In vitro gastric digestion characteristics of goat and cow infant formulas

Abstract

Although breast milk (BM) represents the ideal food for an infant, infant formula (IF) also has a role as a complete food source when BM is not available. The number of IFs using goat milk as a protein source has increased in recent years. Goat IF is often marketed as being more easily digested when compared to their cow counterparts. The main objective of the study was to determine if differences exist in the gastric digestion of proteins in goat and cow IFs. Differences in the microstructure of IFs gels acidified using glucono-δ-lactone were also examined using ultra-small angle neutron scattering (USANS), small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS). In this study, the in vitro gastric digestion of the protein in goat and cow IFs was studied in the absence of lipases. Using SDS-PAGE caseins were found to be more rapidly digested for all samples regardless of animal origin, while whey protein demonstrated greater resistance to digestion. IFs with an 80:20 whey to casein ratio demonstrated larger particle sizes and higher viscosities than samples with a 40:60 whey to casein ratio. Samples of a cow origin demonstrated larger particle sizes than samples of a goat origin. Gastric digestion leads to an initial increase in particle size due to protein aggregation followed by a decrease in the particle size as digestion progresses. The viscosity of all samples decreased over time and exhibited a two-phase exponential decay. USANS and SANS analysis demonstrated that goat IF gels had looser, less dense protein compared to cow IF gels. While SAXS revealed that differences in the internal structure of goat and cow casein micelle might exist. Colloidal calcium phosphate nanoclusters were found to be solubilised upon acidification.