Physicochemical properties of starch in rice flour with different hardening rates of glutinous rice cake (mochi)

The hardening rate of glutinous rice cake (mochi) made by Kagura-mochi (Kag) was two times higher than that of Hakusanmochi (Hak). Protein in the waxy rice indicated a similar distribution and content; therefore, the textural properties of the rice product were dependent on the physicochemical properties of starch in the rice flour. Urea-induced gelatinization, differential scanning calorimetry, and rapid visco analysis revealed that starch in Kag was less easily gelatinized than that in Hak. The solubility and swelling power at 70 degrees C of starch in Kag rice flour were slightly lower than that in Hak. Relative crystallinities of starch in Kag and Hak rice flour were 55.1% and 49.3%, respectively. The chain length distribution of the short chain of amylopectin in Kag rice flour was lower than that in Hak. The low short-chain content in Kag may be related to the increase in the hardening rate of the mochi made by Kag.