Design And Optimization Of Low-Pressure Cooking Process And Low-Pressure Cooked Rice Quality Evaluation

In this paper, we design, optimize and establish the low-pressure cooking process, compare and analyze the sensory quality, physicochemical properties and nutritional quality of ordinary pressure cooking process, low-pressure cooking process and high-pressure cooking process, and try to estimate the gelatinization degree of rice during low-pressure cooking process by visual inspection technology.The main contents and results as follows:1. Based on the pressure cooking process which had been investigated, the low-pressure cooking process was designed and optimized, established. When the low temperature, low temperature controlling time, pressure, pressure controlling time, rice braising time were 55℃,12min, 10kPa,12min,5min respectively, the desirable low-pressure cooking process was established.2. The sensory quality evaluation indicate that the color, luster, integrity, palatability of low-pressure cooked rice was significantly improved, and the low-pressure cooked rice has strong consumer preference. The fragrance of the cooked rice of three kinds of cooking process is normal, there are no significant differences.3. During the low-pressure cooking process, the optimum time of activities of endogenous enzymes in rice grain were increased because of water diffusion within rice kernels time was prolonged, the damage on surface of rice kernels which formed by friction between rice kernels was decreased because of rice-water boiling time reduced. Therefore, the low-pressure cooked rice kernels surface was smoother. More amylose, reducing sugar, amino acid, et al. leached out during cooking. And the taste was improved. In addition, the red and yellow pigments dissolve more; the whiteness is higher.4. During cooking, the grains swell, the out-layer starches of rice grain gelatinize earlier than inner-layer, the surface occurs cracks, and the internal part occurs voids. When the braising stage is over, water and solid fill up the cracks on the surface, water in the cooked rice grain is balanced, the volume of the rice kernel decrease. And the starch-lipid compounds formed in the rice kernels which cause the crystal structure changed and the crystal size increase. During the low-pressure cooking process, rice grains mainly absorb water in the early time and the starch rapidly gelatinizes later. There are fewer cracks, better morphology. But the hollows in the kernels are larger. In addition, for low-pressure cooked rice, the greater of the swelling ratio and the lower of the hardness, the more poor of resisted damage ability. The starch digestion of low-pressure cooked rice was close to high-pressure cooked rice, but was higher than ordinary pressure cooked rice.5. The correlation between sensory evaluation and texture properties indicate that Fragrance will be stronger when chewiness and hardness decrease; luster will be better when resilience and adhesiveness decrease; color will be more attractive and taste will be sweeter when hardness decreases; morphology will be more slightly damaged when resilience and cohesiveness increase.6. We firstly try to estimate the gelatinization degree of rice during low-pressure cooking process. The multilayer feed-forward network for estimatingthe gelatinization degree of rice during low-pressure cooking process was established by extracting and analyzing the image feature information of rice grain and was trained to distinguish the model again and again. The result of visual inspection system estimated indicates the regularity between image feature parameters and the changes of starch gelatinization degree in rice. It means the gelatinization degree of rice can be evaluated by analyzing the image information.