Impact of fat content on the modulation of viscosity, microstructure and enzymatic hydrolysis of UHT milk during simulated gastrointestinal digestion

Digestion of ultra‐high temperature milk with different levels of fat content was examined in vitro under semi‐dynamic conditions with real‐time measurements of viscosity. All milk viscosity increased during the gastric phase despite digestive fluid dilution due to protein aggregation. Higher fat formulations presented greater viscosity and denser microstructure with larger mean droplet size. It experienced faster proteolysis and lipolysis throughout digestion with 524 μmol free fatty acids released compared with semi‐skimmed milk (467 μmol), but had lower conversion of triglycerides at the intestinal phase terminus. This study has provided a rheological understanding of the dynamics of UHT milk digestion as impacted by fat content.