Effects of rehmannia (Jiwhang) powder on the properties of Korean wheat-type noodles

Korean-type dry noodles were prepared with composite flours mixed with various amounts of freeze-dried rehmannia (jiwhang) powder. Composition of the composite flours affected flour and final product qualities. Gelatinization temperature of the composite flour increased linearly, while peak viscosity decreased logarithmically, with increases in the rehmannia powder content. Water absorption determined by both a Farinograph test and cooking test decreased linearly with increases in the rehmannia powder content. Swelling index (SI) also decreased, while cooking loss and turbidity of cooking water increased progressively, with increasing rehmannia powder content. In terms of turbidity of cooking water, rehmannia noodles with rehmannia powder content of up to 4% (w/w) were comparable to control wheat flour noodles. Sensory evaluation tests also indicated a similar result in that rehmannia noodles with rehmannia powder content up to 4% (w/w) were more acceptable than or comparable to the control wheat flour noodles.