Effects of HMW-GS Dx2 absence on the protein aggregation characteristics and thermal stability of wheat flour during maturation

Abstract

Wheat flour maturation affects the aggregation and structural stability of proteins. The number of high-molecular-weight glutenin subunits (HMW-GSs) differs in various wheat varieties. The effects of Dx2 absence on the protein aggregation characteristics and thermal stability of flour were investigated during 120 days of maturation using near-isogenic lines (NILs). The absence of Dx2 delayed and decreased the protein aggregation of flours during the maturation, i.e., the maturation-induced increases were later and smaller for glutenin, glutenin macropolymer (GMP), glutenin/gliadin ratio, 𝛽-sheets, and 𝛽-sheet/𝛼-helix ratio in HMW-D1a without Dx2 than those in HMW-D1p with Dx2; these differences were ascribed to the weaker interactions between the sulfhydryl (-SH) groups, disulfide bonds (-S-S-), and hydrophobicity in the flours without Dx2. Flour maturation caused the dough microstructures to be more compact and denser, thereby increasing the flour thermal stability as observed by a higher denaturation peak temperature (Tp), enthalpy of thermal transition (ΔH), and degradation temperature (Td), These changes led to better dough properties such as dough development time, dough stability time, and protein weakening, but the optimal stage in HMW-D1a without Dx2 was reached later. These findings deepen the understanding of how HMW-GS Dx2 modifies protein structures during flour maturation.