Comparison of physical and biochemical methods to evaluate the gluten strength of Canadian hard red winter wheats

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Date
2019
Authors
Isaak, Carly
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Abstract
Gluten strength is a critical attribute of bread wheats and a key factor influencing dough properties and end-product quality. The goal of this research was to develop an improved understanding of the nature of the variation in gluten strength of Canadian hard red winter (HRW) wheats, which has not been previously studied. A diverse set of 52 HRW genotypes was evaluated using a 2-g mixograph and a 4-g Z-arm blade dough mixer, with varying operating parameters depending on the mixer type. Protein composition was intensively studied. Results indicated that using the mixograph with constant absorption and salt for dough mixing was very effective to discriminate gluten strength; using ascorbic acid in addition to salt produced marginal benefits. There were significant salt x genotype interactions; stronger flours tended to respond to salt more strongly. Both types of dough mixers were equally effective to discriminate gluten strength, although operating the Z-arm mixer at higher speeds improved accuracy of measurement of development time, repeatability precision, and sample throughput. Gluten strength as defined by mixograph work input was well predicted (R2=0.61) by results of an efficient and effective protein fractionation protocol and a parameter quantifying the ratio of HMW glutenin content to soluble protein (mainly gliadins) which was a measure of the molecular weight distribution of gluten proteins. Multiplying this ratio by flour protein content (FPC) further strengthened the relationship (R2=0.76), although FPC by itself was poorly related to gluten strength (R2=0.29). There was no obvious relationship between absolute amounts of individual HMW-glutenin subunits (GS) when comparing the same GS in the soluble (LMW) and insoluble (HMW) fractions of glutenin. Total insoluble (HMW) and soluble (LMW) glutenin fractions were positively and negatively correlated with gluten strength, respectively, supporting the concept that gluten strength is fundamentally related to the molecular size distribution of polymeric glutenin.
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wheat, glutenin, gluten
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