Controlled Reduction Study of Modifications Induced by Gradual Heating in Gluten Proteins

Abstract

The stepwise reduction with dithiothreitol (DTT) of proteins in native and heat-treated gluten (1 h, 45−110 °C) was studied by SDS−PAGE. In native gluten and after heating at 45 °C, up to 0.02 mM DTT led to no apparent change. Subunits from glutenins and high-molecular weight (HMW) albumins were released with 0.4−10 mM DTT, indicating the presence of disulfide bonds with different susceptibilities to reduction. Monomeric proteins were more resistant to reduction; low-molecular weight (LMW) albumins/globulins were reduced at 2 mM DTT and α- and γ-type gliadins at 4 mM DTT. At 65 °C, only the HMW albumins were affected; they lost water solubility and amylase activity and were released at higher DTT concentrations. When heated above 90 °C, all the proteins, except the ω-gliadins, formed disulfide-bonded aggregates. The supposed D glutenin subunits were released at 0.4 mM DTT, the HMW glutenin subunits at 2 mM DTT, and the other proteins at 4 mM DTT. Gluten proteins therefore appeared to be involved differently in heat-induced aggregation. Keywords: Gluten; heat treatment; disulfide-dependent aggregation; controlled disulfide reduction