Postharvest Chinese Winter Jujube (Zizyphus Jujube Mill.) Fruit Red Turning And Its Controls

Chinese Winter Jujube (Zizyphus Jujube Mill cv. Winter Jujube) which originated from China has high nutritional quality, and one of the most serious problems of postharvest storage Chinese Winter Jujube is quick red-turning. The red pigment of the pericarp of the winter jujube has been extracted, and the red pigments quality was analysised. The effect of different plant growth regulator, different temperature, illumination and oxidize hydrogen on red-turning were studied.The result of study indicates that the red pigment of the pericarp of the winter jujube is the water soluble pigment, spectral analysis and qualitative test indicate this pigment is flavonoids, include the orange ketone, chalcones flavanones chemical compound mainly. The red-turning is closely related to ripening and senescence. The ethylene can raise the activity of PAL enzyme, advance the appearance of the active peak of PAL enzyme, promote degradation of chlorophyll, accelerate starch enzyme activity, increase reducing sugar content and LOX enzyme activity, promote maturity of winter jujube, and accelerate the red-turning speed obviously. GA3 and 6- BA postpone peak activity of PAL enzyme, decrease reducing sugar content and loss rate of Vc, and postpone red speed of winter jujube. Also, the effect of GA3 is stronger than 6- BA. Illumination plays an important role in the red turning of and luster. Results show that dark can decrease reducing sugar content, delay the active peak of PAL enzyme, and postpone red speed, although decrease the content of Vc at the same time. Under the low temperature, the winter jujube can still turn red, but the turning speed is more slowly than normal. Treatment at 65 and 70℃ for 1min can accelerate pericarp turning speed, which turns red drastically after 1h. The pericarp can not turn red after treatment at 95℃. Low concentration H2O2 can obviously reduce red-turning speed.