Aim: Insufficient protein intake can lead to a condition called sarcopenia, characterized by the loss of muscle mass, strength and function. To avoid this condition healthy older adults need to increase the amount of high-quality proteins in their diet, particularly foods rich in leucine, to promote muscle health. However, it is still unclear if changes in protein digestibility and absorption kinetics in old age may affect the anabolic effect of high-protein foods. The objective of this study was to investigate the digestion of two high-protein (10% w/w) dairy products in vitro: a fermented dairy product formulated with a ratio of whey proteins to caseins of 80 to 20% (WBD), and a Skyr containing mainly caseins. Method: The new static in vitro digestion model adapted to the general older adult population (≥65 y) proposed by the INFOGEST international consortium was implemented to investigate the digestion of these products, and compared to the standard version of the protocol. Kinetics of proteolysis were compared between both models for each product, in the gastric and intestinal phase of digestion. Protein hydrolysis was studied with the OPA method, SDS-PAGE, and LC-MS/MS, and amino acids were quantified by HPLC. Results: Protein hydrolysis by pepsin was slower with the older adult model than with the young adult model, and consequently, in spite of a longer gastric phase duration, the degree of proteolysis (DH) reached at the end of the gastric phase was lower. Two different scenarios were observed depending on the type of dairy product studied: -10 and -40% in DH for Skyr and WBD, respectively. In the intestinal phase, lower concentrations in free leucine were observed in older adult conditions (approx. -10%), but no significant differences in proteolysis were measured overall between models. Conclusion: The digestion conditions used influenced significantly the kinetics and extent of proteolysis in the gastric phase but not in the intestinal phase. A clinical study comparing the effect of WBD or Skyr on older adults’ postprandial muscle synthesis is underway, which should improve our understanding of differences in digestion between whey protein and casein-based products.