Proteolysis of Hen's Egg Yolk Incubated in Acidic Condition

Abstract

Proteolysis of egg yolk in an acid solution was investigated. Egg yolk solutions (yolk 1: water 4), adjusted to pH 4.0 by acetic acid, were kept at 40°C for 3 hours and at 5°C for 3 weeks. Tyrosine contents of 5% trichloroacetic acid filtrates increased in both conditions to give 20μg/ml tyrosine after 3 hours at 40°C and 50μg/ml after 3 weeks at 5°C respectively. According to SDS-PAGE analysis, the patterns changed with incubation time, and especially the protein of relative molecular mass of about 200KDa decreased clearly. Addition of pepstatin A prevented these changes. It may be concluded from these results that the proteolysis of egg yolk under acidic conditions is caused by egg yolk aspartic proteinase.