Effect of Refrigerated Fermentation on Lactic Acid Bacteria Growth in Milk Kefir

Background: Kefir, a probiotic-rich fermented milk product, offers significant health benefits. However, its ethanol content remains a concern for halal compliance. This study assesses the impact of low-temperature fermentation on ethanol content, Lactic Acid Bacteria (LAB) viability, and antioxidant activity of milk kefir as key quality indicators relevant to halal compliance and potential health benefits. Methods: Milk kefir was fermented at ۲–۱۰ °C using varying starter concentrations (۵–۵۰%) and analyzed for pH, LAB viability, ethanol content (determined by iodometric titration), and antioxidant activity (using the ۲,۲-diphenyl-۱-picrylhydrazyl [DPPH] method). Sensory properties were assessed using a hedonic quality test with ۱۵ semi-trained panelists. Statistical analysis was conducted using analysis of variance (ANOVA) with Tukey's post hoc test (p<۰.۰۵), and LAB growth kinetics were modeled using Gaussian regression. Results: Fermentation at low temperatures (۲–۱۰ °C) for ۷۲ h reduced ethanol levels (<۰.۵%), ensuring compliance with halal certification standards while maintaining optimal LAB growth (۱۰۷ Colony Forming Unit [CFU]/ml) and strong antioxidant activity (Half Maximal Inhibitory Concentration [IC۵۰] = ۱.۷۵۸۶ parts per million [ppm]). The Gaussian kinetic model best represented LAB growth dynamics (R² = ۰.۹۴۸). The optimized kefir formulation with ۵۰% starter concentration exhibited enhanced sensory properties and favorable probiotic characteristics. Conclusion: In summary, low-temperature fermentation offers a practical approach to better control ethanol formation while maintaining LAB viability and enhancing antioxidant activity. These improvements support the production of kefir with more favorable quality attributes relevant to halal compliance and product acceptability; however, broader health-related claims should be confirmed in future studies through targeted metabolite profiling and expanded functional assays. DOI: ۱۰.۱۸۵۰۲/jfqhc.۱۳.۲.۲۲۱۴۱

کلیدواژه ها:

Kefir ، Fermentation ، Lactic Acid Bacteria ، Ethanol ، Antioxidants