Exploring coffee processing stages: Wet fermentation with and without Saccharomyces cerevisiae vs. Conventional...

The present study aimed to perform a wet coffee fermentation process using self-induced anaerobic fermentation (SIAF), with or without a starter culture, and a subsequent pulping stage to verify the influence on the beverage's quality. The ripe fruits were fermented in water using the SIAF method, with and without inoculating S. cerevisiae CCMA 0543, and were compared to a Conventional process (direct drying on suspended terraces). Samples were collected at different times of fermentation and drying for analysis of yeast population (qPCR), carbohydrates and organic acids (HPLC), protein profile (2-D SDS-PAGE), and volatile compounds (GC-MS). Sensory analysis was performed by certified tasters (Q-Graders). The treatment with S. cerevisiae (SC) demonstrated greater efficiency in consuming glucose and fructose, resulting in the lowest concentrations of these sugars at the end of fermentation (1.30 and 2.64 g/Kg, respectively). This treatment also showed increased lactic acid (8.76 g/Kg) and reduced acetic acid (6.40 g/Kg). The Conventional process presented a higher acetic acid content (10.12 g/Kg). Proteomic analysis revealed a unique protein expression profile in the SC treatment. After fermentation, a higher abundance of esters, aldehydes, alcohols, and acids was identified in the inoculated treatment. After roasting, furans, pyrazines, and other volatile compounds were predominant in this coffee. This treatment was the only one classified as specialty coffee (score 85.00). The inoculation of S. cerevisiae using the SIAF method proved effective in enhancing the quality of wet coffee, producing consistent and high-quality beverages that meet specialty coffee standards.