METHIONINE LIBERATION BY PEPSIN-PANCREATIN HYDROLYSIS OF BEAN PROTEIN FRACTIONS: ESTIMATION OF METHIONINE BIOAVAILABILITY

Abstract

Albumin (ALB), globulin (GLO), globulin G1 (G1), glutelin (GLU), and a protease inhibitor-lectin rich fraction (PIL) were extracted from IAC-Carioca 80 SH (Phaseolus vulgaris) based on differential solubility. The purpose of the study was to search for different susceptibilities to proteolysis and methionine liberation among protein fractions. The fractions were submitted to pepsin digestion for 3 h, then to pancreatin digestion for another 3 h, under optimum pH and 37C. Degree of hydrolysis (DH) was followed by the TNBS reaction and methionine liberation (Met%) by the chloramine-T method. DH for undenatured proteins was higher for GLO, Gl and GLU (62–71%) and lower for ALB and PIL (51–53%). After denaturation, DH was higher for Gl, GLU and GLO (81–86%) and lower for PIL and ALB (66–78%). For undenatured proteins Met% was higher for GLO, Gl and GLU (42–48%), and lower for ALB and PIL (22–29%). For denatured proteins Met% was higher for Gl, ALB and GLO (66–73%) and lower for PIL and GLU (50–53%). Overall, hydrolysis and methionine liberation followed the same general pattern for both pepsin and pancreatin digestion, individually.