INFOGEST in vitro digestion: protein breakdown in relation to food composition and moisture content

Driven by environmental sustainability, the transition to alternative food proteins is introducing a variety of plant-based products that simulate animal-derived foods. This study investigated the in vitro protein digestibility of a blend of pea protein isolate and wheat flour (75 : 25) as the basic proteinaceous ingredient in model foods. The selected vegetable foods included plant-based milk and pudding as high-moisture foods, a burger as a medium-moisture food, and a breadstick as a low-moisture food. A selection of protein-free foods were digested to measure the impact of digestive enzyme autolysis. Protein digestion depended on the level of food hydration, composition, and structure. High-moisture foods achieved the highest digestibility scores, with plant-based milk at approximately 83% and pudding at 81%. The burger followed with a digestibility score of around 71%, while the breadstick had the lowest score at approximately 69%. The viscosity of the soluble duodenal content was similar across the duodenal soluble samples. We determined the amount of digestible protein per food category using the digestibility scores and reference portion sizes. This study highlights the importance of food formulation and processing in protein digestibility, emphasising the significance of macro- and micronutrient interactions in defining the nutritional quality of a food product.