Biochemical analysis and rheological properties of gluten modified by transglutaminase

A transglutaminase from Streptoverticillium sp. was used to create new cova lent intermolecular cross-links between proteins in gluten. This modificati on induced drastic changes in its physicochemical properties as well as in its rheological behavior. To understand these changes, we characterized the gluten extractability in acetic acid and identified the proteins of supern atant and pellet by immunoblotting using antibodies specific for each prola min class. The proportion of soluble proteins decreased drastically after t ransglutaminase treatment due to the formation of large insoluble polymers as shown by SDS-PAGE. Among the constitutive proteins of gluten, the high m olecular weight glutenin subunits were the most affected in the transglutam inase reaction. The rheological behavior of gluten after 18 hr of incubatio n with transglutaminase was studied in shear by dynamic measurements over 1 0(-3) - 10(1) Hz frequency range and by creep and recovery tests. The behav ior of treated glutens remained that of a transient network, but the viscoe lastic response was shifted toward shorter times and the steady-state visco sity was greatly increased. The enzymatic treatment caused a considerable r einforcement of the network. The modified glutens were also less sensitive to thermal processing than unmodified glutens, as shown by a lower amplitud e of variation of storage modulus G' with temperature after enzymatic treat ment.