Effect Of Phospholipase D On Browning Of Litchi Fruit During Shelf Life At Room Temperature After Cold Storage

Litchi is a subtropical fruit,it is rich in Guangdong province of China.The main preservation method of postharvest litchi is low temperature storage in the market.Litchi pericarp is especially thin,therefore,it is subjected easily to chilling injury during low temperature storage.Litchis are very easy to browning and decay when they are going to shelf life at room temperature after cold storage,which restricts the development of litchi industry.Membrane lipid system is the key part in the cell.Phospholipase D hydrolyzes phospholipids,that may damage the membrane lipid system and cause cell aging.In this paper,the effect of phospholipase D on browning of Litchi during shelf life at room temperature after cold storage was studied from the aspects of the quality of litchi fruit,the metabolism of phenolic substances,the active oxygen metabolism,the structure changes of membrane lipids and gene expression of phospholipids D.In this experiment,the inhibitor of phospholipase D(n-butanol)was used to treat postharvest litchi,compared with quality of litchi fruit of the blank control group,n-butanol treatment could significantly inhibit the activity of phospholipase D in the pericarp of litchi fruit,delay litchi fruit browning and decay and improve the quality of litchi fruit,but the soluble solids content of litchi fruit was not affected by n-butanol treatment during shelf life at room temperature after cold storage.In the aspect of phenolics metabolism of litchi fruit,the total phenolic content of Litchi Fruit during shelf life at room temperature after cold storage was in a downward trend.Effects of n-butanol treatment on litchi total phenolic content and the activity of PPO during shelf life at room temperature after 10 days and 20 days low temperature storage were not significant.But after 30 days’ cold storage,n-butanol treatment could keep the total phenolic content of litchi,significantly reduce the activity of PPO of litchi pericarp.The n-butanol treatment could observably inhibit the activity of PPO of litchi fruit during shelf life of room temperature after cold storage.In the aspect of activated oxygen metabolism of litchi pericarp,n-butanol treatment could significantly inhibit superoxide anion content,reduce hydrogen peroxide content accumulation of litchi pericarp during shelf life at room temperature after cold storage.It also stimulated the activity of SOD of litchi pericarp and eliminated the accumulation of MDA increasement effectively.In the aspect of membrane lipid functional structure of litchi pericarp,through the determination of cell membrane relative permeability,cell membrane fluidity and fatty acid content in the membrane lipid by gas chromatography,it found that n-butanol treatment significantly decreased cell membrane relative permeability of Litchi during shelf life at room temperature after cold storage,decreased the membrane lipid permeability,enhanced membrane lipid fluidity,prevented unsaturated fatty acids oxidation in membrane lipid,and reduced unsaturated fatty acids generation.N-butanol treatment can effectively maintain the membrane structure of litchi during shelf life at room temperature after cold storage.In the aspect of gene expression of phospholipids D of litchi pericarp,through Real-time quantitative PCR of gene expression of phospholipids D of litchi pericarp,it found that n-butanol treatment significantly decreased gene expression of phospholipids D of litchi pericarp during shelf life at room temperature after cold storage when litchi were at cold storage of the long time.After short time of Cold storage,n-butyl alcohol stimulates cell phospholipase D gene expression.This may be associated with damage degree of cell membrane.Above all,N-butanol can influenced gene expression of phospholipids D of litchi pericarp,reduce the hydrolytic activity of phospholipase D,reduce the damage of membrane structure,maintain membrane integrity and membrane area,so then it reduces the direct effect of phenolic compounds and enzymes,reduce quinones production,inhibit the browning of litchi.At the same time,n-butanol inhibited the activity of phospholipase D,protected the cell membrane from persecution,and reduced the free radical production,improve their antioxidant capacity,to delay the senescence and browning of Litchi during room temperature shelf life after cold storage.Therefore,phospholipase D plays an special role in browning of Litchi during shelf life at room temperature after cold storage.Litchi is susceptible to chilling injury under low temperature,what could cause physiological function of litchi fruit disorder,produce a large sum of free radicals to disrupt the operation and damage cell membranes,and promote fruit senescence and browning.Phospholipase D can accelerate browning of Litchi fruit by degrading membrane lipids.On phospholipase D gene and active regulation,we can delay the process of frozen litchi Browning during room temperature shelf.