Nitrogen and sulfur effects on hard winter wheat quality and asparagine concentration

Authors: WILSON, TARA - Kansas State University; Guttieri, Mary; NELSON, NATHAN - Kansas State University; FRITZ, ALLAN - Kansas State University; Tilley, Michael - Mike

Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2020
Publication Date: 4/15/2020
Publication URL: https://handle.nal.usda.gov/10113/6876637
Citation: Wilson, T., Guttieri, M.J., Nelson, N., Fritz, A., Tilley, M. 2020. Nitrogen and sulfur effects on hard winter wheat quality and asparagine concentration. Journal of Cereal Science. 93:102969. https://doi.org/10.1016/j.jcs.2020.102969.
DOI: https://doi.org/10.1016/j.jcs.2020.102969

Interpretive Summary: Grain protein quantity and quality are affected by wheat variety, nutrient availability, and growing conditions. Asparagine is an essential amino acid precursor of protein in wheat grain. Any interruption in grain protein assembly in the developing seed can potentially increase asparagine concentration in harvested grain and can be detrimental to grain protein quality. In the preparation of some foods, asparagine is converted to acrylamide, which is a health concern. This research examined the role of sulfur and nitrogen fertilization in regulating protein quantity, protein quality, and asparagine concentration in harvested grain of winter wheat varieties grown on sulfur-deficient soil. Sulfur fertilizer application substantially improved the functionality of grain protein for bread making. Asparagine concentration was 8-fold greater in grain grown without supplemental sulfur. These results indicate that adequate sulfur fertility is an important component of producing wheat with low asparagine concentration.

Technical Abstract: Grain protein concentration and composition are key factors affecting winter wheat quality and are influenced by wheat genotype, available fertility, and growing conditions. These same parameters can affect free asparagine concentration in grain, and elevated asparagine can lead to acrylamide production in baked food products, which can be a health concern. The objectives of this study were to determine the effect of genotype, nitrogen (N), and sulfur (S) fertility on protein concentration, protein quality, dough rheology, and asparagine concentration in winter wheat grown on S-deficient soils. Treatments were arranged in a 3x2x4 factorial design in 2017 and 3x2x5 factorial design in 2018. There were three levels of N (56, 101 and 146 kg ha-1), two levels of S (0 and 22 kg ha-1), 4 levels of genotype in 2017, and five levels of genotype in 2018. Protein composition was evaluated as the percent polymeric protein using size exclusion high performance liquid chromatography. In both years, the ratio of polymeric to monomeric protein was increased by sulfur fertilization. Solvent retention capacity (SRC) was evaluated using the whole grain lactic acid-sodium dodecyl sulfate test. In 2018, S application increased the SRC from 217% to 308%. Free asparagine concentration averaged 9.8 µmol/g and 20.9 µmol/g in 2017 and 2018, respectively. Asparagine concentration in grain was affected by N, S, genotype, and their interactions. Sulfur application substantially reduced asparagine concentrations in both years. Dough rheology was evaluated in the 2018 trial using the farinograph test. Sulfur application increased average farinograph stability from 9.2 min to 14.6 min. Farinograph stability was effectively predicted by the SRC test (R2=0.78). These results demonstrate the importance of ensuring adequate S fertility in winter wheat production.