| We studied the effects of different ripeness levels, storage temperatures, vacuum packing in addition to varied storage temperatures, ultraviolet light treatment, ozonization,air-conditioned storage and treatment with wampee essential oils on the postharvest physiology, storage quality and preservation effect of "Da Ye" samples, a variety of wax apples [Syzygium samarangense], so as to provide a theoretical basis for achieving longer transportation and storage periods and better preservation qualities. The results of our finding were as follows:1. Changes in the physiology and quality of wax apples of different ripeness levels(70%, 80%, 90%) during storage. The results showed: the 70% and 80% grown wax apples,compared with the 90% growns, could remarkably restrain the decrease of TA and Vc,deter the decline of wax apples’ color values and rise of membrane permeability, maintain a higher SOD and POD activity, and inhibit the accumulation of MDA, which delayed the fruits’ ripening and senescence substantially. In comparison, the 80% grown fruits contained 1% more TSS, tasted better and were more advantageous for marketing than the 70% growns. The final result was that the 80% ripe wax apples were best preserved, and more available for extension on a large scale.2. Effects of different storage temperatures (3℃, 5℃, 10℃, 15℃, 20℃, 25℃) on wax apples’ physiology and quality during storage. The results showed: by the 16th day,the rotting rates of those wax apples stored at 3℃, 5℃ 10℃, 15℃, 20℃, 25℃ were 20%, 5%,30%, 35%, 60% and 70%. respectively. Those stored at 5℃ enjoyed the lowest rotting rate(P < 0.05), whose storage quality, including hardness and anthocyanin, changed most slowly and whose SOD and POD activity remained at a higher level. The quality of those stored at 3℃ was sound in earlier stages, but plunged since the 12th day, as evidenced in the great drop of their anthocyanin content and color and seemingly damage caused by low temperature, such as water leaching in the rears, serious color fading and odor. The results indicated that 5℃ was the best storage temperature at which both the quality and commercial value of wax apples could be well preserved.3. Effects of vacuum packing in addition to varied storage temperatures (5℃, 10℃,15℃, 20℃, 25℃) on wax apples’ quality. The results showed: by the 21st day, the anthocyanin contents of wax apples stored at 5℃, 10℃, 15℃, 20℃and 25℃were 0.32,0.29. 0.28, 0.271, 0.263U/g FW, respectively. Such content of those stored at 25 ℃was the lowest (P<0.05), suggesting vacuum packing plus low temperature could effectively deter wax apples from decaying and their VC content from dropping and extend their shelf life.And vacuum packing plus 5℃was the best storage condition of all.4. Effects of different time of short wave ultraviolet irradiation (1,2, 3min; 0.12,0.24. 0.36kJ/m2) on wax apples’ quality and postharvest physiology. The results showed:by the 14th day, the MDA contents of those irradiated with 0.12. 0.24 and 0.36kJ/m2 and treated with CK were 38.11, 33.736, 38.765 and 50.236 μmoL/g, respectively. Samples in the control group had a notably higher MDA content than those treated under other conditions (P < 0.05), showing that UV-C treatment with different dosage had significant effects on the preservation of wax apples, of which UV-C with 0.24kJ/m2 was the best.5. Effects of ozonization with different concentrations (1.98, 3.30, 4.95 ppm) on wax apples’ physiology and quality. The results showed: by the 12th day, the TA contents of those ozonized with 1.98, 3.30 and 4.95 ppm were 0.109%, 0.119% and 0.117%,respectively, much higher than that of the control group (CK-treated), 0.09% (p<0.05).The results indicated that ozonization could well preserve wax apples’ flavor, sensory and nourishment quality. To sum up, ozonization with 3.30 ppm could best preserve the flavor.6. Effects of air-conditioned storage with different gas compositions (100% N2; 95%N2 + 2% 02 + 3% CO2; 95% N2 + 3% O2 + 2% CO2; 95% N2 + 1 % O2 + 4% CO2) on wax apples’ postharvest physiology and quality. The results showed: by the 20th day, the weight-loss rate of wax apples under different air-condition storage conditions were 31.98%, 28.65%, 32.7% and 30.3%, respectively, much higher than that of CK-treated samples (control group), 46.27% (P < 0.05). According to the results, air-conditioned storage with a certain gas composition had substantial effects on the preservation of wax apples, whose SOD and POD activity remained at a higher level, and the composition of 95% N2+2% O2 + 3% CO2 was the most effective.7. Finally, effects of treatment with wampee essential oils on wax apples’bacteriostatic mechanism and quality by way of in vitro and in vivo experiments. The results showed: all essential oils of Clausena lansium of different concentrations displayed antibacterial effects over the testing soft rot and the inhibition rate of 0.6 μl/mL EO reached 48.99%; the mycelia processed with 0.6 μl/mL EO was sparse with less branches;essential oils of Clausena lansium had significant impacts over the permeability of pathogenic fungus membrane, which reduced the content of soluble protein and reducing sugar and hindered the fungus’s absorption of nutrients. To conclude, we identified the antibacterial mechanism of essential oils of Clausena lansium preliminarily and found 0.6μl/mL EO had the best antibacterial effect. In vivo experiment, by the 14th day, the rotting rate of wax apples treated with 3, 6, 10 and 12 μl/L essential oils and with CK were 25%,15%, 35%, 50% and 60%, respectively. It was easy to find that those treated with 6 μl/L essential oils had the lowest rotting rate (P<0.05), while that of the samples treated with 12 μl/L essential oils or CK was much higher, which had poor effects on preserving wax apples. |
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