Relationship between Baking Quality and Proportion of SDS-Insoluble Gluten in Wheat Flour.

The relationship between loaf volume and the proportion of SDS-insoluble gluten in wheat flour was studied using N-ethylmaleimide (NEMI) as a modifying reagent of gluten. The loaf volume responded to NEMI and was maximum at 10 ppm NEMI, but was minimum in the absence of yeast food. SDS-insoluble gluten had the same response to NEMI. Therefore, it was concluded that the loaf volume was positively related to the proportion of SDS-insoluble gluten. With excess NEMI (100 ppm), a substantial decrease in SDS-insoluble gluten was observed in the doughs. This was accompanied by a decrease in the relative viscosity of the ethanol-insoluble fraction (glutenin). This result suggested that excess NEMI caused a decrease in the molecular size of glutenin, probably by a thiol radical mechanism, leading to the decrease in SDS-insoluble gluten and then to deterioration of the baking quality of wheat flour. On the other hand, a lower amount of NEMI may determine the proportion of SDS-insoluble gluten and loaf volume.