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

Reduction of the retrogradation of Injeolmi (IM) during storage for 3 days at 4 °C due to the addition of 0.8 % (w/w) wheat flour was analyzed. The optimum reaction temperature for the hydrolytic enzyme activity of α-amylase in the wheat flour was 30 °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°, while no distinct diffraction peak was observed for WFIM starch after storage. Enthalpy changes (ΔH) 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.