Kefir protein
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Kefir Protein: Composition, Digestion, and Health Benefits
Kefir Protein Composition
Protein Profiles in Kefir Grains
Kefir grains, which are used to ferment milk into kefir, contain a variety of proteins that are essential for their structure and function. Studies have shown that kefir grains subcultured in goat milk contain proteins such as αs1-casein, αs2-casein, and β-casein from the milk, which interact with polysaccharides to maintain the grains' stability . Additionally, these proteins are closely related to the microbiota within the kefir grains, indicating a symbiotic relationship between the proteins and the microorganisms .
Peptide Composition During Fermentation
The fermentation process of kefir significantly alters the protein composition, resulting in the formation of numerous peptides. For instance, a comprehensive proteomic analysis of goat milk kefir identified 2328 unique peptides, with the highest concentration observed after 24 hours of fermentation . These peptides are primarily derived from caseins, which are the main proteins in milk, and exhibit various biological activities .
Proteolytic Activity of Kefir Microorganisms
Digestion of Milk Proteins
Kefir microorganisms exhibit substantial proteolytic activity, breaking down milk proteins into smaller peptides. Research using peptidomics technologies has revealed that kefir grains can digest major milk proteins such as α-lactalbumin and caseins, but not β-lactoglobulin, even after extended incubation periods 34. This selective proteolysis is influenced by factors such as the kefir-to-milk ratio and incubation time .
Bioactive Peptides
The proteolytic activity of kefir grains results in the release of bioactive peptides with various health benefits. These peptides have been identified to possess antihypertensive, antimicrobial, immunomodulatory, opioid, and antioxidative properties . Specific peptides such as DKIHPF, LGPVRGPFP, and QEPVLGPVRGPFP have been found in kefir grains, highlighting their potential therapeutic applications .
Health Benefits of Kefir Proteins and Peptides
Anti-Inflammatory and Antioxidant Effects
Kefir peptides have demonstrated significant anti-inflammatory and antioxidant effects. In studies involving animal models, kefir peptides were shown to reduce lung inflammation induced by particulate matter by inhibiting the NF-κB pathway . This suggests potential applications in treating inflammation-related conditions.
Cardiovascular and Gut Health
Kefir peptides also contribute to cardiovascular and gut health. In hypertensive rat models, kefir peptides improved gut morphology and enriched beneficial intestinal microbiota, which are linked to better blood pressure regulation and overall gut health . These findings indicate that kefir peptides can ameliorate conditions associated with high salt intake and hypertension.
Calcium Absorption
A novel peptide isolated from kefir, known as KFP-1, has been found to enhance calcium absorption in intestinal cells. This peptide promotes calcium influx through TRPV6 channels, suggesting its potential as a functional nutraceutical additive to improve calcium uptake and bone health .
Conclusion
Kefir proteins and peptides play a crucial role in the structural integrity of kefir grains and offer numerous health benefits. The proteolytic activity of kefir microorganisms leads to the formation of bioactive peptides with anti-inflammatory, antioxidant, and cardiovascular benefits. Additionally, specific peptides like KFP-1 enhance calcium absorption, highlighting the potential of kefir as a functional food with diverse health-promoting properties.
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