| Quick-frozen cooked rice is a new kind of instant rice, which needs to be heated before consumption and owns the closest tastes and flavors with freshly cooked rice. Quick-frozen dishes have the advantages of simple process, profuse nutrition and convenient consumption. Therefore, quick-frozen instant food possesses broad application prospects. In view of the market demand, this paper made specific researches, mainly including establishing a method to evaluate the quality of quick-frozen cooked rice, study on the production technology and a quality improver of cooked rice and researches on quality control of quick-frozen dishes. Those studies could provide a theoretical reference for the development of frozen cooked rice, and a practical guide for industrialized production of the product. The main conclusions were listed as follows:Seven kinds of material rice were selected to make quick-frozen instant rice and the quality evaluation method was established. Results showed that the hardness and adhesiveness measured by TPA mode could evaluate the quality of quick-frozen cooked rice. The extremely significant correlation between amylose content and hardness, extremely significantly negative correlation between amylose content and adhesiveness were found. While none of protein content, moisture content and fat content went in correlation separately with product quality. The study showed that the rice with about17%amylose content was appropriate for producing quick-frozen cooked rice.Soaking temperature, soaking time and adding amount of water were investigated to select the optimal soaking condition by measuring water absorption and moisture content. Pseudo-level method of L9(34) orthogonal design results showed that the optimal cooking process was maintaining pressure at80KPa for4min and stewing rice for15min. The studies on the freezing rate of cooked rice showed that freezing temperature, weight, package had a great influence on freezing rate. Moreover, microwave power and reheating time had a significant effect on temperature rising, moisture content and sensory quality. As for about200g cooked rice,800W microwave power for3min was recommended to adopt. Different evaluation indexes of quick-frozen rice were studied at different temperatures during storage. Results showed that the total bacteria counts exceeded standard and sensory quality couldn’t be accepted after1day at25℃and37℃,after22days at4℃and after7months at-18℃. As a result, frozen storage could retard starch retrogradation and the growth of bacteria in order to prolong the shelf life.Three additives, including GML, β-CD and alcohol on the evaluation indexes were optimized using RSM and PCA. Addition of0.025%GML,0.58%β-CD and0.41%alcohol considered as a quality improver could help obtain the optimum quality of instant rice. Additives formulated by the optimum condition had no significant effects on the starch digestion, but the quality improver could retard short-term starch retrogradation and improve the textural properties.The processing conditions of quick-frozen pork with potatoes were optimized by orthogonal tests. Results showed that the optimal conditions were:pork was fried at100℃for60s, potatoes were fried at160℃for90s and sauce was reserved at210℃. Different nutrients of pork and potatoes were analyzed during storage period. Results showed that water content, protein content, fat content and starch content varied differently with the increase of storage time, and the frozen pork with potatoes could be kept in at least6months at-18℃. |
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