| The total income of catering industry in China has exceeded 4672.1 billion RMB in 2019.To promote the development,automation,and standardization of Chinese cuisine,it is necessary to carry out a systematic and in-depth study so as to obtain the inherent principles of heat transfer and the corresponding quality changes during the cooking process.Chinese stir-frying is one of the most distinctive and widely used cooking method,and numerical simulation is the only way to study the heat transfer process of food particles during the Chinese stir-frying.The Chinese stir-frying is considered as a complex thermal processing under high-temperature and short-time treatment.This is significantly different from any other cooking operations.In order to study the mechanism of heat and mass transfer and the changes of maturity and quality of food particles during the Chinese cuisine process,a heat and mass transfer model including multiphase coupling phase transition and shrinkage was developed to simulate the Chinese stir-frying process of food hygroscopic porous medium based on the porous media theory,Fourier's law,Newton's cooling law,and Darcy's law.In order to get a reasonable solution for this Chinese stir-frying model,the following hypothesis were proposed:(1)the transfer of oil to the internal of food particles could be ignored;(2)the water evaporation only occurred on the particle surface and the shell obstruction was also ignored;(3)the particle shrinkage was uniform;(4)the particle was homogeneous and isotropic,and the fluid phase in the particles was continuous;(5)there was no internal heat source and chemical reaction in food particles,and only convection heat transfer and heat conduction were calculated.The non-equilibrium evaporation formulation,shrinkage formulation,energy,momentum and mass conservations of water,and gas governing equations were considered in this model and it was finally solved using finite element method and mesh moving method.The temperature history,moisture content,and volumetric shrinkage rate of the Chinese stir-fried pork loin were used as comparations to validate the model accuracy.The results indicated that the accuracy and robust properties of this model was greatly increased after considering the shrinking process.To reveal the mechanisms of heat and mass transfer inside food particle,water evaporation rate of particle surface,volumetric shrinkage rate,pressure variations,moisture content and temperature distributions were all simulated for Chinese stirfrying process.The simulation results showed that the water loss,which was induced by strong convection heat transfer,was the main reason for shrinkage.The moisture loss rate and volumetric shrinkage rate were increased by the surface evaporation rate,and the particle internal pressure was affected by volumetric shrinkage.Since the volumetric shrinkage rate was similar to water loss rate,the moisture content and shrinkage were associated as an important indicator for evaluating cooking quality of food particles.Additionally,the heat transfer efficiency of particles was greatly enhanced by shrinkage because of the increasing surface area to volume ratio.The shrinkage could be used to improve the overall moisture content of food particles if evaluated from the perspective of cooking quality optimization.Based on Maturity value theory combined with deep learning technology,this paper initially explores the rapid and real-time classification method of cooking Maturity,and constructs a set of classification system for judging the Maturity value of meat slices in the process of Chinese stir-frying.The convolutional neural network model trained by transfer learning is used to classify central Maturity value of meat slice images,and the test accuracy rate is 99.7%.At the same time,the model is deployed on the Android mobile terminal,so that it can quickly classify the Central Mature value of the meat slices in real time. |
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