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.

Effect of fermentation on the physicochemical characteristics and sensory quality of Arabica coffee

This work aims to assess the physicochemical characteristics and final sensory quality of Yellow Catuai IAC 62 Arabica coffee fermented with Saccharomyces cerevisiae. For such a purpose, a Composite Central Rotational Design (CCRD) was performed to investigate how fermentation time,temperature and pH conditions, moisture content and concentration of sugars and organic acids affect its sensory quality on two different roast levels in accordance with Specialty Coffee Association (SCA) protocols. It was found that fructose concentration decreased from 12 g/L to around 5 g/L during fermentation, regardless of temperature condition. Furthermore, longer fermentation times and higher temperatures have lowered sucrose and glucose concentrations from 4 to 2 g/L and 7 g/L to zero, respectively. Glycerol concentration was higher as time and temperature increased, and optimal conditions ranged at temperatures between 24 °C and 32 °C from 35 to 45 h of fermentation time. pH decreased as fermentation time elapsed, but there was a more significant reduction due to higher temperatures, starting at around pH 5 and, lower than 4 under extreme conditions. Contents of organic acids such as acetic, propionic, succinic, and lactic acids, were measured at the final stage of each fermentation process under studied conditions. It was observed that coffee samples achieved final scores ranging from 81 to 85 (SCA score), even in longer times and extreme temperature conditions, thus all samples have been classified as specialty coffees. This work described the initial step towards parameterizing fermentation processes, given that the response variables of temperature and fermentation time, were optimal and enhanced the sensory quality of coffee as beverage. Saccharomyces cerevisiae, a commercial product which has already been made available for producers, can ensure an increase in the sensory quality of coffee.

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.

Coffee Flavor: A Review

Flavor continues to be a driving force for coffee’s continued growth in the beverage market today. Studies have identified the sensory aspects and volatile and non-volatile compounds that characterize the flavor of different coffees. This review discusses aspects that influence coffee drinking and aspects such as environment, processing, and preparation that influence flavor. This summary of research studies employed sensory analysis (either descriptive and discrimination testing and or consumer testing) and chemical analysis to determine the impact aspects on coffee flavor.

Antioxidant Properties of Fermented Green Coffee Beans with Wickerhamomyces anomalus (Strain KNU18Y3)

A few yeast species have been tested frequently to improve the tastes, flavors, and other important quality parameters of coffee. However, continuing evaluations of different yeast species for fermenting green coffee beans will have a significant positive contribution to the coffee industry. This experiment was conducted to evaluate the antioxidant properties, total phenol content (TPC), total flavonoid content (TFC), total tannin content (TTC), and the consumer acceptability of fermented green coffee beans with Wickerhamomyces anomalu. The coffee beans were roasted at different roasting conditions (light, medium, and dark). There was no significant (p > 0.05) difference between the yeast-fermented and non-fermented coffee with regard to the oxygen radical absorbance capacity (ORAC) values in medium and dark roasted coffee. Similarly, the superoxide dismutase-like (SOD)-like activity did not significantly differ in all roasting conditions. However, the SOD-like activity was significantly different (p < 0.05), particularly within light roasted and medium roasted, and between light roasted and dark roasted in both the control and fermented coffee extracts. The 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and ferric reducing antioxidant power (FRAP) were improved in fermented coffee beans. There was a significant (p ≤ 0.05) difference between the yeast-fermented and non-fermented coffee with respect to the TPC and TFC in all roasting types and the TTC in the light and dark roasting conditions. The fermentation of green coffee beans with W. anomalus increased the TPC and TFC. However, the TTC was lower in the fermented coffee beans compared to the non-fermented coffee beans in medium and dark roasted coffee. In general, fermentation of green coffee beans with W. anomalus has the potential to improve the functionality of coffee beans.

Antioxidant Activity, Total Polyphenol, Flavonoid and Tannin Contents of Fermented Green Coffee Beans with Selected Yeasts

We examined the antioxidant activity, total polyphenol content (TPC), total flavonoid content (TFC), total tannin content (TTC) and physical characteristics of green coffee beans fermented with selected yeasts. There was no significant (p > 0.05) interaction effect between yeast-fermented coffee extracts and duration of fermentation on antioxidant activity (oxygen radical absorbance capacity [ORAC] and superoxide dismutase-like [SOD-like] activity). However, the mean of the antioxidant activity (ORAC and SOD-like activity) significantly (p < 0.05) increased in the fermented coffee extracts compared to unfermented coffee. There were significant (p < 0.05) interaction effects between yeast-fermented coffee extracts and duration of fermentation (24 h and 48 h) on the TPC, TFC, TTC and pH of the fermented solution and on the colors of the ground-roasted coffee. The TPC showed a pattern of increase in samples Ferm-1 and Ferm-3 as fermentation time increased from 24 h to 48 h. However, a decreasing TPC trend was observed in Ferm-2 as the number of fermentation hours increased from 24 to 48. The fermented coffee beans had a significantly higher flavonoid content than the unfermented coffee beans, while fermentation significantly decreased the tannin content compared to that in unfermented coffee.

The Role of Microbes in Coffee Fermentation and Their Impact on Coffee Quality

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 flavour and aroma of the coffee. This is the result of a new insight into the development of unique flavoured coffee and into engaging with the coffee market to better benefit. This 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.