Depolymerisation and re-polymerisation of wheat glutenin during dough processing .2. Changes in composition

In view of the importance of the glutenin macropolymer (GMP) for dough properties and bread-making quality, the changes of composition of glutenin subunits in GMP were investigated for flours and doughs from three cultivars (Rektor, Camp Remy, Obelisk) and from a blend of two of those cultivars (Camp Remy/Obelisk). After mixing, the content of GMP, and the contents of high M(r) and low M(r) glutenin subunits in GMP, decreased. The two subunit classes, and the individual subunits, decreased to different extents, however. This resulted in large changes in their proportions in GMP. After mixing, high M(r) glutenin subunits accounted for 8-17% of the GMP of dough, whereas in flour they accounted for 29-31%. During dough resting, the amounts of all glutenin subunit classes increased as the amount of GMP increased, but in most cases to lower final levels than those present in the flour. The proportions of high M(r) glutenin subunits in the GMP of dough increased to levels similar to those present in the GMP of flour (22-31%). The x-type/y-type high M(r) glutenin subunit molar ratio decreased significantly from 2.42 in the GMP from flour or 2.38 in the GMP from dough directly after mixing, to 1.78-1.83 after 90 min dough resting or longer. This indicates that the GMP became more enriched in y-type subunits during re-polymerisation. In contrast, the high M(r) glutenin subunit 12/subunit 9 molar ratio in GMP fell significantly from 1.79 for GMP from flour to 1.13 for dough directly after mixing, and increased upon resting to a level similar to that in the GMP from flour. The changes in composition during dough mixing and resting indicate that specific reactions involving glutenin subunits occur during depolymerisation of GMP and during re-polymerisation of the SDS-extractable glutenin polymers. (C) 1997 Academic Press Limited.