Chemical, Microbiological, and Functional Characterization of Kefir Produced from Cow’s Milk and Soy Milk

Abstract

Kefir is a functional beverage that contains lactic and acetic acid bacteria (LAB, AAB) and yeasts. This work’s aim was to study the chemical, microbial, and functional characteristics of kefir produced from cow’s milk and soy milk. After fermentation, free amino acids were 20.92 mg 100 mL−1 and 36.20 mg 100 mL−1 for cow’s milk and soy milk kefir, respectively. Glutamic acid was majority in both, suggesting that microbial proteolysis leads to an increase in free amino acids including glutamic acid. 108–109 CFU mL−1 LAB, 106–107 CFU mL−1 AAB, and 106–107 CFU mL−1 yeasts were counted in cow’s milk kefir, whereas soy milk kefir contained greatly lower yeasts and AAB. Lactococcus lactis, Kazachstania unispora, and Saccharomyces cerevisiae were isolated as major microorganisms in both kefirs. Acetobacter orientalis only existed in cow’s milk kefir. Cow’s milk and soy milk showed ACE inhibitory activity, which significantly increased after fermentation. Both kefirs also exhibited antioxidant activity and bactericidal activity against Escherichia coli, Salmonella Typhimurium, and Staphylococcus aureus.

Bioactive Compounds from Kefir and Their Potential Benefits on Health: A Systematic Review and Meta‐Analysis

“…However, there was no antimicrobial effect against Pseudomonas aeruginosa [ 17 , 60 ]. Other organic acids present in kefir, such as acetic and pyruvic acid, also demonstrated an antimicrobial effect when administered together with lactic acid [ 14 , 31 , 70 ]. Kakisu et al [ 31 ] identified that organic acids act against the germination of B. cereus spores in a dose-dependent manner.…”

“…Smaller fractions present in kefir, such as bioactive peptides, also demonstrated an antioxidant effect. An enhancement in scavenging ability of oxidized 2,2′-zino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) ranged from 2% to 25.6% for sheep's milk kefir and 35.8% for cow's milk kefir both compared to control [ 14 , 64 ]. A significant improvement (111.6%) in oxygen radical absorbance capacity (ORAC) for cow's milk kefir confirmed the antioxidant activity of bioactive peptides [ 14 ].…”

“…An enhancement in scavenging ability of oxidized 2,2′-zino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) ranged from 2% to 25.6% for sheep's milk kefir and 35.8% for cow's milk kefir both compared to control [ 14 , 64 ]. A significant improvement (111.6%) in oxygen radical absorbance capacity (ORAC) for cow's milk kefir confirmed the antioxidant activity of bioactive peptides [ 14 ]. We believe that the observed difference between the antioxidant activity of sheep's milk kefir and cow's milk kefir may be associated with the difference in composition between milk, especially about the protein content and its design which are precursors of bioactive peptides.…”

Evaluation of the probiotic potential of Pediococcus strains from fermented dairy product kefir

“…Their colonisation in the intestinal tract improves the intestinal microbiota balance, strengthens the defence against pathogens, and improves oxidative stress resistance. In addition, other beneficial effects are lowering of blood cholesterol levels, synthesis of some vitamins, anticarcinogenic and antimicrobial metabolites (Gamba et al 2020).…”

“…citrovorum, and Str. diacetylactis), and its LAB content varies depending on the origin of kefir grains (Gamba et al 2020).…”