澱粉質食品素材の調理・加工適性に関する理化学的研究

Abstract

1. The cooking and processing properties of newly developed rice. Newly developed rice was studied for its cooking and processing properties as milled rice, flour, and starch. To clarify the cooking, taste and physicochemical properties of rice is important in order to use it in cooked and processed foods. For the purpose of clarifying the factors influencing the taste of rice, the structure of starch was analyzed by measuring the amylose content and amylopectin unit-chain distribution using gel filtration. The average chain-length of amylopectins was determined by the rapid Smith degradation method and non-reducing residue measurement. The cooked rice, whose starch was low in apparent amylose content measured by gel chromatography, high in longer chain length fraction (Fr. II) and short in average chain-length of amylopectin, had a soft and sticky texture, and it was preferred in sensory evaluation. Thus, the relationship between the taste of rice and the rice starch structure was observed. In addition, a rapid, convenient and accurate method of evaluating rice texture is essential because the firmness and adhesiveness of cooked rice is important in the evaluation of sensory attributes. Using the new model of tensipresser at low and high compressibilities, the new texture evaluation method for cooked rice was applied to measure the firmness, adhesiveness, strength, and flexibility of cooked rice. The relationship between the texture and sensory attributes was clarified. II. Cooking and processing properties of starch derivatives. Laboratory samples of starch derivatives from corn and wheat starches were studied for the influences of chemical treatment and lipid on their gelatinization, swelling, and gelforming properties and the experiment was carried out in cooperation with Dr. Seib. In addition, the effect of starch derivatives on Japanese foods was examined. A commercial sample of hydroxypropylated wheat starch, obtained from Midwest Grain Products Inc., was used for Udon noodles, pie fillings, and oriental dumplings, and the texture and sensory attributes were compared with those of hydroxypropylated waxy maize, which isthe most popular starch derivative in United States and was obtained from National Starch and Chemical Co. Those Japanese foods prepared with hydroxypropylated wheat starch showed improved softness of the gel, texture and preferences, reduced preparation time and increased storage stability at low temperature, compared with those prepared with wheat starch. The result indicated that starch derivatives had the effect of improving the quality of cooked foods.