INFLUENCE OF PROCESSING METHODS ON CITRIC ACID CONCENTRATION IN MACAW COFFEE.

Citric acid is an organic acid naturally present in coffee fruits. Along with other acids, it directly contributes to the sensory attributes and overall quality of the beverage by promoting acidity. During fermentation processes, citric acid and other organic acids are catabolized by microorganisms such as lactic acid bacteria. Its biosynthesis, on the other hand, results from carbohydrate metabolism through the Krebs cycle, primarily carried out by yeasts. Yeasts and lactic acid bacteria are commonly isolated during the coffee fermentation process. The metabolism of these microorganisms is one of the main factors responsible for changes in citric acid content observed in the fruit. The variation in its levels is influenced by the fermentation methods and microbial activity. Thus, the aim of this study was to evaluate how different fermentation methods of coffee fruit affect citric acid concentration. Solid-state fermentations were carried out using coffee fruits in hermetically sealed 200-liter high-density polyethylene bioreactors for 84 hours, following the SIAF methodology. Coffee fruits of the species Coffea arabica, cultivar Arara, were used, either whole or pulped, referred to as natural cherry (NC) and pulped cherry (PC), respectively. The experiments were conducted at the Estrela Carvalho farm, located at an altitude of 1100 meters in the municipality of Coromandel (MG), in the Cerrado Mineiro region. Citric acid concentrations in the fruits were determined at the beginning (0 h) and at the end (84 h) of fermentation by liquid chromatography. At the end of fermentation, both NC and PC fruits showed a decrease in citric acid concentration. The levels of this acid, in mg/g, at 0 and 84 hours were 2.31±0.03 and 1.26±0.21 for NC, and 2.43±0.11 and 2.07±0.31 for PC, respectively. The initial acid content was not influenced by the fruit treatment (p>0.05), but after fermentation, the concentration in NC was lower than in PC (p<0.05). The method of processing the fruit prior to fermentation played a significant role in the citric acid content and possibly in the resulting acidity of the coffee. NC fruits tend to result in lower acidity after fermentation compared to PC fruits. Careful selection and control of these methods can consistently produce coffees with distinct sensory profiles. Since citric acid influences the acidity of the beverage, it is up to the producer to choose between NC and PC, depending on the desired sensory profile of the coffee.