Development and quality evaluation of apple-enriched fermented whey beverage from dairy whey

Abstract

Six fermented apple-whey beverage formulations were initially evaluated sensorially for formulation selection. The formulation containing 60% fermented whey and 40% apple concentrate was selected for further characterization and storage studies. The selected formulation was inoculated with Lactobacillus delbrueckii subsp. bulgaricus (YC-381) and then stored at 4, 20, and 40 °C for up to 60 days and evaluated in triplicate for microbiological and physicochemical properties. Escherichia coli , Salmonella , and Shigella remained below the detection limit (< 1 log CFU/mL) throughout storage. Storage conditions significantly influenced measured quality parameters ( P < 0.05). Vitamin C content decreased during storage at all temperatures from 1.00 ± 0.06 mg/L on day 1 to 0.36 ± 0.04 mg/L at day 60 under refrigerated storage (4 °C), while total phenolic content also declined during storage. Lactic acid bacteria (LAB) counts remained above the commonly accepted viability threshold (> 7 log CFU/ml) for up to 30 days under refrigerated storage (4 °C), whereas counts declined more rapidly at 20 and 40 °C. pH and titratable acidity varied significantly with storage temperature, with faster acidification observed at 40 °C. Among the formulations evaluated, the beverage containing 60% fermented whey and 40% apple concentrate received the highest consumer acceptability scores, with hedonic ratings exceeding 7.5. Overall, refrigerated storage was associated with improved preservation of vitamin C and LAB survival compared with storage at 20 °C and 40 °C. These findings indicate the potential of producing apple–whey beverages as value-added dairy products with acceptable quality characteristics during the storage period evaluated. Nevertheless, reductions in vitamin C, phenolic compounds, and LAB counts were observed during storage, particularly at elevated temperatures. Further studies at pilot and industrial scales are needed to evaluate long-term stability and industrial acceptability.