Martina Gastl

Technical University of Munich | TUM

Brewing is an energy and water intensive operation. Efforts to increase the resource efficiency of a brewery usually only focus on the production itself in the form of internal measures. Wastewater and residual materials are usually neglected, although they have a high potential for reuse in a circular economy and for energy recovery. To be prepare...

Background The market for beverages is highly changing within the last years. Increasing consumer awareness towards healthier drinks led to the revival of traditional and the creation of innovative beverages. Various protein-rich legumes were used for milk analogues, which might be also valuable raw materials for refreshing, protein-rich beverages....

The removal of husks before the mashing process, also known as the Kubessa method, is an established brewing practice often positively associated with smoothness and better flavor-stability of beer. Empirical evidence on the effect of the Kubessa method on beer, however, has been lacking. Similarly, our study’s comprehensive analysis of established...

Lupines and faba beans are rising stars among legumes as sources of valuable, vegan plant‐based proteins. To enter new application areas like the production of protein‐rich refreshing beverages, the typical beany aroma impression has to be overcome, and the sensory appearance has to be improved, as it can be accomplished with lactic acid fermentati...

The application of high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) revealed the origin and evolution of antioxidants during the brewing process of hopped and unhopped reference beer. As tachioside (3-methoxy-4-hydroxyphenyl-β-d-glucopyranoside), arbutin (4-hydroxyphenyl-β-d-glucopyranoside), and hordatines clearly increased du...

Background and Objectives Starch is the main component of malting barley ( Hordeum vulgare L.), and its physical and chemical characteristics are particularly important in further processing in the beverage industry. This study investigates how the parameters (i) growing temperature (high/low) and (ii) water deficit (drought stress) during grain fi...

Palate fullness (PF) and mouthfeel are important sensory attributes influencing beer quality. The molar mass of starch (dextrins) and non-starch (β-glucans) polysaccharides may influence PF (pleasant) or mouthfeel (sliminess, unpleasant), respectively. Therefore, this research aims to generate beer with wide physico-chemical responses based on vari...

The study of fermentation and brewing has a long history of pioneering discoveries that continue to influence modern industrial food production. Since then, numerous research endeavors have yielded conventional criteria that guide contemporary brewing practices. However, the intricate open challenges faced today necessitate a more exhaustive unders...

Faba beans are a promising source of valuable plant protein. However, their aroma impression is often a hindrance for the use in a broad range of food products. To develop mitigation strategies, a deeper insight into the faba bean aroma is required. Therefore, for the first time, the SENSOMICS concept was applied. First, 52 aroma active compounds i...

Barley (Hordeum vulgare L.) is the traditional malting cereal and is primarily used for beverages, whereas rye (Secale cereale L.) is mainly used in baked goods. Conversely, quinoa (Chenopodium quinoa Willd.) is a gluten‐free pseudocereal, rich in starch and high‐quality proteins, and can be used in a similar manner to cereals. The sharp bitterness...

Barley (Hordeum vulgare L.) remains the traditional malted cereal used for beverages, whereas rye (Secale cereale L.) is mainly used in baked goods. To evaluate the potential of rye malt for beverage production, malt quality indicators and the volatile composition of different rye malts were compared to barley malt. Sensory assessment revealed that...

Lupines and faba beans are protein-rich legumes, which can be utilized as a plant-based substitute for animal proteins in human nutrition in general and in the beverage industry in particular. However, their application is hampered by low protein solubility in the acidic pH range and by antinutrients such as flatulence-causing "raffinose family oli...

Reverse osmosis (RO) is a widely used membrane technology for producing process water or tap water that is receiving increased attention due to water scarcity caused by climate change. A significant challenge in any membrane filtration is the presence of deposits on the membrane surfaces , which negatively affect filtration performance. Biofouling,...

Kilned specialty malts provide relevant colour and flavour characteristics to beer and other beverages. Alongside the thermal load, the availability of Maillard precursors directly affect the malt aroma formation. To investigate the influence of process parameters on the flavour characteristics of kilned specialty malts, a full factorial design of...

To assess the impact of black-colored grain on Alternaria mycotoxin concentrations in different stages of the brewing process, brewing experiments were conducted in a microscale brewhouse. Different mixtures of visually unaffected and black-colored batches of two malt samples were used, which were obtained by an optical sorting device. The 13 Alter...

Palate fullness intensity and mouthfeel descriptors are essential sensory characteristics of non-alcoholic beers (NABs). The descriptor's perception might be influenced by the molar distribution of the non-volatile matrix in cereal-based beverages like NABs. However, only limited information is available on the molar mass of different substances in...

Dispensing systems are essential in the beer supply chain and form one of the last steps to its final link - the consumer. The maintenance and hygiene of dispensing systems are crucial as they influence the beer quality directly. Dispensing systems comprise various equipment and components necessary to pour a beer in the quality desired by the brew...

Background Quinoa (Chenopodium quinoa Willd.) is a gluten‐free pseudocereal, rich in starch and high‐quality proteins. It can be used as a cereal. Recently, a variety of nontraditional food products were developed; however, the sharp bitterness and the earthy aroma of unprocessed quinoa interfered with the acceptance of these products. Malting of c...

A short history of beer brewing alcoholic fermentation and yeast technology over time.

Rye is used in some applications in the food and beverage industry and for the preparation of functional foods. It is an interesting raw material in malting and brewing due to its characteristic contribution to the beer’s color, turbidity, foam and aroma. The aim of this work was to optimize the micro-malting process of a rye landrace. The response...

Specialty malt beers are brewed with the intention of providing distinct flavour and colour. To this end, special malts have different chemical compositions. More specifically, the availability of enzymes, small peptides, organic acids, Maillard products, low-molecular sugars and amino acids depend on the malting procedure applied and thus vary bet...

Local and alternative raw materials are of growing interest to the malting and brewing industry. These include wheat landraces, old varieties characterized by high protein content and resistance to biotic and abiotic stress. One of the basic ingredients of beer is malt, i.e., a grain that have been subjected to germination under controlled conditio...

There is a relationship between antioxidant activity and ageing stability of beer. The high-throughput antioxidant capacity assays ORAC and FRAP, which rely on specific reaction mechanisms, are validated as an addition to the established ESR-ST method with a focus on hop-derived antioxidants. Beers were brewed with systematic variations in hop vari...

Trace metals, particularly zinc, influence the growth and metabolism of yeast. In the literature the recommended concentration of zinc in pitching wort is > 0.15 mg/L; lower concentrations cause fermentation problems and reduce in consequence final beer quality. The aim of this study was the exploration of changes in bioavailability (available zinc...

Lupines and faba beans are promising ingredients for the beverage industry. They contain high amounts of protein and can be grown in different climate zones and agricultural areas. Therefore, these legumes appear as ideal raw material for vegan, functional, and sustainable beverages. Nevertheless, the sensory characteristic of legumes is generally...

Specialty malts are strategic ingredients regarding their contribution to colour and flavour of beer. Malts with the same colour may present distinct flavour characteristics and intensities. Contradictorily, colour is the benchmark in practical quality control. To investigate the correlation between colour and flavour of kilned barley specialty mal...

A liquid chromatography tandem mass spectrometry (LC–MS/MS) multi-mycotoxin method was developed for the analysis of the Alternaria toxins alternariol (AOH), alternariol monomethyl ether (AME), tentoxin (TEN), altertoxin I (ATX I), altertoxin II (ATX II), alterperylenol (ALTP), and altenuene (ALT), as well as the modified toxins AOH-3-glucoside (AO...

During the germination of legumes, raffinose family oligosaccharides (RFOs) are decomposed into mono- and disaccharides. As legumes are a traditional part of the human nutrition, storage carbohydrates are generally incorporated in the daily meals and can cause flatulence or even abdominal pain. However, their decomposition products can be metaboliz...

Flavor instability of beer is affected by the rise of aroma-active aldehydes during aging. Aldehydes can be either released from bound-state forms or formed de novo. This second part of our study focused on the de novo formation of aldehydes during the Maillard reaction, Strecker degradation, and oxidation reactions. Key precursor compounds for de...

Flavor instability of pale lager beer depends decisively on aroma-active aldehydes from the Maillard reaction, Strecker degradation, and lipid oxidation, which are formed in various oxidative and non-oxidative reactions. Therein, aldehydes can be formed de novo and be released from bound states to a free, aroma-active form during aging. During malt...

The dynamic changes in beer flavor are determined by its aging potential, which comprises of present free and bound-state aldehydes and their precursors. Rising flavor-active aging compounds cause sensory deterioration (flavor instability). These compounds are mainly formed upstream in the brewing process through the Maillard reaction, the Strecker...

High temperatures are maintained in a lauter tun to reduce the filtration time. The temperature affects the flow rate through the changing viscosity. In addition, the sedimentation behaviour of the particles also depends on the temperature. Changes in the settling velocity are assumed to affect the filter cake resistance and thus the flow rate. The...

Sedimentation combined with a broad particle size distribution in the suspension results in multilayered filter cakes, where a fine particle layer forms on top of a compressible bottom layer. Owing to their high resistance, the fine particles act as a stiff layer and compress the bottom layer during filtration. This was investigated using a model c...

The metabolite 3-deoxyglucosone (3-DG) is formed by carbohydrate caramelisation or the Maillard reaction. 3-DG is a precursor in the Strecker reaction forming beer ageing compounds, such as 2-methylbutanal or 3-methylbutanal. Although 3-DG is known as intermediate, recent studies have focused on 3-DG in beer. Foremost, the thermal load during wort...

Specialty malts comprise a promising field for innovative approaches concerning their potential in terms of color, aroma, and taste influence on the composition of beer and other beverages. Nevertheless, poor reproducibility of aroma and taste is a recurrent struggle between maltsters, leaving color as a practical parameter for quality control. How...

Efficient enzymatic hydrolysis of cereal starches requires a proper hydrothermal pre-treatment. For malted barley, however, the exact initial temperature is presently unknown. Therefore, samples were micro-mashed according to accurately determined gelatinization and pasting temperatures. The impact on starch morphology, mash viscometry and sugar yi...

Dealcoholisation of beer has gained prominence over the last decade. A well-known procedure involves the combination of a rectification column for thermal dealcoholisation and a downstream column for aroma recovery. However, the recovery of valuable fermentation by-products is rarely performed due to limited data about the enrichment and depletion...

Analytical and sensory profiles of non-alcoholic beers (NAB) vary on the process used for their production. The style and production procedure with blending and subsequent aroma enhancement lead to a wide range of product specific characteristics, which have so far only been evaluated using attributes and schemes developed for standard alcoholic be...

Sensory, olfactometry (using the sums of odour intensities for each class of compounds) and chemometric analyses were used to evaluate Portuguese wild hops’ sensory characteristics and the aroma that those hops impart to dry-hopped beer. CATA analysis and agglomerative hierarchical clustering was applied for the sensory characterization of 15 wild...

The enzymatic properties of brewing malts are an important and sometimes limiting factor in malt and beer production. In order to observe malt quality, multiple analytical tests were developed for determining the various enzymatic activities of brewing-related enzymes in brewing cereals and their corresponding malts. When using the prevailing detec...

The filter cake resistance determines the flow rate in cake filtration. The resistance depends not only on the mean size of the particles but also on their overall distribution. An example of where we have insufficient understanding of the effect of particle size is lautering—a separation process used in beer production. In this type of filtration,...

3-Deoxyglucosone (3-DG) is a Maillard reaction intermediate, which forms known beer aging compounds such as Strecker aldehydes. However, the role of 3-DG in beer aging stability has not been described yet. To investigate the influence of 3-DG toward beer aging stability, different concentrations of 3-DG were added to the freshly brewed beer at the...

During lautering, a filtration process in beer production, an inhomogeneous filter cake composed of different horizontal layers is formed. Fine particles settle slower than coarse particles and form a layer on top of the cake. Due to its low permeability, the fine layer acts as a stamp on the compressible bottom layer, thus resulting in cake compre...

Palate fullness and mouthfeel of beer are key attributes of sensory beer quality. Non-volatile substances and molar mass fractions influence sensory perceptions of palate fullness and mouthfeel. However, systematic correlations between sensory attributes and native beer compounds have not been evaluated within the concentration range found in lager...

The cytolytic malt criteria viscosity and β-glucan are used as an integral part of routine laboratory control measures to classify the malt modification level and to ensure good processability. Part one of this two-part publication demonstrated that barley varieties with high cytolytic modification along with low β-glucan content tend to have a hig...

The malt criteria of viscosity and β-glucan are used as an integral part of routine laboratory control measures to classify the cytolytic malt modification level and to ensure good processability. To optimize separation processes in general, the main focus of barley breeding has been on intensifying the cytolytic modification level and reducing the...

The sensory attribute palate fullness of cereal-based beverages was shown to be affected by polymeric compounds and their macromolecular profile. During malting, the enzymatic degradation of polymers is technologically controlled by the malting parameters, namely the degree of steeping, germination time, and germination temperature. The macromolecu...

Beer is prone to flavor changes during aging that influence consumer acceptance within shelf life. The shelf life of beer is defined as the period over which flavor changes remain acceptable. Assessment of flavor changes caused by volatiles is typically achieved with a combination of sensory evaluation and gas chromatography–mass spectrometry (GC–M...

Mandarina Bavaria is a “Special Flavor” hop variety, described as fruity, with pronounced mandarin and citrus, combined with traditional hoppy sensations. The relationship between fruity-citrus intensity and the volatile profile of dry-hopped beers was assessed in order to predict the sensory perception of those dry-hopped beers using the content o...

BACKGROUND Many studies have confirmed a wide variation in the phenolic content and antioxidant activity of beers. However, when commercial beers are studied, there is usually no information available on the brewing technology applied. In this study, technological parameters were varied systematically to influence the antioxidant content of beer wi...

The hop pelletizing is not only influenced by the hop variety and the associated α-acid contents, but also by many annual and regional variations. In this context, the particle size distribution of the hop products had a subordinate role due to its main application in the brewhouse with its principle focus on α-acid content. But due to a high use o...

The purpose of lautering in beer brewing is to separate the wort, which contains soluble malt components from the solids, the brewer’s spent grains. Lautering is a critical point in wort production and its primary objective is the efficient recovery of extract. Lautering is a special type of cake filtration; the particle sedimentation behavior of t...

3-Deoxyglucosone (3-DG) is a metabolite from sugar degradation obtained by the Maillard reaction. It is an important precursor compound in Strecker reactionism that directly leads to known beer aging indicators and can influence the final sensory beer quality. However, the conditions of 3-DG formation in the malting process have not yet been descri...

Fusarium spp. are ubiquitous field pathogens, which are known to affect quality characteristics of cereals. Infections with Fusarium pathogens in brewing cereals are problematic and augur for a poor malt quality. The negative effects of Fusarium infections are various. Besides causing agronomic losses, kernel discoloration, and the production of se...

The filterability of beer is influenced by filtration technology as well as beer composition. Because of this, it is difficult to predict the filterability of beer at a laboratory scale. Over the years, various approaches for the measurement of filterability have been proposed, which are neither informative nor practical for the assessment of cross...

Due to changing consumer habits, non-alcoholic beer is the fastest-growing market within the beverage industry. Different processing technologies for limiting the alcohol content of beer yield in completely different matrix compositions and sensory profiles. Especially the specific sensory attributes of palate fullness, mouthfeel, and the perceptio...

The most common way to predict the shelf life and sensory stability of lager beer is via forced ageing at elevated temperature (40 °C). However, practical results often indicate that forced ageing alters the flavour profile unlike natural ageing. To assess the prediction power of forced ageing using both sensorial and analytical approaches, a lager...

For the past 100 years, polyphenol research has played a central role in brewing science. The class of phenolic substances comprises simple compounds built of 1 phenolic group as well as monomeric and oligomeric flavonoid compounds. As potential anti‐ or prooxidants, flavor precursors, flavoring agents and as interaction partners with other beer co...

Despite years of research, sensory deterioration during beer aging remains a challenge to brewing chemists. Therefore, sensorial and analytical tools to investigate aging flavors are required. This review aims to summarize the available analytical methods and to highlight the problems associated with addressing the flavor-stability of beer. Carbony...

2-Methoxy-4-vinylphenol and 4-vinylphenol are important odorants in wheat beer, which are mainly enzymatically formed by decarboxylation during fermentation with the top fermenting yeast Saccharomyces cerevisiae from their respective precursors, the free phenolic acids ferulic acid and p-coumaric acid. However, also the undesired toxicologically re...

Modern varieties of malting barley allow mashing to proceed efficiently to enable saccharification and other biochemical processes. A prerequisite for starch hydrolysis is the disruption of starch granule structure by exceeding a grain specific pasting temperature. For grains, several viscometric methods based on the Rapid-Visco-Analyser were devel...

Cereal-based beverages contain a complex mixture of various polymeric macromolecules including polysaccharides, peptides, and polyphenols. The molar mass of polymers and their degradation products affect different technological and especially sensory parameters of beverages. Asymmetrical flow field-flow fractionation (AF4) coupled with multi-angle...

en The changes on the molecular weight distribution (MWD) and particle size distribution (PSD) during hydrolysis of barley malt in isothermal mashing procedures were determined using asymmetrical flow field flow fractionation coupled to multiangle laser light scattering and refractive index (AF4/MALS/RI). Mash/trials were focused on amylolytic star...

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