THE RELATIONSHIP OF FREE LIPIDS AND FLOUR PROTEIN TO BREADMAKING QUALITY

Fourteen cultivars of wheat of diverse wheat quality were grown over two seasons using six rates of applied nitrogen fertilizer. The relationships between protein and hexane extractable (free) lipid in flour together with the effects of year and grain hardness on breadmaking quality were investigated. As expected, there was protein response to the fertilizer treatments with the magnitude dependent upon grain hardness and year (or initial soil fertility). Free lipid response was independent of applied nitrogen and only weakly correlated with protein concentration of the grain. Hard-grained cultivars had higher levels of free lipid than the softer grained wheats. Both flour protein and free lipid had a significant effect on loaf volume, the effect of free lipid remaining significant after adjustment for protein. A regression model was developed for prediction of loaf volume in terms of flour protein and free lipid and tolerance limits calculated to quantify the precision of prediction. For example, a sample with free lipids = 0·12 g/10 g and protein = 10·0% has predicted loaf volume of approximately 1645 ml and no more than 1763 ml with 90% confidence. An efficient baking quality screening strategy based on this predictive model for use in wheat breeding programmes is proffered and evaluated. © 1993 Academic Press Limited.