Determination Of The Physical Properties Of Wrappers And Fillings Of Dumplings And Simulation Of Immersion Freezing Process Of Dumplings

The thermophysical properties of food are important parameters for the design of food cold storage and food processing refrigeration equipment,and also an important basis for determining the processing time of food refrigeration,freezing and drying.The process of food freezing is an extremely complicated process.Specific heat and thermal conductivity are the two factors that have the greatest impact on the quality of quick-frozen dumplings.Calculating the specific heat and thermal conductivity of dumplings is the most critical step in simulating the quick-frozen dumpling process.For optimization The process of quick-frozen food and reducing the production cost are of great significance.This article uses shiitake and pork stuffed dumplings as the research object.First,the inversion method is used to obtain the specific heat and thermal conductivity of the dumpling skin and stuffing.The adsorption and diffusion process of the dough is studied,and the moisture diffusion coefficient of the dough is obtained by inversion method.Finally,the specific heat,thermal conductivity,and water diffusion coefficient are substituted into the dumpling geometric model.The three-dimensional dumpling model was established to simulate the frozen process of dumpling.The main results are as follows:(1)During melting and crystallization,a DSC temperature rise curve of 10 C / min is more suitable as the calculation data of specific heat.As the moisture content of the dough increases,the downward trend of the temperature curve of the measured point of the dough becomes slower;at the same time,the freezing point increases and the freezing time becomes longer.For the obtained specific heat curve,peak shape correction and freezing point correction are needed to use.The peak value of the specific heat curve after correction is higher,and the specific heat decline trend is steeper after reaching the initial freezing point.As the moisture content increases,the specific heat curve of the dough shifts less.(2)The thermal conductivity of dumpling skins and fillings can be successfully calculated using the inversion method.Before the temperature reaches the initial freezing point,the thermal conductivity of dumpling crusts and fillings slowly decreases as the temperature decreases;after reaching the initial freezing point,the thermal conductivityincreases as the temperature decreases.The established dough model can simultaneously predict the effects of moisture and temperature on thermal conductivity,which can provide basic data for the processing of quick-frozen products in the freezing range.(3)The equilibrium moisture absorption isotherm and moisture absorption curve of dumpling dough can be fitted by GDW and Weibull models,respectively.When the water activity is the same,the equilibrium moisture content increases with decreasing temperature.The adsorption moisture and rate increase with increasing temperature.The parallel exponential model can better simulate the change of adsorbed moisture at different temperatures,and the calculated moisture diffusion coefficient decreases with temperature at the same time.Through verification,it was found that the moisture diffusion coefficient is a curve that changes with time,and cannot be simply expressed by a constant.(4)The method of combining CT and Comsol software can accurately establish a three-dimensional model of dumplings.Dumplings model using Comsol software operation,can be observed in real time,dumplings in the process of cooling temperature changes of different time through dumpling skin was compared with the filling temperature difference,we can clear out dumplings in different cooling stage of the quick-freezing process of change,at the same time also can change the boundary condition to find the best frozen condition.