PHYSICOCHEMICAL PARAMETER PROFILE THROUGHOUT ARABICA COFFEE FERMENTATION

Coffee fermentation is a post-harvest technology capable of accentuating desired sensory characteristics and making the product more attractive. The objective of this study was to evaluate the variation of pH, °Brix and temperature during solid state fermentation (FES) and submerged fermentation (FSub) of coffee fruits of the cultivars Arara and Catuaí. Fruits grown on the campus of the Federal University of São João del-Rei, in Sete Lagoas/MG (latitude 19°46'47" S, longitude 44°24'53" W)  were harvested manually and washed. To start the FES, 1.5 L of fruits were transferred to reactors with 2 L capacity. In the FSub, 450 ml of water was also added to the reactors. Lyophilized cells of Saccharomyces cerevisiae were resuspended in water (10¹⁰ cells/mL) and 1% (v/v) of this suspension was added to each reactor. After being closed, the reactors remained in the field for 48 and 72 hours. At the beginning and end of the fermentations, the temperature of the coffee bed was measured and fruit samples were taken to determine the °Brix and pH. In fermentations with the Catuaí cultivar, the pH started from 6.07 (+0.01), reaching, in 48 and 72 hours of process, respectively, 5.27 (+0.03) and 4.26 (+0.14) in Fsub and 5.26 (+0.02) and 4.82 (+0.15) in FES. The fermentations with the Arara cultivar followed a similar behavior: the initial values, around 5.62 (+0.03), decreased in 48 and 72 hours of fermentation to 4.61 (+0.03) and 4.44 (+0.03) in the FSub, and to 5.03 (+0.06) and 4.70 (+0.06) in the FES. Temperatures showed similar values between the FES and Fsub processes, and progressive increases. In the processes with the Catuaí cultivar, the initial temperature was approximately 26°C, reaching 29°C in 72 h; in the fermentations with Arara coffee, the initial temperatures were 24.5°C, reaching 27.7°C in Fsub and 26.5°C in FES. Regarding °Brix, a significant drop was observed in Fsub: with Catuaí, the values ​​went from 21.0 (+4.1) to 5.0 (+0.3); with Arara, from 18 (+5.5) to 4.00 (+0.0). In FES, in 72 h of process, °Brix dropped to 13.0 (+1.3) and 11 (+0.6) for the Catuaí and Arara cultivars, respectively. These data confirm the occurrence of appropriate fermentation.