Does protein enrichment in yogurts have an effect on gastric emptying and impact on proteolysis kinetics?

Obesity has dramatically increased during the last 30 years and has become one of the major threats for the world population. On a nutritional point of view, overweight people need specific foods providing a slow nutrient release. Therefore, food that could exhibit a higher time of residence in the stomach could be particularly adapted to obese people. In this context, effect of milk protein enrichment on digestion was studied both in vivo and in vitro using yogurt as food matrix. Digestion of two yogurts supplemented with milk proteins (protein content 8.1%) and fibers with either a low (LV) or a high viscosity (HV), was compared to the digestion of a “standard” control yogurt CT, (protein content=3.1%). The caloric content was similar for the three yogurts. First of all, the gastric emptying of the three yogurts labelled with colloidal 99mTc was determined by gamma scintigraphy on pigs (n=12) used as human model for digestion. In a second part, dynamic in vitro digestions were performed to determine the effect of the protein enrichment by monitoring and evaluating the kinetics of protein digestion. Two digestions were conducted on each yogurt using the parameters of the gastric emptying determined in vivo. In vivo results showed that half gastric emptying time was significantly (p < 0,05) longer for LV as compared to CT (69min +/-13.3 and 58min +/- 13, respectively). HV, more viscous, showed an intermediate behavior (65min +/-12). As previously observed, caseins were hydrolyzed faster than the whey proteins in the first hour of digestion. Whey proteins were resistant to proteolysis up to one hour of digestion. Overall, proteolysis kinetics indicated a faster disappearance of proteins in the gastric compartment with the control yogurt compared to the two enriched yogurts. An in vivo study is actually conducted on Humans and will demonstrate the effect of protein enrichment on satiety.