Study of physicochemical parameters and spontaneous fermentation during traditional production of munkoyo, an indigenous beverage produced in Democratic Republic of Congo

The evolution of physicochemical parameters and spontaneous fermentation were investigated during traditional production of munkoyo. During munkoyo preparation, starch hydrolysis by amylolytic enzymes contained in munkoyo roots was performed at temperatures above 43 °C. After 90 h, pH decreased from 6.4–6.2 to 3.7–3.6; lactic acid concentration and acidity increased respectively from 4.4–15.0 mmol l−1 to 42.0–44.0 mmol l−1 and 0.05% to 0.45–0.6%; alcohol content did not exceed 394 mmol l−1. When the temperature dropped from 43–42 °C to 29–25 °C, in the first 15 h of fermentation, the rate of pH decrease was significant, from 6.4–6.2 to 4.1–4.0. The acidification of munkoyo was due to lactic acid, largely in the form of the d (−) lactate isomer. At temperatures around 20 °C, secondary products also contributed to the acidification of the beverage. Lactic fermentation, observed from 43 °C in the wort, was promoted by thermophilic lactic acid bacteria. Lactobacillus delbrueckii lactis was identified as the representative lactic acid bacteria. Alcohol production in munkoyo, beginning only after 15 h of fermentation, is due mainly to Saccharomyces cerevisiae.