Abstract

This study evaluated the effects of milk type, UV-C treatment condition and refrigerated storage on selected quality characteristics of ayran. Cow and buffalo milk was standardised to 1.5% fat and subjected to UV-C treatment at flow rates of 20 or 40 mL/min, corresponding to calculated nominal doses of 54 and 27 J/mL, respectively. Conventionally pasteurised milks were used as controls. During ayran production, all samples were subsequently heated at 90 °C for 5 min, fermented to pH 4.30 and stored at 4 °C for 14 days. Physicochemical, instrumental textural, colour, starter culture and organic acid characteristics were evaluated during storage. The measured responses varied according to milk matrix, UV-C treatment condition and storage duration, and no single treatment was consistently favourable for all parameters. At day 14, C20 showed the highest dry matter content (5.12%), firmness (15.43 g), consistency (292.32 g·s) and Lactobacillus delbrueckii subsp. bulgaricus count (7.52 log CFU/mL). In contrast, B40 showed the highest Streptococcus thermophilus count (8.14 log CFU/mL), lactic acid concentration (15,092.95 mg/kg) and concentrations of most of the other organic acids evaluated, whereas C20 showed the highest acetic acid concentration (1122.14 mg/kg). During storage, pH, dry matter, citric acid, ascorbic acid and starter culture counts generally decreased, while most other organic acids increased. Instrumental colour parameters also changed according to treatment group and storage duration. These findings provide preliminary laboratory-scale evidence that UV-C pretreatment can influence selected quality characteristics of ayran. However, because UV-C-treated samples subsequently underwent thermal processing, the results represent a combined UV-C and thermal processing sequence rather than an exclusively non-thermal process. Sensory acceptability, pathogenic and spoilage microorganisms, oxidative stability, extended shelf life, and scale-up performance should be evaluated before practical application is considered.

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