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Effects of Nitrogen and Sulfur Fertilizer on Protein Composition, Mixing Requirements, and Dough Strength of Four Wheat Cultivars

¹Grain Quality Research Laboratories, CSIRO Division of Plant Industry, PO Box 7, North Ryde, NSW 1670, Australia. ²Grain Foods Research Unit, New Zealand Institute for Crop and Food Research, Private Bag 4704, Christchurch, New Zealand. ³Present address: 2 Turi Ave., Whenuapai, Auckland, New Zealand. ⁴Present address: Department of Grain Science and Industry, Kansas State University, Manhattan 66506-2201. ⁵Corresponding author. Plant Breeding Institute, Woolley Bldg A20, The University of Sydney, NSW 2006, Australia and Quality Wheat CRC Ltd., Locked Bag No 1345, North Ryde, NSW 1670, Australia. Phone +61 2 9351 4594; Fax +61 2 9351 4172; E-mail stoddard@mail.usyd.edu.au

Two field trials using four New Zealand wheat cultivars were undertaken to observe the effects of nitrogen and sulfur fertilization on protein composition, mixing requirements, and dough strength and to compare the results with that observed with a single cultivar, Otane. The results confirmed that adequate sulfur fertilization was necessary to ensure lower dough mixing requirements. The existence of a nexus between mixing requirements and dough strength was confirmed and genotype has significant effects on it. Variation in the content of HMW-GS in the protein corresponded to changes in dough mixing requirement of Otane. Across the four cultivars, dough mixing requirements (mechanical dough development work input and mixograph development time) and dough strength (Extensigraph resistance to extension) depended on different aspects of protein composition. As the content of polymeric proteins increased, MDD work input increased, but mixograph development time decreased, while the effect on Rmax was small. Rmax, however, was more affected by either the content of small monomerics in the flour or the ratio between HMW-GS peak area to total gliadin peak area. The ratio of MDD work input to Rmax was largely explained by the gliadin content of the flour. Thus, depending on the genetic background, it should be possible to adjust dough mixing requirements by modifying overall HMW-GS, LMW-GS, or gliadin content while maintaining dough strength.