Industrial-scale fermentation of Arara coffee in A 15,000 L bioreactor: Impacts of process variables on quality and sensory profiles.

Controlled fermentation is a strategic tool in coffee production, capable of enhancing the sensory attributes when integrated with appropriate pre- and post-harvest practices, thereby increasing market value and competitiveness. However, scaling up the production of fermented specialty coffees remains limited by technological and operational challenges. In this study, we demonstrate the feasibility and consistency of large-scale fermentation using 15,000 L stainless-steel bioreactor under different self-induced anaerobic fermentation (SIAF) conditions, with temperature control over 48 h. The homogeneity of the fermentations was assessed by sampling different positions along the bioreactor for physicochemical analyses. The industrial-scale fermentations behaved similarly to those observed on a smaller scale. Fermentation led to a reduction in pH and soluble solids content, an increase in temperature, and effective sugar consumption, accompanied by the production of alcohols and organic acids. Among the acids evaluated, lactic acid was predominant. Although the physicochemical parameters suggested homogeneity in the bioreactor, PERMANOVA indicated that only solid-state fermentations were uniform between positions. All processes produced specialty coffees. Solid-state SIAF, combined with the inoculation of Saccharomyces cerevisiae, improved the sensory score of the coffee by up to 2.7 points according to the SCA protocol, and increased the number of identified volatile compounds by 46 %. Sixty-one volatiles were identified in total, with ketones, aldehydes, and pyrazines accounting for 55 % of the profile. The results show that controlled fermentation in stainless steel bioreactors is a viable and effective way to produce specialty coffees with quality, uniformity and a differentiated sensory profile, especially in solid-state fermentations.