| Summary: | 碩士 === 國立宜蘭大學 === 食品科學系碩士班 === 106 === Rice is recommended as a safe food for celiac patients since it is gluten free and can be utilized in the production of rice pasta. However, the long cooking time was required for the dried rice pasta. The purposes of this study are to analyze the rehydration properties of rice pasta through the water sorption kinetics according to the evaluation of their cooking time, cooking loss and texture to design the desirable formula and drying conditions of raw rice pasta and steamed rice pasta. The results exhibited that the cooking time (until the disappearance of white point) of rice pasta added with high pressure homogenized rice flour (HPHRF) and gums (HPMC : guar gum = 1:1) is 5.8 min and the cooking quality is improved by giving lower cooking loss from 12.94% to 11.14%, and raising hardness to 16.56 N. Such results may be due to HPHRF possesses better gelation ability and higher adhesion than rice flour, and the gelation ability of gums improve the firm structure of rice pasta. The formula with supplementing additives (1% salt, 0.15% polyphosphates, 2% palm oil, 1% emulsifiers and 0.15% sodium carbonate) can reduce the cooking time to 2.7 min which is 50% cooking time of blank rice pasta. Rice pasta or steamed rice pasta with formula dried under oven drying, air-blast drying, freeze drying and fry drying only exhibited a falling rate period which was characterized by less water content of rice pasta. According to the water sorption kinetics, the highest initial sorption rate of rice pasta with 0.53 mm2·g-water/(min·g-d.s.) and steamed rice pasta with 1.13 mm2·g-water/(min·g-d.s.) are obtained prepared by freeze drying and 150oC fry drying, respectively. These results revealed that the porous structured of rice pasta and steamed rice pasta are formed by freeze drying and fry drying, respectively, to exhibit desirable rehydration ability, but the loose structure is fracture easily during cooking. Although addition of gums improved the mechanical properties and reduced the fracture of rice pasta during cooking. However, the slower water sorption rate resulting in the longer cooking time and caused conspicuous swelling, disintegration and dissolution of starch on rice pasta surface, which affected the rice pasta texture during cooking. Rapidly rehydration (cooking time 4.65.0 min and soaking time 7.58.5 min in 95oC hot water), lower adhesiveness, high springiness and cohesiveness are obtained in thinner rice pasta when the size is decreased from 5.0 mm 2.0 mm to 2.0 mm 1.0 mm. Overall, appropriate modification of formula, freeze drying for rice pasta, fry drying for steamed rice pasta and thinning the noodle can effectively improve the rehydration properties and texture of rice pasta.
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