Coffee fermentation is a complex process, mainly involving bacteria and yeasts, whose interaction influences beverage quality. The way this process is conducted affects the interactions between these microorganisms. To identify microbial diversity in fermenting coffee, samples were collected from 20 farms in the Department of Quindío, Colombia. Metataxonomic analyses using high-throughput sequencing and volatile organic compound identification in green coffee beans were performed with HS-SPME and GC-MS. Potential relationships between some families and genera with different fermentation types and coffee quality were evaluated. In our results, samples presented with high richness and diversity were greater for bacteria than for yeast/fungi. The Enterobacteriaceae family dominated at the beginning of fermentation, while Leuconostoc, Lactobacillus, Gluconobacter, and Acetobacter genera dominated at the end, a finding related to pH reduction and final coffee quality. Overall, 167 fungal families were identified, but Saccharomyceaceae dominated from the beginning. Alcohols and esters were the main chemical classes identified in green coffee bean samples from these fermentations. These results will facilitate the identification process conditions that influence the presence and abundance of microorganisms related to quality as well as contributing to the design of strategies to conduct fermentations to improve the final quality of coffee.

Fermentation of coffee mucilage is a spontaneous process caused by microorganisms growing in the environment, which is influenced by factors such as the variety, climate and fruit maturity. These external factors play an important role in fermentation evolution because they have effect on the microorganism activity and the substrate transformation time. The objective in this research was to evaluate the effect of different fermentation wet process and evaluated their effect on coffee quality (Coffea arabica L.), as well as on organic acid concentrations and volatile organic compounds content, in the green coffee beans. The study was divided in two phases, one in which the pulping time was delayed and the fermentation methods were modified, and the second phase in which a bioreactor was used to control the pH and temperature of the coffee mass during fermentation. Two control treatments were used: without fermentation (mechanical removal of mucilage) and the traditional fermentation done in the farm. Significant differences in coffee quality were observed. The best quality was obtained from the treatments that used short process times and low temperatures. The concentrations of acetic, lactic and citric acids between the treatments and the control treatments were different. Higher contents of esters and ketones were found in the coffee that obtained the highest quality. The assessed processes lead to the conclusions that it is possible to improve coffee quality throughout introducing changes in the fermentation process, as well as modulating the acidity and fragrance of the final product.

Controlled fermentation processes have high potential for improving coffee quality. The effect of fermentation temperature on beverage quality was investigated with coffee cultivated at elevations between 1166 and 1928 m. A completely randomized design was carried out at five elevation ranges at 200 m intervals in five farms per elevation range, and two temperatures (15 °C and 30 °C), which were maintained in a temperature-controlled bioreactor. Each temperature-controlled fermentation batch had a spontaneous fermentation batch (control treatment). Microbial identification of LAB and yeast was performed using a Biolog™ MicroStation™ ID System, and cup quality tests were performed following the SCA protocol. Tests conducted at 15 °C showed higher microbial community activity on the substrates used, indicating greater transformation potential than those conducted at 30 °C or those of spontaneous fermentation. According to Wilcoxon and Kruskal–Wallis tests, temperature-controlled fermentation resulted in high-quality coffee for all elevation ranges, with coffee from higher elevations and processed at controlled temperatures of 15 °C receiving the highest cup scores compared to coffee that was subjected to 30 °C. These results suggest that controlled temperature can be used to design standardized fermentation processes in order to enhance coffee quality through differentiated sensory profiles.

Con el fin de contribuir a que la subjetividad en la identificación de los estados de madurez disminuya, Cenicafé desarrolló una escala de color para frutos de café, que permite reconocer ocho estados de madurez, basados en el cambio de color de los frutos, identificándolos mediante una escala numérica, que va desde 1 para los frutos inmaduros hasta 8 para los frutos secos. Este Avance Técnico presenta información acerca del desarrollo de la herramienta, la manera de usarla y cómo lograr su mejor aprovechamiento.

Temperature control is the starting point for the development of controlled fermentation and improving coffee quality. The characteristics of coffee varieties can influence fermentation behavior. To evaluate the effect of the coffee variety on the behavior of controlled fermentation and on coffee quality, a completely randomized design was used with three varieties (Castillo, Cenicafé1 and Tabi) and two control temperatures (15 and 30 °C). Spontaneous fermentation was the control for each controlled process. The fermentation time, pH, glucose and lactic acid contents, as well as, the count of mesophiles, yeasts, lactic acid bacteria (LAB) and acetic acid bacteria (AAB), were assessed. The sensory quality of the coffee was classified as very good and excellent based on the variety, with averages above 82 Specialty Coffee Association (SCA) points. The highest values were for the Cenicafé1 variety. Fermentation behaviors were similar among varieties but not based on the given condition. Compared with spontaneous fermentation, the treatment at 15 °C prolonged the degradation of mucilage in more than 24 h; additionally, there were differences in the final pH values, less than 3.5 and close to 4.0, respectively. Quality was not significantly different between the controlled fermentation and the spontaneous fermentation (Wilcoxon test p > 0.05) or between fermentation temperatures (Kruskal–Wallis test p > 0.05).

En Cenicafé se desarrolló un método a través del cual se utiliza un dispositivo sencillo, con el que se determina objetiva y confiablemente el punto de lavado.