Effect of consumption temperature of whole milk on in vitro gastric digestion using a biomimetic digestion simulator

This study evaluates the effect of consumption temperature on the gastric digestion behaviour of whole milk using a dynamic in vitro model (NERDT™, computer-controlled biomimetic system). Human intragastric temperature profiles in response to cold, warm, and hot beverages were accurately reproduced to mimic the conditions encountered after consumption of milk at 4 °C, 37 °C and 60 °C. For comparison, control experiments were performed with milk at 37 °C without any pepsin addition. Results show that milk coagulated more rapidly within the stomach when consumed at 37 °C or 60 °C compared to 4 °C and 37 °C without pepsin. Moreover, the gastric emptying rate of milk proteins in the presence of pepsin was slower with milks at 37 °C and 60 °C compared with the milk at 4 °C. The hydrolysis of milk proteins also appeared to be temperature-dependant, with proteolysis increasing with higher milk temperatures towards the end of digestion. Regarding the fat fraction of milk, our data suggest that both hot (60 °C) and cold milk (4 °C) could plausibly increase the gastric emptying rate of milk fat, compared to a 37 °C milk, but further studies remain needed to verify this hypothesis. At the end of the experiments, the wet and dry masses of the residual gastric digesta was similar across the three conditions with pepsin, but significantly lower than in the absence of pepsin at 37 °C. This study enhances our understanding of how consumption temperature influences the kinetics of pepsin-induced milk coagulation and the subsequent gastric disintegration of dairy particles.