Brazilian Kefir-Fermented Sheep’s Milk, a Source of Antimicrobial and Antioxidant Peptides

Abstract

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.

Inhibitory Effect of Different Types of Fermented Milk on Candida albicans

“…At the end of the storage period (day 20), the pH of goat and camel kefir samples decreased to 3.65 ± 0.07 and 3.25 ± 0.05, respectively, while that of sheep and cow kefirs reached 4.02 ± 0.07 and 4.19 ± 0.03 (P < 0.01). It is reported that the pH of sheep milk kefir decreased from 4.50 to 3.70 during the 28-day storage period 12 , which showed more pH changes compared to our results for sheep kefir. Yilmaz-Ersan et al found that the pH of cow kefir was slightly higher in comparison to sheep kefir 13 , which is similar to our results.…”

Advances on Food-Derived Peptidic Antioxidants—A Review

“…Due to the action of microorganisms and endogenous proteolytic enzymes, PAs can be produced during the fermentation process [124,125]. Many kinds of fermented milk have been proven to be an important source of bioactive peptides [126][127][128]. Four peptides with high antioxidant activity in both chemistry and cell model evaluations have been purified and identified from the pasteurized milk fermented with Lactobacillus acidophilus NCFM ® , Lactobacillus delbrueckii subs.…”

Effect of milk kind on the physicochemical and sensorial properties of synbiotic kefirs containing Lactobacillus acidophilus LA-5 and Bifidobacterium bifidum BB-11 accompanied with inulin

“…It is a fermented milk drink produced from kefir grains containing microorganisms in a complex and specific mixture of polysaccharide matrix, which has a fresh and slightly acidic taste. Kefir is usually produced from cow's milk, but it can also be successfully made from sheep milk (Larosa et al, 2021a;de Lima et al, 2018), buffalo milk (Tomar et al, 2020) and colostrum (Setyawardani, et al, 2020). This fermented milk drink is different from other fermented milk products in terms of the complex Effect of milk kind on the physicochemical and sensorial properties of synbiotic kefirs containing Lactobacillus acidophilus LA-5 and Bifidobacterium bifidum BB-11 accompanied with inulin metabolic activity based on several microbial species as well as the production methods of the kefir grains (Farnworth & Mainville, 2008).…”