Effect Of Freezing Temperature On Storage Quality Of Walnut Fresh Fruit

Fresh walnut has a unique taste and higher nutritional value.In recent years,it has been popular among consumers,and its sales have increased.However,due to its physiological characteristics such as postharvest respiratory metabolism and high water content,it cannot meet the needs of the market.Frozen storage is currently used in the storage of fruits and vegetables,but has not been reported in the storage of fresh walnut fruits.The experiment used 'Xiangling' walnut as the material to study the quality and physiological changes at 0 ?(control),-1 ?,-20 ?,first-40 ? after-20 ?(-40 ?).To provide a theoretical basis for walnut fresh fruit frozen technology.The main conclusions are as follows:(1)Treatment at-20 ? and-40 ? can effectively avoid the browning of green skin.At-1 ?,the quality of fresh walnut fruit can be maintained for a short period of time.However,after one month,the freezing damage of walnut green skin accelerates browning and the quality is degraded.(2)The sensory quality and color difference of fresh walnut fruit treated at-20 ? and-40 ? were not significant,but the two conditions effectively delayed the degradation of fat in walnut fresh fruit.The treatment of crude fat content at-20 ? was better than-40 ?.The crude fat content decreased rapidly under storage conditions of-1 ?.(3)In the initial stage of storage,the changes of AV and PV of walnut were small under the condition of-1 ?,and the quality of oil remained good.The AV and PV treated at-40 ? during the 14-month storage period were higher than-20 ?,-20 ? maintains better quality of walnut oil.(4)The total phenolic content and POD activity at-40 ? were higher than-20 ?,the PPO activity was lower than-20 ?,and the antioxidant capacity was stronger.The total phenolic content of seed kernels at-20 ? was higher than-40 ?.PPO activity and POD activity were all lower than-40 ?,but there was no significant difference.The color difference of fresh walnut fruit at-20 ? and-40 ? was not significant.The total phenolic content and POD activity at-40 ? were higher than-20 ?,PPO activity was lower than-20 ?,and the antioxidant capacity was stronger.The total phenolic content of the-20 ? was higher than-40 ?,and the PPO activity and POD activity were lower than-40 ?,but there was no significant difference.At-20 ?,the oil quality and taste of the kernels were better than-40 ? at the end of storage.