Study On Postharvest Physiological Changes And Storage Effects Of Strawberry And Dongzao Jujube Under Intermittent Nitrogen And Pressure

As people pursue a better quality of life,the demand for fresh fruits and vegetables is increasing.However,the domestic fruit and vegetable storage technology started late,and the post-harvest preservation technology developed backward,resulting in huge losses of vegetables.According to statistics,the rot loss of fresh fruits and vegetables in China is about 20%,which is 3 times higher than that of developed countries.Therefore,it.is imminent to develop new technologies for fruit and vegetable storage and preservation.The development of new fruit and vegetable storage and fresh-keeping technology can effectively reduce the loss caused by decay and improve economic efficiency.Pressurized storage is a new fresh-keeping technology.By applying a certain gas pressure to surround fruits and vegetables,the pressure of the storage environment is higher than the internal pressure of the fruits and vegetables,forming a positive pressure difference from the outside to the inside,which can effectively prevent water loss and nutrient consumption of fruits and vegetables,and reduce the respiratory intensity of fruits and vegetables,delay the aging process,thereby effectively prolonging the storage period.At present,there are few studies on pressurized storage,mainly focusing on fruits and vegetables such as tomatoes,persimmons,and plums.Besides,there are also few reports on the application of pressurized storage technology to strawberries and Dongzao jujube fruit.In this study,strawberries and Dongzao jujube fruit were used as test materials.Fruits were packed in six foam boxes with a diameter of 1.0 cm,then placed in a container and passed nitrogen(N2)to bring the pressures to 150 kPa,200 kPa,and 250 kPa,respectively.Maintain the set pressure during storage.The effects of nitrogen-filled and pressurization on post-harvest physiology,anti-oxidation,fruit softening,cell structure changes and diseases in storage period of frozen strawberry were studied by the following methods:the storage quality and physiological indexes of pressurized strawberries were measure regularly,the changes of strawberry cell structure before and after pressurization were observed by a microphotograph,and the identification and infection reconnection test of strawberry diseases were conducted during storage period.Meanwhile,the effect of nitrogen-filled pressurization on the storage quality of refrigerated Dongzao jujube fruit was studied by periodically measuring the quality indexes of Dongzao jujube fruit under pressurized storage.Exploring the relationship between the quality changes of strawberry and Dongzao jujube fruit and the nitrogen filling pressure,and optimizing the best method for storage and preservation of strawberry and Dongzao jujube fruit will help to prolong the fruit freshness period and improve the storage quality.The experimental results are as follows:1?The stored strawberries were treated at a temperature of 0?1?,a relative humidity of 85%?90%,and a nitrogen pressure of 200 kPa.In terms of improving storage quality:this treatment effectively reduces the MDA content of the fruit and slows the rate of increase in relative permeability,inhibits respiratory intensity,reduces water loss and maintains a higher content of soluble solids,titratable acids and reducing sugars.In terms of enhancing oxidation resistance:this treatment can effectively delay the decline of Vc and total phenol content,maintain the high DPPH free radical scavenging capacity and SOD,CAT activity of the fruit,slow down the decrease of anthocyanin content in the early storage period,and prevent the toxic effect of active oxygen on fruits,thereby delay the senescence process of the fruit In terms of preventing fruit softening:this treatment can effectively delay the decrease of the original pectin content and the increase of the soluble pectin content,reduce the PL activity of strawberry fruits,and inhibit the increase of the four enzyme activities of PG,PME,cellulase and ?-Glu.Moreover,it can also delay cell degradation,slow down fruit softening,maintain high fruit hardness and have a significant inhibitory effect on the pathogenic bacteria(Botrytis cinerea)during storage.Under this condition,the strawberry was stored for 25 days,the good fruit rate was 80%,and the color and flavor were all good,indicating that the pressure storage has an excellent fresh-keeping effect on strawberries.2?The fruits of Dongzao jujube were processed at a temperature of-1?0?,a relative humidity of 85%?90%and a nitrogen pressure of 200 kPa,which can significantly inhibit the increase of fruit respiration strength and weight loss rate,and maintain a high content of soluble solids and reducing sugar.Furthermore,this treatment also effectively slow down the reduction of fruit firmness,titratable acid and vitamin C content,thereby delaying the senescence of Dongzao jujube fruits.Under this condition,the Dongzao jujube fruits were stored for 100 days,and the good fruit rate was 83.3%.The fruits of Dongzao jujube after storage are of good quality and high commodity value.