Characterization of acetic acid soluble and insoluble fractions of glutenin of bread wheat

The breadmaking potential of wheat flour depends strongly on its protein content and quality. Research has shown that for bread wheat varieties of diverse breadmaking potential, loaf volume is inversely related to the amount of acetic acid soluble (AAS) glutenin fraction and directly related to the amount of acetic acid insoluble (AAI) glutenin fraction. The objective of the present research was to identify the molecular properties of glutenin controlling its solubility in acetic acid, which in turn might explain the significant correlations with loaf volume. Two wheat cultivars of diverse breadmaking quality (Glenlea and Katepwa) contained different proportions of AAS and AAI fractions. The AAS fractions contained similar amounts of glutenin but that of Katepwa contained significantly more gliadin. Both fractions of Glenlea contained significantly more high molccular weight glutenin subunit (HMW-GS) 7. Quantitative differences in individual HMW-GS and the ratio of HMW-GS to (low molecular weight) LMW-GS could not explain differences in solubility of glutenin. The higher content of the AAI fraction in the stronger cultivar Glenlea appears to be related to its higher content of HMW-GS 7 and weaker interaction with gliadin. Interaction of glutenin with gliadin appears to be related to the solubility of glutenin in acetic acid solution ; the greater the interaction the higher the solubility and vice vcrsa. The same phenomenon may be involved in dough development during mixing.