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Abstract
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Kefir, a traditional fermented milk product, is considered as a rich source of biofunctional compounds like peptides that are beneficial to human health. The objective of this study was to extract water-soluble peptides from cow and ewe milk kefir (produced by local kefir grains of Semnan, Iran) and investigate their antioxidant and antimicrobial activities. Evaluation of the chemical composition of the cow and ewe pasteurized milk and kefir showed a decrease in protein, total carbohydrate, and lactose content. There was no difference between the mineral profile of fresh milk and kefir. The count of lactic acid bacteria was almost stable during the 28 days of storage period. From the 1st to the 28th day of storage, the population of Lactococci (LC) was 11.5–12.1 and 11.4–12.2 log10 CFU/mL for cow and ewe milk kefir, respectively. A great antioxidant potential (DPPH and ABTS assay) was observed for the peptides extracted from cow and ewe kefir (at a concentration of 1.25 mg/mL) on day 28 storage. Also, ewe kefir peptides had higher antioxidant activity than peptides of cow kefir. The antimicrobial activity of water-soluble peptides of ewe milk kefir was superior to those of cow milk kefir (at the same concentration of 20 mg/mL). The results of this work expressed great functional properties of peptides derived from ewe milk produced by local kefir grains of Semna
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