VARIATIONS IN THE GLIADIN PATTERN OF FLOUR AND ISOLATED GLUTEN ON NITROGEN APPLICATION - IMPLICATIONS FOR BAKING POTENTIAL AND RHEOLOGICAL PROPERTIES

Dough properties and protein composition of wheat and gluten samples of two wheat varieties, Obelisk and Urban grown, at different levels of nitrogen (N) fertilization have been studied. Rheological and gluten yield data revealed differences in the response of the wheats tested to increasing levels of N application. Dough resistance showed a strong decline, especially in samples of Obelisk. Energy requirements during mixing also declined for Obelisk doughs, whereas hardly varied for those of Urban. Gluten yield increased at higher protein levels, being more efficient for Obelisk wheat. For both varieties, loaf volume showed a non-linear relationship with protein or gluten content. Biochemical studies revealed intervarietal differences in the extent of changes observed in the total gliadin content. Obelisk produced relatively more gliadins than Urban at higher protein contents. Examination of the chromatograms of wheat and gluten also revealed characteristic quantitative changes in individual gliadins differing between varieties and between levels of fertilizer. However, a previously report sulphur-rich protein fraction, called P3, showed absence of changes as grain protein increased.