Milling and Baking Quality of Low Phytic Acid Wheat

Low phytic acid (LPA) wheat (Triticum aestivum L.) is one approach to improving nutritional quality of wheat by reducing the major storage form of phosphorus and increasing the level of inorganic phosphorus, which is more readily absorbed by humans and other monogastric animals. Milling and baking quality evaluations were conducted on hard red, hard white, and soft white spring wheat grain from field trials to evaluate the effects of the LPA genotype on the end-use quality of wheat. In hard wheat backgrounds, the LPA genotypes were not associated with detrimental effects on flour protein concentration, dough mixing properties, or bread loaf volume. LPAwheats had consistent, substantial increases (up to 0.93 g kg) in flour ash concentration relative to wild-type (WT) wheats. Higher flour ash in WT wheats is often a sign of higher aluerone and bran fragments which are visually evident in dulling of Asian noodles color. However, initial alkaline noodle brightness (L* 5 86.8–87.5) from hard white LPA flours was at least as high as from hard white wild-type flours (L* 5 86.1–87.9). LPA genotypes have demonstrated a significant redistribution of minerals from the bran to the endosperm; this redistribution of minerals most likely caused the increase in flour ash rather than greater partitioning of bran into the flour. In the soft wheat background, LPA genotypes had greater sodium carbonate and sucrose SRC (31 and 43 g kg greater than wild type, respectively), suggesting that LPA wheats milled with greater apparent starch damage and/or pentosan content than WT sib lines. WE HAVE IDENTIFIED low phytic acid (LPA) mutations in wheat (Guttieri et al., 2004). Low phytic acid mutants of other crops, including barley (Hordeum vulgare L.; Larson et al., 1998), rice (Oryza sativa L.; Larson et al., 2000), soybean [Glycine max (L.) Merr.; Wilcox et al., 2000], and maize (Zea mays L.; Raboy et al., 2000) were identified earlier. Although the biochemical characteristics of the seed of these mutants are well described, reports of the effect of the LPA trait on manufacturing quality are limited. LPA wheat is of interest as one approach to improving the nutritional quality of wheat fed to humans and livestock. Animals fed diets with LPA corn and barley have demonstrated greater feed efficiency, improved digestibility, better retention of P, Ca, and N, and significant decrease in P excretion compared with animals fed WT grain (reviewed byMendoza 2002). Human diets high in phytic acid (PA) can lead to zinc deficiency, since PA is negatively correlated with zinc absorption. PA does not affect copper absorption in humans but slightly inhibits manganese absorption. PA forms insoluble complexes with iron that are nutritionally unavailable at the pH of the small intestine. Diets high in PA and low in iron can lead to iron deficiency (reviewed by Lönnerdal, 2002). Previous research with this mutant concluded that the LPA mutants identified in wheat reduce seed phytate by approximately 33% to only nominal changes, depending on the environment and genetic background. Yet, in multiple genetic backgrounds and environments, significant increases of approximately 100 to 300% in inorganic P were observed in seed of LPA wheat when compared with similar (WT) selections (Guttieri et al., 2006a). The distribution of P within the kernel also was affected by the LPA trait with mutant lines having three times the concentration of P in the endosperm than was observed for similar WT lines, even though total P per seed was similar for both LPA and WT lines (Guttieri et al., 2006b). Similarly, LPA mutations elevated the concentration of magnesium in the endosperm relative to paired WT genotypes (Guttieri et al., 2006b). In earlier work, we were able to demonstrate that the LPA mutations can affect yield and plant development. However, those effects appear dependent on genetic background and are difficult to generalize into a simple relationship (Guttieri et al., 2006a). This led us to conclude that it was possible through prebreeding to develop LPA wheats that were agronomically competitive withWT genotypes. We have undertaken studies to address the effects of the LPA phenotype on wheat quality in three genetic backgrounds: soft white spring, hard red spring, and hard white spring. Flour extraction and flour ash concentration are key quality considerations in all three classes of wheat (Souza et al., 2002). Flour protein concentration and dough rheological properties are critical quality considerations in hard wheat classes. Bread loaf volume is of particular importance in hard red wheat, and noodle brightness and color stability are of particular importance in hard white wheat. Water absorption properties are a primary consideration for soft wheat pastry quality, and flour pasting parameters are important considerations for Asian noodle products. The studies presented in this manuscript describe the effects of the LPA phenotype on these end-use quality parameters. MATERIALS AND METHODS Generation of Experimental Materials