RELATIONSHIP BETWEEN pH AND ORGANIC ACIDS IN THE ACIDITY OF FERMENTED COFFEES

The application of fermentation in coffee processing has proven to be a promising technique for enhancing its sensory qualities. Acidity, a valued sensory attribute in coffee, is influenced by the presence of organic acids, which are natural constituents of coffee fruits and can also be produced during the fermentation stage. This study aimed to evaluate the correlation between titratable acidity, pH, and organic acids in coffee fruits subjected to fermentation. Arabica coffees from the cultivars Arara and IPR 103 were used, obtained from the Federal University of São João del-Rei (Sete Lagoas–MG; 19°28′4″S, 44°14′52″W), as well as Catuaí 144, sourced from Fazenda São João–DB (Varjão de Minas–MG; 18°22′40″S, 46°01′55″W). Ripe cherry fruits were harvested, washed, and placed in sealed 2 L bioreactors. Fermentation was carried out for 24, 48, and 72 hours without temperature control. After fermentation, fruit samples were collected and preserved at -20°C until analysis. The fruits were thawed, blended in water, and the liquid fraction was used for the quantification of organic acids (citric, malic, succinic, lactic, and acetic) by liquid chromatography. The pH and titratable acidity analyses were performed using the powder of lyophilized fruits reconstituted in water, following methodologies from the Association of Official Analytical Chemists. The correlation between variables was analyzed using Pearson's correlation coefficient, calculated with Excel software. Results showed a negative correlation between pH and titratable acidity (r = -0.79), a behavior that is expected, since a reduction in pH reflects an increase in acidity. Acidity showed moderate correlation only with succinic acid (r = 0.68) and lactic acid (r = 0.77), indicating that increased concentrations of these compounds contribute to higher acidity. pH showed a negative correlation with lactic acid (r = -0.86). More acidic environments favor the proliferation of lactic acid bacteria, which produce this acid. A negative correlation was observed between malic acid and lactic acid (r = -0.53), which may reflect the occurrence of malolactic fermentation, in which malic acid is converted into lactic acid. The positive correlation between pH and malic acid (r = 0.69) suggests that higher pH conditions inhibit this conversion. It is concluded that the dynamics of certain organic acids during coffee fermentation directly influence acidity and are related to pH behavior, which in turn affects microbial activity. Understanding these correlations contributes to guiding fermentation practices that promote coffees with greater sensory value.