Structural modification of wheat gluten by dry heat-enhanced enzymatic hydrolysis

In this paper, a dry heat method is used to modify wheat gluten, and the effects of dry heat on the enzymatic hydrolysis and structure of wheat gluten are investigated. The results show that the degree of hydrolysis of wheat gluten after dry heating increased from 20 to 30 % within 1 h of hydrolysis. Meanwhile, the percentage of the fraction with [M.sub.r] < 1000 Da in the obtained hydrolysate increased from 17.6 to 30.7 %, which was revealed by size-exclusion high-performance liquid chromatography (SE-HPLC). Further analysis of the structure of dry-heated gluten was done and it showed disappearance of extended structures with the concomitant increase in [beta]-sheet for secondary structure, exhibited by Fourier transform infrared spectroscopy (FTIR), a decrease in the hydration and increases from 56.7 to 74.5 of surface hydrophobicity and from 4.74 to 16.18 mmol/g of the sulphydryl content. The higher [beta]-sheet proportion and surface hydrophobicity as well as sulphydryl content of dry-heated wheat gluten was assumed to be the reason for the enhancement of its enzymatic hydrolysis. Key words: wheat gluten, dry heat, FTIR, SE-HPLC, enzymatic hydrolysis