CHARACTERIZATION OF PROTEIN HYDROLYSATES FROM ANIMAL AND PLANT SOURCES BY SIMULATED DIGESTION

Food peptides have been explored due to their diverse functionalities. However, to promote a greater supply of bioactivity, they must withstand the conditions of intestinal gastric digestion. Animal and plant protein sources can produce a varied set of bioactive peptides in the digestive system with greater or lesser absorption capacity. This study determined the chemical characterization of commercial whey protein isolate (Glanbia Nutritionals) and sunflower protein (isolated by the authors in the laboratory). The isolates were submitted to the INFOGEST 2.0 simulated digestion protocol, resulting in digestates, whey (DSL) and sunflower (DG) that were characterized for protein content by the Kjeldahl method, degree of hydrolysis with OPA reagent, particle molecular size by size exclusion chromatography (FPLC), amino acids by RP-HPLC and cytotoxicity evaluated in Caco-2 cell cultures (0.01, 0.05, 0.5, 1 and 2 mg/mL) by the MTT assay. The degree of hydrolysis of DSL (66.01%) was higher than that of DG (61.72%). This data corroborated with the FPLC that showed that DSL has a higher amount of free amino acids, since most of the particles were found below 0.4 kDa (76.7%). DG showed a higher particle distribution between 5 and 1 kDa, with a significantly higher amount of particles in the range of 1 to 2 kDa than DSL. The amino acid composition showed that DG presented lysine as a limited amino acid, while DSL presented all the indispensable amino acids, following the FAO recommendation. None of the hydrolysates tested in Caco-2 cells showed no cytotoxicity. These data show that proteins of animal origin must be better digested in amino acids than those of plant origin. Both samples may contain peptides with absorption capacity that will be identified in the bioavailability analysis. Tests in cell culture show that the hydrolysate concentrations were safe for future absorption/permeability studies.