Study On Drying Characteristics And Technology Optimization Of Beef Jerky By Mid-infrared-vacuum Combined Drying

Combined with the characteristics of high heat transfer efficiency of mid-infrared and low temperature drying of materials in vacuum environment,aiming at the problems of low drying efficiency and poor product quality of existing drying equipment,the mid-infrared-vacuum combined drying equipment is improved and designed,it can monitor the temperature of heating pipe,the temperature of material,the weight of material and the vacuum in the cabin in real time,and realize the intellectualization of material drying.First of all,the main structure and working principle of mid-infrared-vacuum combined drying equipment are described in detail.After debugging,it is found that the equipment is stable,safe and reliable,and easy to operate and control by field technicians.It can provide technical support and theoretical basis for high efficiency and high quality dehydration drying of beef jerky.Secondly,Jingyuan yellow beef was used as experimental material in this paper,the water distribution and migration of Jingyuan yellow beef dried by mid-infrared(MI)drying,low temperature vacuum(LTV)drying and mid-infrared combined electric heating(MICEH)drying were studied by low field nuclear magnetic resonance(LF-NMR)technique.Combined with the drying characteristic curve of Jingyuan yellow beef,the effects of different drying methods on the drying characteristics and the moisture distribution and migration law of beef in different drying process were revealed through the parameters of internal moisture state,peak integral area,transverse relaxation time T2 and hydrogen proton density during the drying process.The results showed that under the conditions of MICEH drying,MI drying and LTV drying,the wet-based moisture content of Jingyuan yellow beef decreased from 72%to less than 20%in 330 min,420 min and 450 min respectively,the average drying rates were 0.4179,0.3308 and 0.3099 g·g-1·h-1,respectively;when the wet base moisture content of beef was about 35%,the combined water peak area A21 was obviously decreased,and when the wet base moisture content reached 25%,the combined water signal disappeared;under different drying conditions,there was a significant linear relationship(P<0.05)between the moisture content of beef and the total integral area of peak,the linear regression equation of MICEH is y=16913x-1102.3(R2=0.9852);and the moisture in the early stage of the drying process decreases rapidly,at the later stage,the water diffusion rate was significantly lower than that of MI and LTV drying(P<0.05),but the hydrogen proton density distribution of MICEH drying was relatively uniform and the drying quality of beef was higher.Finally,the regression mathematical model of mid-infrared-vacuum combined drying beef was established by using Box-Behnken Design(BBD)experimental design method,the effect of mid-infrared-vacuum combined drying technology on the quality of beef jerky was studied,and the technological parameters of mid-infrared-vacuum combined drying were optimized.On the basis of single factor experiment,mid-infrared drying temperature,mid-infrared drying time and vacuum drying temperature were selected as independent variables,and the comprehensive values of drying time,color brightness,shearing force and sensory score were selected as evaluation indexes,a three-factor three-level response surface optimization experiment was designed,and the corresponding regression model was established to find the relationship between the comprehensive value of product drying and the selected three factors,the optimal drying parameters were obtained as follows:The beef was dried at 60? mid-infrared temperature for 120 min,then was dried at 70? vacuum temperature until the moisture content was 20%.The maximum synthesis value is 0.7295,which is consistent with the theoretical prediction value of the model,and proves the reliability of the model.Then the optimized mid-infrared-vacuum combined drying process was compared with MI drying and LTV drying to verify the optimal process.The results showed that mid-infrared-vacuum combined drying could significantly reduce the drying time(P<0.05)and improve the quality of beef jerky,and compared with vacuum drying can also significantly improve the color of products(P<0.05).