Enzymatic assay to determine collagen thermal denaturation and solubilization

Analysis of collagen in fresh and cooked meat products typically separates the heat-solubilized portion from the insoluble. However, extensive changes in the insoluble portion can occur during heat treatment that greatly affect cooked meat texture. This study evaluated a method of determining the proportion of solubilized and heat-altered collagen using a nonspecific protease from Streptomyces griseus to digest heat-altered collagen. Bovine semitendinosus muscle was heated to either 50, 60, or 70°C. Warner-Bratzler shear forces, Ringer's-soluble and insoluble collagen, and enzyme-labile collagen (digested with pronase) were determined on all samples. The enzyme-labile fraction (ELF) increased as endpoint temperature increased, and a corresponding decrease occurred in the total unaltered fraction (TUF). The Ringers-soluble fraction (RSF) increased slightly. Correlations of peak shear force and peak energy with TUF (0.65 and 0.81) were stronger than those with RSF (0.53 and 0.57). Use of this method should provide further insights into the role of collagen in the development of cooked meat texture.