Pepsin, secreted by the stomach’s parietal cells, is the first protease encountered during digestion. The stomach slowly acidifies thefood intake and it is generally said that pepsin is active at acidic pH only (pH ≤ 4), with an optimum around pH 21. However, the impact of pH on gastric proteolysis has not been studied on complex mixes of alimentary proteins, only on few neat globular proteins. The goal of this study was to compare the kinetics of peptic hydrolysis of dairy caseins and egg white proteins as a function of both pH and in-vitro gastric digestion time.