Effects Of Packaging Methods And Storage Temperature On The Quality Of Thin-skinned Walnuts

Thin-skinned walnut is one of Xinjiang’s local characteristic walnut varieties.It is famous for its thin skin,thick flesh and high oil content.It is loved by consumers and has become one of the pillars of Xinjiang’s characteristic forest and fruit industry.However,walnuts contain more than 90%of unsaturated fatty acids and are susceptible to oxidative rancidity due to factors such as light,heat,oxygen,moisture,enzymes,and microorganisms,resulting in bad odors,thereby reducing nutritional value and economic value.The research on walnuts mainly focuses on fresh walnuts.There are few studies on dried walnuts,and there are few reports on storage methods that combine packaging materials with deoxidizers.In addition,Xinjiang is located in the northwestern border of my country.Green-peeled walnuts cannot be sold in time and the transportation cost is high.Therefore,it is urgent to study the methods of facilitating transportation and storage of dried walnuts in order to solve the problem of walnut storage and export.This experiment uses"Wen 185"thin-skinned walnuts as materials,uses different packaging to treat thin-skinned walnuts,determines the changes in walnut quality-related parameters,analyzes the changes in storage temperature on the nutritional quality and physiological metabolic indexes of thin-skinned walnuts,and studies the packaging methods for antioxidant enzyme activity,The relative content of fatty acids and the influence of infrared spectroscopy on the determination of walnut spectra,to explore the optimal storage conditions for the shelf life extension effect of thin-skinned walnuts in the accelerated test storage of high temperature and high humidity.The main findings are as follows:（1）The effects of four packaging methods,namely vacuum packaging,vacuum deoxidation packaging,air-filled packaging and air-filled deoxidation packaging,on the storage quality of thin-skinned walnuts were studied.Packaging treatment can effectively delay the increase in peroxide value,acid value and saponification value of thin-skinned walnuts,inhibit the decline of iodine value and moisture content,and increase the activities of SOD,CAT and POD,inhibit lipase and LOX activities,delay the increase in MDA content,and maintain walnuts The sensory qualities of benevolence.When stored at（25±1）℃,the most suitable treatment is air-filled deoxygenation packaging;when stored at（5±1）℃,the effect of vacuum deoxygenation packaging is better.Therefore,vacuum deoxygenated packaging and air-filled deoxygenated packaging were selected for the next experimental study.（2）The effects of five temperatures of 0,5,10,15 and 25℃on the sensory and nutritional quality of packaged thin-skinned walnuts were studied.When the walnuts are processed in the same packaging,the quality effects of walnuts stored at 0℃and 5℃are obvious,which can effectively inhibit the increase of peroxide value,acid value and saponification value of walnuts,delay the decline of iodine value,maintain moisture content and fat content,and have no obvious protein content.difference.Among them,vacuum deoxidation packaging can effectively delay the oxidative rancidity of walnuts and maintain the good quality of walnuts.In addition,it was found that there was no significant difference in quality between walnuts stored in vacuum deoxidized packaging at 10°C or 15°C and untreated walnuts at 0°C or 5°C.（3）The effect of packaging on the antioxidant activity and fatty acid content of thin-skinned walnuts was discussed,and the mechanism of fatty acid oxidation in walnuts was revealed.Packaging treatment can effectively maintain the activities of walnut SOD,CAT and POD,slow down the decline in total phenol content,inhibit the rate of O₂^-·radical production,delay the decline of DPPH·radical scavenging rate,and maintain a higher content of unsaturated fatty acids.The infrared spectrum frequency is within The absorption peaks of 3008.85 cm^-1unsaturated carbon,1161.11 cm^-1triglycerides and 721.35 cm^-1carbon chain skeleton were higher than those of other groups,and the absorption peak of free fatty acids at1743.59 cm^-1was lower than other groups.Among them,the walnuts packed in vacuum deoxidation have the least oxidative rancidity.（4）Through the accelerated test of high temperature and high humidity,the optimal conditions for storage of thin-skinned walnuts in medium-sized packaging were studied.Medium-sized packaging treatment can increase the activity of walnut SOD,CAT and POD,maintain LOX activity,inhibit the increase of peroxide value,acid value,saponification value and MDA content,reduce the decline of iodine value,enhance the antioxidant capacity of walnuts,and delay the deterioration of walnut quality.Among them,the quality of walnuts stored in vacuum deoxygenated packaging is better than other groups.