Impact of scaling up on coffee fermentation using starter cultures

Abstract

Bioreactors are crucial for controlling the fermentation process and improving coffee quality. Bioreactors of different sizes have been suggested to meet the increasing demand for specialty coffees. This study aimed to assess the quality of fermented coffees under anaerobic conditions induced by microbial strains (SIAF) in bioreactors of 50, 1400, and 7000 liters. A key aspect of this study was the use of starter cultures, particularly Saccharomyces cerevisiae CCMA 0543, which was inoculated and monitored using qPCR. The volatile and non-volatile compound profiles of fruits and dried coffee were analyzed using gas and liquid chromatography-mass, respectively. The highest microbial population was observed in the 7000 L bioreactor (6.47 Log10 cells/g), followed by the 1400 L (6.06 Log10 cells/g) and 50 L (5.83 Log10 cells/g) bioreactors. Aldehydes were found in higher concentrations in the 50 L (5.08 mg/g) and 1400 L (4.43 mg/g) bioreactors, contributing to fruity and chocolate sensory notes. Ester compounds were predominant in the 7000 L bioreactor and were associated with floral and sweet notes. Lactic acid was detected in greater abundance (11.59 g/kg), contributing to the beverage's acidity. All treatments were classified as specialty coffees (with scores of 86, 87, and 83, respectively). Using bioreactors designed for coffee fermentation and starter cultures under SIAF holds promise for generating volatile, non-volatile, and sensory compound profiles.

Keywords

• Solid fermentation
• S. cerevisiae CCMA 0543
• Specialty coffees
• Bioreactor