Effects Of Modified Atmosphere Packaging On Quality And Physiology And Biochemistry Of Walnut Kernels During Cold Storage

Walnut kernels have high fat and especially prone to fat oxidative rancidity, which seriously affecting the nutritional value and shelf life of walnut kernels and their processed products. Modified atmosphere packaging has been widely used as an effective storage method of postharvest agricultural products, but it lacks in-depth study of modified atmosphere storage technology for walnuts. This paper studied the nitrogen packaging, nano-packaging and vacuum packaging on the walnut kernels’nutrition control and postharvest physiology. The amber walnut kernels’quality characteristics were also observed. The contents and results are as follows:1. Effects of modified atmosphere packaging on chilled walnut kernels’quality and physiology and biochemistryRaw walnut kernels were stored under the conditions of air temperature at (2±1)℃and with the package of nitrogen(N2), nano-materials, vacuum-packaging, respectively. The control was packaged with ordinary polyethylene materials. The quality and physiological indicators were regularly tested. The results showed that nitrogen packaging, nano-packaging could keep the fresh quality of walnut kernels, both of which could significantly inhibit the increase of peroxide value, acid value, control the decline of total phenols, soluble protein and soluble reducing sugars, and maintain high activity of antioxidant enzymes, which were beneficial to remove the excess accumulation of free radicals and protect the cell membrane system integrity, restrain the lipase and lipoxygenase to slow down the oxidative rancidity of fat.2. Quality changes of amber walnut kernels with three different modified atmosphere packageProcessed the raw walnut kernels stored by different modified atmosphere packaging into amber walnut kernels. The amber walnut kernels were stored at38℃for30d. The total phenolic content, peroxide value, acid value, carbonyl value were measured to study the processed products quality. The results showed that the two storage methods of nitrogen packaging and nano-packaging could reduce the raw walnut kernels’ fat oxidation rate, and the processed products’ shelf life was significantly longer than the control.3. Modified atmosphere packaging technology in walnut kernels’ middle model application experimentWith the assistance of Nanjing mimosa Food Co., Ltd., the nitrogen packaging, nano-packaging were used in walnut kernels’ middle model application experiment. The results showed that modified atmosphere storage significantly inhibited the oxidative rancidity of postharvest walnut kernels, and verified that the nitrogen and nano-modified atmosphere had the excellent preservation effects. The study provided guidance for the commercial application of walnut kernels’ modiffied atmosphere storage.