The essential role of spontaneous and starter yeasts in cocoa and coffee fermentation.

Yeasts are important microorganisms used in different fermentation processes. The cocoa beans must go through a correct fermentation process to obtain good-quality chocolate, which involves the action of yeasts and bacteria, and yeasts play a crucial role since they act in the first days of fermentation. In coffee, several studies have shown that the microbiota in the fruits is also a relevant factor. The fermentation process (regardless of the processing type) improves the beverage's quality. In this sense, studies using starter cultures in these two raw materials are important for better control of the process, and optimization of fermentation time, in addition to the improvement and diversification of volatile and non-volatile compounds produced by yeasts. Thus, this review discusses the importance and role of yeasts during fermentation, their metabolism, the produced compounds, and how yeast and the different chemical reactions help increase the quality of chocolate and coffee.

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.

Dominant microbial communities and biochemical profile of pulped natural fermented coffees growing in different altitudes.

Altitude changes the coffee fruits and beans composition before and after harvesting. We aimed to evaluate the effect of altitude on the microbial community structure associated with pulped coffee fruits under self-induced anaerobic fermentation (SIAF) and their acids, volatiles, and antioxidants biochemical profiles. The most abundant bacterial genera were Gluconobacter (800 m), Weissella (1,000 m), and Leclercia (1,200 and 1,400 m). Yeasts dominated the pulped natural fermentations within the fungal species, containing high abundances of Cystofilobasidium infirmominiatum, Wickerhamomyces anomalus, and Meyerozyma caribbica. Citric, alcohols, and caffeine were the most dominant compounds in SIAF among acids, volatiles, chemical groups, and antioxidants. High altitude coffees favor alcohols, aldehydes, and esters groups, while low altitude coffees favor phenols.

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.

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.

The use of mesophilic and lactic acid bacteria strains as starter cultures for improvement of coffee beans wet fermentation.

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; ß-linalool; ethyl linoleate; and ethyl 2-hydroxypropanoate could improve cupping qualities.

Organic acids produced during fermentation and sensory perception in specialty coffee using yeast starter culture.

Volatile and non-volatile compounds in coffee directly affect the beverage's quality. This study aimed to demonstrate how the organic acids and volatile profiles were impacted by coffee fermentation using four starter cultures (Meyerozyma caribbica (CCMA 0198), Saccharomyces cerevisiae (CCMA 0543), Candida parapsilosis (CCMA0544), and Torulaspora delbrueckii (CCMA 0684)) inoculated in two varieties of coffee (Bourbon Amarelo and Canário Amarelo) using natural and pulped natural processing methods and sensory perception. Real-time PCR (qPCR) was used to verify the dynamic behavior of yeast populations. Organic acids were detected using high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) was used to detected volatile compounds. Sensory analysis was performed on the roasted coffee. Citric, malic, succinic, lactic, oxalic, isobutyric, and propionic acids and 105 volatile compounds were detected. At the beginning of fermentation, treatments with natural processing presented higher number of volatiles compounds. After fermentation, the main compounds groups were acids, alcohols, and aldehydes. The perception of sensory attribute (fruity, nutty, cocoa) varied with the coffee variety, type of processing, and type of inoculum. The use of yeasts is an alternative for sensorial differentiation of coffee variety Canário Amarelo and Bourbon Amarelo. The stainless-steel containers showed good results for coffee fermentation.

Effect of Bacterial and Yeast Starters on the Formation of Volatile and Organic Acid Compounds in Coffee Beans and Selection of Flavors Markers Precursors During Wet Fermentation.

Coffee quality has recently become a high demand of coffee consumers, due to all the specialty coffees available on the market. Specialty coffees can be generated by favoring growth of some groups of microorganisms during fermentation or by using starters. Just as yeast, a variety of bacteria can be used to generate important flavor precursors. The aim of this work was to test the efficiency of coffee sterilization and adhesion of microbial cells on beans, to evaluate the effect of yeast and bacterial starters on the production of organic and volatile compounds, and selection of potential flavor marker precursors during the wet fermentation. Three yeast and six bacterial starters were inoculated in coffee beans. Coffee sterilization and microbial adhesion was observed by scanning electron microscopy (SEM). Organic compounds were detected by high performance liquid chromatography (HPLC) and volatile compounds by gas chromatography-mass spectrometry (GC-MS). Micrographs from the SEM showed that sterilization was efficient, because there were no microbial cells after autoclaving for 5 min. Also, it was observed an increase of microbial cells from 0 to 48 h of fermentation. Malic, lactic, and acetic acid were only detected in the bacterial treatments. Volatile compounds: 4-ethenyl-1,2-dimethoxybenzene, heptadecanol, 4-hydroxy-2-methylacetophenone, and 1-butanol,2-methyl were only found in yeast treatments. Guaiacol was only produced by the inoculated B. subtilis starters. In conclusion, yeast starters were better producers of volatile alcohols and bacterial starters of acid compounds. This study allowed the selection of potential flavor marker precursors, such as heptadecanol, 4-hydroxy-2-methylacetophenone, 7-methyl-4-octanol, and guaiacol.

Different inoculation methods for semi-dry processed coffee using yeasts as starter cultures.

This study evaluates the behavior of Saccharomyces (S.) cerevisiae (CCMA 0543), Candida (C.) parapsilosis (CCMA 0544), and Torulaspora (T.) delbrueckii (CCMA 0684) as starter cultures for semi-dry processed coffee using two inoculation methods: (1) direct inoculation and (2) bucket inoculation. The microbial population was evaluated by plating and real-time polymerase chain reaction (qPCR). The microbial metabolic changes of both bucket and direct inoculation methods during fermentation were evaluated using high performance liquid chromatography (HPLC), and gas chromatography-mass spectrometry (GC-MS). A sensorial test was also carried out. Citric and succinic acids were detected throughout the fermentation period. Chlorogenic acid concentration levels were higher for the bucket method after roasting. Roasted coffee beans also had a higher caffeine concentration, with the exception of the T. delbrueckii (CCMA0684) assay. Acids, pyrazines and pyridines were the main volatile compounds in both green and roasted coffee beans. Coffee cupping results proved that both inoculation methods scored well in terms of coffee quality. The bucket method favored the permanence of the microorganisms during coffee processing, especially the treatment inoculated with S. cerevisiae.