Microbiological and Quality Assessment of Ready-to-serve Beverage Produced from Blends of Yoghurt and Watermelon Juice

Abstract

This study evaluated the microbiological and qualitative properties of a ready-to-serve beverage produced from blends of yoghurt and watermelon juice. Yoghurt, known for its probiotic benefits, and watermelon juice, valued for its hydrating and antioxidant properties, were combined in varying proportions (10%–50% substitutions) to assess their impact on microbial load and product stability. The microbiological analysis focused on Total Viable Bacterial Count (TVBC), Total Coliform Count (TCC), and Yeast and Mould Count. Results showed that pure yoghurt exhibited the highest TVBC (5.87 × 10⁴ CFU/mL) due to the presence of live probiotic cultures, while blends with higher watermelon juice content demonstrated significantly reduced bacterial counts, suggesting a possible inhibitory effect of watermelon components. All samples tested negative for coliforms, indicating good hygienic practices during processing. Interestingly, yeast and mould counts were highest in yoghurt-watermelon blends (especially YG70–WM30: 1.71 × 10² CFU/mL), suggesting that the combination of sugar, moisture, and protein provided favourable conditions for fungal growth. These findings highlight the importance of careful formulation and preservation in dairy-fruit beverages. Future work should explore spoilage dynamics during storage and investigate natural antifungal strategies to improve shelf life and safety.