Production Preocesses And Quality Improvement For Heated-air Dried Instant Rice

Twelve rice cultivars were selected for producing heated-air dried instant rice. Physical-chemical indexes, cooking test of rice, texture profile and sensory indexes were measured and the relationships among them were analyzed. The result showed that hardness of texture profile parameters exhibited negative correlation with total score, flavour and form of instant rice. Adhesiveness was negatively correlated with total score and texture, it showed significant negative correlation with flavour. Protein content of rice had negative correlation with flavor and total score, and showed a significant negative correlation with texture. Amylose content showed significant negative correlation with flavour and texture, and was negatively correlated with total score. It is revealed that the texture profile analysis (TPA) can be adopted to evaluate the sensory quality of the product. Protein content and amylose content of rice have marked effects on flavour, texture and total score of heated-air dried instant rice. The japonica rice with amylose content<18% and protein content<7% is the appropriate candidate for producing heated-air dried instant rice.The effect of soaking condition, cooking condition and drying condition on final qualities of heated-air dried instant rice was investigated. A significant effect of soaking time, temperature and pressure on absorbency rate and the moisture content of rice was observed. Textural attributes as well as microstructure were found to be influenced by cooking temperature. It was found that 100℃was the optimal temperature for making instant rice. The reabsorbing ratio and moisture content of instant rice were found to be affected by drying temperature and time. The optimum drying condition was 100 min at 100℃. Single-factor and orthogonal experiments were employed to conformed the optimal parameters of preparing heated-air dried instant rice. The first soaking time and the second soaking time had a significant effect on the rehydration rate of instant rice. The second soaking temperature had a significant effect on the rehydration rate of instant rice. The first soaking time had a significant effect on the degree of starch gelatinization of instant rice. The obtained optimal procedures were showed as follows:soaking rice at 30℃for 60 min, removing from water, cooking rice at 100℃for 10 min, soaking rice at 50℃for 20 min again, then cooking rice at 100℃for 10 min again and drying at 100℃for 100 min.The effect of (3-cyclodextrin, sucrose ester of fatty acid, citric acid and a-amylase on final qualities was investigated. It was found thatβ-cyclodextrin, sucrose ester of fatty acid and citric acid were the appropriate food additives for improving the quality of instant rice, while a-amylase was not. Orthogonal experiment were employed to conformed the optimum formula of composite food additives was 0.2%β-cyclodextrin,0.2% sucrose ester of fatty acid and 0.4% citric acid.