米粉パン中における米粉割合の推定方法の検討

Abstract

In this study, a method of estimating the rice flour content of rice bread was discussed to ensure the food labeling information of products.1) The absorption spectrum of iodine-starch of rice (Koshihikari) flour was different from that of the strong-type wheat grain. Under a microscope, only the smaller 5μm starch grains were detected in the Koshihikari rice. On the other hand, 15-40μm starch grains were observed in the strong-type wheat grain.2) The maximum absorption wavelength in the spectra of the iodine-starch complexes (λmax) was specifically different among every rice cultivar, although the λmax among the various products from wheat were similar. In products made from rice, the λmax values were not affected by the size of the starch grains in the rice flour and the contents of the other materials except for the rice.3) Based on the increase in the rice flour content, the λmax of breads made from flour mixed with rice and wheat decreased. Many large starch grains considered to come from the wheat were examined from the 100% whole wheat bread. On the other hand, the large starch grains decreased as the rice flour content increased and no large starch grains were detected in the 100% whole rice bread.4) For the marketed products, the λmax of the 100%whole rice bread was lower than that of the 100% whole wheat bread. Only small starch grains considered to be rice starch were observed in the 100% whole rice bread. However, large starch grains regarded to come from the wheat were found in bread containing wheat flour. The results of this study indicated that the method to examine the λmax of rice bread and to observe the size and form of starches from rice and wheat under a microscope was useful to estimate the rice flour rough content of rice bread.