The effect of nitrogen fertilization on protein content and bread baking properties of wheat flour

Abstract

The effects of variation in nitrogen application during two growing seasons to Coker 916, a soft red winter wheat, on wheat grain and flour protein content and bread baking properties were examined. Nitrogen fertilization regimens tested included the single spring application of 168 kg/ha in growth stages 25 or 30, the split spring application of 224 kg/ha in growth stages 25 and 30, and no nitrogen application either in growth stages 25 and 30.

Variation in rate of nitrogen application had a more consistent effect on grain and flour protein than did variation in timing. Grain and flour protein content increased with increased nitrogen fertilization. The gliadin to glutenin protein ratio of the flour was reduced as the rate of grain nitrogen application increased. Significant differences were found in the flour gliadin percent protein with variation in spring nitrogen management. Fractionation and resolution of gliadin and glutenin components using SDS-PAGE revealed changes in the relative quantities present of two high molecular weight glutenin subunits (108,000 and 91,000 daltons), one low molecular weight glutenin subunit (40,500 daltons) and the <i>ω</i>-gliadin (44,000 daltons) fraction of experimental flours.

Differences in dough rheological properties and baking characteristics of the flour were associated with variation in nitrogen management. Increased nitrogen fertilization resulted in a stronger, more extensible dough with improved mixing tolerance and dough handling characteristics. Increased flour protein was associated with larger bread loaf volume and darker crust color. Sensory panelists found significant differences in the bread crust color, texture and taste, bread aroma, crumb texture and chewiness. This experiment demonstrated that a change in nitrogen management of Coker 916 wheat resulted in a distinct change in protein composition and bread baking properties of experimentally milled flour.