Effect Of Ethylene Regulaton Additional Controlled Atmosphere On The Preservation And Physiology Of Fresh In-husk Walnut During Storage

Storage of fresh in-husk walnut?Juglans regia L.?has drawn much attentions of researchers in recent years.Aimed to improve the storage technology of the product,this study explored the effect of controlled atmosphere storage?CA?under different O₂,CO₂concentration with or without the pretreatment of ethylene compensation?ethylene?or ethylene inhibition?1-MCP?on the preservation of fresh in-husk walnut,using‘Xifu 1'?J.regia L.cv.Xifu 1?as material,stored at 0±0.5?,RH 70%-80%.Refrigeration storage was set as control.During storage,kernel quality,activities of phenolic metabolism and stress assistant related enzymes were assayed to elucidate the physiological basis of the action of single CA,ethylene control added CA.The main results were as follows:?1?The three concentration combinations of O₂ and CO₂ can effectively delay the development of soft browning and reduce the browning index of fresh in-husk walnut.After storage of 90 d,the change range of kernel sensory quality and physichemical quality varied.The sensory quality of the kernel from 5%O₂+7.5%CO₂ group was the least and the soluble protein content was significantly higher than that of the control,the acid value of oil had no significant difference when compared with the control and the 0 d value,while the contents of crude fat and soluble sugar were significantly lower than those of control.Compared with the other two combinations,5%O₂+6%CO₂ significantly increased the browning rate and cracking rate,accelerated the increase of kernel acid value.The sensory evaluation scores of kernel from 3.5%O₂+6%CO₂ group were the worst among all the groups due to the bad smell.5%O₂+7.5%CO₂ was selected the best O₂ and CO₂ condition for fresh-keeping.?2?The additional of 0.5?L/L 1-MCP to the 5%O₂+6%CO₂ treatment increased fruit cracking rate,browning index when compared to the single 5%O₂+6%CO₂ treatment,and the sensory evaluation quality of kernel was poor and had a bad smell.The 5%O₂+6%CO₂condition plus propylene compensation had little effect on the cracking rate,soft brown rate and sensory quality of fresh in-husk walnut.?3?When compared to the single CA,treatment of 5%O₂+7.5%CO₂ condition in addition to 500?L/L ethylene reduced the fruit cracking rate and MDA content,promoted the accumulation of proline in both husk and kernel,improved the activities of PPO and CAT,and maintained lighter color of the husk and seed coat,but had no significant different effect on the soft browning,decay process and kernel nutritional quality,oil quality,electrical conductivity,total phenol content,POD and SOD activity.?4?When compared to the singe CA treatment,the addition of 0.5?L/L 1-MCP to the5%O₂+7.5%CO₂ CA significantly increased the browning index and decay rate of the walnut,accelerated the increase of acid value,peroxide value and carbonyl value of the kernel,promoted the accumulation of proline in the husk and reduced the content of crude fat,crude protein and soluble sugar of the kernel and inhibited the activities of POD,SOD and chitinase in fresh in-husk walnut.The addition of 1-MCP has a negative effect on the preservation of fresh in-husk walnuts.