Heating affects protein digestion of skimmed goat milk proteins with different casein:whey ratios under simulated infant conditions

Abstract

This research compared effects of heating on the digestion of goat milk proteins in skimmed goat milk model systems with different casein-to-whey protein ratios. The digestion was evaluated both the supernatant and gastric clot part of the digesta. Whey protein concentrates were added in skimmed goat milk (80% casein, C80 sample) to make a 40% casein sample (C40 sample). Heating at 65 °C showed limited influence on digestibility of proteins in supernatant and clot of both model systems. In the supernatant, the C80 sample had a higher soluble protein concentration after 85 °C heating, compared to the C40 sample. After heating at 85 °C for 30 min, the digestibility of proteins in the supernatant of C40 and C80 samples was increased. This heating also increased the casein digestibility of the gastric clot of C80 sample, but resulted in more undigested whey protein aggregates in C40 sample. For the difference between C80 and C40 sample, the proteins in the supernatant of C80 samples showed a higher digestibility than those in the supernatant of C40 samples, both in non-heated and in 85 °C heated samples. The clots of C40 sample showed a relatively higher digestion rate than C80 sample clots, which may be due to their higher water content and looser microstructure. Overall, this study showed that heating induced different digestion kinetics of goat milk model systems with different casein-to-whey ratios.