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Fermented milks are a source of bioactive peptides and may be considered as functional foods. Among these, sheep’s milk
fermented with kefir has not been widely studied and its most relevant properties need to be more thoroughly characterized. This
research study is set out to investigate and evaluate the antioxidant and antimicrobial properties of peptides from fermented
sheep’s milk in Brazil when produced by using kefir. For this, the chemical and microbiological composition of the sheep’s milk
before and after the fermentation was evaluated. The changes in the fermented milk and the peptides extracted before the
fermentation and in the fermented milk during its shelf life were verified. The antimicrobial and antioxidant activities of the
peptides from the fermented milk were evaluated and identified according to the literature. The physicochemical properties and
mineral profile of the fermented milk were like those of fresh milk. The peptide extract presented antimicrobial activity and it was
detected that 13 of the 46 peptides were able to inhibit the growth of pathogenic microorganisms. A high antioxidant activity was
observed in the peptides extracted from fermented milk (3.125 mg/mL) on the 28th day of storage. Two fractions displayed
efficient radical scavenging properties by DPPH and ABTS methods. At least 11 peptides distributed in the different fractions
were identified by tandem mass spectrometry. This sheep’s milk fermented by Brazilian kefir grains, which has antioxidant and
antimicrobial activities and probiotic microorganisms, is a good candidate for further investigation as a source for bioactive
peptides. The fermentation process was thus a means by which to produce potential bioactive peptides.