Effect of wheat flour addition on retardation of retrogradation in waxy rice cake, Ingeolmi

Abstract

Reduction of the retrogradation of Injeolmi (IM) during storage for 3 days at 4 degrees C due to the addition of 0.8 % (w/w) wheat flour was analyzed. The optimum reaction temperature for the hydrolytic enzyme activity of a-amylase in the wheat flour was 30 degrees C for gelatinized waxy rice. Activity sharply increased until 7 h and then leveled off. The amylose content of IM remained almost constant, while that of wheat flour-added Injeolmi (WFIM) increased by 24 % during storage. Average amylopectin chain lengths of the starches in IM and WFIM increased from 27.91 to 30.36 and from 29.57 to 57.98, respectively, during storage. In the X-ray diffraction pattern, IM starch showed the characteristic peak located at 17 degrees, while no distinct diffraction peak was observed for WFIM starch after storage. Enthalpy changes (Delta H) indicated by differential scanning calorimetry of IM and WFIM were 1.1060 and 0.6159 J/g, respectively. The hardness of IM significantly increased from 149.27 to 2202.52 g(f) during storage while that of WFIM increased only from 112.14 to 128.08 g(f) which was 5.82 % compared to that of IM.