Impact of the stepwise implementation of INFOGEST semi-dynamic conditions on in vitro starch and protein digestion: A case study on lentil cotyledon cells.

The impact of food design parameters on digestion is mostly studied using static in vitro digestion models. In this work, the complexity of the static model was gradually increased, by implementing several dynamic gastric reactor conditions, i.e., gradual (i) acidification, (ii) pepsin addition, and (iii) emptying, as well as (iv) saliva in the oral phase. As a relevant case study, starch and protein digestion was studied in lentil cotyledon cells under these conditions. Implementation of these dynamic parameters affected gastric proteolysis, linked to the pH-dependence of pepsin, and amylolysis, linked to the pH-dependence of salivary amylase activity. Though gastrointestinal hydrolysis kinetics were affected by the applied simulation conditions, similar levels of starch and protein digestion were generally reached at the end of the simulated digestion. Salivary amylase was not completely inactivated at the low gastric pH conditions, resulting in significantly higher levels of small intestinal starch digestion upon saliva inclusion. Gastric emptying significantly affected macronutrient hydrolysis kinetics. In that regard, an approach separately considering gastric samples taken upon different gastric emptying times should be preferred over the pooling of gastric samples before simulating small intestinal digestion.