Effect Of Preharvest Sprays With Chitosan And Gaoliangjiang On Quality And Postharvest Physiology Of Longan

The experiment was conducted with two levels of chitosan and Gaoliangjiang(GLJ) sprayed at one week and one day before harvest. The two levels of chitosan solution were A1: 6g/L and A2: 3g/L. A1 and A2 were sprayed on longan fruit on 7th Aug and 12th Aug respectively. B1 was sprayed water on 7th Aug and 20% GLJ solution on 12th Aug. B2 was sprayed water on 7th Aug and 10% GLJ solution at 12th Aug. Control was sprayed water both on 7th Aug and 12th Aug. The fruits were harvested on 13th Aug. The results were as follows: 1 For fruit charactersThere was a little effect of both chitosan and GLJ on size of fruit. The treatments of chitosan and GLJ significantly increased water content of fruit at harvest, and the differences between treatments and control were significant at 0.01 level. The water content increased as the concentration of chitosan and GLJ increased. Meanwhile, both of themalso decreased the rate of weight lose of fruit during storage. The treatments of chitosan had remarkable effect on increasing the water content in pericarp and flesh at harvest. The higher concentration of chitosan solution was, the more remarkable the effect was. The effect of GLJ on water content in pericarp and flesh at harvest was not significant. Both of chitosan and GLJ didn't significantly increase water content of seed. At the last day of storage, the differences of rate of intact fruit between all treatments and control were significant at 0.01 level. The higher the concentration of solutions was, the greater the rate of intact fruit was. 2 For pericarp characteristicDuring storage, the O2- and MDA content of pericarp increased as time passed by. The O2- and MDA content in pericarp of treatments were lower than control. And the increment of O2- and MDA decreased with the concentration of solutions increased. During storage, the membrane permeability of pericarp had uptrend. The cell membrane of pericarp was destroyed seriously during the early storage and the membrane permeability increased rapidly. The increment of membrane permeabilityof control was significant greater than treatments. During the middle and later storage, the increase speed of all membrane permeability was slowdown. The SOD activity of pericarp had downtrend during the storage. The POD activity of pericarp rose at thefirst 5 days of storage and then decreased till the last day of storage. The changes of SOD and POD activity in all treatments were more moderate than control and the SOD activity of GLJ treatments was always higher than control during storage. 3 For flesh characteristicAt the day of harvest, the content of soluble solids, soluble sugar and Vc treatments increased as the concentrations of chitosan and GLJ increased. The soluble solids, soluble sugar and Vc content of chitosan treatments were significant higher than control and the differences were significant at 0.01 level, while the reducing sugar content of chitosan treatments was lower than control at the day of harvest. The content of the soluble solids, soluble sugar and reducing sugar of GLJ treatments were higher than control. While the Vc content of low GLJ concentration was lower than control. The protein content was not remarkable difference between treatments and control at harvest and storage, the soluble solids, soluble sugar, reducing sugar and Vc content decreased gradually, but the decreased speed of treatments was lower than control during storage. The titratable acidity content in flesh of treatments had downtrend in the early and middle storage but had uptrend in later storage. But the drop amount of acid of treatments was smaller than control. The changes of the O2- and MDA content, SOD activity in flesh were similar to the changes in pericarp, but the POD activity kept risingduring storage.Conclusion: preharvest sprays with chitosan and GLJ solution significantlyincrease the eating quality and the rate of intact fruit at harvest and storage. The effect increased as the concentration of chitosan and GLJ solution increased.