This study focuses on the development of an in vitro digestion model simulating oral, gastric and small intestinal fluids, applicable to the digestion of all three macronutrients, carbohydrates, proteins and lipids. To that aim, the effect of integrating intestinal mucosal enzymes in the small intestinal phase of the digestion reaction was investigated, together with that of other parameters including pepsin and pancreatin concentration, and pH of the small intestinal phase. Individual carbohydrate and protein ingredients for which digestive properties in vivo are generally understood (i.e. common corn starch, whey protein isolate) were used as reference substrates to validate the model and, at the end of development, the model was applied to evaluate the digestion of a reference lipid ingredient (i.e. olive oil) and of all three macronutrients present in a whole food system. Carbohydrate, protein and lipid hydrolysis was monitored, respectively, by quantitation of glucose, free amino groups and free fatty acids released at different times of digestion. The results demonstrate that including intestinal mucosal enzymes in the intestinal phase of digestion in vitro allows efficient digestion of starch and other carbohydrates into final product glucose and it also influences protein hydrolysis. Digestion profiles consistent with published in vitro and in vivo data support the validity of the developed method as an advanced tool for screening digestion of all three macronutrients whether presented alone or in a whole food system, all in a single digestion reaction.
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