Influence of fermentation temperature on microbial community composition and physicochemical properties of mabisi, a traditionally fermented milk

Fermentation temperature is a crucial factor in the production of fermented dairy products. This study investigated the influence of fermentation temperature on physiochemical properties and the composition of the microbial communities of two types of mabisi: tonga and barotse mabisi. Mabisi is a traditionally fermented milk product made in Zambia by spontaneous fermentation of raw milk at ambient temperature. The two types of mabisi were produced with tonga mabisi fermented at 20, 22, 25 and 30 degrees C, and barotse mabisi at 25 and 30 degrees C. The pH, titratable acidity, syneresis, consistency, microbial community composition and aroma compounds were determined. We found that fermentation at 20 and 22 degrees C was slower than at 25 degrees C but they all produced tonga mabisi with medium acidity (pH 4.2) and 'medium' consistency within 48 h. Fermentation was most rapid at 30 degrees C but resulted in a product with a 'thin' consistency. Fermentation temperature did not affect the microbial community composition of tonga mabisi, which remained diverse and complex with Lactococcus as the dominant fermenting genus. However, in barotse mabisi, at 25 degrees C, the product had 'thick' consistency and the microbial community composition was dominated by Lactococcus whereas at 30 degrees C the product was thicker, more acidic and dominated by Lactobacillus.