Microbiological and chemical quality of raw milk, Bongo and yoghurt from diverse sources in Mbarara District, Uganda: a cross-sectional analysis of contamination and safety indicators

Abstract

This study assessed the microbiological and chemical quality of milk, Bongo, and yoghurt collected from different points along the dairy value chain in Mbarara District, Uganda, over three sampling rounds between October and December 2024. A total of 270 samples were analyzed, comprising 162 milk samples from farms, collection centers, and processors, as well as 54 yoghurt and 54 Bongo samples from processors. Microbiological quality was evaluated using standard plate count methods to determine total viable counts (TVC), Escherichia coli, and yeasts and moulds, while Salmonella was detected qualitatively. Chemical quality was assessed through pH and titratable acidity following ISO protocols. Overall results showed that milk from informal collection centers had the highest contamination (TVC 8.73 log CFU/mL; E. coli 4.02 log CFU/mL). Yeasts and moulds were highest (5.55 log CFU/mL) in yoghurt from small-scale processors. Salmonella was detected only in milk from farms and informal collection centers. Milk from formal farms had the highest pH (7.01), whereas yogurt from small-scale processors highest titratable acidity (0.93% lactic acid). Statistical analysis (one-way ANOVA, Tukey’s test, p < 0.05) showed variation in quality along the dairy value chain hence the need for improved hygiene and processing practices, especially in informal sectors.