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Impact of “ecological” post-harvest processing on the volatile fraction of coffee beans: I. Green coffee
Abstract
Green coffees produced by three variants of the wet process and a new “ecological” process were characterised for their aroma using combined headspace solid-phase microextraction/gas chromatography–mass spectroscopy (HS-SPME/GC–MS) and headspace solid-phase microextraction/gas chromatography–olfactometry (HS-SPME/GC–O). The effect of each post-harvest processing operation on the volatile fraction of the coffee produced was studied, particularly the effect of reducing the amount of water used in the process. The comparison of the green coffees from the different treatments revealed the importance of mucilage removal in distinguishing between the samples, and showed the merits of microbial mucilage removal in water to obtain coffees with a better aroma quality. These latter coffees were in fact characterised by pleasant and fruity aromatic notes, whereas those obtained after mechanical mucilage removal used in the ecological process were characterised by volatile compounds with an unpleasant note.
... The characterization of the volatile fraction has helped to identify defects [6][7][8], the different roasting levels [9], the origins of [10,11] raw or roasted coffee, and the influence of altitude and the climatic conditions of farming [12,13] on raw and roasted coffee. Some studies have also evaluated the influence of the post-harvesting processes on the volatile compounds found in coffee [14,15]. ...
... As per Gonzalez-Rios et al. [14], the volatile fraction of green coffee beans is primarily given by the alcohols, acids, esters, and aldehydes which are mainly formed during the fermentation stage of the post-harvesting process. Acids and aldehydes may also be Interestingly, reducing the variability to only a post-harvesting process, the continent of origin was also discriminated considering only washed processed samples. ...
... Data were statistically treated via discriminant canonic analysis to detect whether the volatile profile allowed one to discriminate among different countries and continents of origin, roasting levels, and post-harvesting processes. As per Gonzalez-Rios et al. [14], the volatile fraction of green coffee beans is primarily given by the alcohols, acids, esters, and aldehydes which are mainly formed during the fermentation stage of the post-harvesting process. Acids and aldehydes may also be formed during drying. ...
The aroma of coffee is a complex mixture of more than 1000 compounds. The volatile compounds in green and roasted coffee were analyzed to detect several features related to quality, roasting level, origins, and the presence of specific defects. With respect to specialty coffee, the flavor profile and peculiarities of the aforementioned characteristics are even more relevant knowing the expectations of consumers to find, in a cup of coffee, unicity bestowed by its origin and post-harvesting processes. In this work, which dealt with 46 lots of specialty Arabica coffee, we used HS-SPME/GC–MS to detect the volatile compounds in green coffees together with those in the same coffees roasted at three different levels to identify whether differences in headspace composition were ascribable to the origin, the post-harvesting processes, and the roasting profiles. The main results are related to the discriminant power of the volatile compounds in green coffee, which are impacted by the origins more than the post-harvesting processes. Compounds such as linalool and 2,3-butanediol were more concentrated in natural coffees, while hexanal was more concentrated in washed varieties (p < 0.05). In roasted coffees, the differences in composition were due to roasting levels, countries of origin, and the post-harvesting processes, in descending order of significance.
... Regarding the wet process that is mostly occurred in regions such as Central America, Colombia and Hawaii using Arabica coffees, the skin and pulp of coffee cherries are removed first by pulping machines ( Fig. 4 a), leaving the two seeds surrounded by the sticky mucilage, which is removed by either submerged fermentations or de-mucilage machines ( Cleves, 2009 ;Gonzalez-Rios et al., 2007 ;Lee et al., 2015 ). In the wet fermentation process, water conveys the de-pulped beans into a tank filled with water, where the beans are subjected to submerged fermentation for 6-72 h depending on the surrounding climate conditions ( Agate & Bhat, 1966 ;Masoud & Jespersen, 2006 ). ...
... Other non-volatile components such as polysaccharides, chlorogenic acids and free amino acids concentration were also reported with significant differences between the processing methods ( Arruda et al., 2012 ). Furthermore, wet fermented coffee were reported with floral, caramel and fruity notes while dry processed beans were buttery and nutty ( Gonzalez-Rios et al., 2007 ;Mussatto et al., 2011 ). These sensory changes are believed to corelated to the several volatiles that might be biosynthesized by the microbial activities occurred during fermentation as discuss in more details next. ...
... beans ( Gonzalez-Rios et al., 2007 ). Recently, a few studies have investigated the metabolic activities of endogenous microorganisms identified during coffee fermentation and their ability to produce secondary metabolites that may migrate into the beans and impact coffee quality. ...
Traditionally, harvested coffee cherries are subjected to fermentation processes during primary methods either wet, natural dry or semidry. The main function of the fermentation is to remove the outside bean layers leaving two dried seeds. A wide range of endogenous isolates was detected with pectinolytic activities including bacteria such as Klebsiella, Erwinia, Bacillus and Lactobacillus and yeasts such as Pichia, Saccharomyces, and Candida. Fermentation was also impacting coffee's sensory quality. Studies have shown that desired microbial metabolites were produced during fermentation that is believed to migrate inside coffee seeds and correlated to modulation of the final product flavor, aroma, and sensory quality. Converting spontaneous fermentation into a controlled and standardized process using starter culture and bioreactors is currently employed. This review provides a detailed explanation of these topics and mainly explores the main roles of the microflora detected during spontaneous coffee fermentation and the possible ways to convert the traditional process into a more controlled and industrialized one compromising the needs of the current extending and sustainable economy.
... The changes caused by PHP influence the amount and quality of flavor and flavor precursors determining the aromatic profile of the beverage [8]. In general, CN coffee has a beverage with a strong aroma, moderate acidity, intense body and a natural sweetness. ...
... In these conditions of luminosity and weight loss, greater production of volatile compounds was observed [8], and these parameters are normally used to evaluate the quality of coffee beverage. The luminosity and component a* (red-green) are similar between the PHP, but CF and CP coffees showed higher intensity of component b* (yellow) than the CD and CN coffees. ...
... The heating of green coffee beans during roasting promotes the evaporation of water and volatile substances with changes in weight and color of the beans [7,8]. Usually, the value of weight loss range between 15% [3,8] to 16% [34] to achieve dark brown color and developing typical coffee flavor. ...
Post-harvest processing (PHP) modifies the quality of the coffee and increases the value of coffee production. The choice of PHP to apply depends primarily on the available infrastructure, local climatic conditions and the desired end-value. The objective of this study was to evaluate the influence of PHP on the physico-chemical characteristics of green and roasted coffee beans and their sensory attributes. Coffee cherries from IAPAR 59 cultivar were processed as natural coffee (CN), semi-dry coffee (CD), de-pulped coffee (CP) and floating coffee (CF). Total and reducing sugars, phenolic compounds, chlorogenic acids, lipids, proteins, caffeine and water content were determined in coffee beans collected during (10 th day) and at the end of each processing. The roasted beans and their sensory attributes were also analyzed. The greatest changes at the ending point of the processes were found in total and reducing sugars, phenolic compounds, chlorogenic acids and lipids contents. The PHP presented different weight loss to achieve the same visual brown color and luminosity. Beverage sensory attributes were influenced by the PHP: CN and CP coffees presented similar intensities of coffee aroma, but higher intensity of green grassy aroma, and taste were found in CF and CN coffees. Aroma and taste precursors were modified during the PHP and these were associated to husk removal of the coffee beans, suggesting an activation of the germination metabolism during the PHP. This study allowed the characterization of the effects of the different 701 AIMS Agriculture and Food Volume 5, Issue 4, 700-714. post-harvest processing on the roasted coffee beans and provides the foundations to monitor their efficiencies in the future.
... In doing so, the different factors that influence the complexity of the beverage, including, among other factors, variety, environmental conditions, altitude, latitude, processing type, and the degree of roasting, are considered. Moreover, sensory notes can be potentially linked to certain compounds present in both dry and roasted beans [11,[47][48][49]. Figure 9 is the fragrance and aroma wheel for Category IV, with the intensities for each note or sensory descriptor. The coffee varieties in this category predominantly had fruity notes, those of sweets and greens. ...
... In doing so, the different factors that influence the complexity of the beverage, including, among other factors, variety, environmental conditions, altitude, latitude, processing type, and the degree of roasting, are considered. Moreover, sensory notes can be potentially linked to certain compounds present in both dry and roasted beans [11,[47][48][49]. ...
This study proposed a classification model for 125 agricultural productive units (APUs) in Tolima, Colombia, to establish whether they are related to the quality of coffee produced. The model considered two aspects related to farmer profile and farm profile. The following proposed categories resulted from the coordinate obtained in relation to the two aspects: Low-Low, High-Low, Low-High, and High-High. The variables for each aspect were prioritized using the analysis hierarchical process (AHP). The coffee’s quality, sensory profile by attribute, and specific descriptors for each category were determined employing the Specialty Coffee Association (SCA) protocol. The sensory attributes were analyzed by way of one-way analysis of variance (ANOVA), and the Bonferroni test was used to compare by category, both with a significance level of α = 0.05. The model grouped the APUs by category and cup quality, with the High-High category achieving the best scores in the sensory analysis. The variables with the greatest relative weight within the AHP model constituted farmer stance regarding the use of good agricultural practices (44.5%) and farmer attitude toward excellence (40.6%) in the farmer’s profile. As part of the farm’s profile, environmental commitment level (38.0%) and international certifications (29.1%) were the greatest relative weights. Coffee in the High-High category was characterized by its notes of cinnamon, cocoa, chocolate, and dried vegetables.
... Although there has been some studies which examined the contribution of fermentation on coffee flavor and aroma, these studies were mostly conducted in coffee producing countries with a warm climate such as Brazil [9,[12][13][14][15]. In a previous study [16], we examined the microbial ecology of wet coffee fermentation under Australian conditions, and found that the microbial community had species unique to Australia, such as Pichia kudriavzevii and members of Nectriaceae, which have not been previously reported in other countries. ...
... Ethanol contributes to the viscosity and alcoholic flavor of the beverage and acts as a solvent for other volatile compounds, while isoamyl alcohol was reported to have a fruity flavor (i.e., banana and pear) [21]. Accumulation of ethanol and isoamyl alcohol during fermentation has been reported previously [12] and confirmed in our study. 3-Methyl-2buten-1-ol was detected in several fermented foods and mainly synthesized by both yeasts and LAB from amino acid metabolism [21]. ...
This study investigates the impact of wet fermentation on flavor volatiles and sensory quality of coffee beans and beverage. Pulped coffee beans were kept underwater for 36 h before air-drying and roasting, and volatiles in the beans were characterized by solid-phase microextraction and gas chromatography–mass spectrometry. A total of 79 volatiles were identified. Fermented roasted beans had higher concentrations of ethanol, isoamyl alcohol, 3-methylbutanal, benzaldehyde, acetaldehyde, and ethyl acetate compared with mechanically processed (no fermentation) beans; whereas, ketones, pyrazines, pyrroles, pyridines, furans and sulfides were not significantly different between the two treatments. Coffee made with fermented beans was rated significantly higher in flavor, aroma, acidity, body and uniformity scores with noted fruity aroma compared with beverage made with mechanically processed beans in sensory evaluation (cup test) by a 3 Q-Grade Coffee Certification Panel. The findings demonstrated wet fermentation played an important role in coffee flavor, aroma and sensory quality.
... It is well considered that bigger beans give more aroma though there is a conflicting opinion on this aspect. (Gonzalez-Rios et al. 2007;Kathurima et al. 2009). Nevertheless, DaMatta et al. (2018 reported that the smaller beans of the same variety designated as lower grades realise low prices. ...
In coffee, both physical quality attributes as assessed by the colour and size of the beans and cup quality of the beverage rated based on sensory analysis are the important criteria for determining market price. In general, quality is dependent on genotype and also influenced by the growing conditions. The bean and beverage quality of pure C. arabica varieties is far superior to diploid introgressed arabica genotypes developed for improved host resistance. Thus, integrating the host resistance without affecting quality parameters is very imperative in arabica coffee breeding. Four F1 hybrids (S.5083, S.5084, S.5085 & S.5086) developed from reciprocal crosses between the most popular semi-dwarf arabica variety ‘Chandragiri’ and Sln.10, an auto-tetraploid of a diploid inter-specific hybrid, used as a donor for rust resistance, were evaluated for physical quality traits for four seasons and cup profiles for two seasons. Among the four hybrids, S.5085 and S.5086 recorded bold bean size with 70.05 per cent and 69.75 per cent of mean ‘A’ grade beans, respectively. The ‘B’ grade ranged from 9.5 per cent to 10.4 per cent in hybrids as against 16.8 per cent in Chandragiri. The Pea berry ranged from 10.1 per cent to 12.5 per cent, indicating high fertility in hybrids. The cup qualities of S.5085 and S.5086 were also found superior with a cumulative average score of 80.3 and 78.3 respectively, compared to parents; 71.6 in Chandragiri and 77.3 in Sln.10. The present study established the superiority of S.5085 and S.5086 in quality parameters and therefore has potential implications in the commercial exploitation of these two F1 hybrids that also manifested high levels of field tolerance to coffee leaf rust.
... In this process, skin, pulp, and mucilage are removed using water and fermentation (Poltronieri and Rossi, 2016). This method involves more stages than the dry process, it also has the largest number of variants (Gonzalez-Rios, 2007). However, wet processing exhibits some drawbacks, such as high amount of water usage, which generating excessive contents of organic pollutants, timedemanding, and uncontrolled fermentation on farms resulting in the lack of coffee quality predictability (Ghosh and Venkatachalapathy, 2014). ...
Choosing a suitable method of green coffee beans processing is one of the first steps that can significantly affect the final product. Thus, the objective of this study was to evaluate how the processing method affects the selected observed parameters (dry matter, water activity, pH, hardness, color). The postharvest processing of coffee cherries involves natural dry, semi-washed, or wet processing. On-farm postharvest coffee processing is essential for ensuring high quality of coffee cup and constitutes a chain of interlinked phases mainly aimed at removing the cherries' mucilage and drying the beans to a low moisture content of 10 to 12% (mass/mass). The coffee samples were of American origin Coffea arabica. A total of 12 samples from multiple regions were used. Samples of Coffea arabica were collected into three groups natural (dry), pulped natural (semi-washed), and wet processing (fully washed). The processing results, to some extent, influence the values of the monitored parameters. The highest dry matter value was indicated in dry processing, and the highest value of water activity was in wet processing. The average value of pH was 5.74. Natural processing showed the most significant differences between individual groups concerning color processing. On the other hand, wet and dry processing showed very similar colors. Values of hardness were in range 86549.05 - 100674.90 g. The final quality of the green coffee beans is thus dependent on the different agricultural, and farm practices applied, which depend on the coffee plant cultivar, geography, weather conditions, and available infrastructure.
... Volatile compounds are either naturally present in green beans or develop during post-harvest operations (Gonzalez-Rios et al., 2007). Processing is one of the main operations for the production of volatiles. ...
The aim of this study was to determine the effect of various methods of processing, such as natural, washed, honey, anaerobic fermentation, and carbonic maceration, on the antioxidant activity and bioactive and volatile compounds in green and roasted specialty coffees from various countries of origin (Nicaragua, Ethiopia, Peru, Burundi). Chlorogenic acids were different between green coffees (P = 0.04). Roasting increased the total polyphenol and total flavonoid (TF) contents. TF content in roasted Peruvian (PER) beans was significantly higher (4.20 μg quercetin (QE)/mg) for natural processing than carbonic maceration (CM; 2.22 μg QE/mg), and antioxidant capacity was significantly higher for CM (85.7 μg Trolox (TE)/mg) than natural processing (59.5 μg TE/mg). Burundian coffees had the highest antioxidant capacity, with the highest values for naturally processed beans (128.8 μg TE/mg) compared to beans processed by anaerobic fermentation (105.4 μg TE/mg). 2-Furanmethanol, a volatile compound, was a major compound in all roasted coffees, with a mean relative abundance of 21.52–32.53%. The type of processing affected the content of bioactive and volatile compounds in specialty coffees. However, anaerobic fermentation maintained a high level of bioactive compounds and contributed to the antioxidant activity of the roasted coffee, depending on the country of origin.
... In the wet processing of coffee, the unripe berries are submerged in a tank of water, low quality coffee fruits rise to the water surface and are removed with screens (Batista et al., 2009). A fermentation step is also included in the wet process, this facilitates the removal of any residual mucilage from the bean and imparts a high-quality aroma to the coffee (Gonzalez-Rios et al., 2007). After the fermentation, the beans are roasted at a high temperature to give them their aroma, texture, and colour (Fujioka and Shibamoto, 2008). ...
Enzymes are biological catalysts capable of speeding up biochemical reactions, providing a novel and eco-friendly alternative to chemical catalysts. Enzymes are widely employed in industrial food processing particularly the beverage industry. The main enzymes used in the beverages industries are hydrolytic and they are categorised into carbohydrases, proteases, and lipases. Due to increased awareness regarding sustainability and the extensive range of advantages enzymes provides to the beverage industry, such as alcoholic fermentation and enhanced organoleptic properties, more focus is directed toward immobilized and microbial-derived enzymes. These enzymes not only make processing more efficient but also reduce costs and waste generation. In this chapter, an introduction to the main processes involved in the beverage industry and the rationale for utilising enzymes in the industry are provided. In addition, the current enzymes used in both alcoholic and non-alcoholic beverages, the sustainability of enzymes, and recommended future work will be discussed.
... Additionally, we had three different origins in this study, and origin was the next most substantial driver of difference, which likewise is unsurprising given that different regions have different terrain, soil microbiology, and weather patterns which will all contribute to flavor [31][32][33][34]. Furthermore, the different origins also underwent different postharvest processing methods (washed, honey, and wet-hulled), which have been well documented to contribute to the flavor profile in coffee [9,[35][36][37][38][39][40]. Ultimately, our results confirmed existing and known differences between roasts and origins. ...
Cold brew coffee is often described as sweeter or less acidic than hot brew coffee. Such comparisons, however, are potentially confounded by two key effects: different brew temperatures necessarily change the extraction dynamics and potentially alter the resulting brew strength, and different consumption temperatures are well known to affect perceived flavor and taste. Here, we performed a systematic study of how extraction temperature affects the sensory qualities of full immersion coffee. The investigation used a 3 × 3 × 3 factorial design, with coffee from three different origins representing different post-harvest methods (washed, honey-processed, and wet-hulled), each roasted to three different levels (light, medium, and dark), and each brewed at three different temperatures (4 °C, 22 °C, and 92 °C). All coffees were brewed to equilibrium, then diluted to precisely 2% total dissolved solids (TDS) and served at the same cold temperature (4 °C). We find that four attributes exhibited statistically significant variations with brew temperature for all origins and roast levels tested, with bitter taste, sour taste, and rubber flavor all higher in hot brewed coffees, and floral flavor higher in cold brewed coffee. However, there were strong interactions with origin and roast, with several additional attributes significantly impacted by temperature for specific origins and roast levels. These results provide insight on how brew temperature can be used to modulate the flavor profile of full immersion coffee.
... Em estudos anteriores, avaliando o potencial de algumas espécies de levedura para melhoria da qualidade sensorial através da fermentação, encontrou a produção de níveis significativos de acetoína e furfural em meios fermentados por C. parapsilosis, os quais são caracterizados como contribuidores da percepção sensorial cremoso (Lee et al., 2017) e amêndoa/doce (Yang et al., 2016), respectivamente. Por outro lado, em meios fermentados por P. guilliermondii apresentou maiores concentrações de 2-feniletanol, contribuidor de notas florais (Gonzalez-Rios et al., 2007) . Na mesma linha, a S. Cerevisiae apresentou concentrações significativas de acetaldeído, comumente relacionada à percepção sensorial frutada (Ott et al., 2000). ...
... Meanwhile, unfermented coffee has lower volatile compounds and emits an unpleasant sulfur odor [93]. Microbes release metabolites throughout the fermentation process, which disperse into the beans. ...
Coffee is consumed not just for its flavor, but also for its health advantages. The quality of coffee beverages is affected by a number of elements and a series of processes, including: the environment, cultivation, post-harvest, fermentation, storage, roasting, and brewing to produce a cup of coffee. The chemical components of coffee beans alter throughout this procedure. The purpose of this article is to present information about changes in chemical components and bioactive compounds in coffee during preharvest and postharvest. The selection of the appropriate cherry maturity level is the first step in the coffee manufacturing process. The coffee cherry has specific flavor-precursor components and other chemical components that become raw materials in the fermentation process. During the fermentation process, there are not many changes in the phenolic or other bioactive components of coffee. Metabolites fermented by microbes diffuse into the seeds, which improves their quality. A germination process occurs during wet processing, which increases the quantity of amino acids, while the dry process induces an increase in non-protein amino acid γ-aminobutyric acid (GABA). In the roasting process, there is a change in the aroma precursors from the phenolic compounds, especially chlorogenic acid, amino acids, and sugars found in coffee beans, to produce a distinctive coffee taste.
... • Fermantasyondan sonra, temiz çekirdekler yaklaşık %12 neme gelene kadar kurutulmakta ve daha sonra parşömen çıkarılmak üzere kabukları alınmaktadır. Elde edilen katı atık (parşömen ve kahve çekirdeği zarı) toplu olarak parşömen kabukları olarak adlandırılmaktadır [49,50,47] ...
... Muchos de los residuos agroindustriales son candidatos para la digestión anaerobia por su alto contenido de materia fácilmente biodegradable. Un inconveniente que limita el tratamiento vía anaerobia de los residuales sólidos del beneficio del café es su contenido de sustancias tóxicas y su naturaleza lignocelulósica, la cual dificulta la biodisponibilidad del carbono (González-Ríos et al. 2007, Rossmann et al. 2012. ...
En la etapa de despulpe del beneficio húmedo de café se generan residuales sólidos constituidos fundamentalmente por cáscara y pulpa. Debido a que el contenido de materia orgánica que presentan en su composición se encuentra en el intervalo del 90.5 ± 1.69 % en base seca, estos aportan una elevada carga contaminante al medio en que son vertidos. Esta característica también otorga a dichos residuales potencialidades como fuente de carbono para el proceso de digestión anaerobia. En el presente trabajo se determinó el potencial de biometano y el efecto del incremento de la carga orgánica volumétrica al tratar pulpa de café fresca (Pc I) tras un periodo de almacenamiento congelada (Pc II) y cáscara de café secada naturalmente (Cs). Los ensayos se desarrollaron a temperatura mesofílica (37 ± 1 ºC), en régimen discontinuo y semicontinuo. La pulpa de café fresca presentó un rendimiento de metano de 259.80 ± 15 NmL CH4/g SV. Los ensayos semicontinuos se evaluaron en términos de rendimiento y productividad de metano. Al implementar diferentes estrategias de alimentación, variando las cargas orgánicas volumétricas iniciales en los sistemas, se constató que los mejores resultados se reflejan con la menor carga aplicada (0.2 g SV/L d). No se recomienda la operación de sistemas anaerobios para el tratamiento de residuos sólidos cafetaleros a cargas superiores a 0.5 g SV/L d.
... Traditionally, the coffee is roasted, ground and prepared in hot water. The concentrations of phenolic (Mills, Oruna-Concha, Mottram, Gibson, & Spencer, 2013) and aromatic (Gonzalez-Rios et al., 2007a;2007b) compounds depend on the degree of coffee roasting. The presence of beneficial compounds in the coffee can be affected as from harvesting of the coffee cherries to the preparation of the beverage for consumption (Nunes & Coimbra, 2007;Wei et al., 2012;Lee, Cheong, Curran, Yu, & Liu, 2016). ...
During the coffee beans roasting process, occurs the formation of polycyclic aromatic hydrocarbons, which are associated with the incidence of cancer in humans. This study aimed to evaluate the influence of coffee bean quality and roasting degree regarding mutagenicity, cytotoxicity and genotoxicity. Six samples of coffee drink made with roasted and ground Coffea arabica beans from different qualities and roast degrees were used after freeze-drying. Both commercial and special quality grains suffered light, medium and dark roasting. According to the Salmonella/microsome assay, the highest concentration of commercial grain sample (dark roast) significantly increased the number of revertants of the TA98 strain in the absence of metabolization. All the samples induced cytotoxicity to HepG2 cells. These effects can be ranked in the following order from most to least toxic: medium roast – special grain > light roast – special grain > dark roast - commercial grain > dark roast – special grain > light roast – commercial grain > medium roast – commercial grain. None of the samples induced genotoxicity in HepG2 cells. Our findings show that the harmful effects of coffee depend not only on the degree of roasting but also on the grain quality.
... This method has the advantage of being technologically simpler than the wet method, reducing water consumption, and consequently the wastewaters generation during the process. Nevertheless, scientific reports emphasize that the reduction of water in the process reduces the aromatic quality of the coffee grain (Gonzalez-Rios et al. 2007), affecting the final coffee product (Chanakya and De Alwis 2004). The wet method consists in a mechanical separation of the pulp and skin of the fresh cherry coffee, assisted by water as a transport media. ...
The global demand of coffee beverages stimulates high levels of production in coffee-growing countries. Contradictorily, this does not contribute to eradicate the imbalances in social benefits, economic growth, and environmental impact that are identified when analyzing the different stages of this agroindustry. This phenomenon is palpable in the primary processing or benefit of the coffee fruit, in which the green coffee bean is obtained. The benefit (wet, dry, or semi-dry) is developed in agricultural areas mainly of developing countries, where the financial resources available for the implementation of cleaner production strategies and effective waste treatment are limited. As a consequence, both liquid and solid wastes become a source of severe pollution of surrounding ecosystems and deterioration of farmers’ living conditions. This chapter addresses the alternatives to transform coffee wastes into value products through bioprocesses, with a focus on circular economy and its contribution to the sustainability concept in developing countries. It was confirmed that the particularities of the scenarios in which coffee production and trade are developed make it complex to generalize alternatives of waste treatment or use. Furthermore, a production model that meets the multiple factors involved is also very complex but not difficult to be achieved. Sustainability initiatives and the role of biotechnology, with emphasis in anaerobic digestion, for the coffee production are analyzed. A holistic approach to solve the problems that persist in the process and the coffee value chain is exposed. It was concluded that it is necessary to incorporate into the concept of products of excellence and high quality standards in the coffee agroindustry the requirement of production conditions in which the waste streams are reused or returned to nature with non-aggressive characteristics for the environment. Biophysical indicators play an important role in making it possible.
... The quality of the coffee is not only influenced by several parameters during the production such as the plant genotype, environmental conditions, cultivation techniques and the associated microbiota (Toledo et al., 2016;Martins et al., 2020), but also by the type of postharvest processing (Gonzalez-Rios et al., 2007b;Lee et al., 2015;Poltronieri and Rossi, 2016), the storage conditions (Bucheli et al., 1998;Urbano et al., 2001;Geremew et al., 2016), and the roasting and brewing methods (Gonzalez-Rios et al., 2007a;Frost et al., 2020;Hu et al., 2020). ...
Intensive coffee production is accompanied by several environmental issues, including soil degradation, biodiversity loss, and pollution due to the wide use of agrochemical inputs and waste generated by processing. In addition, climate change is expected to decrease the suitability of cultivated areas while potentially increasing the distribution and impact of pests and diseases. In this context, the coffee microbiota has been increasingly studied over the past decades in order to improve the sustainability of the coffee production. Therefore, coffee associated microorganisms have been isolated and characterized in order to highlight their useful characteristics and study their potential use as sustainable alternatives to agrochemical inputs. Indeed, several microorganisms (including bacteria and fungi) are able to display plant growth promoting capacities and/or biocontrol abilities toward coffee pests and diseases. Despite numerous studies emphasized the potential of coffee associated microorganisms under controlled environments, the present review highlights the lack of confirmation of such beneficial effects under field conditions. Nowadays, next-generation sequencing technologies allow to study coffee associated microorganisms with a metabarcoding/metagenomic approach. This strategy, which does not require cultivating microorganisms, now provides a deeper insight in the coffee associated microorganism’s community and its implication not only in the coffee plant fitness but also in the quality of the final product.
The present review aims at (i) providing an extensive description of coffee microbiota diversity both at the farming and processing levels, (ii) identifying the “coffee core microbiota”, (iii) making an overview of microbiota ability to promote coffee plant growth and to control its pest and diseases and (iv) highlighting the microbiota potential to improve coffee quality and wastes management sustainably.
... Fats (8-18%), proteins and amino acids (9-12% w/w), Minerals (3-5% w/w) have been reported. [2][3][4][5] Phenolic compounds found in green coffee beans are mainly the Chlorogenic acids (up to 12% solids). They are the esters of trans-cinnamic acids and quinic acids. ...
An overview of green coffee, the unroasted bean enriched with antioxidants, is presented in the following article. Green coffee beans are known to have a higher content of chlorogenic acid (CGA) with potential health benefits like activity against hypertension, diabetes, obesity, etc. There are three major classes of chlorogenic acids present in green coffee beans, namely: caffeoylquinic acid (CQA), di-caffeoylquinic acid (diCQA) and feruloylquinic acid (FQA). Another pivotal component of the green beans is caffeic acid. A compilation of the different research studies and reviews pertaining to the diverse biomolecules present in the green coffee, their structure and the different sources of CGA is presented. The traditional and modern methods of the extraction of CGA are also studied. Green coffee upon roasting develops its aromatic characteristics but the flavor development comes with a reciprocation of reduced chlorogenic acid content. Thus, the effect of processing is also addressed. There are numerous studies conducted to show the health benefits associated with the consumption of green coffee out of which, anti-diabetic and anti-obesity effects are particularly concentrated in this article.
Keywords: Chlorogenic acid, diabetes, green coffee, obesity, roasting
... The other odor-active compounds, with FD factors 64-16, have already been described in roasted beans and coffee beverages, except for γ-nonalactone. This lactone has never been detected in those matrices but some studies reported its presence in green beans [28,29]. Volatiles identified in CS with low FD factors (8-1) were 3-methyl-2-buten-1-thiol, 2,3,5-trimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, 2-acetylpyrazine, 2-acetyl-2-thiazoline, 2-hydroxy-3-methyl-2-cyclopenten-1-one, 2-phenyl-2-butenal, indole, 2-/3-methylbutanal, butanoic acid, 2-phenylethanol, 2,3-pentanedione, and 3,7-dimethylocta-1,6-dien-3-ol (linalool). ...
For the first time the volatile fraction of coffee silverskin has been studied focusing on odor-active compounds detected by gas chromatography-olfactometry/flame ionization detector (GC-O/FID) system. Two approaches, namely headspace (HS) analysis by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and odor-active compounds analysis by gas chromatography-olfactometry/flame ionization detector (GC-O/FID), have been employed to fully characterize the aroma profile of this by-product. This work also provided an entire characterization of the bioactive compounds present in coffee silverskin, including alkaloids, chlorogenic acids, phenolic acids, flavonoids, and secoiridoids, by using different extraction procedures and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) system. Coffee silverskin was shown to be a good source of caffeine and chlorogenic acids but also of phenolic acids and flavonoids. In addition, the fatty acid composition of the coffee silverskin was established by GC-FID system. The results from this research could contribute to the development of innovative applications and reuses of coffee silverskin, an interesting resource with a high potential to be tapped by the food and nutraceutical sector, and possibly also in the cosmetics and perfumery.
... The volatile compounds of coffee treated with various processing methods were identified using static headspace gas chromatography-mass spectrometry (SHS-GC/MS). The volatile compounds in coffee are either naturally present in the green beans or develop during the post-harvest operations (mucilage removal process, drying, and storage) [50]. Green coffee beans are characterized by an unpleasant taste. ...
There are different types of coffee processing methods. The wet (WP) and dry processing (DP) methods are widely practiced in different parts of coffee-growing countries. There is also a digestive bioprocessing method in which the most expensive coffee is produced. The elephant dung coffee is produced using the digestive bioprocessing method. In the present experiment, the antioxidant activity and volatile compounds of coffee that have been processed using different methods were compared. The antioxidant activity, total phenolic content (TPC), total flavonoid content (TFC), and total tannin content (TTC) of green coffee beans from all treatments were higher as compared to roasted coffee beans. Regarding the green coffee beans, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of elephant dung coffee beans was higher as compared to that of the DP and WP coffee beans. The green coffee beans had higher DPPH activity and ferric reducing antioxidant power (FRAP) value compared to the roasted coffee beans. The green beans of elephant dung coffee had a high TPC than the beans obtained by WP and DP methods. TFC in elephant dung coffee in both green and roasted condition was improved in contrast to the beans processed using dry and wet methods. The elephant dung coffee had an increased TTC in comparison to the DP and WP coffee (green beans). About 37 volatile compounds of acids, alcohols, aldehydes, amide, esters, ethers, furans, furanones, ketones, phenols, pyrazines, pyridines, Heterocyclic N, and pyrroles functional classes have been found. Some of the most abundant volatile compounds detected in all treatments of coffee were 2-furanmethanol, acetic acid, 2-methylpyrazine, 2,6-dimethylpyrazine, pyridine, and 5-methylfurfural. Few volatile compounds have been detected only in elephant dung coffee. The principal component analysis (PCAs) was performed using the percentage of relative peak areas of the volatile compound classes and individual volatile compounds. This study will provide a better understanding of the impacts of processing methods on the antioxidants and volatile compounds of coffee.
... Only beans of larger size are marketable for ''Specialty Coffee''. A bigger bean contains a priori more aroma even if it is a controversial fact (Gonzalez-Rios et al. 2007;Kathurima et al. 2009). Nevertheless, smaller beans of the same variety are attributed to them lower grades and lower prices (DaMatta et al. 2012). ...
Conventional American cultivars of coffee are no longer adapted to global warming. Finding highly productive and stable cultivars in different environments without neglecting quality characteristics has become a priority for breeders. In this study, new Arabica F1 hybrids clones were compared to conventional American varieties in seven contrasting environments, for yield, rust incidence and volume of the canopy. The quality was assessed through size, weight of 100 beans, biochemical analysis (24 aroma precursors and 31 volatiles compounds) and sensory analysis. Conventional varieties were the least productive , producing 50% less than the best hybrid. The AMMI model analysis pointed out five hybrids as the most stable and productive. Two F1 hybrids clones, H1-Centroamericano and H16-Mundo Maya, were superior to the most planted American cultivar in Latin and Central America showing a high yield performance and stability performance. H1-Centroamerica and Starmaya contain more D-limonene than Caturra, while Starmaya contain more 3-methylbutanoic acid than the control. Those two latter volatiles compounds are linked with good cup quality in previous studies. In terms of sensory analysis, Starmaya and H1-Cen-troamericano scored better than control. Electronic supplementary material The online version of this article (https://doi.
... Only beans of larger size are marketable for ''Specialty Coffee''. A bigger bean contains a priori more aroma even if it is a controversial fact (Gonzalez-Rios et al. 2007;Kathurima et al. 2009). Nevertheless, smaller beans of the same variety are attributed to them lower grades and lower prices (DaMatta et al. 2012). ...
Conventional American cultivars of coffee are no longer adapted to global warming. Finding highly productive and stable cultivars in different environments without neglecting quality characteristics has become a priority for breeders. In this study, new Arabica F1 hybrids clones were compared to conventional American varieties in seven contrasting environments, for yield, rust incidence and volume of the canopy. The quality was assessed through size, weight of 100 beans, biochemical analysis (24 aroma precursors and 31 volatiles compounds) and sensory analysis. Conventional varieties were the least productive, producing 50% less than the best hybrid. The AMMI model analysis pointed out five hybrids as the most stable and productive. Two F1 hybrids clones, H1-Centroamericano and H16-Mundo Maya, were superior to the most planted American cultivar in Latin and Central America showing a high yield performance and stability performance. H1-Centroamerica and Starmaya contain more d-limonene than Caturra, while Starmaya contain more 3-methylbutanoic acid than the control. Those two latter volatiles compounds are linked with good cup quality in previous studies. In terms of sensory analysis, Starmaya and H1-Centroamericano scored better than control.
... Coffee flavor is enormously complex and ascends from 700 chemicals compounds currently identified, biological and physical characteristics intensely depending on cultivar, coffee cherry maturity, geographical growing location, production, processing, roasting and cup preparation [4] [5]. Not shockingly there is a large volume of published research defining the volatile and non-volatile compounds in coffee and that are likely to be playing a role in coffee flavor [6]. Roasting temperature, time, method of roasting and cooling all affect the volatile composition [7]- [9]. ...
The coffee aroma is one of the most important quality evaluation criteria employed for coffee commercialization and consumption.
The purpose of this study was following the roasting process VOCs creations with the novel Electronic Nose equipped whit 2 of 6 MOX nanowire sensors.
The nanowires exhibit exceptional crystalline quality and a very high length-to-width ratio, resulting in enhanced sensing capability as well as long-term material stability for prolonged operation.
Four different methods of roasting, made by ROSTAMATIC (Table 1) machine, were applied to gain a clearer picture of the differences in roasted coffee aromas by means of a volatile compound analysis. Different methods applied on four different origins of green coffee (India, Indonesia, Honduras, Santos and Nicaragua).
The commercial coffees products are made from a blending from minimum five different kinds of coffee and the consumers have developed an addiction/expectation to a specific flavor and taste. Different methods of roasting process will provide the coffee different aroma that will add flexibility to those one that already posses the matrix due to different origins.
This work tests and illustrates the broad spectrum of potential uses of the EN technique in food quality control.
... The type of coffee processing methods (wet and dry) that are performed to obtain the green beans determined the flavour properties and created a typical quality difference [3,19]. Several reports also stated the final cup quality and chemical composition are also defined by the adopted method in wet processing [20][21][22]. The effect of different modified wet-processing methods on the final quality of coffee is evaluated and compared by Gonzalez-Rios et al. [21]. ...
Coffee is one of the most important agricultural commodities in the world. The coffee quality is associated with pre-harvest and post-harvest management activities. Each step starting from selecting the best coffee variety for plantation until the final coffee drink preparation determines the cupping quality. The overall coffee quality influenced by the factors which involve in changes the physicochemical properties and sensorial attributes, including the post-harvest operations. The post-harvest processing activities contribute about 60% of the quality of green coffee beans. The post-harvest operations include pulping, processing, drying, hulling, cleaning, sorting, grading, storage, roasting, grinding, and cupping. This chapter comprises the harvest and post-harvest operations of coffee and their impacts on coffee quality.
... The application of soaking facilitated the removal of the fermentation effects, as reflected in a significant loss of both volatile and non-volatile compounds. Furthermore, these processing parameters also affected the volatile profiles of the green coffee beans and could be linked to the cup quality (Gonzalez-Rios et al., 2007). The volatiles related to floral and fruity notes of the green coffee beans seemed to be enhanced by a long fermentation duration. ...
Post-harvest wet coffee processing is a commonly applied method to transform coffee cherries into green coffee beans through depulping or demucilaging, fermentation, washing, soaking, drying, and dehulling. Multiple processing parameters can be modified and thus influence the coffee quality (green coffee beans and cup quality). The present study aimed to explore the impacts of these parameters, including processing type (depulping or demucilaging), fermentation duration, and application of soaking, on the microbial community dynamics, metabolite compositions of processing waters (fermentation and soaking) and coffee beans, and resulting cup quality through a multiphasic approach. A large-scale wet coffee processing experiment was conducted with Coffea arabica var. Catimor in Yunnan (China) in duplicate. The fermentation steps presented a dynamic interaction between constant nutrient release (mainly from the cherry mucilage) into the surrounding water and active microbial activities led by lactic acid bacteria, especially Leuconostoc and Lactococcus. The microbial communities were affected by both the processing type and fermentation duration. At the same time, the endogenous coffee bean metabolism remained active at different stages along the processing, as could be seen through changes in the concentrations of carbohydrates, organic acids, and free amino acids. Among all the processing variants tested, the fermentation duration had the greatest impact on the green coffee bean compositions and the cup quality. A long fermentation duration resulted in a fruitier and more acidic cup. As an ecological alternative for the depulped processing, the demucilaged processing produced a beverage quality comparable to the depulped one. The application of soaking, however, tempered the positive fermentation effects and standardized the green coffee bean quality, regardless of the preceding processing practices applied. Lastly, the impact strength of each processing parameter would also depend on the coffee variety used and the local geographical conditions. All these findings provide a considerable margin of opportunities for future coffee research.
... In the wet processing, pulp remnants and mucilage need to be degraded through controlled fermentation conditions, while in the mechanical processing, the separation is achieved using finer pulping equipment, avoiding the fermentation step. After fermentation, the beans are still covered by parchment, which can be removed after drying and hulling steps, while the silverskin can be removed by a polishing machine (Belitz et al., 2009;Gonzalez-Rios et al., 2007;Joët et al., 2010). In general, wet-and semi-dry-processed coffees are considered to have a superior aroma and higher acceptance (Knopp, Bytof, & Selmar, 2005). ...
... Of these, the sulfur-containing compounds, furans, and pyrazines are most abundant and have a major influence on the coffee aroma (Cecilia et al., 2012). Gonzalez-Rios et al. (2007) reported that ketones, pyrazines, pyridine, and pyrrole make up of the main chemicals in Arabica coffee. Rocha et al. (2004) determined that espresso coffee majorly contains furans, followed by pyrazines, aldehydes, and pyridines. ...
Coffee can be blended to create a variety of products to meet consumer's needs. In order to uncover the blending effect of coffee beans, we performed an experiment using principal component analysis (PCA). Twelve varieties of green beans were tested in 11 experimental groups, and the volatile compounds of the beans were analyzed. A total of 41 volatile compounds were identified. PCA was performed on 13 compounds that had a low odor threshold value or a high concentration among the identified compounds. PCA of total volatile compounds showed that principal component (PC) 1 and PC2 were extracted within 80% cumulative dispersion level. In PC1 and PC2, furfuryl alcohol and formic acid ethyl ester showed the greatest positive correlation coefficients among all the volatile compounds. The largest negative correlation coefficients in PC1 and PC2 were 4-hydroxy-2-butanone and 3-(ethylthio)propanal, respectively. Using PCA of the major volatile compounds in coffee, propanal and 1-methylpyrrole were found to have the largest positive correlation coefficients in PC1 and PC2, respectively. In the score plot of the major volatile components, 4 kinds of blended coffee were closely grouped, therefore showing similar aroma qualities. However, 5 kinds of other blended coffees showed a positive correlation with PC2. This is probably due to 3-(ethylthio)propanal acting as a specific value. The application of statistical methods to blended coffee allows for logical and systematic data analysis of data and may be used as a basis for quality evaluation.
... Over 900 volatile compounds have already been identified in green and roasted coffee beans [27,44]. Among the major volatiles found, pyrazines, furans, ketones, aldehydes, higher alcohols, esters, and sulphur compounds can be highlighted [45][46][47]. Although some of these flavor-active compounds originate from the beans itself, recent studies have revealed that microbial-derived metabolites can also diffuse into the beans [11,14,27,33,[48][49][50]. Upon characterization of the volatile composition of fermented coffee beans, it was observed that inoculation of P. fermentans and P. acidilactici, both in pure and combined treatments, resulted in the modulation of the volatile constitution of coffee beans. ...
Removal of the mucilage layer of coffee fruits by a fermentation process has became an interesting strategy to improve coffee quality, which is able to assist the formation of flavored molecules. In this study, four sets of inoculation protocols were evaluated using ripe and immature coffee fruits, respectively, including (i) pure culture fermentation with Pichia fermentans, (ii) pure culture fermentation with Pediococcus acidilactici, (ii) combined fermentation with P. fermentans and P. acidilactici, and (iv) spontaneous, non-inoculated control. The initial pulp sugar concentration of ripe coffee fruits (0.57 and 1.13 g/L glucose and fructose content, respectively) was significantly higher than immature coffee pulp (0.13 and 0.26 g/L glucose and fructose content, respectively). Combined inoculation with P. fermentans and P. acidilactici of ripe coffee beans increased pulp sugar consumption and production of metabolites (lactic acid, ethanol, and ethyl acetate), evidencing a positive synergic interaction between these two microbial groups. On the other hand, when immature coffee fruits were used, only pure culture inoculation with P. fermentans was able to improve metabolite formation during fermentation, while combined treatment showed no significant effect. Altogether, 30 volatile compounds were identified and semi-quantified with HS-solid phase microextraction (SPME)-gas chromatography coupled to mass spectrophotometry (GC/MS) in fermented coffee beans. In comparison with pure cultures and spontaneous process, combined treatment prominently enhanced the aroma complexity of ripe coffee beans, with a sharp increase in benzeneacetaldehyde, 2-heptanol, and benzylalcohol. Consistent with the monitoring of the fermentation process, only P. fermentans treatment was able to impact the volatile composition of immature coffee beans. The major impacted compounds were 2-hexanol, nonanal, and D-limonene. In summary, this study demonstrated the great potential of the combined use of yeast and lactic acid bacteria to improve fermentation efficiency and to positively influence the chemical composition of coffee beans. Further studies are still required to investigate the mechanisms of synergism between these two microbial groups during the fermentation process and influence the sensory properties of coffee products.
... Mucilage scratching has the advantage of using little water and therefore causes less pollution compared to fermentation, but the disadvantages are physical damage to the beans, incomplete removal of mucilage, and high power requirements (Wintgens, 2009). Mucilage fermentation removes certain soluble bitter components such as polyphenols and diterpenes from the coffee beans to the liquefying water (Gonzalez-Rios et al., 2007;Wintgens, 2009;Murthy and Naidu, 2012). The endogenous enzymes of cherry colonizing microorganisms degrade the cell-wall pectic polysaccharides of the mucilage (Avallone et al., 2001b). ...
A greenhouse pot experiment was carried out to assess the effects of fermented coffee mucilage applied as mulch together with maize leaves on the growth of young coffee plants of two different varieties and on soil microbial biomass indices. The coffee variety Catuai required 32% more water per g plant biomass than the variety Yellow Caturra, but had a 49% lower leaf area, 34% less shoot and 46% less root biomass. Maize and mucilage amendments did not affect leaf area, shoot and root yield, or the N concentration in shoot and root dry matter. The amendments always reduced the water use efficiency values, but this reduction was only significant in the maize+mucilage‐14 (= 14 g mucilage pot−1) treatment. Soil pH significantly increased from 4.30 in the control to 4.63 in the maize+mucilage‐14 treatment. Microbial biomass C increased by 18.5 µg g−1 soil, microbial biomass N by 3.1 µg g−1 soil, and ergosterol by 0.21 µg g−1 soil per g mucilage added pot−1. The presence of mucilage significantly reduced the microbial biomass‐C/N ratio from a mean of 13.4 in the control and maize treatments to 9.3, without addition rate and coffee variety effects. The application of non‐composted mucilage is recommended in areas where drought leads to economic losses and in coffee plantations on low fertility soils like Oxisols, where Al toxicity is a major constraint.
... On the other hand, innovations in the postharvest process of coffee should also present advantages in benefit and cost, abide by environmental standards, and obtain products that comply with quality standards and take into consideration consumer preferences. The effect of the postharvest method on the quality of the beverage is an important factor that is being studied more and more (Arruda et al., 2012;Bytof, Knopp, Schieberle, Teutsch, & Selmar, 2005;Bytof, Selmar, & Schieberle, 2000;Daniels, 2009;Duarte, Pereira, & Farah, 2010;Fernandes, da Silva, Oliveira, & Miranda, 2014;Garo, Shara, & Mare, 2016;González-Ríos et al., 2007;Hamdouche et al., 2016;Joët et al., 2010;Knopp, Bytof, & Selmar, 2006;Koskei, Patrick, & Simon, 2015;Lee, Cheong, Curran, Yu, & Liu, 2015;Leloup, Gancel, Liardon, Rytz, & Phiton, 2004;Ribeiro et al., 2017;Selmar et al., 2005;Silva, 2014;Tarzia, Dos Santos Scholz, & De Oliveira Petkowicz, 2010). However, there is little information on the impact that postharvest processes might have on consumer assessments. ...
Evaluating how the postharvest processes of coffee influence the sensory characteristics of the obtained beverage makes it possible to innovate to satisfy niche markets, increase cost–benefit advantages, and comply with environmental and quality standards. In this study, four postharvest processes (“natural,” “depulping,” “fermenting,” and “washing”) were carried out on the “Garnica” variety coffee fruit. The beverage resulting from each process underwent a sensory evaluation by (a) expert cuppers to characterize it with a descriptive analysis, as well as by (b) consumers to find out its overall acceptance. The red wine bouquet of the beverage, as obtained through the “natural” process, conditioned the overall acceptance of consumers, and the acceptance of the other coffees was conditioned by the fragrance having a note of lemon. The “depulping” and “fermentation” processes represented viable options to the “washed” coffee: These processes resulted in similar sensory characteristics and general acceptance but had a lower environmental impact. With an acceptance map from a multiple factor analysis of the sensory and hedonistic data, it was found that, when applied to Garnica variety coffee, the “depulping” process represents a viable option to replace “washed” coffee processing.
Practical applications
The results obtained allow for the presentation of information about the possibility of transitioning to postharvest processes that represent an alternative to the traditional “washed” method for the agents and organisms that manage the coffee sector to raise awareness among them. These results also offer information to consumers regarding the existence of other coffee options with similar sensory characteristics to “washed” coffee, but which have a lower environmental impact.
... Although "cup quality" is a subjective descriptor, attempts have been made to predict it based on NIR spectra (4) or from the thermo-labile coffee diterpene content of green coffee beans (5). The volatile and nonvolatile compositional agents influencing coffee flavor have been studied (6), and the impact of chemical changes to coffee beans during storage postharvest have been the subject of numerous studies (7)(8)(9)(10)(11)(12)(13). ...
Background:
The driving factors for the commercial adulteration of coffee are reviewed.
Objective:
Methods have been assessed for the identification of the most common materials used to adulterate coffee by dilution, to establish the geographic origins, the genotypes of beans, and to assess the authenticity of Kopi Luwak coffee.
Method:
The literature was surveyed manually and electronically from 1820 to 2018.
Results:
A flow diagram has been developed to summarize the best approaches to deal with the authentication of coffee.
Conclusions:
Encouragement is given to the interlaboratory validation of spectroscopic approaches, the exploration of civet cat deoxyribonucleic acid for the identification of Kopi Luwak, and the development of appropriately large and well-curated datasets of authenticity information across multiple techniques.
Highlights:
The current analytical difficulties in the authentication of coffee are highlighted and suggestions made to improve the situation.
... Pederson and Breed [37] summarized early studies on the implication that fermentation improves coffee quality. Wet-processed coffee has superior aroma qualities to dry-processed coffee because of the aromatic compounds produced during the removal of the mucilage layer in wet processing [38]. e selection of appropriate microorganisms that have a positive impact on coffee flavour and aroma during fermentation is critical, and the fermentation process should be controlled to achieve this positive impact. ...
Coffee is one of the most important and widely used commercial crops in the world. After ripe coffee cherries are harvested, coffee must pass through several steps to become (green) raw coffee beans. Commonly, there are three different processing methods used to obtain green coffee beans from coffee cherries, namely, the wet, dry, and semidry methods. Microorganisms (yeasts and bacteria) play a major role in coffee fermentation process by degrading mucilage by producing different enzymes (pectinase), acids, and alcohols. Starter culture development is crucial and is done by selecting microorganisms that have certain characteristics, such as mucilage degradation ability, tolerance to stress during fermentation, the ability to suppress the growth of pathogenic fungi, and a positive impact on the sensory quality of the coffee. Currently, green coffee beans obtained from farms that use any of the above processing methods are fermented with selected microorganisms to improve the favour and aroma of the coffee. This is the result of a new insight into the development of unique favoured coffee and into engaging with the coffee market to better benefit. is review gives a comprehensive overview of the fermentation process, microorganisms and starter cultures, and fermentation’s impact on coffee quality. Future prospects are also discussed through the incorporation of recent research.
Wet fermentation of coffee beans is critical for developing sensory and perception properties of coffee beverages. This study aimed to investigate its impact on the appearance, chemical composition, and volatile compounds in coffee from four grinding sizes. There was no significant difference (p<0.05) between fermented and unfermented coffee in salt content whereas fermented coffee had lighter appearance and relatively lower pH values (4.78). The total voltage of e-nose obtained from fermented coffee were significantly higher, particularly with 250 and 350 µm coffee powder. Although the most of overtones detected by NIR from both coffee types were within 1700 – 2000 nm and 2200 – 2396 nm, the enhanced peaks responses of fermented coffee were lower. A total of 15 volatiles were identified using SPME/GC-MS. Fermented coffee showed lower total concentration but higher content in furfuryl acetate and 2-methoxy-4-vinylphenol, which could contribute to its unique caramel and fruity flavour.
In this study, green coffee beans were fermented using three yeast and three lactic acid bacteria (LAB) starters. The effects of each starter on the metabolite profiles of green coffee beans were comparatively analyzed. The principal component analysis (PCA) biplot showed a clear separation between the groups fermented with LAB (Leuconostoc mesenteroides, Lactobacillus plantarum, and Pediococcus pentosaceus) and the groups fermented with yeast (Saccharomyces cerevisiae, Candida parapsilosis, and Pichia guilliermondii). Various metabolites, including palmitic acid, stearic acid, and piperidine, were associated with the LAB strains. 2-Palmitoylglycerol, ribonic acid, and arabitol were related to C. parapsilosis and P. guilliermondii. Phenylethyl alcohol, succinic acid, shikimic acid, and methylamine contributed greatly to the separation of S. cerevisiae from the other strains in the PCA biplot. In addition, chlorogenic acid levels were higher in the LAB strains than in the yeast strains after fermentation. In particular, C. parapsilosis and P. guilliermondii showed much lower levels. The level of caffeine was highest in P. pentosaceus and lowest in C. parapsilosis after fermentation. This study provides comprehensive information on the metabolic changes after green coffee bean fermentation according to the type of microbes used.
Indonesia is the fourth largest country in the world as a coffee producer. Coffee has complex chemical structure with volatile and non-volatile compounds, this composition has an important role in the distinctive coffee’s taste. Fermentation is an important stage in coffee processing, it has a direct effect on the coffee’s quality. So far, many people have done traditional fermentation relying on natural microbes in fresh coffee. The purpose of this study was to improve coffee’s quality by controlled fermentation using added yeast, thereby encouraging the sustainability of coffee production. The coffee cherries were taken from a coffee plantation in Merapi mountain area, Yogyakarta. Yeast isolates used were Saccharomyces cerevisiae and Pichia kudriavzevii. The experimental processes of fermentation were carried out on three different environmental variables, namely: fermentation in bioreactor with inoculum, fermentation in bioreactor without inoculum, and traditional fermentation in an open container. Coffee cherries were peeled by pulper machine then kept underwater for 72 hours, except for fermentation in an open container. Data logger was used to monitor the temperature changes, the moisture content, brix, PH, and color change were measured for each 24 hours during fermentation. From the data analyzed, the moisture content and brix were increased during fermentation. The result indicated that fermentation by yeast addition raised acidity in the final coffee result, this can be shown from the PH result that eventually decreased from 5.83 to 5.49 and 6.15 to 4.29, respectively. The maximum temperature for both yeast species addition was reached at a 24 to 48 hours period. The result showed that the color parameter (LAB) was elevated, except the lightness value from Pichia kudriavzevii fermentation. Result in this study revealed that the type of microorganism will determine the characteristics of the coffee produced, such as the acidity. The specific taste and aroma compound were generated during fermentation by different yeast species.
Single-dose coffee capsules have revolutionized the coffee market, fueling espresso coffee popularity and offering access to a wide selection of coffee blends. Nevertheless, scarce information related to coffee powder and brew’s combined volatile characterization is available. In this study, it is hypothesized that coffee brew aroma characteristics can be predicted based on coffee powder’s volatile composition. For this, headspace solid-phase microextraction (HS-SPME) combined with comprehensive twodimensional gas chromatography with time-of-flight mass spectrometry detection (GC × GCToFMS) was used. The data were combined via chemometric tools to characterize in depth the volatile composition of eight blends of capsule-coffee powder and respective espresso brews, simulating the consumer’s perception. A total of 390 volatile compounds were putatively identified, 100 reported for the first time in roasted coffee or brews. Although the same chemical families were determined among the coffee powders and espresso brews, a different volatile profile was determined for each matrix. The Pearson correlation of coffee powders and respective brews allowed to identify 15 volatile compounds, mainly terpenic and esters recognized by their pleasant notes, with a strong relationship between the amounts present in both matrices. These compounds can be key markers to predict the volatile aroma potential of an espresso brew when analyzing the coffee powder.
The research about fermentation of coffee Coffea arabica using a consortium of probiotic bacteria which is a collection from the microbiology laboratory of the Faculty of Mathematics and Natural Sciences, Hasanuddin University has been carried out on. This study aims to determine the flavor of arabica coffee C. arabica and its chemical composition after the fermentation process. The length of fermentation time was divided into 2 times, namely 24 hours and 36 hours, fermentation using a consortium of probiotic bacteria that had been rejuvenated on coffee peel media for 2 x 24 hours. Organoleptic testing was carried out to see the panellists preference for the taste, color and aroma of coffee after fermentation. The results showed that coffee with a 24-hour fermentation time with the addition of probiotic bacteria was the most liked by the panellists with the category slightly less acidic taste, slightly black color, and normal aroma. The GC-MS test results showed organic compounds formed after the fermentation process. In the 24-hour control sample there were 14 types of organic compounds, the sample with the addition of a consortium of probiotic bacteria contained 11 types of organic compounds, the 36-hour control sample contained 11 types of organic compounds, and samples with the addition of a consortium of probiotic bacteria contained 13 types of organic compounds.
Coffee is arguably the most popular drink in the world after water and it is estimated that global coffee consumption exceeds 2 billion cups every day. Today, coffee is not only consumed for pleasure but it is also used as a catalyst for social gatherings and networking. This is due to the fact that coffee can provide pleasurable taste and aroma. In order to optimize these organoleptic properties, technology interventions during postharvest processing are needed to unleash the potential flavor in coffee beans. This study was done to address this issue, especially for improving flavor and aroma potential of arabica coffee beans from Enrekang and Tanah Toraja in the highland of Sulawesi. Technology interventions in the form of fermentation (wet process) and drying were carried out and flavor notes and aroma were assessed through cup test. The results indicated that cup test scores can be improved and different flavor notes can be generated through different processing conditions.
Os microrganismos atuam diretamente na qualidade da bebida do café, seja pela degradação de compostos presentes nos grãos ou pela excreção de metabólitos que difundem para o interior dos frutos. Portanto, o conhecimento dos microrganismos e seu papel na fermentação é de grande importância para se obter um produto de qualidade. A fermentação é utilizada para remover a camada de mucilagem aderida ao pergaminho do grão, com o potencial de melhoria da qualidade do café. Este estudo teve como objetivo avaliar a qualidade global do café em função de diferentes processamentos e tempos de fermentação. Para este estudo foram utilizados cafés cereja descascado e cafés cerejas naturais com fermentação espontânea e fermentações induzidas, nas quais foram inoculadas levedura e bactéria em tempos diferentes de fermentação. O estudo evidenciou que o uso de culturas starters durante a fermentação do café contribuiu para a obtenção de uma bebida de qualidade com características sensoriais aceitas pelos provadores, indicando que levedura Saccharomyces Cerevisae em ambiente anaeróbico e sem adição de água, melhorou significativamente a qualidade sensorial da bebida.
Coffee quality is strongly related to post-harvest processes. This sensorial variation is undoubtedly mostly related to changes in the chemical composition caused by the different post-harvest processes, which are influenced by microbiota, mainly in fermentation processes.
The use of starter cultures during food fermentation aims to standardize the process and to obtain a higher quality product. The objectives were to study mesophilic bacteria (MB) and lactic acid bacteria (LAB) isolated from wet coffee processing and evaluate their performance in a pulped coffee medium. Eighty-six bacteria isolates (59 MB and 27 LAB) were assessed for pectinolytic activity, metabolite production, and pH value decrease in coffee-based culture (CPM). Seven bacteria strains (3 MB and 4 LAB) were selected and used as starter cultures in the wet fermentation of pulped coffee. The MB and LAB populations varied from 4.48 to 8.43 log CFU g⁻¹ for MB and 3.54 to 8.72 log CFU g⁻¹ for LAB during fermentation. Organic acid concentration (ranged from 0.01 to 0.53 for succinic acid; 0.71 to 8.14 for lactic acid and 0.06 to 0.29 for acetic acid), and volatile compounds (44 compounds were detected in green beans and 98 in roasted beans) were evaluated during fermentation. The most abundant compounds found in roasted beans belong to furans [15], ketones and esters [14], pyridines [13], and pyrazines [12]). Leuconostoc mesenteroides CCMA 1105 and Lactobacillus plantarum CCMA 1065 presented volatile compounds important for coffee aroma. Isovaleric acid; 2,3-butanediol; phenethyl alcohol; β-linalool; ethyl linoleate; and ethyl 2-hydroxypropanoate could improve cupping qualities.
Graphic abstract
This study investigated the microbiological and biochemical characteristics of six endogenous yeast species isolated from spontaneous wet coffee fermentation for their potential as starter cultures. The yeasts were cultured under elevated temperature, osmotic pressure, ethanol and acid concentrations to assess their tolerance to these coffee fermentation-related stress conditions. Their ability to produce hydrolytic enzymes for pectin, protein, cellulose and starch were evaluated using plate assays. Hanseniaspora uvarum and Pichia kudriavzevii were the most stress-tolerant species and also exhibited high pectinase, amylase, cellulase and protease activities compared with P. fermentans, Candida railenensis, C. xylopsoci and Wickerhamomyces anomalus. When the yeasts were inoculated in a synthetic coffee pulp extract medium all the isolates grew and produced several important aromatic compounds, including isoamyl alcohol, 2-phenylethyl alcohol, ethanol, ethyl acetate, acetaldehyde, and 2-propanone. The concentrations of these volatiles produced by the yeast species differed significantly. H. uvarum and P. kudriavzevii produced significantly higher concentration of total alcohols (42.5, 57.6 mg/l), esters (31.0, 33.7 mg/l) and aldehydes (0.7, 1.9 mg/l). Overall, H. uvarum and P. kudriavzevii demonstrated the strongest potential as starter cultures for wet coffee fermentation.
Direct fermentations of sterilised green coffee beans by monocultures of Saccharomyces cerevisiae and Pichia kluyveri were investigated for coffee flavour biotransformation. During fermentation, fruity esters were generated in the green coffee beans by yeasts. 2-Phenylethyl acetate was elevated by 1.1 mg/kg and 0.03 mg/kg in P. kluyveri- and S. cerevisiae-fermented green beans, respectively, as compared to the untreated sample. Ethyl octanoate (0.51 mg/kg) and isoamyl acetate (1.69 mg/kg) only existed in S. cerevisiae- and P. kluyveri-fermented green beans, respectively. After roasting, higher levels of 2-phenylethyl acetate were detected in fermented coffees, and ethyl octanoate was found only in the S. cerevisiae-fermented sample, despite the loss of isoamyl acetate in P. kluyveri-fermented coffees during roasting. The fruity esters generated by the yeasts during green coffee bean fermentations were directly transferred to the volatile profiles formed after roasting and enhanced the fruity attribute in the roasted coffees, with a more noticeable effect observed from S. cerevisiae fermentation. Higher productions of N-heterocyclic volatiles occurred during roasting of S. cerevisiae-fermented coffees and contributed to elevated nutty and roasted aromas. S. cerevisiae and P. kluyveri are considered suitable starter cultures for controlled coffee flavour biotransformation through controlled fermentations of green coffee beans.
The microbial ecology in the fermentation of Australian coffee beans was investigated in this study. Pulped coffee beans were kept underwater for 36 h before air dried. Samples were collected periodically, and the microbial communities were analyzed by culture-dependent and independent methods. Changes in sugars, organic acids and microbial metabolites in the mucilage and endosperm of the coffee beans during fermentation were monitored by HPLC. Culture-dependent methods identified 6 yeast and 17 bacterial species, while the culture-independent methods, multiple-step total direct DNA extraction and high throughput sequencing, identified 212 fungal and 40 bacterial species. Most of the microbial species in the community have been reported for wet fermentation of coffee beans in other parts of the world, but the yeast Pichia kudriavzevii was isolated for the first time in wet coffee bean fermentation. The bacterial community was dominated by aerobic mesophilic bacteria (AMB) with Citrobacter being the predominant genus. Hanseniaspora uvarum and Pichia kudriavzevii were the predominant yeasts while Leuconostoc mesenteroides and Lactococcus lactis were the predominant LAB. The yeasts and bacteria grew significantly during fermentation, utilizing sugars in the mucilage and produced mannitol, glycerol, and lactic acid, leading to a significant decrease in pH. The results of this study provided a preliminary understanding of the microbial ecology of wet coffee fermentation under Australian conditions. Further studies are needed to explore the impact of microbial growth and metabolism on coffee quality, especially flavour.
The objective of this research was to reduce the drying time of coffee to obtain an average of 12% humidity, through the use of solar dryers implemented with a continuous air flow system powered by photovoltaic energy. The research was carried out in the province of Rioja, San Martin region, Peru. The research was of the experimental type using a complete random design with a factorial scheme including two factors (use of prototypes and drying time); with 7 repetitions. A greenhouse solar dryer of 4 x 8 m was used. with nine measurements per day. The moisture of the grain was measured, which was reduced to 12.3% in five days in the average. It is recommended to use the solar dryer with prototype for drying coffee bean.
Coffee is one of the most widely consumed beverages in the whole world. The drying process for the storage of coffee beans is decisive for the physical and sensory characteristics of the final product. The objective of this study was to evaluate the effect of two types of dryers (mechanical and traditional) at five altitudes on coffee quality. The research was conducted in the Alto Mayo valley, San Martín region, Peru. Five farms were selected at different altitudes (873, 1079, 1248, 1348, 1430 m.a.s.l.). The prototype used works through a system of thermal heat tunnels, built with solar micas and calamine. 150 samples of 1 kg were extracted. The variables evaluated were the physical and organoleptic characteristics of the dry grain, as well as the number of drying days. The results showed that there were no significant differences for any parameter evaluated between the selected altitudes. However, there were significant differences for the parameters of humidity and amount of first category grain, where mechanical drying was superior. Also, in the case of organoleptic quality, mechanical drying was presented as the best option, indicating that its use can optimize the organoleptic quality of coffee
Coffee is one of the most important agricultural commodities in the world. Data from International Coffee Organization (ICO) indicate that total world production increased from 8.945 million metric tons in 2014 to 9.126 million metric tons in 2015, 9.462 million metric tons in 2016, and 9.580 million metric tons in 2017. Data from ICO also show that coffee is commercially cultivated in 56 countries and Indonesia with total production of about 720 thousand tons in 2017 was the fourth largest producer after Brazil (3.06 million tons), Vietnam (1.77 million tons), and Colombia (840 thousand tons). To increase the economic value of this commodity, the quality of coffee bean must be improved through both agronomic and postharvest aspects. This study was designed to develop a new ohmic-based fermentation technology for coffee cherry to improve flavor quality of coffee beans. Results of this study indicate that this technology can produce coffee with cup-test scores ranging from 84.38 to 86.88 with an average score of 85.713. This score is higher than the cup test score of Indonesia civet coffee ( luwak coffee) reported by several researchers. Therefore, application of ohmic heating based technology for coffee fermentation can significantly improve flavor quality of coffee beans.
In this work, the characterization of volatile carbonyl compounds profiles in healthy and defective green coffee beans was performed. The objective of this characterization was to identify carbonyl marker compounds related to the main bean defects of both arabica and robusta species (black, sour, immature and bored) in non-aged and aged beans. A simple and innovative procedure for volatile compounds extraction was developed, so that usual heating procedures that may adulterate samples' identity can be avoided. The coffee sample and an acceptor solution containing a carbonyl derivatizing reagent are placed inside a screw-cap flask featuring an inner electric fan. The efficiency of the volatile carbonyl compounds mass transfer could be increased due to the fan's operation. The experimental parameters, fan rotation speed, extraction period and sample mass were studied to improve the volatile compounds extraction before HPLC analysis. Defective green beans showed higher contents of some volatile carbonyl compounds than healthy green beans. The volatile carbonyl compounds profile obtained during the forced ageing assay revealed that butanal, benzaldehyde, 3-methylbutanal and hexanal were, consistently, found in higher amounts in both arabica and robusta defective beans, in comparison with healthy beans of the same lot.
Specific fermentation processes such as digestive bioprocessing and monsooning have been of interest to coffee consumers. Volatile compounds of beans during the different fermentation processes vary considerably and exhibit different profiles. The representative flavor compounds for the luwak green bean were found to be pentamethyl heptane and 3‐methyl‐1‐butanol, while more diverse and distinct compounds were observed from the monsooned green bean, namely alkyl butanals, pinenes, benzaldehyde and butanediols. However, after roasting, the fermented form of both beans contained similar types of volatiles and their relative contents compared to those of non‐fermented roasted beans, except for α‐pinene in luwak and 2‐methyl furan in monsooned beans. In principal components analysis and partial least squares‐discriminant analysis (PLS ‐DA ), the different fermented beans were clearly distinguished by the extracted peak entities from their total ion chromatograms. The s‐plot and variable importance on projection (VIP ) values related to PLS ‐DA showed the significant compounds contributing to the identification of the groups. 3‐Methyl‐1‐butanol was the most distinctive compound for the luwak green bean, and β‐pinene, ethylbenzene and benzaldehyde were found to be the significant compounds in the monsooned green bean. In roasted beans, the most significant compounds to distinguish luwak were furfural, α‐pinene and 3‐carene with high variable in the projection (VIP ) values. A significant presence of pyrazine, alkyl pyrazines, pyridine and alkyl pyridines contributed to differentiating both fermented roasted coffee beans from the unfermented roasted beans.
Cup quality of coffee processed by either natural fermentation, mechanical removal of mucilage, without removal of mucilage; washing; without washing, well dried, kept as wet parchment coffee before drying or dry processed was evaluated. Aroma, acidity, bitterness body and global impression of coffee cups were measured by descriptive quantitative sensory analysis using 9 point's scale. By the wet coffee process washing with clean water, and drying carefully were produced the best coffee cups, in comparison to the others types and process conditions. It was found that either ripe or immature coffee beans processed by dry process present stinker defect. By drying coffee with its mucilage it was produced dark and sticky coffee beans, and ferment smell and flavor. The storage of wet parchment coffee affected the coffee cup quality due earthy, fermented, and dirty flavors perceived. It was demonstrated that by washing coffee after either natural or mechanical removal of mucilage, can be obtained good quality cups no strange flavors. It is concluded that coffee process has a significant effect on coffee quality. Drying process is one of the most important stages of the coffee process in order to maintain coffee quality.
The aromas of a reference green Mexican coffee (Arabica) and of a coffee from the same origin, but having a pronounced earthy/mouldy off-taint, were characterised. From comparison of the two aroma profiles, the compounds causing the defect were detected by gas chromatography olfactometry, isolated and concentrated by preparative bi-dimensional gas chromatography, and characterised by gas chromatography-mass spectrometry. Six compounds participated in the off-flavour. Geosmin, 2-methylisoborneol, 2,4,6-trichloroanisole were found to be the main culprits, while three methoxy pyrazines (2-methoxy-3-isopropyl/-3-sec-butyl/-3-isobutyl pyrazine) contributed to a lesser extent to the earthy/green undertone. The occurrence of the off-flavour could tentatively be linked to post-harvest drying.
Volatile organic compounds (VOCs), emitted from green coffee beans, during coffee roasting and from a cup of coffee, were all analysed by proton-transfer-reaction mass spectrometry. Firstly, the headspace (HS) of green beans was investigated. Alcohols dominate the HS, but aldehydes, hydrocarbons and organic acids were also abundant. Secondly, we roasted coffee under two different conditions and monitored on-line the VOCs emitted during the process. In a first roasting series, a batch of beans was roasted. After an initial drying phase, dominated by evaporation of water and methanol, the HS concentrations of VOCs such as acetic acid, acetaldehyde, pyridine and methylbutanal rapidly increased and went through a maximum at medium roast level. In a second series, just six beans were roasted. We observed sporadic bursts of some volatiles (furans, butanal, 2,3-pentanedione), coinciding with popping sounds. Other VOCs showed smooth time-intensity profiles (pyridine, pyrazine). These experiments gave a real-time insight into the complex processes taking place during roasting. Finally, the HS of coffee extracts, prepared from beans roasted to different roast levels, were analysed. Most VOCs showed a maximum concentration at medium roast level (e.g. pentanedione, furfural, 5-methyl furfural), while others showed a gradual increase (e.g. pyrrol) or decrease (e.g. methanol).
Analyses for the investigation of aroma components are routinely performed on coffee aromatic extracts. Various extraction methods exist. Ideally, the extraction method used should provide an extract with sensory characteristics as close as possible to the complete product. This is particularly relevant in the case of coffee, as no single key compound has been demonstrated as being responsible for the typical flavour of roasted and ground coffee. The purpose of this study was to compare various methods to see which provided an aromatic extract most representative of coffee. Five different extraction methods were compared: supercritical fluid extraction with carbon dioxide, simultaneous distillation extraction, oil recovery under pressure and vacuum steam-stripping with water or with organic solvent. In addition, Arabica Colombia coffee was used at three different roasting levels, i.e. green coffee as well as the same coffee light-roasted and medium roasted. Sensory testing of the extracts showed that vacuum steam-stripping with water provided the most representative aroma extract, for all three coffees.
One of the reasons for the worldwide growing coffee consumption is the pleasant flavor of the final coffee beverage. It is well known that the character impact compounds of coffee are not present in the green state but are mainly formed during roasting. However, an extensive literature review indicated that more than 200 green coffee volatiles have been identified so far. Furthermore, the isolation and chemical identification of a range of compounds that have not been described in green coffee yet is reported by the present work. Results of GC-olfactometry reveal that only a few have an aroma impact on the typical flavor of green coffee. Some compounds may survive roasting and may contribute to the final roasted coffee flavor.
The application of solid-phase microextraction (SPME) far flavor analysis has been studied. SPME headspace and liquid sampling were tested for 25 common flavor components in dilute aqueous solution. The addition of salt generally enhances SPME adsorption. Larger sample volume and a smaller volume of headspace over the liquid sample also increase the sensitivity of SPME-based analysis. For thermal desorption following SPME, a GC injector liner with small diameter, e.g., 1 mm i.d., improves resolution and obviates the need for cryogenic focusing. The SPME technique was applied to authentic samples: ground coffee, a fruit juice beverage, and a butter flavor in vegetable oil. The advantages and limitations of SPME are discussed.
About 20% of Brazil coffee production presents the so-called Rio defect characterized by a strong off-flavor, often described as medicinal, phenolic, or iodine-like. Occasionally, this defect also occurs in coffees from other origins. An extensive investigation was carried out to identify the compound(s) responsible for the coffee samples. Volatiles were isolated from green beans by simultaneous distillation-extraction and analyzed by capillary GC, GC-sniffing, and GC-MS. 2,4,6-Trichloroanisole (TCA) was identified as the most likely key compound for the Rio off-flavor. TCA was found in all Rio samples in concentrations ranging from 1 to 100 ppb. Less than 50% of TCA present in green beans was lost during roasting. 2,4,6-Trichlorophenol (TCP), the probable precursor of TCA, was also found in most of these samples. Adding TCA to freshly brewed coffee imparted to it the same off-flavor notes as described in actual Rio coffee. The perception threshold of TCA in coffee brew was found to be 8 ppt for direct odor perception and 1-2 ppt for flavor by mouth.
A method that differentiates between different roasted coffees and coffee beverages is described. Characterization is achieved by applying principal component analysis (PCA) to the chromatographic results obtained by solid phase microextraction−gas chromatography (SPME−GC), applied to the vapor phase in equilibrium with coffee (HS−SPME), or to coffee extracts (LS−SPME). The capabilities of this method are illustrated by some examples defining the differentiation of coffee samples of different origins or in mixtures of different compositions. Keywords: Roasted coffees; beverages; solid phase microextraction (SPME); GC; principal component analysis (PCA)
IntroductionMethodologyRaw CoffeeRoasted CoffeeCoffee BrewFormation of OdorantsConclusions
References
Solid-phase microextraction (SPME) is based on the affinity of different headspace compounds for the coating on a fiber. In
the work described in this paper we evaluated and compared two different coatings, a medium polarity coating, Carbowax divinylbenzene
(CW-DVB), and an apolar coating, polydimethylsiloxane (PDMS), for the analysis and classification of coffee. PCA (principal-component
analysis) was used to evaluate the results obtained by use of the two fibers and, at the same time, to determine their suitability
for use for the classification and differentiation of coffee. When PCA is used as a method of classification, using the 30
major peaks as variables, the results obtained with the CW-DVB fiber enable classification according to geographic origin;
those obtained with the PDMS fiber enable classification based on variety (Arabica orRobusta).
In the food industry, routine analysis of food flavours is done with physical–chemical analytical tools such as GC-MS or with sensory analysis techniques. These techniques are not only time consuming but also require expensive apparatus. An alternative technique to evaluate food quality has been developed: the gas sensor arrays. Gas sensors have a characteristic electric resistance, which varies rapidly with the adsorption of volatile molecules. In this paper, we compared the aroma of nine coffee varieties by means of electronic aroma detection using an AromaScan apparatus equipped with a multisampler headspace device. The aroma patterns were evaluated and compared using the AromaScan software based on the Sammon mapping technique. Although this method is not able to give any structural information it allowed the separation of Arabica andRobusta coffees into two distinct groups. Coffees were also differentiated by geographic origin. The sensor array technique was compared with solid-phase microextraction-gas-chromatography (SPME-GC) results. Sampling conditions used for SPME were optimized with respect to headspace developing temperature and adsorption time. Results of the SPME-GC analyses were treated by principal component analysis (PCA). Thirty major peaks were chosen. The compounds responsible for the differentiation ofArabica and Robusta in the product space were tentatively identified by GCMS. Separations obtained by each method were similar. Both methods clearly separate Arabica and Robusta varieties. The SPME-GC method results did not show any separation according to geographic origin, whilst by electronic sensor array device a trend in this sense could be drawn. The sensor array technique was faster than the GCMS, taking only 7 min; GCMS analysis took 1 h. An abnormal sample, classified as fermented by the sensory panel, sent as blind test, was clearly separated in both methods.
Aroma extract dilution analysis of raw Arabica coffee revealed 3-isobutyl-2-methoxypyrazine (I), 2-methoxy-3,5-dimethylpyrazine (II), ethyl 2-methylbutyrate (III), ethyl 3-methylbutyrate (IV), and 3-isopropyl-2-methoxypyrazine (V) as potent odorants. The highest odor activity value was found for I followed by II, IV, and V. It was concluded that I was responsible for the characteristic, peasy odor note of raw coffee. Twelve odorants occurring in raw coffee and (E)-beta-damascenone were also quantified after roasting. The concentration of I did not change, whereas methional, 3-hydroxy-4, 5-dimethyl-2(5H)-furanone, vanillin, (E)-beta-damascenone, and 4-vinyl- and 4-ethylguaiacol increased strongly during the roasting process.
Solid-phase microextraction (SPME) fibers were evaluated for their ability to adsorb volatile flavor compounds under various conditions with coffee and aqueous flavored solutions. Experiments comparing different fibers showed that poly(dimethylsiloxane)/divinylbenzene had the highest overall sensitivity. Carboxen/poly(dimethylsiloxane) was the most sensitive to small molecules and acids. As the concentrations of compounds increased, the quantitative linear range was exceeded as shown by competition effects with 2-isobutyl-3-methoxypyrazine at concentrations above 1 ppm. A method based on a short-time sampling of the headspace (1 min) was shown to better represent the equilibrium headspace concentration. Analysis of coffee brew with a 1-min headspace adsorption time was verified to be within the linear range for most compounds and thus appropriate for relative headspace quantification. Absolute quantification of volatiles, using isotope dilution assays (IDA), is not subject to biases caused by excess compound concentrations or complex matrices. The degradation of coffee aroma volatiles during storage was followed by relative headspace measurements and absolute quantifications. Both methods gave similar values for 3-methylbutanal, 4-ethylguaiacol, and 2,3-pentanedione. Acetic acid, however, gave higher values during storage upon relative headspace measurements due to concurrent pH decreases that were not seen with IDA.
Equilibration time and temperature were the factors studied to choose the best conditions for analyzing volatiles in roasted ground Arabica coffee by a static headspace sampling extraction method. Three temperatures of equilibration were studied: 60, 80, and 90 degrees C. A larger quantity of volatile compounds was extracted at 90 degrees C than at 80 or 60 degrees C, although the same qualitative profile was found for each. The extraction of the volatile compounds was studied at seven different equilibration times: 30, 45, 60, 80, 100, 120, and 150 min. The best time of equilibration for headspace analysis of roasted ground Arabica coffee should be selected depending on the chemical class or compound studied. One hundred and twenty-two volatile compounds were identified, including 26 furans, 20 ketones, 20 pyrazines, 9 alcohols, 9 aldehydes, 8 esters, 6 pyrroles, 6 thiophenes, 4 sulfur compounds, 3 benzenic compounds, 2 phenolic compounds, 2 pyridines, 2 thiazoles, 1 oxazole, 1 lactone, 1 alkane, 1 alkene, and 1 acid.
Headspace sorptive extraction (HSSE) and stir bar sorptive extraction (SBSE), two recently introduced solventless enrichment techniques, have been applied to the analysis of the headspace of Arabica roasted coffee and of the headspace of the brew and of the brew itself. In both HSSE and SBSE enrichment is performed on a thick film of poly(dimethylsiloxane) (PDMS) coated onto a magnet incorporated in a glass jacket. Sampling is done by placing the PDMS stir bar in the headspace (gas phase extraction or HSSE) or by immersing it in the liquid (liquid phase extraction or SBSE). The stir bar is then thermally desorbed on-line with capillary GC-MS. The performance of HSSE and SBSE have been compared through the determination of the recoveries and relative abundances of 16 components of the coffee volatile fraction to classical static headspace (S-HS) and to headspace and in-sample solid phase microextraction (HS-SPME and IS-SPME, respectively) applying the fibers PDMS 100 microm, Carbowax/divinylbenzene 65 microm (CW/DVB), Carboxen/PDMS 75 microm(CAR/PDMS), polyacrylate 85 microm(PA), PDMS/divinylbenzene 65 microm(PDMS/DVB), and Carboxen/divinylbenzene/PDMS 50-30 microm(CAR/PDMS/DVB). In all cases, HSSE and SBSE gave higher recoveries, and this is entirely due to the high amount of PDMS applied.
A dynamic solid-phase microextraction (SPME) method to sample fresh headspace volatile compounds released during the grinding of roasted coffee beans was described and the analytical results using gas chromatography/mass spectrometry (GC/MS) and GC/olfactometry (GC/O) were compared to those of the conventional static SPME sampling methods using ground coffee. Volatile compounds released during the grinding of roasted coffee beans (150 g) were obtained by exposing the SPME fiber (poly(dimethylsiloxane)/divinylbenzene, PDMS/ DVB) for 8 min to nitrogen gas (600 mL/min) discharged from a glass vessel in which the electronic coffee grinder was enclosed. Identification and characterization of volatile compounds thus obtained were achieved by GC/MS and GC/O. Peak areas of 47 typical coffee volatile compounds, separated on total ion chromatogram (TIC), obtained by the dynamic SPME method, showed coefficients of variation less than 5% (n = 3) and the gas chromatographic profile of volatile compounds thus obtained was similar to that of the solvent extract of ground coffee, except for highly volatile compounds such as 4-hydroxy-2,5-dimethyl-3(2H)-furanone and 4-ethenyl-2-methoxyphenol. Also, SPME dilution analysis of volatile compounds released during the grinding of roasted coffee beans showed linear plots of peak area versus exposed fiber length (R (2) > 0.89). Compared with those of the headspace volatile compounds of ground coffee using GC/MS and GC/O, the volatile compounds generated during the grinding of roasted coffee beans were rich in nutty- and smoke-roast aromas.
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