Influence of fermentation conditions on the sensorial quality of coffee inoculated with yeast

Metataxonomic, chemical, and sensory aspects of cocoa fermentation using single hybrids and combinations of hybrids and their effects on chocolate quality

Extensive research has been conducted on cocoa fermentation in single hybrids. However, comparisons between hybrid combinations and single hybrids are limited. This study investigated cacao fermentation using a hybrid combination (PS 1319, PH 16, BN 34, CEPEC 2002, SJ02, CCN 10, and Ipiranga) and SJ02 hybrid alone. Microbial diversity was determined by next-generation sequencing (NGS), organic acids, carbohydrates, and alcohols by HPLC, volatile compounds by GC/MS, and the sensory analysis by acceptance test and Check-All-That-Apply (CATA). The NGS analysis identified 64 fungal species and 60 bacterial species with Hanseniaspora uvarum, Hanseniaspora opuntiae, Pichia manshurica, Pichia kluyveri, and Saccharomyces sp. as the dominant yeasts. Carbohydrates were metabolized entirely in the hybrid combination by the end of fermentation. Higher ethanol concentrations were found in SJ02 at 72 h. As the fermentation progressed, citric acid concentrations decreased, while lactic and acetic acid concentrations increased by 72 h on SJ02 fermentation. Acetobacter sp. was strongly correlated with acetic acid production in hybrid combination fermentation. SJ02 showed higher concentrations of volatile compounds, with fatty acids being the most abundant class, followed by esters. The alcohol 2-nonanol was detected only in the hybrid combination fermentation. SJ02 chocolate was attributed to higher taste, texture, and overall score. The descriptors bitter and citric acidity were more perceived in chocolates from the hybrid combination, while the earthy descriptor was more evident in the SJ02 hybrid. Thus, fermentations using a hybrid combination and the SJ02 hybrid allow the production of fine chocolates with varied sensory profiles.

Coffee Biotransformation in Volcanic Process: A Chemical and Sensory Analysis

Volcanic fermentation is an innovative technique in post-harvest coffee processing that involves forming conical mounds, called "volcanoes", to create specific biotransformation conditions. This study investigates the impact of different volcano fermentation methods on the chemical composition and sensory attributes of coffee. Four methods were evaluated: asphalt patio (E1), on pallets (E2), in steel containers under the sun (E3), and in steel containers in the shade (E4). The chemical composition was analyzed in terms of sugars (sucrose, glucose, fructose), organic acids (citric, malic, succinic, lactic, acetic) and alcohols (glycerol, ethanol). In addition, color differences (ΔE) and sensory analysis of the fermented coffees were evaluated. The results of this study reveal that volcanic fermentation produces high-quality specialty coffees, but with divergent profiles of acids and alcohols, thus influencing the sensory characteristics of the resulting beverage. However, the different methods of volcanic fermentation did not significantly affect pH and soluble solids, indicating that the microbiota developed an efficient and consistent fermentation regardless of the solar exposure conditions. The most frequently mentioned sensory descriptors were chocolate, citrus fruits, honey/molasses, caramel, floral, and brown sugar. These findings highlight the significant influence of the volcanic fermentation method on the chemical and sensory quality of coffee fermented.

Metataxonomic identification of microorganisms and sensory attributes of Coffea canephora under conventional processing and Self-Induced Anaerobiosis Fermentation

This study evaluates for the first time the modifications in the microbial communities and sensory attributes caused by Self-Induced Anaerobiosis Fermentation (SIAF) compared to the Conventional processing of Coffea canephora var. Conilon. Microorganisms were identified through high-throughput sequencing of the 16S rRNA V3/V4 region for bacteria and the ITS region for fungi. Sensory attributes of roasted coffee were evaluated by Q-Graders. The relationship between microbial population, processing methods, and sensory attributes was investigated using principal component analysis. Before fermentation, 74 bacterial and 21 fungal species were identified in the natural coffee, whereas 44 bacterial and 15 fungal species were found in the pulped coffee. Torulaspora, Wickerhamomyces, and Meyerozyma exhibited more ITS region sequences, while Acetobacter, Enterobacter, and Lysinibacillus were predominant in the 16S region. In the natural coffee, Wickerhamomyces showed the highest relative abundance (45%) at 0 h. After 72 h, Meyerozyma (45%) and Torulaspora (75%) prevailed in Conventional processing and SIAF, respectively. In the pulped coffee, Torulaspora was the most abundant in the SIAF method, before (92%) and after (81%) fermentation, while Wickerhamomyces (39%) dominated after 72 h in the Conventional method. Enterobacteriaceae levels decreased, while Lactobacillaceae levels increased in SIAF natural coffee during the fermentation process. SIAF favored the presence of yeast and LAB while inhibiting mycotoxigenic fungi and Enterobacteriaceae. Torulaspora, Lactiplantibacillus, and Lactococcus showed the highest Pearson correlation coefficient with flavor (0.92), aftertaste (0.99), and bitterness/sweetness (0.89), respectively. Changes in coffee microbiota during SIAF improved sensory attributes, resulting in better-quality beverages.

Insight into how fermentation might contribute to the distinctiveness of Australian coffee

With a view to modulating the flavour profiles of Australian coffee, this investigation focused on three estates in New South Wales. Coffee cherries were processed into beans with wet fermented and non-fermented methods to evaluate the effects of fermentation and terroir on microbial population dynamics, volatile composition, and sensory properties. Thirty-three volatiles were quantified in green and roasted coffee beans - 12 esters, 9 alcohols, 6 acids, 3 monoterpenes, 2 norisoprenoids, 1 aldehyde - and 5 thiols were quantified in roasted coffee brews. Sensory descriptive analysis defined appearance, aroma, and flavour attributes to describe the coffee brews. Fermented coffees were characterised by increased intensity of 'black tea leaves' and 'dark chocolate' aromas and 'burnt toast' flavour. Results suggested that wet fermentation of Australian coffee cherries could enhance the content of some volatile compounds known to convey "floral" and "fruity" aromas commonly ascribed to premium coffees from traditional producing regions.

Self-induced anaerobiosis fermentation in coffees inoculated with yeast: Effect on key enzymes of the germination process and its relationship with the decrease in seed germination

Our objective was to monitor the main enzymes of coffee germinal metabolism and chemical composition during Self-Induced Anaerobiosis Fermentation (SIAF) with yeasts (Saccharomyces cerevisiae (CCMA0543), Candida parapsilosis (CCMA0544) and Torulospora delbrueckii (CCMA0684)) evaluating their relationship with seed germination. The starter cultures were assessed by qPCR. The organic acids were analyzed by liquid chromatography. Catalase (CAT), Esterase (EST), Alcohol dehydrogenase (ADH), and Isocitrate Lyase (ICL) enzyme activity was confirmed by the presence of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-Page) gel bands. The formation of a white halo confirmed the activity of the enzyme endo-β-mannanase, and its quantification was performed using the diameter of the halo of both the samples and the standard curve. At the end of the fermentation process, S. cerevisiae and T. delbrueckii presented the highest populations (>7 log10 cells/g). Succinic acids (average -1.11 g/kg) were consumed during SIAF. Lactic acid increased after 180 h in coffees fermented by the SIAF method (average 3.57 g/kg). CAT and EST showed high activity in the conventional process. ADH activity was detected in both processes after 180 h of the SIAF method. Yeast inoculation during the SIAF method increased the activity of ICL andshowed more intense activity in the first 96 h of fermentation, especially the pulped coffee. Endo-β-mannanase activity was intense during conventional coffee processing (9.89-10.99 pmol/min/g). Natural processing tends to preserve a higher percentage of viable seeds. Therefore, the processing and fermentation methods impact seed quality differently.

The potential of dried Ginkgo Biloba leaves as a novel ingredient in fermented beverages of enhanced flavour and antioxidant properties

Fermentation enhances the nutritional profile of foods and beverages like beer, wine, and fermented teas. Ginkgo biloba, long utilized for its health-enhancing properties, contains bioactive compounds like terpene trilactones and flavonoids, known for their antioxidant and neuroprotective effects. This study explores the feasibility of using dried Ginkgo biloba leaves in SCOBY-mediated fermentation to produce novel health-promoting beverages similar to kombucha. Infusions of dried Ginkgo biloba leaves with varying sugar concentrations are fermented over 21 days. Results showed that these beverages exhibited potent antioxidant properties, notably higher than tea-kombucha, attributed to increased polyphenol content. HPLC analysis identified significant levels of bioactive compounds such as catechin and apigenin. Sensory evaluation highlighted optimal acceptance of the seven-day fermented product. This research underscores the potential of Ginkgo biloba as a functional ingredient in fermented beverages, offering a healthier alternative to conventional soft drinks.

Challenges in coffee fermentation technologies: bibliometric analysis and critical review

Advancements in coffee processing technologies have led to improved efficiency in field operations, but challenges still exist in their practical implementation. Various alternatives and solutions have been proposed to enhance processing efficiency and address issues related to safety, standardization, and quality improvement in coffee production. A literature review using SciMAT and ScientoPy software highlighted advancements in fermentation tanks and the emergence of novel fermentation methodologies. However, these innovations lack sufficient scientific evidence. Researchers are now focusing on systematic approaches, such as controlled fermentations and evaluating the influence of microorganisms and process conditions on sensory attributes and coffee composition. Brazil is the leader in coffee bean fermentation research, but the number of published papers in the field has recently decreased. Despite this, efforts continue to improve process control and optimize product quality. The study emphasizes the need for further innovation in coffee fermentation technologies to increase efficiency, sustainability, and profitability while minimizing environmental impact. Implementing these advancements promises a more sustainable and quality-driven future for the coffee industry.

Refermentation with yeast and lactic acid bacteria isolates: a strategy to improve the flavor of green coffee beans

BACKGROUND

Yeast and lactic acid bacteria (LAB) play an important part in the post-harvest fermentation of coffee. This study applied lab-scale fermentation to commercial green coffee beans using dry coffee pulp as the substrate, with the aim of modifying coffee-bean flavor. In addition to spontaneous fermentation, yeast and LAB isolated from coffee beans and dried coffee pulp were added during fermentation.

RESULTS

Co-inoculation of yeast and LAB showed a significant effect on the chlorogenic acid content after between 24 and 72 h of fermentation. Acetic, citric, malic, lactic, and quinic acids were shown to be affected significantly (P < 0.05) by fermentation and inoculation. Gas chromatography detected that esters, alcohols, aldehydes, furans, and pyrazines were the primary compounds in the coffee beans. Certain volatile groups were present in greater concentrations and broader varieties within the inoculated beans. The highest cupping scores were given to beans that had been co-inoculated with yeast and LAB.

CONCLUSION

Overall, the use of yeasts and LAB starters showed potential to create coffee beverages with desirable characteristics by standardized fermentation. © 2024 Society of Chemical Industry.

Genetic diversity of the fungal community that contributes to the sensory quality of coffee beverage after carbonic maceration and fermentation

Understanding the effects of microorganisms on coffee fermentation is crucial to ensure sensory quality and food security. The analysis of the dynamics of the microbial community during fermentation can contribute to a better understanding of the beneficial and harmful effects of microorganisms and help select starter cultures to improve coffee quality. Furthermore, the anaerobic environment produced by carbonic maceration of the coffee fruits inhibits aerobic respiratory processes and stimulates fermentative metabolism, modulating the microbial community during coffee fermentation. This study evaluated the effects of carbonic maceration in the fungal community dynamics during the fermentation of Coffea arabica fruits at 18, 28, and 38 °C for 24, 48, 72, 96, and 120 h. Fungal diversity was accompanied by high-throughput sequencing (NGS) of the Internal Transcribed Spacer (ITS) region. During the coffee fermentation, the fungal community changed over time, with the most significant changes occurring at 18 and 28 °C after 72 h. However, at 38 °C, there were greater variations in fungal composition and fungal diversity was highest after 120 h. The yeast Pichia cephalocereana was predominant in the fermentations. These results indicated that temperature and fermentation conditions influence the fungal community during coffee fermentation. Lower temperatures might favor a more stable microbial environment, while higher temperatures lead to more intense changes. Thus, our data from NGS can help in the identification, isolation, and metabolic characterization of fungi for the fermentation of coffee fruits.

Impact of different fermentation times on the microbiological, chemical, and sensorial profile of coffees processed by self-induced anaerobiosis fermentation

Variation in fermentation time may be an essential alternative to provide coffee beverages with different and unique sensory profiles. This work investigated the microbiological, chemical, and sensory changes in coffees submitted to different fermentation durations (0, 24, 48, 72, and 96 h). Self-induced anaerobiosis fermentation (SIAF) was used, and two treatments were performed: spontaneous fermentation and inoculation with S. cerevisiae CCMA0543. Microbiological analyses were performed, and the permanence of the inoculum was monitored. Chromatography (sugars, organic acids, and volatile compounds) was analyzed, and sensory analysis (temporal dominance of sensations - TDS) was performed. A total of 228 isolates were identified during spontaneous fermentation. The dominant bacteria and yeasts were Leuconostoc mesenteroides, Lactiplantibacillus plantarum, Staphylococcus warneri, Bacillus sp., Torulaspora delbrueckii, Hanseniaspora uvarum, and Meyerozyma caribbica. High concentrations of citric (18.67 mg.g- 1) and succinic (5.04 mg.g- 1) acids were detected at 96 h in SIAF fermentation. One hundred twenty-one volatile compounds were detected, but 22 were detected only in inoculated coffees. In spontaneous fermentation, 48 h of fermentation showed woody notes, while 72 h showed chestnuts. However, in the inoculated coffee, 72 h of fermentation showed high fruity dominance, and 96 h of fermentation was the only one with herbaceous notes. In addition, yeast inoculation increased the intensity of caramel notes in the first 48 h and increased the fruity flavor after 72 h of fermentation. Therefore, the type of fermentation (with or without inoculation) and the chosen fermentation time will depend on the sensorial profile the producer intends to obtain.

Effects of cherries Sanitization methods and fermentation times on quality parameters of coffee beans

For the first time, the dual effect of coffee cherry sanitization methods to control the microbial load in processing and the influence of fermentation time on coffee quality parameters was evaluated. Two assays were carried out by wet processing: I) Sanitization of the coffee cherry (ST1: Unclassified processed cherries; ST2: Classified and sanitized cherries with drinking water; ST3: Classified and sanitized cherries with a chemical agents and II) Fermentation times (FT1: 12 h; FT2: 24 h; FT3: 48 h; FT4: 72 h and FT5: 96 h). pH, temperature, and dissolved oxygen were monitored during fermentation. Counts of Lactic Acid Bacteria - LAB, mesophiles, and yeasts were carried out on the coffee mass before and after fermentation. Caffeine and chlorogenic acid contents were determined by HPLC-DAD and the sensory profile by methodology for specialty coffees (SCA). The main findings showed that: sanitization with Timsen® did not significantly influence the evolution of pH during fermentation (p > 0.05), but it can reduce to a small extent the action of LAB at the end of the process. It was observed that the temperature of the coffee mass tends to balance with the ambient temperature, with significant effects (p < 0.05) of sanitization (ST2 and ST3) on the stability of this variable during fermentation. Timsen® as a disinfectant affected microbial populations and improved the sensory profile in the cup. In prolonged coffee fermentations (FT3, FT4 and FT5), the pH of the coffee mass tended to stabilize after 36 h, regardless of the process time. Likewise, a correlation was evident between a higher microbial load correlated with better sensory profiles in FT4 and FT5. Neither the sanitization process nor the fermentation time significantly affected the caffeine and chlorogenic acid contents of the coffee, both in its green and roasted states. Consequently, the sanitization of cherry coffee with Timsen® and prolonged fermentation times favor the safety and coffee final quality in the cup.

Characterization of yeast mutant strains for starter culture in Arabica coffee fermentation

Arabica coffee is the most popular and best-selling type of coffee. During coffee fermentation, microorganisms are essential for the production of metabolites and volatile compounds that affect coffee flavor quality. This work aimed to study the mutation, selection, and characterization of the Wickerhamomyces anomalus strain YWP1-3 as a starter culture to enhance the flavor quality of Arabica coffee. The results revealed that six mutants could produce relatively high levels of the pectinase enzyme on pectin agar media and exhibited high activity levels, ranging from 332.35 to 415.88 U/ml in mucilage broth. Strains UV22-2, UV22-3, UV41-1 and UV32-1 displayed higher levels of amylase activity than did the wild type. The UV22-2 and UV22-3 mutants exhibited the highest pectin degradation indices of 49.22% and 45.97%, respectively, and displayed significantly enhanced growth rates in nitrogen yeast base media supplemented with various sugars; thus, these mutants were evaluated for their ability to serve as a starter for fermentation of Arabica coffee. The cupping scores of coffees derived from UV22-2 and UV22-3 were 83.5 ± 1.5 and 82.0 ± 2.14, respectively. The volatile compounds in the roasted coffee fermented by UV22-2 were analyzed by GC‒MS, which revealed higher levels of furfuryl alcohol and furfuryl acetate than did the other samples. These findings suggested that UV22-2 could be an influential starter culture for Arabica coffee fermentation.

Evaluation of Arabica Coffee Fermentation Using Machine Learning

This study explores the variances in the organic, chemical, and sensory attributes of fermented coffee beans, specifically examining how post-harvest processes influence cup quality. Coffee fruits from the Catuaí IAC-144 variety were processed using both natural coffee (NC) and pulped coffee (PC) methods. The fruits were then subjected to self-induced anaerobic fermentation (SIAF) using one of the following fermentation methods: solid-state fermentation (SSF) or submerged fermentation (SMF). Within these methods, either spontaneous fermentation (SPF) or starter culture fermentation (SCF) was applied. Each method was conducted over periods of 24, 48, and 72 h. For this purpose, two-hundred-liter bioreactors were used, along with two control treatments. Numerous parameters were monitored throughout the fermentation process. A comprehensive chemical profiling and sensory analysis, adhering to the guidelines of the Specialty Coffee Association, were conducted to evaluate the influence of these fermentation processes on the flavor, aroma, and body characteristics of the coffee beverage across multiple dimensions. Data analysis and predictive modeling were performed using machine learning techniques. This study found that NC exhibited a higher production of acids (citric, malic, succinic, and lactic) compared to PC, resulting in distinct chemical and sensory profiles. The decision tree showed that fructose and malic and succinic acids were identified as the main factors enhancing sensory notes during cupping. SMF promoted higher concentrations of lactic acid, while SSF led to increased ethanol content. Consequently, the SIAF process enhances the sensory quality of coffee, adding value to the product by generating diverse sensory profiles.

Protein profile and volatile compound associated with fermented coffees with yeast co-inoculation

This work aims to analyze the protein profile and volatile compounds of coffees fermented with the indigenous microbiota and with the co-inoculation of three yeasts (Saccharomyces cerevisiae, Torulaspora delbrueckii, and Candida parapsilosis). Two-dimensional gel electrophoresis (2D-PAGE), MALDI-ToF/ToF (MS/MS), and gas chromatography (GC-MS) were performed. A total of 72 "spots" were detected by 2D-PAGE. 16 spots were selected for identification by MALDI-ToF/ToF, and 12 were identified (11S protein, 13S globulin basic chain, 17.6 kDa class II heat shock protein (HSP17.6-CII), 18.0 kDa class I heat shock protein, Seed of Late Development Stage, Pru ar 1, and FAR-1 protein). 81 main volatile compounds were detected and classified into alcohols, acids, aldehydes, esters, hydrocarbons, pyrazines, furans, thiols, and pyridines/pyrrols. The difference between the identified volatile compounds and their concentrations was detected in the treatments with and without inoculation after drying. The compounds formed in green coffee during fermentation can participate in several reactions during roasting, presenting different sensory profiles and contributing to coffee quality.

Isolation of Yeast and LAB from Dry Coffee Pulp and Monitoring of Organic Acids in Inoculated Green Beans

Yeast and lactic acid bacteria (LAB) are known to play an important role in the fermentation process of coffee post-harvest. This study aimed to isolate and screen yeast and LAB to be applied in lab-scale refermentation of commercial green coffee beans and coffee pulp with the aim of modifying the composition of organic acids (OAs) in coffee beans. Yeast and LAB strains were isolated from green coffee beans and dry coffee pulp and identified, and their effect on OA concentration in the coffee beans was quantified. In addition, the effects of different fermentation conditions (additional carbon source, different inoculum dose, and different types of coffee pulp) were evaluated based on OA quantification. Nine yeast isolates of Rhodotorula mucilaginosa and Wickerhamomyces anomalus were identified, and 11 LAB isolates of the species Enterococcus mundtii were identified. Of the 7 OAs quantified, quinic acid was the most abundant. The inoculation of isolated yeasts and LAB led to higher concentrations of OAs, showing the potential to realize modification of the OA composition of green coffee beans by re-fermentation with coffee-originated isolates.

Coffee bean processing: Emerging methods and their effects on chemical, biological and sensory properties

Emerging processing methods have been applied in coffee bean processing for improved sensory quality. The processes focus on optimizing the fermentation process of the coffee cherries and beans. This involves various pathways, including the formation of volatiles, flavor precursors and organic acids and the reduction in the concentrations of bioactive compounds. Comprehensive information regarding the effect of these emerging processes on the chemical, biological and sensory properties of the coffee beans is summarized. Emerging processes affected the coffee bean to various degrees depending on the raw material and the method used. The emerging methods promoted the reduction of bioactives such as caffeine and phenolics in coffee beans. Substantial improvement of these processes is needed to obtain coffee beans with improved biological activities. Effort to simplify the methods and optimize the post-fermentation process is crucial for the methods to be easily accessible by the producers and to produce defect-free coffee beans.

Unlocking the Aromatic Potential of Native Coffee Yeasts: From Isolation to a Biovolatile Platform

Postharvest processing of coffee has been shown to impact cup quality. Yeasts are known to modulate the sensory traits of the final cup of coffee after controlled fermentation at the farm. Here, we enumerated native coffee yeasts in a Nicaraguan farm during dry and semidry postharvest processing of Arabica and Robusta beans. Subsequently, 90 endogenous yeast strains were selected from the collected endogenous isolates, identified, and subjected to high-throughput fermentation and biovolatile generation in a model system mimicking postharvesting conditions. Untargeted volatile analysis by SPME-GC-MS enabled the identification of key aroma compounds generated by the yeast pool and demonstrated differences among strains. Several genera, including Pichia, Candida, and Hanseniaspora, showed both strain- and species-level variability in volatile generation and profiles. This fermentation platform and biovolatile database could represent a versatile opportunity to accelerate the development of yeast starter cultures for generating specific and desired sensory attributes in the final cup of coffee.

Performance of Mixed-Microbial Culture from Civet Fecal Suspensions on Physicochemical Composition of Wet Fermented Arabica Coffee

This study aimed to evaluate the effects of mixed microbial culture from civet fecal suspension used as the inoculum for the fermentation of Arabica coffee. The type of Arabica coffee used for the research was the unpeeled coffee or the Arabica coffee cherries. Different proportion of inoculum introduced was thoroughly evaluated to assess the appropriate concentration of inoculum (0-40% inoculums represented in treatment 0-4 or T0 to T4) that would be applied to the fermentation of Arabica coffee cherries. Results revealed that treatment 4 (T4) containing 40% of the inoculum could degrade the sugar of the coffee beans faster than that of the other treatments in which within 24 hours of the incubation approximately 84% of the sugar was converted. T4 also reached the lowest caffeine content (1.8%) of the fermented coffee beans among other that of other treatments while the control had higher caffeine content (2.2%).This was substantially significant as the Arabica coffee cherries fermented with mixed microbial civet fecal suspensions can remarkably reduce the sugar and caffeine content of the Arabica coffee beans.

Molecular, Chemical, and Sensory Attributes Fingerprinting of Self-Induced Anaerobic Fermented Coffees from Different Altitudes and Processing Methods

Coffee quality is achieved by performing good practices. This study aimed to evaluate coffees from different altitudes fermented with the self-induced anaerobic method (SIAF) and processed via natural (N) and pulped natural (PN). Molecular (PCR-DGGE), chemical (HPLC, ABTS, DPPH, ATR-FTIR, and GC-MS), and sensory analyses were performed. Leuconostoc predominated both processes and all altitudes. Hanseniaspora and Pichia predominated both processes at 800 and 1200 m. Acids were higher in N coffees for all altitudes. Acetic, malic acid and alcohols were the most abundant. Higher sensory scores were obtained in N (mainly at 1400 m-88.13). Floral and spices were perceived in all samples. ABTS capacity in roasted coffee increased with altitude in PN (2685.71, 2724.03, and 3847.14 µM trolox/g); meanwhile, the opposite was observed in N. High sensory scores were obtained in high altitudes. Alcohols and acids in roasted beans increase with altitude. Leuconostoc and Pichia showed potential as future coffee starters.

Chemical and sensory characterization of coffee from Coffea arabica cv. Mundo Novo and cv. Catuai Vermelho obtained by four different post-harvest processing methods

BACKGROUND

After the harvest, green coffee beans are dried on the farm using several methods: the wet process, natural process, pulped natural process, or mechanical demucilaging. This study evaluated how the choice of a specific processing method influenced the volatile organic compounds of the coffee beans, before and after roasting, and the sensory characteristics of the beverage. Coffea arabica beans of two varieties (cv. Mundo Novo and cv. Catuai Vermelho) were subjected to these four processing methods on a single farm in the Cerrado area of Brazil.

RESULTS

Analysis by gas chromatography-mass spectrometry headspace solid-phase microextraction identified 40 volatile organic compounds in green coffee beans and 37 in roasted beans. The main difference between post-harvest treatments was that naturally processed green beans of both varieties contained a different profile of alcohols, acids, and lactones. In medium-roasted beans, those differences were not observed. The coffee beverages had similar taste attributes but distinct flavor profiles. Some of the treatments resulted in specialty-grade coffee, whereas others did not.

CONCLUSION

The choice of a specific post-harvest processing method influences the volatile compounds found in green beans, the final beverage's flavor profile, and the cupping score, which can have a significant impact on the profitability of coffee farms' operations. © 2022 Society of Chemical Industry.

Effect of Prolonged Fermentations of Coffee Mucilage with Different Stages of Maturity on the Quality and Chemical Composition of the Bean

The sensory quality of coffee begins in the plant tree, where the characteristics of the fruits define the composition of the chemical precursors, which can be preserved or transformed in stages such as mucilage fermentation, and are the basis for the beverage attributes. This study evaluated three degrees of maturity and their comportment in fermentation under two temperatures and two-time extensions, establishing their sensory and chemical characteristics through analytical techniques such as liquid and gas chromatography. The effect of the prolongation time was evidenced for oxalic, quinic, citric acids, glucose, and fructose in two of the three degrees of maturity evaluated. The interaction of the process conditions increased the content of fructose and glucose in one of the states, being more evident at 20 °C. The treatments associated with the most advanced stage of maturity and with higher temperature decreased the scores of five sensory attributes and the fructose content increased by 48.50% and the glucose content increased by 47.31%. Advanced stages of maturity preserve quality standards, but their performance can be differential in postharvest processes, especially in those that are beyond the standards, such as those involving prolongations in different processes such as fermentation.

Microencapsulation by spray drying of coffee epiphytic yeasts Saccharomyces cerevisiae CCMA 0543 and Torulaspora delbrueckii CCMA 0684

The objective of this work was to evaluate the microencapsulation feasibility of Saccharomyces cerevisiae CCMA 0543 and Torulaspora delbrueckii CCMA 0684 in three different compositions of wall material by spray-dryer. The yeasts (109 CFU mL-1) were microencapsulated separately using maltodextrin (15%), maltodextrin (15%) with sucrose (2%), or maltose (2%) as wall material. The viability was evaluated for 6 months at two different temperatures (7 and 25 °C). The yield, cell viability after spray drying, and characterization of the microcapsules were performed. Results indicate that cell viability ranged between 94.06 and 97.97%. After 6 months, both yeasts stored at 7 °C and 25 °C presented 107 and 102 CFU mL-1, respectively. Regarding Fourier-transform infrared spectroscopy analysis, all microencapsulated yeasts presented typical spectra footprints of maltodextrin. After 6 months of storage, S. cerevisiae CCMA 0543 obtained a 10.8% increase in cell viability using maltodextrin with maltose as wall material compared to maltodextrin and maltodextrin with sucrose. However, T. delbrueckii CCMA 0684 obtained a 13.5% increase in cell viability using only maltodextrin. The study showed that maltodextrin as a wall material was efficient in the microencapsulation of yeasts. It is possible to assume that maltose incorporation increased the cell viability of S. cerevisiae CCMA 0543 during storage.

Interactive effect of post-harvest processing method, roasting degree, and brewing method on coffee metabolite profiles

Our study aims to characterize metabolite profiles, varying by major determinants in brewed coffee as follows: three post-harvest processing, three roasting degrees, and two brewing methods for C. arabicacv. Geisha. The major discriminant factor was the roasting degree, explaining 58.84% of the total variance of metabolite profiles. Despite a lesser degree of influence, specific metabolite profiles were retained in temperature-based brewing (Light, 11.11%; Medium, 12.01%; Dark, 22.15%) and post-harvest processing (Light, 35.29%; Medium, 29.64%; Dark, 22.03%), respectively. The effect of pressure application on the coffee metabolome was significant only for the light roasted beans (9.88%). Of note, the post-harvest processing method was featured by norharman (anaerobic), pimelic acid (natural), and xanthine (washed). In addition, our study proposed novel compounds, DiHOMEs, associated with potential health benefits, which will step-up the coffee values and suggest future direction of the development of coffee processing.

Microencapsulation of epiphytic coffee yeasts by spray drying using different wall materials: Implementation in coffee medium

The storage of microorganisms in liquid form is the main drawback of commercializing epiphytic coffee yeasts. This work aimed to evaluate the fermentative performance of microencapsulated yeasts by spray drying in a coffee peel and pulp media (CPM). The yeasts, Saccharomyces cerevisiae CCMA 0543, Torulaspora delbrueckii CCMA 0684, and Meyerozyma caribbica CCMA 1738, were microencapsulated using maltodextrin DE10 (MD), high maltose (MA), and whey powder (WP) as wall materials. A Central Composite Rotational Design (CCRD) was used to investigate the effect of operating parameters on the microcapsules' cell viability, drying yield, and water activity. Yeasts reached cell viability and drying yields above 90 and 50 %, respectively. WP maintained the cell viability of the three yeasts over 90 days of storage at room temperature (25 °C) and was selected as a wall material for the three yeasts. M. caribbica showed to be more sensitive to spray drying and less resistant to storage. Some differences were found in the fermentation of the CPM medium, but the microencapsulated yeasts maintained their biotechnological characteristics. Therefore, the microencapsulation of epiphytic coffee yeasts by spray drying was promising to be used in the coffee fermentation process.

Volatile Compound Characterization of Coffee (Coffea arabica) Processed at Different Fermentation Times Using SPME-GC-MS

Coffee is a beverage that is consumed due to its flavor and fragrance. In this investigation, we demonstrated the relations between different dry fermentation processes of coffee (aerobic, anaerobic, and atmosphere modified with CO2) and fermentation times (0, 24, 48, 72, and 96 h), with pH, acidity, and seven volatile marker compounds of coffee. Volatile compounds were extracted by solid phase microextraction (SPME) and an analysis was performed by gas chromatography−mass spectrometry (GC−MS). A significant effect (p < 0.05) between the fermentation time and a decrease in pH was demonstrated, as well as between the fermentation time and increasing acidity (p < 0.05). Acetic acid was positively correlated with the fermentation time, unlike 2-methylpyrazine, 2-furanmethanol, 2,6-dimethylpyrazine, and 5-methylfurfural, which were negatively correlated with the fermentation time. The aerobic and anaerobic fermentation treatments obtained high affinity with the seven volatile marker compounds analyzed due to the optimal environment for the development of the microorganisms that acted in this process. In contrast, in the fermentation process in an atmosphere modified with CO2, a negative affinity with the seven volatile compounds was evidenced, because this gas inactivated the development of microorganisms and inhibited their activity in the fermentation process.

Review on factors affecting coffee volatiles: from seed to cup

The objective of this review is to evaluate the influence of six factors on coffee volatiles. At present, the poor aroma from robusta or low-quality arabica coffee can be significantly improved by advanced technology, and this subject will continue to be further studied. On the other hand, inoculating various starter cultures in green coffee beans has become a popular research direction for promoting coffee aroma and flavor. Several surveys have indicated that shade and altitude can affect the content of coffee aroma precursors and volatile organic compounds (VOCs), which remain to be fully elucidated. The emergence of the new roasting process has greatly enriched the aroma composition of coffee. Cold-brew coffee is one of the most popular trends in coffee extraction currently, and its influence on coffee aroma is worthy of in-depth and detailed study. Omics technology will be one of the most important means to analyze coffee aroma components and their quality formation mechanism. A better understanding of the effect of each parameter on VOCs would assist coffee researchers and producers in the optimal selection of post-harvest parameters that favor the continuous production of flavorful and top-class coffee beans and beverages. © 2021 Society of Chemical Industry.

Characterization of bioactive, chemical, and sensory compounds from fermented coffees with different yeasts species

Selected yeasts for coffee fermentation are correlated with changes in chemical compounds and beverage sensory characteristics. This work aimed to evaluate the chemical and sensory modifications of coffee fermented with one yeast (Saccharomyces cerevisiae CCMA 0543, Candida parapsilosis CCMA 0544, or Torulaspora delbrueckii CCMA 0684) and in co-inoculation (from two to two and the three together) by dry processing. Real-time PCR analyzes, total phenolic content and antioxidant activity (DPPH, ABTS, and FRAP), liquid and gas chromatography, and sensory analysis were performed. Caparaó coffees showed a higher C. parapsilosis (6.14 Log cell.g^-1) population followed by S. cerevisiae (5.85 Log cell.g^-1) and T. delbrueckii (4.64 Log cell.g^-1). The total phenolic content has a strong and positive correlation with the fermentation time and the roasted beans and a moderate and positive correlation with DPPH, FRAP, and ABTS. Coffee inoculated with T. delbrueckii reduced caffeine concentration during the fermentation process. In co-cultivation, the trigonelline concentration showed the most significant decrease (around 4 mg.g^-1) when inoculated with S. cerevisiae and T. delbrueckii. Detection of some organic acids and volatile compounds during fermentation may indicate that the starter cultures used different metabolic routes. All co-inoculation treatments presented the best sensory scores (>86 points). In the inoculated fermentation, fruity, citric, molasses, freshness, and wine notes appeared. The co-inoculated treatment with S. cerevisiae CCMA 0543, C. parapsilosis CCMA 0544, and T. delbrueckii CCMA 0684 was the best, considering the diversity of sensory notes descriptors and the final concentration of organic acids.

Biotechnological Importance of Torulaspora delbrueckii: From the Obscurity to the Spotlight

Torulaspora delbrueckii has attracted interest in recent years, especially due to its biotechnological potential, arising from its flavor- and aroma-enhancing properties when used in wine, beer or bread dough fermentation, as well as from its remarkable resistance to osmotic and freezing stresses. In the present review, genomic, biochemical, and phenotypic features of T. delbrueckii are described, comparing them with other species, particularly with the biotechnologically well-established yeast, Saccharomyces cerevisiae. We conclude about the aspects that make this yeast a promising biotechnological model to be exploited in a wide range of industries, particularly in wine and bakery. A phylogenetic analysis was also performed, using the core proteome of T. delbrueckii, to compare the number of homologous proteins relative to the most closely related species, understanding the phylogenetic placement of this species with robust support. Lastly, the genetic tools available for T. delbrueckii improvement are discussed, focusing on adaptive laboratorial evolution and its potential.

Multivariate calibration applied to study of volatile predictors of arabica coffee quality

The chemical complexity of coffee influences the sensory evaluation of the beverage, the main method used to define the quality of the coffee. In view of the subjectivity that method offers, we propose the association of an instrumental method with multivariate calibration (PLS and GA-SVR) to predict the quality of arabica coffee as support for sensory analysis. Arabica coffee samples were submitted to sensory evaluation using the Specialty Coffee Association (SCA) protocol and HS-SPME-GC/MS analysis. The models presented RMSEp results from 0.20 to 0.25, within the evaluation range the quality levels of sensory attributes (0.25). For the fragrance/aroma attribute, a value of R²p equal to 0.8503 was reached. 15 volatile compounds were identified as responsible for predicting the quality of arabica coffee, among which, 1-nonadecene was first reported as an impact compound in the prediction of important sensory attributes.

The Altitude of Coffee Cultivation Causes Shifts in the Microbial Community Assembly and Biochemical Compounds in Natural Induced Anaerobic Fermentations

Coffee harvested in the Caparaó region (Minas Gerais, Brazil) is associated with high-quality coffee beans resulting in high-quality beverages. We characterize, microbiologically and chemically, fermented coffees from different altitudes through target NGS, chromatography, and conventional chemical assays. The genera Gluconobacter and Weissella were dominant in coffee’s fruits from altitudes 800 and 1,000 m. Among the Eukaryotic community, yeasts were the most dominant in all altitudes. The most dominant fungal genus was Cystofilobasidium, which inhabits cold environments and resists low temperatures. The content of acetic acid was higher at altitudes 1,200 and 1,400 m. Lactic acid and the genus Leuconostoc (Pearson: 0.93) were positively correlated. The relative concentration of volatile alcohols, especially of 2-heptanol, was high at all altitudes. Bacteria population was higher in coffees from 800 m, while at 1,000 m, fungi richness was favored. The altitude is an important variable that caused shifts in the microbial community and biochemical compounds content, even in coffees belonging to the same variety and cultivated in the same region under SIAF (self-induced anaerobic fermentation) conditions. Coffee from lower altitudes has higher volatile alcohols content, while high altitudes have esters, aldehydes, and total phenolics contents.

Co-inoculation of yeasts starters: A strategy to improve quality of low altitude Arabica coffee

The study aimed to improve the quality of dry-processed coffee grown at low altitudes through yeast inoculation, using three species (Saccharomyces cerevisiae CCMA 0543, Torulaspora delbrueckii CCMA 0684, and Candida parapsilosis CCMA 0544) singly and with co-inoculation for fermentation. Important chemical compounds and groups were analyzed by liquid and gas chromatography and Fourier-transform infrared spectroscopy (FTIR). The inoculated coffees with yeast populations around 10⁶ cell/g obtained the highest scores, and the co-inoculation with C. parapsilosis CCMA 0544 and T. delbrueckii CCMA 0684 had the highest score in the sensory analysis (85). Different descriptors were observed in each treatment, and body, flavor, balance, and aftertaste are strongly related to C. parapsilosis CCMA 0544. The fermentation process improved the quality of low-altitude coffees, and the combination of non-Saccharomyces yeasts (C. parapsilosis CCMA 0544 and T. delbrueckii CCMA 0684) was the most indicated as starter cultures.

Influence of yeast inoculation on the quality of fermented coffee (Coffea arabica var. Mundo Novo) processed by natural and pulped natural processes

Starter cultures during fermentation of Coffea arabica var. Mundo Novo processed in open stainless-steel vessels by natural and pulped natural methods were studied. The yeasts Meyerozyma caribbica (CCMA 0198), Saccharomyces cerevisiae (CCMA 0543), Candida parapsilosis (CCMA 0544), and Torulaspora delbrueckii (CCMA 0684) were inoculated separately in two different coffee processes: natural and pulped natural. The qPCR (real-time quantitative polymerase chain reaction) was used as a culture-independent method to monitor the inoculum's permanence. Changes in microbial metabolites (organic acids and volatile) production were evaluated by high-performance liquid chromatography (HPLC) and gas chromatograph-mass spectrometry (GC-MS), respectively. The sensory analysis was assessed in roasted beans. The fermentation lasted 27 h, and the coffee temperature ranged from 16.5 to 24.0 °C. The starter culture population was dominant throughout fermentation. S. cerevisiae (CCMA 0543) and T. delbrueckii (CCMA 0684) presented a higher population in natural processing. However, in pulped natural processing, M. caribbica (CCMA 0198) and C. parapsilosis (CCMA 0544) were the dominant populations. Citric, malic, and succinic acids were naturally present in coffee. Lactic, isobutyric, and isovaleric acids were detected at the end of the fermentation in different treatments. Lactic acid was detected in samples at the end of fermentation in Control and CCMA 0198 treatment. NAT coffee inoculated with CCMA 0684 presented isobutyric acid and isovaleric acid concentrations. Volatile compounds, such as 2,6-diethylpyrazine was detected in treatments inoculated with yeasts, but not in Controls. 2-acetoxymethylfuran was only detected in samples inoculated with CCMA 0198 from both NAT and PN methods. Samples fermented with S. cerevisiae (CCMA 0543) presented the highest sensorial scores in both processing (84.75 and 84.92). The inoculated coffee beans showed higher scores of sweetness, long aftertaste, and greater complexity. The starter cultures influenced the sensorial profiles through the synthesis of specific volatile constituents. However, considering all parameters analyzed, S. cerevisiae (CCMA 0543) would be the most suitable yeast for the var. Mundo Novo processed by both fermentation methods.

Novel stainless steel tanks enhances coffee fermentation quality

Fermenting in bioreactors can improve coffee quality, standardize the fermentation process, and generate specialty coffees. This work aimed to evaluate novel stainless steel bioreactors with inoculated and non-inoculated coffees processed via natural and pulped natural. Yeast and bacteria populations were evaluated and grown on Yeast Extract Peptone Glucose; De Man, Rogosa, and Sharpe; and Nutrient agar media. Volatile compounds from roasted beans were analyzed in a Gas Chromatography-Mass Spectrometry equipment, and the sensory perception was evaluated through a cup test. The mesophilic bacteria population was statistically significant in pulped natural coffee compared to yeast and lactic acid bacteria. Furans had the highest concentration among the chemical groups. Beverage inoculated with CCMA 0535 presented the highest SCA score. Prune, peach, and floral attributes were only perceived in Nat CCMA 0535. The sensory perception indicated that the inoculated yeasts modified the flavor attributes, enhanced the quality, and increase their SCA scores.

Coffee and Yeasts: From Flavor to Biotechnology

Coffee is one of the most consumed beverages in the world, and its popularity has prompted the necessity to constantly increase the variety and improve the characteristics of coffee as a general commodity. The popularity of coffee as a staple drink has also brought undesired side effects, since coffee production, processing and consumption are all accompanied by impressive quantities of coffee-related wastes which can be a threat to the environment. In this review, we integrated the main studies on fermentative yeasts used in coffee-related industries with emphasis on two different directions: (1) the role of yeast strains in the postharvest processing of coffee, the possibilities to use them as starting cultures for controlled fermentation and their impact on the sensorial quality of processed coffee, and (2) the potential to use yeasts to capitalize on coffee wastes—especially spent coffee grounds—in the form of eco-friendly biomass, biofuel or fine chemical production.