BEHAVIOR OF MALIC ACID IN COFFEE PARAISO SUBMITTED TO FERMENTATION

Malic acid, naturally present in coffee fruit, is very important for beverage quality, influencing the chemical profile and sensory attributes. During the fermentation process, malic acid can be produced or consumed by the microbial community, mainly by lactic acid bacteria. This study aimed to evaluate malic acid levels in coffee cherries subjected to different fermentation processes. Fermentations were carried out using coffee of the species Coffea arabica, cultivar Paraíso, in 200-liter high-density polyethylene bioreactors. Two types of cherries were used: natural cherry (NC) and pulped cherry (PC). The fermentations were conducted according to the SIAF methodology, in both dry (solid-state) and submerged conditions, without temperature control, for 60 and 108 hours. The experiments were carried out at the Estrela Carvalho farm, located at an altitude of 1100 meters, in Coromandel (MG), in the Cerrado Mineiro region. At the end of the fermentation, samples of the fruits were taken to determine the concentration of malic acid by high-performance liquid chromatography. The NC and PC fruits initially showed malic acid levels of 4.82±0.59 and 1.14±0.069 mg/g, respectively. These results revealed that pulping alone already caused differences in acid content. Throughout fermentation, a decrease in concentrations was observed. In solid-state processes, the levels at 60 and 108 hours were 2.48±0.32 and 1.30±0.048 mg/g for NC fruits, and 0.77±0.044 and 0.61±0.22 mg/g for PC fruits, respectively. In submerged fermentations, the values found were 2.41±0.37 and 1.23±0.23 mg/g for NC fruits, and 0.17±0.072 and 0.21±0.13 mg/g for PC fruits at 60 and 108 hours, respectively. For NC fruits, both solid-state and submerged fermentations resulted in similar malic acid levels at the same processing times. However, for PC fruits, the presence of water during fermentation led to a greater reduction in acid content. This difference is likely associated with the presence of the skin, which can protect against compound leaching during fermentation. These results show that microorganisms were able to consume and degrade malic acid during fermentation, converting it into other acids, such as lactic acid. Although both methods can produce high-quality specialty coffees, they lead to distinct chemical and sensory profiles. Therefore, the choice of fermentation pathway should align with the desired characteristics of the product and production goals.