Amino acid profile modulates gastrointestinal digestion and potential bioactive peptide release in liquid infant formula: an in vitro study.

The amino acid profiles plays an important role in promoting protein synthesis and maintaining nitrogen balance in infants by optimizing the proportion of essential amino acids. In order to clarify the relationship between the amino acid pattern of liquid infant formula and its gastrointestinal digestion behavior, this study designed standard liquid infant formula (IF-ST), branched-chain amino acid-enriched (IF-BC) and tryptophan-enriched (IF-TP) with different whey protein compositions based on the amino acid pattern of breast milk. The static in vitro digestion model was used to evaluate how these differences affect protein degradation and peptide release characteristics. The results showed that IF-BC exhibited a higher protein degradation rate during gastric digestion, whereas IF-ST displayed a higher degree of protein hydrolysis throughout gastrointestinal digestion. And molecular weight distribution analysis indicated that all three samples were completely digested by the end of intestinal digestion (I120). Notably, IF-ST and IF-BC released the largest number of peptides at I120 (2498 and 2506, respectively), and these peptides were predominantly of low molecular weight. Biological activity score predicted that IF-TP, IF-ST and IF-BC all contained bioactive peptides with potential functional properties such as ACE inhibitory, antioxidant and immunomodulatory activities. These results confirmed that the amino acid pattern could affect the digestion characteristics and peptide release of liquid infant formula. This study provides a theoretical foundation for the development of infant formulas that more closely match the nutritional characteristics of breast milk, and contributes to guiding the precise nutritional design of infant formula.