The use of bovine LF as ingredient in infant formulas to mimic human milk composition is of great interest for the food industry; however, thermal treatments may induce denaturation of LF, reducing its nutritional benefits. In this study, the effect of four salts, authorized as additives for infant formulas (potassium phosphate (PP), sodium phosphate (SP), potassium citrate (PC) and sodium citrate (SC)), in the thermal stability of bovine LF, was studied. The concentration of soluble LF after applying different thermal treatments (90 °C, 2min and 120 °C, 30s) was determined by UPLC, while the structural changes induced by the additives were studied by ζ-potential, CD and DSC analyses. The results evidenced that LF undergoes thermal denaturation under the tested conditions. The addition of SP, PC and SC led to more negative surface charges and promoted a greater degree of unfolding. Contrarily, the LF-PP blend presented a slightly acidic pH and neutral charge and showed the same unfolding degree than LF alone. Interestingly, PP induced partial re-naturation upon cooling. In addition, the results show that PP and SC do not prevent the denaturation of LF, but they inhibit aggregation, keeping a relatively large proportion of soluble LF after the application of heating treatments.

Human milk proteins have shown to vary in concentration and distribution through lactation. However, while some regulatory components, such as hormones, have shown associations with regard to the mothers’ body mass index, there is limited information on the possible influence of this condition on the whole protein distribution. The objective of this study was to evaluate the protein profile of human milk from normal weight and overweight or obese mothers to identify differences in protein expression in colostrum, transitional and mature milk. The mass spectrometry analysis showed the ability to class with a high degree of confidence the lactation state and the milk profile according to the mother’s condition. Individual milk samples were subjected to a digestion in vitro model that takes into account the specificities of the gastrointestinal conditions of full-term newborn infants. The digestion products were compared with available data from the digestive contents in newborns. The behavior of the most abundant proteins and the overall peptide generation and survival, showed good correspondence with in vivo data.

It is known that casein hydrolysis accelerates gastrointestinal transit in comparison to intact casein, although the effect of the protein hydrolysis on the composition of the digests is not fully understood. The aim of this work is to characterize, at the peptidome level, duodenal digests from pigs, as a model of human digestion, fed with micellar casein and a previously described casein hydrolysate. In addition, in parallel experiments, plasma amino acid levels were quantified. A slower transit of nitrogen to the duodenum was found when the animals received micellar casein. Duodenal digests from casein contained a wider range of peptide sizes and a higher number of peptides above five amino acids long in comparison with the digests from the hydrolysate. The peptide profile was markedly different, and although β-casomorphin-7 precursors were also found in hydrolysate samples, other opioid sequences were more abundant in the casein digests. Within the same substrate, the evolution of the peptide pattern at different time points showed minimal changes, suggesting that the protein degradation rate relies more on the gastrointestinal location than on digestion time. Higher plasma concentrations of methionine, valine, lysine and amino acid metabolites were found in animals fed with the hydrolysate at short times (<200 min). The duodenal peptide profiles were evaluated with discriminant analysis tools specific for peptidomics to identify sequence differences between both substrates that can be used for future human physiological and metabolic studies.