Nutritional and Baking Quality of low Phytic Acid Wheat

Abstract

Phytic acid is the major storage form of phosphorus in wheat grain. Non-ruminant animals cannot utilize phytic acid phosphorus, and phytic acid reduces the nutritional availability of important minerals. We have identified a wheat mutant (Lpa1-1) with reduced phytic acid P and increased inorganic P (P_i). Ideally, LPA wheats will have improved micronutrient availability without detrimental effects on baking quality. To test this hypothesis, the mutant phenotype was transferred via backcrossing into the hard red spring wheat cultivar ‘Grandin.’ Wild-type (WT) and low phytic acid (LPA) sib selections from two backcross families were grown in replicated, irrigated yield trials at Aberdeen, ID in 2003 and 2004. Total P, P_i, and phytic acid P (PAP) were measured in grain and in fractions obtained after milling on a Quadrumat Sr. experimental mill. Elemental concentrations (Ca, Cu, Fe, Mg, Mn, P, S, and Zn) were measured in flour and bran fractions by ICP mass spectrometry. Total P concentration in grain of WT and LPA sib lines was similar. However, the distribution of P between phytic acid and P_i was altered: P_i in LPA grain was up to 340% of WT grain, and PAP in LPA grain was reduced to as low as 65% of the concentration in WT grain. This difference in P composition of grain was reflected in flour: P_i in break and reduction flours of LPA wheat was 3- to 4-times the concentration in break and reduction flours from WT wheat. Total P concentration in LPA flours was 20% greater than in WT flours. Mineral concentrations in bran and shorts of LPA and WT wheats were similar. However, magnesium concentrations in LPA break and reduction flours were significantly greater than in WT flours. The LPA genotype had little effect on concentrations of other minerals. Increases in P and Mg concentration in LPA flours were manifested in greater flour ash concentration. Flour ash of WT flours averaged 3.86 g kg^-1; flour ash of LPA flours averaged 4.38 g kg^-1. Protein concentration of LPA and WT flours was similar. However, LPA flours had a longer time to mixograph peak and greater mixograph peak height than WT flours. Bread loaf volume of LPA and WT flours was similar. The results of this study indicate that the LPA trait can produce flours with greater P_i and Mg concentration and little effect on bread flour functionality