*binxiao.fu@grainscanada.gc.ca

Seven composites of AAC Brandon, the dominant variety in Canada Western Red Spring wheat class, were prepared by blending 2021 harvest samples based on their protein content in bands with 1% increments, spanning <11% to >17% (13.5%mb). Farinograph dough development time and stability increased with the increase of protein from 3.25 to 14.5 min and 8.0 to 20.0 min, respectively.

Dough strength, as measured with extensograph Rmax increased from 465 BU to 732 BU, and dough extensibility also increased with protein content, resulting in well balanced dough properties for all composites.

Further analysis of the samples with gluten index and GlutoPeak showed little change in gluten strength parameters. Parameters generated with farinograph and extensograph reflect both the density and strength of gluten network, while gluten index and GlutoPeak measure the strength of the hydrated and aggregated polymers largely independent of protein quantity.

Flour proteins were fractionated into monomeric proteins, soluble glutenin, and insoluble glutenin. The proportion of 0.6% SDS insoluble glutenin remained little changed among the seven aggregates at 17.7-19.0%. With the increase of protein, the proportion of monomeric proteins increased gradually from 55.9% to 58.9% %, and soluble glutenin decreased from 26.4% to 22.2%.

Further analysis of 45% propanol insoluble glutenin with RP-UPLC found little change in the proportions of insoluble glutenins across the samples, and confirmed that the total amounts of insoluble glutenin were exclusively a function of wheat protein content.

The variation was also small among the seven aggregates in the proportions of individual HMW glutenin subunits and the ratio of HMW-GS/LMW-GS.

Results generated from the unique sample set used in this study provided commercially applicable information on the relationship between wheat protein content and processing quality, and the biochemical basis of the changes in functionality with protein content for a given variety.