Retrogradation in some tropical root starches and its influence on vital gluten/starch composite bread quality.
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A Differential Scanning Calorimeter (DSC) was used to study starch retrogradation in 60 percent moisture gels of native root starches of cassava, sweet potato, arrowroot and taro, as well as soft white spring (SWS) and hard Canadian western red spring (CWRS) wheat starches at 24 degrees C, and related to retrogradation as determined by a compressimeter in composite bread crumbs containing 15 percent vital gluten and 85 percent starch. Bread quality was further examined through loaf volume, mass and panel organoleptic assessment of crumb grain, texture and chewability. Root starches retrograded more rapidly and strongly than most wheat starches. The higher the amylose content and solubility, the more prone to retrogradation the root starches were found to be. All starch pastes developed weak retrogradation endotherms between 50 and 60 degrees C. A second set of stronger retrogradation endotherms were developed by cassava, sweet potato and arrowroot starches between 75 and 100 degrees C after the 6th day of storage. DSC endotherms and crumb compressibility proved that cassava starch retrograded most rapidly and intensively, followed by sweet potato, arrowroot, taro and finally the wheat starches. The extent of retrogradation in starch had a corresponding negative influence on the quality of the vital gluten/starch composite bread in comparison to pure wheat flour bread. (AS).