Simulation And Experimental Study On Vacuum Cooling Process Of Cooked Bacon

Vacuum cooling has been popularized in the field of food industry in recent years because of its fast cooling rate,uniform cooling,safety and hygiene and so on.But the water loss rate is serious,the food with low water content is difficult to cool and so on.Bacon,as a traditional food spread for thousands of years,is still favored by consumers.Vacuum cooling can effectively prolong the shelf life and preserve the flavor of smoked bacon.In addition,there is still a lack of related research on water migration and pressure distribution in the vacuum cooling process of meat products.In this paper,based on the theory of porous media and mechanism of heat and mass transfer,Chinese traditional bacon as raw material,a coupled heat and mass transfer model for vacuum cooling of cooked bacon was established.At the same time,in order to explore the effect of final cooling pressure on cooling rate and mass loss,the experiment and theory were compared and analyzed.A vacuum cooling equipment for cooked food with stable pressure is designed and built.The principle of absorbing vacuum chamber gas by volume capacity of vacuum energy storage tank is used to realize the function of stabilizing pressure.The final pressure can be stabilized in a certain range of values by experimental measurement.The ways and energy forms of water migration in vacuum cooling are discussed in detail and the mechanism is analyzed.Combined with the theory of porous media and the law of heat and mass transfer,the mathematical model of heat and mass coupling transfer of cooked bacon during vacuum cooling is established.The model takes into account the diffusion of liquid water and gaseous water.Each physical layer is coupled by COMSOL Multiphysics software and the numerical calculation is carried out.The vacuum cooling experiment of cooked bacon was carried out,and the experimental data were compared with the calculated results of the model.It is found that the simulation results are basically consistent with the cooling changes and mass losses of the experimental data.Real The test results verify the reliability of the mathematical model,which can be used to predict the temperature distribution,mass loss and pressure distribution of cooked bacon during vacuum cooling.It has certain theoretical significance for the subsequent study of heat and mass transfer of vacuum cooling.On the basis of heat and mass coupling transfer model in vacuum cooling process,the temperature drop change and mass loss results are calculated by changing the final cooling pressure,and the result of the study and the experimental data show that the lower the cooling end pressure,the faster the cooling rate,the more uneven the cooling and the greater the mass loss.The increase of mass loss is mainly due to two reasons: first,thelower the final pressure is,the greater the heat absorbed by water evaporation is in proportion to the total heat in the material;Second,under the condition of high final pressure,the rate of gas extraction is slower,and the longer the water vapor stays in the matrix,the more water vapor will be absorbed by the matrix.Based on the simulation results of temperature change and mass loss by changing the final cooling pressure,the final cooling pressure and cooling time,as well as the mass loss,are fitted into the formula,and it is found that the relationship between the final cooling pressure and the cooling time is an exponential function.There is a linear function relationship between the final cooling pressure and the mass loss.