Nutritional profile and microbial stability of whey enriched Jamun juice as a value-added dairy by-product beverage

Abstract The development of functional beverages from dairy by-products and underutilized fruits represents a sustainable strategy for improving nutritional quality while reducing food waste. This study aimed to develop and evaluate pasteurized whey–Jamun ( Syzygium cumini L .) beverages with different whey-to-Jamun juice ratios (T1: 100% whey to T5: 100% Jamun). The formulations were standardized to 18 °Brix, pasteurized at 85 °C for 15 min, and stored under ambient conditions for six months. Physicochemical properties, phytochemical composition, antioxidant activity, microbiological quality, and sensory attributes were evaluated at 0, 3, and 6 months of storage. Increasing the proportion of Jamun juice significantly improved beverage appearance, color, flavor, aroma, and overall sensory acceptability while reducing the characteristic sensory limitations of whey. Formulations containing higher proportions of Jamun juice, particularly T4 (25% whey + 75% Jamun), achieved the best balance between sensory quality, nutritional value, and storage performance. Although vitamin C, anthocyanins, phenolic compounds, and antioxidant activity declined gradually during storage, Jamun-rich formulations retained higher levels of these bioactive constituents than whey-dominant formulations. Total plate counts remained below 4.3 × 10³ CFU mL⁻¹ throughout storage, whereas yeasts, molds, and Escherichia coli were not detected under the analytical conditions employed, indicating satisfactory microbiological quality. Overall, whey–Jamun beverages demonstrated considerable potential as sustainable value-added functional drinks by combining dairy by-product valorization with the utilization of an underexploited fruit resource. The results identify T4 (25% whey + 75% Jamun juice) as the most promising formulation, providing an optimal balance between nutritional quality, sensory acceptability, and microbiological stability during six months of ambient storage. Further studies incorporating instrumental color measurements, alternative preservation technologies, and degradation kinetics are recommended to optimize product shelf life and bioactive compound retention.