Numerical simulation, optimization, study of technical features and operational parameters for Chinese cuisine

So far numerical simulation, optimization and parametric analysis about heat transfer and kinetics for Chinese cuisine has been a virgin area. As the most representative arts for Chinese cuisine, stir-frying should be defined as a rapid cooking operations with stirring using plenty of oil as heat transfer medium in opened vessel. This thesis which consists of two parts focuses on processing optimization, technical features and operational parameters of stir-frying. In the first part, optimization of culinary processing was carried out via numerical simulation based on the existing heat transfer model and kinetics principle put forward by author, and was analogous to optimization of can sterilization and liquid-particulate aseptic processing. The optimization model for stir-frying of sliced pork was established, in which target variables is oil temperature, constraints condition is that maturity value equals terminal maturity value, and objective condition is to make overheated value with average volume to minimum. The parameters of the above model were determined as follows: the quality factors to indicate cooked well done of pork were identified as thermal death of pathogenic microorganisms and thermal denaturation of proteins, both of them have similar Z value range, and the quality factors to indicate pork overheated were identified as moisture diffusion and food nutrition loss, thus Z value of maturity value and overheated value was respectively set at 7℃ and 30℃. According to several references, pork mature value was set to 0.1-1 min at 70℃, surface heat transfer coefficient was set to 1 000 W/m2℃, and the thermal physical parameters of pork were set in the same way. The solutions of optimization model which obtained via compiling program and calculation with Matlab showed that a certain sizes of pork slices has a certain optimum oil temperature with minimum average overheated value. And then the reliability and complexity of the optimal model and the effect of model hypothesis conditions on the model were discussed, the optimization model can be applied for the most of cuisine process effectively. The reason why optimal model of cuisine is exist was considered that cuisine maturing (done well) is more sensitive to temperature than overheating, so better cooking quality can be achieved via rapid heating while the raw materials reach to maturity. The loss of water was regarded as decisive influence on texture of cuisine products, and the diffusion coefficient of water in particulates has greater Z value than mature qualities, so lead to existing of the optimum oil temperature, therefore, water diffusion is the crucial problem concerning products qualities for Chinese cuisine. The rationality of traditional Chinese cuisine was explained via the analysis on the calculation results of the optimal model. The stir-frying that heat animal meat by a larger amount of oil with high temperature and cutting raw materials into small particles to reduce the size of heat transfer agreed with the kinetics and heat transfer principles reflected in the optimal model. In the second part, technical features and operational parameters of stir-frying was studied. First of all, the difference between stir-frying, boiling and steaming were analyzed via numerical simulation of their heat transfer and kinetics, where heat transfer medium are respectively oil, water and steam. Calculation results showed that maturity time of stir-frying (22.18 seconds) is much shorter than steaming (43.75 seconds) and boiling(82.62 seconds), meanwhile the volume average overheated value of stir-frying is also the lowest, consequently, stir-frying has evident advantages on efficiency and quality. However, the surface overheated value of stir-frying is the highest, it meant that the thermal quality loss is serious on the surface. Overall, stir-frying is more suitable for those culinary materials which are heat-sensitive, impact- resisting, oil-resistance, have the necessity to form favorite flavor caused by high temperature. And then, the affect of cutting and stirring on culinary qualities were analyzed. Numerical simulations of the stir-frying process of 0.2-0.6mm sliced pork showed that the smaller the size of particles, the shorter maturity time, and the smaller overheated value . Calculation results showed that the most suitable thickness for sliced pork is 2～4 mm, and this size is commonly used in stir-frying of Chinese cuisine. In terms of the established optimal mathematical model, calculation condition and algorithm, the results computed with hfp=200～30 000 W/(m2℃) and thickness 3mm for sliced pork showed that the higher hfp, the lower optimum temperature and the shorter maturity time. Stirring is indispensable which contributes to uniform heat transfer and increases surface heat transfer coefficient in stir-frying. Thereby, strong agitating and stirring measures adopted in traditional manual cuisine is agree with the principles about heat transfer and kinetics. Finally, heat transfer and operating parameters of stir-frying were listed and analyzed. Six major forms of heat transfer and phase change process in stir-frying were listed. The influences on culinary qualities of several parameters in stir-frying, such as warm-up time of oil, oil-to-material ratio, equipment size and other parameters, were analyzed on whether these factors result in deviation from optimum operating conditions.