Process Optimization And CFD Numerical Simulation Analysis Of Stir-fried Shiitake Mushrooms

As a kind of fast food,prefabricated instant dishes have a good market prospect.Shiitake mushroom is the largest edible fungus species in China.It is moderately priced,widely used and has a unique taste.It is high-quality raw material for the development of prepared dishes,which can not only meet the needs of the current fast-paced catering market,but also enrich the varieties of prepared dishes.Developing a prefabricated mushroom dish on the basis of Chinese cooking technology can not only meet the needs of consumers,but also increase the added value of mushroom products and create higher economic benefits.The main processing method of Chinese cooking is oil frying,while the process is short and the reaction is violent,and it is accompanied by the evaporation of water.With this method it is difficult to measure the transient changes of food during the cooking process by traditional analysis methods.Therefore,CFD numerical simulation technology is used to analyze the cooking process,which is a very effective means.In this paper,according to the technological process of shiitake mushroom dishes,based on the optimization of the process and the theory of mass transfer and heat transfer in porous media,combined with the equation of conservation of mass,energy and momentum of the liquid phase（gas phase）,the heat transfer and mass transfer models of the samples during the cooking process were constructed.The model realized the prediction of the instantaneous change law in the cooking process of shiitake mushrooms.The conclusions of this study are as follows:1.Process parameters of the dishes is optimized through single-factor and response surface optimization experiments.Sensory scores of the dishes,which are taken as the response value,are conducted based on the principle of fuzzy sensory evaluation.A four-factor and three-level response surface optimization test is designed and conducted as a test of quality inspection on the finished product.The results shows that the influence of the four seasonings on the sensory scores of the dishes is extremely significant（p<0.01）,and the order of the four influence factors on the sensory quality of the dishes is salt > light soy sauce > millet spicy > oyster sauce,and the best formula is added 1.9% of salt,6.0% of light soy sauce,8.7% of oyster sauce,and 1.0% of spicy millet.The test results of each quality index based on this formula are optimal.2.Using the COMSOL Multiphysics 6.0 software,a multi-physics field coupled heat and mass transfer model with moisture and unsaturated porous media with gas evaporation suitable for the cooking process of dishes is constructed.Applying numerical simulation on this model realized prediction of temperature and moisture content of shiitake mushrooms during the cooking process at any time.Then experiments are employed to measure the moisture content and center temperature of shiitake mushrooms during the cooking process,which are analyzed and compared the difference between the predicted value of the model and the experimental value.This is to verify the accuracy of the model,and by changing the model parameters in samples to verify the practicability of the model.The simulation results show that under the conditions of frying temperature of 180℃ and thickness of shiitake mushroom slices of 5 mm,the central temperature reaches 85 ℃ when the heating time is 360 s,and most of the water flow lines are evenly distributed,reaching the mature state and consistent with the experimental value,which is a good agreement.While at the frying temperature of 180 ℃,the time to reach the mature value increases by 110 s when the slice thickness increases from 3 mm to 5 mm,and the time to reach the mature value increases by 130 s when the slice thickness increases from 5 mm to 7 mm.The relationship between the two tends to rise as a polynomial function.The particle center temperature decreases with the increase of convective mass transfer coefficient.When the convective mass transfer coefficient increases from 2.5·10^-6 m/s to 3.5·10^-6 m/s,the maturity time increases from 326 s to 354 s,while the convective mass transfer coefficient increases from 3.5·10^-6 m/s to 4.5 · 10^-6 m/s,the maturity time increases from 354 s to 382 s.The greater the particle thermal conductivity is,the more energy is transferred to the interior of the food particle per unit time,and the shorter it takes to mature.The larger the specific heat capacity is,the slower the temperature rise rate is inside the particle,and the longer it takes to mature.