Effects Of Post-harvest Commercial Treatments On Walnut Quality

China is a big country in walnut planting and producing,however,the walnut harvesting and processing are mostly handled by individual farmers,and have the low scale.Therefore,the poor qualities of walnuts may be consumed due to lack of professional and scientific guidance.This paper studies the effects of a series of commercialized processing processes,such as ripening stages,hulling methods,drying ways,and preservation method on walnut quality,in order to provide scientific and technical guidance for getting high quality walnuts.The specific results are as follows:?1?The quality of fresh walnuts and dried walnuts during storage at different ripening stages?stage?,stage?,and stage??are as follows:Fresh walnuts harvested at stage?have superior odor and taste,and have strong antioxidant activities.The green walnut kernels of stage?have good color,and facilitated the accumulation of protein and monounsaturated fatty acids in fresh walnuts.In addition,the dried walnuts obtained at stage?can maintain the brightness of dried walnut kernels and reduce the deepening of yellow and red;the highest antioxidant activities,total phenols and flavonoid content can be maintained;And peroxidation values were significantly lower than stage?and stage?during storage?P<0.05?,which slowed down the level of oxidative of dried walnuts and maintained good quality of dried walnuts.?2?Manually hulled?MH?,natural heaping?NH?,solid ethylene-releasing agent?SERA?and immersion in ethephon?IE?hulling methods are used to study the quality of fresh-eating walnuts and dried walnuts during storage.The results showed that the hulling rate of the SERA and IE treatment groups was higher than that of the NH group,while the fresh walnut kernels obtained by the SERA and IE treatment groups had a poorer taste and odor.In addition,the SERA group had the lowest total phenols content and antioxidant activities,and the IE treatment group contained the lowest percentage of unsaturated fatty acids.The MH and NH treatment groups imparted a good odor and taste to fresh-eating walnut kernels,delayed the increase in acid value and peroxide value of dried walnuts during storage,and maintained the good quality of dried walnuts.In addition,fresh-eating walnuts obtained from the MH group and dried walnuts during storage had strong antioxidant activities and total phenols content,and the fresh walnut kernels of the MH group had the highest percentage of polyunsaturated fatty acids.?3?The green walnuts without peel were processed by drying,vacuum stage drying and vacuum drying,and then stored at room temperature for 120 days.The color values?L*,a*and b*?,antioxidant activities?DPPH free radical scavenging ability and reducing power were measured?,peroxide values?acid value and peroxide value?,flavonoids and total phenols content.The results showed that there was no significant difference in the color among the staged drying,vacuum staged drying and vacuum drying during drying and storage?P>0.05?.However,the reducing power,DPPH free radical scavenging ability,total phenols and flavonoid content of stage drying during drying and storage were significantly lower than those of vacuum drying and vacuum staged drying?P<0.05?,while the acid value and peroxide value were both significantly higher than vacuum stage drying and vacuum drying?P<0.05?.Therefore,vacuum stage drying and vacuum drying can better maintain the walnuts quality during drying and storage.?4?To study the effect of 1-MCP+SO₂ treatment on the fresh-keeping green walnuts during low temperature storage.The results showed that 1-MCP+SO₂ treatment can reduce the respiration rate of green walnuts,maintain the brightness of fresh walnut kernels,reduce the deepening of yellow and red colors of walnut seeds,and maintain the higher antioxidant activities and total phenols content of fresh walnuts during the later storage period.In addition,it can also reduce the degree of oxidative rancidity of the fat and maintain the quality of fresh-eating walnuts.