To investigate the effects of caprine milk casein subfractions and the ratio adjustment on the digestibility of infants, in this study, κ-casein enrichment, β-casein enrichment, and αs-casein enrichment were fractionated by selective precipitation using caprine micellar casein concentrate as raw material and then compounded according to the ratio of breast milk casein subfractions.In vitro simulated gastrointestinal digestion of infants and caprine milk whole casein was used as a control.Key indicators such as gastric clot, protein residue rate, free amino group content, and polypeptide molecular weight distribution of the different casein samples were compared among five casein samples.Results showed that both κ-casein enrichment and β-casein enrichment formed small and loose clots during gastric digestion, which was conducive to protein degradation and the production of more free amino groups and small molecular peptides.However, the gastric clots of αs-casein enrichment were large and dense, and the protein residual rate and degree of hydrolysis were significantly lower.Compared with whole casein, compound casein had smaller particle size, looser structure, lower protein residue rate, higher degree of hydrolysis, and produced more small molecular peptides.The amount of free amino and small molecular peptides produced by proteolysis increased significantly during intestinal digestion.In conclusion, the digestibility of κ-casein and β-casein enrichment was better than that of αs-casein enrichment, and the compound casein adjusted according to the ratio of breast milk casein subfractions was better than that of whole casein.This study provides a reference for the development of caprine milk-based infant formula.
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