The Effect And Mechanism Analysis Of ’Tunisia’ Pomegranate Fruit Quality During Controlled Atmosphere At Cold Storage

Pomegranate fruit is rich in nutrients,with a pleasing appearance,and has various healthcare functions,so it is loved by domestic and foreign consumers.In recent years,the pomegranate industry in China has developed rapidly,and pomegranate has become a golden signboard in the rural revitalization strategy in some areas of China.Due to the high respiratory intensity and transpiration of pomegranate fruit,husk shrinkage,softening rot,browning,and chilling injury had higher occurance after harvest,directly affectingthe commodity value and nutritional value of pomegranate fruit.Controlled atmosphere storage is effective in delaying water loss and browning of fruit husk.At present,the studies on postharvest storage and preservation of ’Tunisia’ pomegranate are few,and the preservation mechanism of controlled atmosphere storage of ’Tunisia’ pomegranate is still unclear.Therefore,in this study,’Tunisia’ pomegranate fuits were harvested at the commercial maturity stage,and stored for 30 days at 5±0.5℃ and 85±1%of the relative humidity with two treatments:CA1(7%O2+4%CO2)and CA2(2%O2+5%CO2)and CK(the regular air).After 30 days,pomegranate fruit was stored for 9 days at 18±1℃ and 98±1%.The samples were collected after harvest and on 0,3,6,and 9 d of the shelf life,and the quality index and related physiological indexes of pomegranate fruits were measured to explore the effects of controlled atmosphere storage treatment of ’Tunisia’pomegranate fruits and screen the most suitable gas combination,which contributed to illuminating the mechanism of the higher quality of pomegranate fruits with controlled atmosphere storage.Therefore,the present study will provide a scientific and theoretical basis for the utilization of controlled atmosphere storage in the’Tunisia’ pomegranate storage.Our results are as follows:1.Cold controlled atmosphere storage effectively maintained the higher fruit quality of pomegranate,especially CA2.Compared with CK,cold controlled atmosphere storage maintained the better color of pomegranate husks and arils during the cold storage and shelf life,and reduced the water loss of fruit.CA2 controlled atmosphere storage effectively reduced the content loss of ascorbic acid,anthocyanin,total phenol,and total flavonoid in pomegranate arils during cold storage,and maintained the high antioxidant capacity of pomegranate arils.In addition,the content of ascorbic acid,total phenols,and total flavonoids in pomegranate arils treated with CA2 was higher than CK in the first 6 days of shelf life.2.Cold controlled atmosphere storage effectively delayed chilling injury and maintained the high cell membrane integrity of pomegranate.In particular,the CA2 treatment had lower electrolyte permeability and MDA content during cold storage and shelf life,maintaining the integrity of the cell membrane.3.Cold controlled atmosphere storage can effectively inhibit the activity of oxidase and enhance the antioxidant activity of pomegranate,especially CA2.During cold storage and 3 days before shelf life,cold controlled atmosphere storage inhibited enzymatic browning caused by increased PPO activity by delaying PPO and POD activities in pomegranate husks and arils.It enhanced the antioxidant activity of pomegranate by maintaining high PAL activity and high phenolic compound content.4.Cold controlled atmosphere storage reduced ROS levels,delayed fruit senescence,and relatively prolonged the storage period.Cold controlled atmosphere storage relatively reduced the fruit senescence caused by excessive respiration by effectively inhibiting the respiratory rate and ethylene production rate of pomegranate fruits and arils.At the same time,cold controlled atmosphere storage maintains a high content of ATP by increasing CCO activity,providing necessary energy for metabolism.Cold controlled atmosphere storage promoted the further conversion of NAD+to NADP+ by increasing NDAK activity,which promoted the accumulation of NADPH during cold storage of pomegranate,and improved the ROS scavenging ability.5.Cold controlled atmosphere storage effectively improved the antioxidant capacity of pomegranate and relatively reduced oxidative damage.Cold controlled atmosphere storage reduces the production of ROS by reducing NOX activity,and combined with maintaining the high antioxidant enzyme activity and improving the total antioxidant capacity,further reducing the content of O2-and H2O2,thus reducing the oxidative damage during cold storage and shelf life of pomegranate.Compared with CK,CA2 controlled atmosphere storage had the lowest O2-and H2O2 content and the strongest antioxidant capacity after 30 days of cold storage and shelf life.In summary,CA2 treatment improvd more greatly the pomegranate fruit quality i than CA1 treatment.Our results indicated that controlled atmosphere storage inhibited the increase of respiration rate,and slows the metabolic rate;it inhibited the increase of oxidase activity,and maintained the high level of ATP content,thus promoting the ROS removal,enhances the antioxidant activity and maintains the integrity of cell membrane of pomegranate,and then maintains the high nutritional quality and commodity value of pomegranate fruit.Therefore,the controlled atmosphere storage is an effective and promising fresh-keeping technology for pomegranate.