Study On The Combined Air-heat Pump Drying Of Fresh Peanut With Shell And The Biological Characteristics Of Peanut During Storage

Peanut plays an important role in oil crops in our country,and plays a great role in promoting the development of agricultural economy in our country.However,fresh peanuts have a high moisture content,and if they are not dried in time after harvest,it is easy to become mouldy and putrefied,and the drying method has a great impact on the quality of peanuts.In addition,peanuts after drying also need to be stored to ensure the annual supply,and in the storage process is often due to improper storage methods,hot and humid weather,pests and other problems to reduce the quality of peanuts.Therefore,in order to ensure the drying quality and storage quality of peanut,it is very necessary to choose a suitable drying and storage method.In this paper,hot air and heat pump drying method was used to study the moisture change and quality change of fresh peanut with shell during the drying process,so as to reveal the drying mechanism of fresh peanut with shell during the drying process.On this basis,the combined drying method was adopted to shorten the drying time and optimize the combined drying technology under the condition of ensuring the quality,and the changes of biological characteristics in peanut storage were investigated.which provided some theoretical basis for the drying and storage of fresh peanut with shell.The main conclusions are as follows:1.Through hot air drying,the moisture change and shrinkage characteristics of fresh peanut with shell were studied.It was found that the temperature increased from 40?to 60?,the drying time was shortened by1.8 times,and the shrinkage ratio of peanut shell and peanut kernel decreased by 8.0%and 7.1%respectively.At 40?drying temperature,the degree of microstructure change and shrinkage are small.Peanut shell contracted earlier than peanut kernel,but not as much as peanut kernel.For shrinkage ratio to build model of peanuts and peanut,peanut shells of the Quadratic model R²value maximum,0.9901,peanut Vazquez model R²value maximum,0.9675.Therefore,peanuts and peanut shell respectively by using the Quadratic model and Vazquez model reaction peanut in hot air drying process of the change of volume contraction.2.The moisture and quality changes of fresh peanut with shell were studied by heat pump drying,and it was found that peanut shell and peanut kernel had different drying characteristics during heat pump drying.The drying temperature increased from 40?to 60?,and the drying time was shortened by 1.73 times.Peanut shell was dried before peanut kernel,and peanut kernel was the main part of water loss in the later drying period.Compared with hot air drying,peanut moisture changes more slowly in the heat pump drying process,causing less damage to peanut microstructure.When the temperature increased by 20?,the porosity of peanut kernel increased by 6.61%and that of peanut shell increased by 2.93%.Nonlinear fitting was performed on the MR data of peanut heat pump drying.At the temperature of 50?,the two-term model R²of peanut shell reached the maximum value,0.9978,and the Approximation of diffusion model R²of peanut kernel reached the maximum value,0.9903.The two-term model and Approximation of diffusion model were selected as the optimal heat pump drying models of peanut shell and peanut kernel,respectively.3.The drying process of fresh peanut with shelled was optimized by combined drying,and the drying time,sensory score and shrinkage ratio were compared with that of hot air and heat pump drying.It is found that the combined drying method is very effective for peanut of two-layer materials.Based on the analysis of the regression model and the adjustment according to the actual situation,the optimal drying process conditions for the combined hot air-heat pump drying of fresh peanut with shelled are as follows:The hot air temperature is 50?,the water content at the conversion point is 0.39 g/g,and the heat pump temperature is 52?.Under this condition,it is found that the quality of combined drying is closer to that of heat pump drying,while the drying time is greatly reduced.4.The changes of dry-base water content,seed germination rate,total amino acid,insect pest rate,AFB₁,fungal infection rate and other biological characteristics of peanut stored with and without shell were studied.The results showed that the peanut stored in shell was superior to the peanut stored with shelled in dry base water content,seed germination rate and total amino acid,but lower than the peanut stored in shell in insect pest rate and fungus infection rate.It shows that peanut shell has a strong protective effect on peanut kernels,and can retain the biological active substances in peanut to ensure the quality of peanut during storage.