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Optimized Methods for Incorporating Glutenin Subunits into Wheat Dough for Extension and Baking Studies

¹Quality Wheat Cooperative Research Centre Ltd., Locked Bag No. 1345, North Ryde, NSW 1670, Australia. ²Corresponding author. Phone: 61 2 9351-7141. Fax: 61 2 93517060. E-mail: suthay@mech.eng.usyd.edu.au ³Plant Breeding Institute, The University of Sydney, NSW 2006, Australia. ⁴CSIRO Plant Industry, Grain Quality Research Laboratory, North Ryde, NSW, 1670, Australia.

In order to study the functional properties of glutenin subunits added to a dough, they must be incorporated into the glutenin polymer. This requires partial reduction to open up the polymer, followed by oxidation to incorporate the added monomer into the polymer. Existing methods for incorporating glutenin subunits were suitable only for studies on mixing properties and needed to be modified for use in studies on extension and baking. A range of concentrations and of reaction times was therefore tested for both the reductant and the oxidant. In addition, mixing time as well as relaxation time before extension were varied. Extension curves and loaf heights were used to evaluate the treatments. Optimum conditions were developed that provided extension curves of normal dimensions but with altered shape. The conditions were reduction with 0.2 mg/mL of dithiothreitol (DTT) solution for 1 min followed by oxidation with 5 mg/mL of KIO₃ solution, then mixing the dough to 70% of the peak dough development time. For microbaking, the conditions of 2 mg/mL of DTT for 1 min, 2.5 mg/mL of KIO₃ for 5 min, and mixing the dough to peak development time allowed loaf height to be retained. The size distribution of the glutenin polymer was analyzed using size-exclusion HPLC and field-flow fractionation methods. This showed that the monomers were incorporated into the polymer and that polymer size was restored to control levels following reduction and oxidation.