Comparison of glycation and glycosylation level between bovine milk-based and goat milk-based infant formula through label-free proteomics techniques

Heat treatment is unavoidable in the processing of infant formula; however, heat treatment causes the proteins to undergo Maillard reaction and form glycation products, which can negatively affect the nutrition and function of the protein. At the same time, glycosylation is a broad post-translational protein modification that is important in a variety of biological processes. However, glycated proteins as well as N-glycoprotein components in infant formula have not been well characterized. Here, a comprehensive comparative analysis of the glycated proteome as well as the N-glycosylated proteome was conducted in both bovine milk-based (BF) and goat milk-based (GF) infant formula. In total, 918 whey proteins were identified from the whey fraction, including 200 glycated proteins and 219 glycosylated proteins. Furthermore, 33 N-glycosylated proteins containing 101 N-glycosylation sites and 64 glycosylated peptides derived from 30 proteins were significantly different (p < 0.05) between BF and GF. Most of the significantly different proteins are associated with innate immunity as well as defense responses. With respect to the differences between BF and GF, ɑ-lactalbumin (LALBA) had higher glycation level in BF than GF; whereas β-lactoglobulin (LGB) had higher glycation level in GF than BF. For glycosylation level, transferin (TF) was highly glycosylated in GF than BF; while serum albumin (ALB) was highly glycosylated in BF than GF. Our results elucidated the proteome, glycated proteome, N-glycosylated proteome in bovine milk-based and goat milk-based infant formulas, which may be useful to researchers in related fields and provide guidance on the improvement of processing technology for infant formula.