Comparative proteomic analysis of casein micelles in human and small ruminant colostrum and mature milk using data-independent acquisition for precision improvement of infant formula.

Increasing attention has been directed toward improving infant formula derived from minor milk sources, given that human milk is widely regarded as the gold standard for infant nutrition. To bridge this gap, this study aims to conduct a comparative analysis of the casein micelle proteomes and particle sizes in human and small ruminant colostrum and mature milk. Colostrum and mature milk from humans, as well as goats and sheep, were collected. Casein micelles were isolated, and their proteomes were analyzed using data-independent acquisition-based proteomics, and particle size and zeta potential were measured by laser scattering. The results indicated that human colostrum contained the smallest casein micelles, whereas colostrum from small ruminants exhibited the largest micelle sizes. Significant differences were observed in the proteomic profiles of human and small ruminant milk. Human colostrum was enriched with unique proteins associated with immunity and phospholipid synthesis, including lectin-related immune proteins, histone family members, serine incorporators, and acyl-CoA synthetases. Additionally, human mature milk exhibited elevated levels of antimicrobial and digestive enzymes compared with the corresponding samples from other species. Small ruminant colostrum was enriched in antioxidant enzymes and matrix Gla protein. This study provides valuable insights into the development of infant formula based on small ruminant milk tailored to infants' developmental stages, with particular emphasis on the unique characteristics of human colostrum in meeting early nutritional needs.