Numerical Simulation And Experimental Study On Microwave Heating Of Packaged Pumpkin Pie

Pumpkin pie and other fermented staple food pastries occupy an important position in the Chinese dietary table.Direct heating in microwave oven will cause serious water loss,which will greatly reduce the taste quality.This phenomenon is caused by a variety of factors,including microwave oven power,heating time,initial moisture content,size,shape,packaging,its own porous structure and so on.In this paper,the effects of the size,initial moisture content,packing hole spacing and heating time on the moisture and temperature of pumpkin cake during microwave heating were analyzed by experiment and numerical simulation technology,and the optimum heating size and heating scheme of pumpkin pie with the best heating quality under this size were determined.Based on the electromagnetic field theory and heat transfer theory,a three-dimensional finite element model of microwave homogeneous food heat transfer was established to simulate the temperature distribution of potatoes heated by microwave in three kinds of geometric models of microwave oven,which were extremely simplified,simplified and real.The temperature distribution of potatoes heated by microwave was determined by comparing with the experimental results.The geometric model of microwave oven simulation is established.On this basis,combined with the theory of heat and mass transfer in porous media,a finite element model of heat and mass transfer in microwave porous media was established to simulate the microwave heating process of pumpkin pie.The simulation results are in good agreement with the experimental results,which verifies the reliability of the model.The weightlessness and temperature uniformity of 25 size pumpkin pies with 5 cm,5.5 cm,6.5 cm,7 cm edge length and 3 cm,3.5 cm,4 cm,4.5 cm and 5 cm height after 60 s of microwave heating were studied.The size of pumpkin pies with low weight loss and good heating uniformity was determined to be 7×7×4.5 cm3.On this basis,the relationship between the distance between holes,initial moisture content and heating time on the moisture loss of pumpkin pie after heating was studied.When the heating time and initial moisture content were fixed,the moisture loss of pumpkin pie gradually decreased with the increase of the distance between holes in microporous packaging;the relationship between heating time and packaging was negative exponential.With the increase of initial moisture content,the loss of moisture decreases gradually,and the relationship between initial moisture content and micropore spacing is linear.With the increase of heating time,the loss of moisture increases gradually,and the relationship between initial moisture content and micropore spacing is linear.The tensile properties and water vapor permeability of microporous films were measured.The effects of micropore spacing on their tensile properties and water vapor permeability were discussed.It was found that with the decrease of micropore spacing,the tensile strength of the films decreased,the elongation at break decreased first and then tended to be flat,and the water vapor permeability coefficient increased.The water vapor permeability of microporous films with different specifications is described as a function of temperature,and is used in the simulation of determining the optimum scheme of microwave heating pumpkin pie.The simulation results were analyzed by orthogonal test method,and the optimum scheme of microwave heating packaging of pumpkin was determined.The results showed that when the initial moisture content was 47%,the pumpkin pie was packed with M1 film.When the microwave heating time was 70 seconds,the heating quality was the best.