Effects of high and low molecular weight glutenin subunits on rheological dough properties and breadmaking quality of wheat

High molecular weight (HMW) or low molecular weight (LMW) subunits of different chemical state (reduced, reoxidized with KBrO3, or KIO3) or gliadins were added in 1% amounts to a base flour of the wheat cultivar Rektor and mixed with water. The corresponding doughs were then characterized by microscale extension tests and by microbaking tests and were compared to doughs from the base flour without additives. The maximum resistance of dough was strongly increased by HMW subunits in a reduced state and by HMW subunits reoxidized with KBrO3. A moderate increase of resistance was caused by HMW subunits reoxidized with KIO3 and by LMW subunits reoxidized with KBrO3 or KIO3. This resistance was strongly lowered by LMW subunits in a reduced state and by gliadins. The extensibility of dough was significantly increased only by gliadins and reduced HMW subunits; HMW subunits reoxidized with KBrO3 had no effect, and all other fractions had a decreasing effect. In particular, glutenin subunits reoxidized with KIO3 induced marked decrease of extensibility, resulting in bell-shaped curve extensigrams, which are typical for plastic properties. The effect of reoxidized mixtures (2:1) of HMW and LMW subunits on maximum resistance depended on the oxidizing agent and on the conditions (reoxidation separated or together); extensibility was generally decreased. Bread volume was increased by addition of HMW subunits (reduced or reoxidized with KBrO3) and decreased by LMW subunits (reoxidized with KBrO3 or KIO3) and by a HMW-LMW subunit mixture (reoxidized with KBrO3). The volume was strongly decreased by addition of reduced LMW subunits. A high bread volume was related to higher values for both resistance and extensibility.