Experimental Study And Numerical Simulation Of Hot Air Drying Process Of Potato

Potatoes are rich in protein,amino acids,vitamins and minerals,is a common food crops.Because of the influence of temperature and moisture content,the shelf life of fresh potato is short.Hot-air drying is a simple and widely used drying method,which can effectively prolong the storage time and ensure the product quality.In this paper,the heat and mass transfer and water transfer of potato chips during hot air drying were studied systematically,including the drying characteristics and quality analysis,the drying kinetics model and the shrinkage kinetics model and the numerical simulation of the heat and mass transfer during the process of potato chips drying.The main contents and conclusions are as follows:(1)The hot air drying characteristics of potato chips under different hot air temperature and slice thickness were tested and the effects of hot air temperature on the color,rehydration rate and sensory evaluation of potato chips were analyzed.The results showed that the higher the hot air temperature and the smaller the slice thickness,the faster the drying rate of potato chips,the higher the temperature rose from 45?to 75?,and the drying time decreased by237 min.Secondly,the temperature of hot air had a significant effect on the color and luster of potato chips,and the brightness(L*)of potato chips decreases with the increase of temperature,while the brightness(a*)and yellow(b*)of potato chips increases with the increase of temperature,from 45?to 75?,and the variation range of?E value was from7.89 to 17.89.Among them,the temperature rose from 65?to 75?,the browning degree increases by 22.32 and browning significantly,which was not conducive to ensuring the color and lustre of potato chips;when the temperature of hot air was 65?,the rehydration rate of potato chips was 3.26 and the sensory score was 72 points,which was the highest.To sum up,65?was the optimal drying temperature of potato chips.(2)The drying kinetics and shrinkage kinetics models of potato chips were studied theoretically,and the effective water diffusion coefficient and activation energy were calculated.The results show that in terms of drying kinetic model,Page model had the best fitting effect with the experimental data,and the coefficient of determination R~2=0.9983,which could accurately predict the change of water content of potato chips during hot air drying.In terms of shrinkage and deformation,the Weibull distribution function could describe the volume change law of potato chips well during the drying process,and the coefficient of determination R~2=0.9982.In the range of study,the effective water diffusivity of potato chips was in the range of 5.02×10^-10?11.53×10^-10 m~2/s,and its value increased with the increase of hot air temperature or the decrease of slice thickness.The drying activation energy and shrinking activation energy of potato chips were 27.35 k J/mol and 46.44 k J/mol,respectively,calculated by Arrhenius equation.(3)The hot air drying process of potato chips was numerically simulated,and the prediction model of heat and mass transfer in hot air drying considering shrinkage deformation was established.Comparison with the experimental results at hot air temperature and slice thickness verifies the effectiveness of the model.Based on the numerical prediction model,the effects of shrinkage deformation on the drying characteristics of potato chips were analyzed,and the drying process of potato chips under different wind speeds and air humidity was predicted.The results showed that the error between the simulation results and the experimental values of the moisture content of potato chips was less than 8%.Based on the model,the temperature and humidity distribution of potato chips in different time periods and the shrinkage deformation of hot air drying process were predicted,and it was found that there was obvious nonlinear shrinkage deformation of potato chips during drying,and the deformation in the slice diameter direction was more significant than in the thickness direction.The predicted drying characteristics of potato chips under different wind speeds and hot air humidity are in agreement with the theoretical values.The model can accurately predict the temperature and moisture content of potato chips under different hot air temperature,wind speed,humidity and slice thickness,which provides a theoretical basis for the optimization of potato drying process.