Studies On Effects And Mechanisms Of Hot Water Combined Glycine Betaine Treatment On Chilling Injury Of Loquat Fruit

Low temperature storage is an important way to preserve fruit,but peaches are highly susceptible to temperature,so chilling injury(CI)usually occurs in peach fruit stored at low temperature for a long time.In this paper,the effect of hot water(HW)combined glycine betaine(GB)treatment on chilling injury of loquat and the possible mechanisms involved were investigated.The results were as follows:1.The effects of different combined treatment conditions of hot water and GB on quality of loquat fruit were investigated and optimized by using the response surface methodology(RSM).Freshly harvested loquat fruit were treated with different temperature(40-50?)-concentrate(5-15mmol/L)-time(5-15min)combinations,and then stored at 1? for 35 days.Fruit internal browning,firmness and extractable juice were measured after the storage.Three second order quadratic equations of fruit internal browning,firmness and extractable juice were established,and the fitting degree were analyzed through RSM.The results indicated that the response and variables were fitted well to each other by multiple regressions,and the optimum conditions for combined treatment of hot water and GB were:temperature 45 ?,concentration 10 mmol/L,time 10 min.2.The combined treatment of HW and GB inhibited the increase in firmness,the decrease in juice percentage and internal browning,and had the positise effects on maintaining the contents of TSS and VC.In addition,we found that HW combined GB treatment could inhibit the activities of PPO and POD in fruit,improve the activities of SOD,APX and CAT,as well as maintain higher level of total phenol,DPPH free radical scavenging activity and reducing power,meanwhile,it could inhibit the accumulation of H2O2 and O2'-,so it could reduce the chilling injury of fruit.The combined treatment maintain higher levels of ATP,ADP and energy charge,thereby providing enough energy for normal metabolism in living tissue and enhancing tolerance to chilling injury of peach fruit,as well as reducing chilling injury.3.During investigating the effects of combined treatment,GABA and GB metabolism in loquat fruit,we found combined treatment could increase the activities of P5CS and OAT in cold-stored peach fruit but repress PDH activity,which could lead to the accumulation of proline.In addition,combined treatment could enhance the activities of GAD and BADH,thereby promoting the accumulation of GABA and GB.The accumulation of these matters were effective in maintaining integrity of cell membrane and biological molecule,thus improving chilling tolerance and mitigating Cl in loquat fruit.