps clusters from Streptococcus thermophilus, Streptococcus macedonicus, Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus and Lactococcus lactis strains. These homologies are striking and imply a common mechanism of EPS biosynthesis. Most interestingly, these clusters contain genes encoding putative glycosyltransferases (GTFs) that can be regarded as a toolbox of enzymes with a large variety of specificities for applications in polysaccharide engineering.
The degradation of the cereal proteins in wheat and rye sourdough fermentations strongly affects the quality of bread. Acidification and the reduction of disulfide bonds of gluten by heterofermentative lactobacilli increase the activity of cereal proteases and substrate accessibility; amino acids are accumulated by strain-specific intracellular peptidases of lactobacilli. Germinated cereals or other proteases enable an extensive degradation of proteins in sourdoughs in fermentation protocols that may be used to develop new products for individuals with gluten intolerance. The increased knowledge on proteolysis in sourdoughs enables a directed optimization of fermentation to improve bread quality.
Food-borne fungi, both yeasts and moulds, cause serious spoilage of stored food. Moulds may also produce health-damaging mycotoxins, e.g. aflatoxins, trichothecenes, fumonisin, ochratoxin A and patulin. Consumer demands for minimally processed foods and reduced use of chemical preservatives have stimulated research on antifungal lactic acid bacteria as biopreservatives. Recently, a number of antifungal metabolites, e.g. cyclic dipeptides, phenyllactic acid, proteinaceous compounds, and 3-hydroxylated fatty acids have been isolated from lactic acid bacteria. This review summarizes these findings and suggests potential applications of antifungal lactic acid bacteria in the preservation of food and feeds.
Sourdough has been used in bread production for more than 5000 years in order to improve the texture and flavour of baked cereals, and still today sourdough is very important to impart superior flavours to wheat and particularly rye bread. After an introduction into the history of sourdough, results of studies aimed at indicating (i) the influence of the dough and bread recipe, (ii) the regime used in dough fermentation, and (iii) the metabolic activities of sourdough bacteria and yeasts on the final bread aroma are summarized in this review. Based on quantitative results obtained from the same batch of flour, sourdough and rye bread, changes in the concentrations of key bread aroma compounds on the way from flour to bread are highlighted with respect to their contribution to the overall aroma. Based on correlations with the bread recipe, it is discussed how the flour and each technological step influences the final concentrations of selected odorants in the bread.
Type II sourdoughs were prepared using Lactobacillus amylovorus DCE 471, a producer of the bacteriocin amylovorin L. The strain was used as a starter culture for rye and wheat sourdoughs on laboratory scale (10 L), and in rye sourdough on pilot scale (100 L). The sourdoughs were acidified to a pH of around 3.5 within 15 h (laboratory dough) to 25 h (pilot-scale dough). Final amylovorin L titres of 0.3-0.4 (laboratory scale) and 0.2 (pilot scale) MAU kg(-1) of sourdough were detected. After baking of wheat dough that was supplemented with the pilot-scale sourdough, no amylovorin L activity was recovered from the breadcrumbs. On laboratory scale, aeration or the addition of complex carbohydrates hardly affected growth or amylovorin L production. Rye and wheat sourdough fermentation were rather similar despite differences in sugar concentrations. The persistence of L. amylovorus DCE 471 during rye sourdough fermentation, both on laboratory and pilot scale, was confirmed by repetitive sequence-based polymerase chain reaction (rep-PCR) and by testing isolates towards an amylovorin L-sensitive organism. Further, rep-PCR indicated that the background microbiota of the flour - probably responsible for the production of low amounts of acetic acid - grew poorly and were overgrown by L. amylovorus DCE 471 during the pilot-scale fermentation. (c) 2007 Society of Chemical Industry.
The exploitation of lactic acid bacteria with their long history in sourdough fermentations forms an emerging field for baking applications and design of added-value food. The deliberate use of functional traits within these bacteria is supported by knowledge on their phylogenetic and environmental status, the characterization of their genome structure and flexibility, gene regulation and metabolic potential. Molecular taxonomy and genetics are major contributors to this development.
The majority of gluten-free breads on the market are of poor sensory and textural quality. Exopolysaccharides (EPS) formed from sucrose during sourdough fermentation can improve the technological properties of gluten-free breads and potentially replace hydrocolloids. In this study, the influence of in situ formed EPS on dough rheology and quality of gluten-free sorghum bread was investigated. Dextran forming Weissella cibaria MG1 was compared to reuteran producing Lactobacillus reuteri VIP and fructan forming L. reuteri Y2. EPS containing bread batters were prepared by adding 10% and 20% of sourdough. As control served batters and bread containing sourdoughs fermented without sucrose and batters and bread without sourdough addition. The amount of EPS formed in situ ranged from 0.6 to 8.0 g/kg sourdough. EPS formed during sourdough fermentation were responsible for the significant decrease in dough strength and elasticity, with in situ formed dextran exhibiting the strongest impact. Increased release of glucose and fructose from sucrose during fermentation enhanced CO₂ production of yeast. Organic acids in control sourdough breads induced hardening of the bread crumb. EPS formed during sourdough fermentation masked the effect of the organic acids and led to a softer crumb in the fresh and stored sorghum bread. Among EPS, dextran showed the best shelf life improvements. In addition to EPS, all three strains produced oligosaccharides during sorghum sourdough fermentation contributing to the nutritional benefits of gluten-free sorghum bread. Results of this study demonstrated that EPS formed during sourdough fermentation can be successfully applied in gluten-free sorghum flours to improve their bread-making potentials.
After isolation from different doughs and sourdoughs, 177 strains of lactic acid bacteria were screened at the phenotypic level for exopolysaccharide production on media containing different carbohydrate sources. Two exopolysaccharide-producing lactic acid bacteria (Lactobacillus curvatus 69B2 and Leuconostoc lactis 95A) were selected through quantitative analysis on solid media containing sucrose and yeast extract. The PCR detection of homopolysaccharide (gtf and lev) and heteropolysaccharide (epsA, epsB, epsD and epsE, and epsEFG) genes showed different distributions within species and strains of the lactic acid bacteria studied. Moreover, in some strains both homopolysaccharide and heteropolysaccharide genes were detected. Proton nuclear magnetic resonance spectra suggest that Lactobacillus curvatus 69B2 and Leuconostoc lactis 95A produced the same exopolysaccharide, which was constituted by a single repeating glucopyranosyl unit linked by an α-(1→6) glycosidic bond in a dextran-type carbohydrate. Microbial growth, acidification, and viscoelastic properties of sourdoughs obtained by exopolysaccharide-producing and nonproducing lactic acid bacterial strains were evaluated. Sourdough obtained after 15 h at 30°C with exopolysaccharide-producing lactic acid bacteria reached higher total titratable acidity as well as elastic and dissipative modulus curves with respect to the starter not producing exopolysaccharide, but they showed similar levels of pH and microbial growth. On increasing the fermentation time, no difference in the viscoelastic properties of exopolysaccharide-producing and nonproducing samples was observed. This study suggests that dextran-producing Leuconostoc lactis 95A and Lactobacillus curvatus 69B2 can be employed to prepare sourdough, and this would be particularly useful to improve the quality of baked goods while avoiding the use of commercially available hydrocolloids as texturizing additives.