Efeitos da utilização de biorreatores de diferentes escalas na fermentação de café

Abstract

The use of bioreactors in the fermentation of coffee becomes a fundamental part for the control of the process, making it possible to increase the quality of the final product and the volume. The objective of this work was to evaluate the quality of coffees fermented under induced anaerobiosis (SIAF) in 50 L, 1400 L and 7000 L bioreactors using the Saccharomyces cerevisiae strain CCMA 0543 as starter culture. The population of S. cerevisiae was measured during fermentation and drying using qPCR technique. The profile of volatile and non-volatile compounds was evaluated during fermentation and drying by GC-MS (gas chromatography coupled to mass spectrometry) and HPLC (high-performance liquid chromatography), respectively. The sensorial quality was evaluated by the SCA (Specialty Coffee Association) method. Fermented coffees of the Acaiá variety were selected from the southern region of the state of Minas Gerais at altitudes of 900 m. The highest microbial population was found in the 7000 L bioreactor (6.47 Log cell.g -1), followed by the 1400 L (6.06 Log cell.g -1) and 50 L (5.83 Log cell.g -1) bioreactor. Aldehydes were found in higher concentrations in the 50 L (5.08 mg/g) and 1400 L (4.43 mg/g) bioreactors, responsible for fruity and chocolate sensory notes. In the 7000 L bioreactor the ethers stood out, reminding floral and sweet notes. Lactic acid was detected in greater abundance (11.59 g/kg), contributing to the acidity of the beverage. Trigonelline was the bioactive compound found in higher concentration in the three bioreactors evaluated and is responsible for the bitterness. The result of the sensory evaluation indicates that the fermentative process when well conducted, generates compounds of interest for the classification of the beverage, influencing the sensory notes and consequently the score given by the tasters. All treatments presented scores above 80 points, classifying the coffees as special coffees according to the SCA. The staggering of bioreactors in coffee fermentation using starter cultures is promising, and can increase the quality of the beverage, as long as all the stages of the process are monitored.