Influence of Amylose Content on Cookie and Sponge Cake Quality and Solvent Retention Capacities in Wheat Flour

Reduced amylose wheat (Triticum aestivum L.) produces better quality noodles and bread less prone to going stale, while little is known about the relationships between amylose content and the quality of soft wheat baking products such as sugar snap cookies (SSC) and Japanese sponge cakes (JSC). Near-isogenic lines developed from wheat cultivar Norin 61, differing in their level of granule-bound starch synthase (Wx protein) activity, were used to produce wheat grains and ultimately flours of different amylose contents. These were tested with regard to their effect on soft wheat baking quality and solvent retention capacities (SRC). Amylose content was strongly correlated to cookie diameter (r = 0.969, P < 0.001) and cake volume (r = 0.976, P < 0.001), indicating that the soft wheat baking quality associated with SSC diameter and JSC volume were improved by an incremental increases in amylose content. Among the four kinds of SRC tests (water, sodium carbonate, sucrose and lactic acid), the water SRC test showed the highest correlation with amylose content, SSC diameter, and JSC volume. When the regression analysis was conducted between the nonwaxy and partial waxy isogenic lines that are available in commercial markets, only water SRC was significantly correlated to amylose content (r = -0.982, P < 0.001) among of four SRC tests. This suggests that, unlike udon noodle quality, high-amylose content is indispensable in improving soft wheat baking quality, a process requiring less water retention capacity.