Compreendendo o impacto da fermentação de café em biorreatores fechados na microbiota e na qualidade sensorial do café

Abstract

Coffee is one of the most popular non-alcoholic beverages consumed worldwide, and its quality is involved with the aroma and taste of the beverage. Fermentation in closed environments, in induced anaerobiosis, with inoculation of starter cultures are some of the recently used methodologies that can contribute to the production of coffee with unique characteristics. The objective of the work was to characterize the chemical, sensorial, and microbiological profile of the process involving fermentation in the whole fruit, followed by peeling and drying in parchment with remaining mucilage. Besides, to know the microorganisms present in spontaneous fermentation and to evaluate the effect of the beverage through the inoculation of Saccharomyces cerevisiae CCMA 0543 in different fermentation times. New World cherry coffees were evaluated in treatment 1 (0 hours), 2 (24 hours), 3 (48 hours), 4 (72 hours), and 5 (96 hours) in the inoculated fermentation and spontaneous fermentation (control). Fermentation took place in closed bioreactors, in a simple batch system. The isolates were identified by the protein profile (MALDI-TOF MS) and DNA sequencing. Real-time PCR quantification (qPCR) was performed to assess the persistence of the inoculated S. cerevisiae strain. Sugars and organic acids were quantified by high-performance liquid chromatography (HPLC) and volatile compounds identified by gas chromatography coupled with mass spectrometry (GC-MS) during fermentation and drying. Sensory analysis was performed in roasted coffee by time dominance of sensations (TDS) analysis. In spontaneous fermentation, the time of 36 and 48 hours presented the largest populations of microorganisms. Bacteria dominated the fermentation process in all treatments. At the beginning of drying, the bacterial population was high, approximately 4.9 CFU/g, decreasing until the end of drying, while the yeast population dominated (5.4 CFU/ml) at the end of drying. A total of 228 isolates of bacteria and yeasts were identified. The inoculated strain remained viable during the process. The fermentation inoculated with S. cerevisiae CCMA 0543 showed high concentrations of citric acid in treatments 1 (15.15 mg/g) and 5 (14.39 mg/g). Succinic acid was present in all treatments, and the highest concentration was in treatment 5 (5.03 mg/g). The acetic acid concentration did not interfere in the quality of the beverage varying from 3.25 to 14.93 mg/g in spontaneous fermentation and from 1.89 to 15.71 mg/g in inoculated fermentation. The concentration of glucose and fructose decreased during fermentation in the bioreactor and drying. A total of 118 volatile compounds were identified in all samples. The CCMA 0543 treatment was characterized by the production of volatile compounds belonging to the classes of furans, pyrazines, and ketones in treatments 2 and 4 and acids in treatments 1, 3, and 5. Coffee inoculated up to 48 hours had caramel flavors as dominant, and fruity in 72 hours, and a complexity of flavors was observed in 96 hours. The integration of semi-solid fermentation technology in anaerobiosis induced by the action of the inoculated yeast in the process used is an innovative strategy. This method has shown positive results for the beverage, adding flavors to the quality of the beverage.