Gluten protein molecular weight distribution effects on bread-making quality

Ten glutenin fractions (R1-RR) were separated by sequential extraction of wheat gluten protein by dilute hydrochloric acid from defatted and glutenin-rich wheat gluten of the Canadian hard red spring wheat (HRSW) cultivar Glenlea. The molecular weight distribution (MWD) of the ten different soluble glutenin fractions was determined by multi-stacking sodium dodecyl sulphate polyacrylamide gel electrophoresis (MS-SDS-PAGE) under unreduced conditions. Also, the subunit composition of different glutenin fractions was determined by SDS-PAGE under reduced conditions, respectively, followed by quantitative densitometric scanning of both the unreduced and reduced stained patterns. The pattern areas of reduced fractions were divided into sub-areas representative of three main protein classes: high molecular weight (HMW), medium molecular weight (MMW) and low molecular weight (LMW) glutenin subunits.; The MWD of the fractions (especially HMW glutenins) varied from fraction to fraction. The early extracted fractions contained more LMW glutenin and less HMW glutenin subunits. From fraction 1 to the residue, the proportion of total HMW glutenin polymers retained at the stacking gels (4-14%) increased. From early to later fractions, the molecular weight distribution shifted from low to high. The later extracted fractions and the residue fraction contained much more HMW subunits (2*, 5 and 7 subunits) than the early extracted fractions. The trend in the amount of 2*, 5 and 7 subunits in each fraction from lowest to highest amount matched the extraction sequence.; Bread-making quality of Glenlea was assessed by enriching (by 1%) a weak HRSW McVey base flour with protein components from Glenlea. The mixograph peak development times and loaf volumes were of enriched flour were measured in an optimized baking test. The results indicated that the higher content of HMW glutenin subunits with higher molecular weight, such as 2*, 5 and 7, may be the critical factor causing the strong mixing properties of Glenlea. It seems the higher the content of higher molecular weight glutenin subunits, the stronger the flour.