Different influences of dietary fiber from various sources on the in vitro digestibility of casein as uncovered by the study of protein-dietary fiber interactions

How different dietary fibers including pectin, cellulose and lignin affect casein digestibility was studied using in vitro static protocols. Peptides' profile, free amino acids (AAs) content, casein-DF interactions and their influences on enzymatic activities of proteolytic enzymes were studied using combined techniques. Under gastric and intestinal digestive conditions, while pectin could reduce casein digestibility (with an averaged decrease of 12.15% and 7.83, respectively) through both depletion flocculation and hydrogen-binding interactions, lignin inhibited the digestion of casein straightly through reducing the enzymatic activity of proteolytic enzymes, thereby altering the production of free AAs. Although cellulose showed the least detrimental effects, it still significantly reduced the content of Thr, Glu, Val, Leu, Phe, Lys, and no Arg was released. Deeper insight into casein-DF interactions and their influences on casein digestibility improves the development of more effective forms of DF for improving AA homeostasis in individuals.