Effects Of Microwave-Pretreatment On Modified Atmosphere Storage Of Sweet Corn

The sugar content of sweet corn was rapid declined after harvest at room temperature, 60% of sugar will be converted to starch within 24 hours, and grain dry depression, and the green of husk will be fade. So, it is difficult to make long-term storage. Sweet corn "Hua Tian Yu No 3" were used as material in this paper, modified atmosphere combined with different microwave treatments to freshing sweet corn, In order to study the influences of different microwave treatments combined with modified atmosphere on the content of sugar and aging of sweet corn, determinated the changes of moisture contents, respiration, soluble sugar contents, reducing sugar contents, starch contents, soluble protein contents, hardness, ethylene production, sucrose phosphate synthase, phosphatase, catalase, peroxidase, lipoxygenase, pectinase and sensory quality of sweet corn during storage,This research will provide the basis for the development of fresh-maintaining techniques of fresh-eating sweet corn. The results were as follows:1. The respiration rate reduced 64.47%, soluble sugar content increased 17.15%, reducing sugar content increased 19.32%, and starch content decreased 63.19%compared with the control group at the condition of 5%O2 and 10%CO2 of sweet corn, but it is can't prevent the lossing of soluble protein content, and the ethanol witch produced by respiration resulting directly affect the quality of sweet corn. Therefore, the modified atmosphere did not meet the established goals of fresh sweet corn.2. The gas ratio in the package will tend to balance after 3 days of atmosphere combined with microwave pretreatment to fresh sweet corn, and O2 is about 1.0%, CO2 is about 20%. Each sample group has a water loss compared with fresh sample during storage of sweet corn, but the samples in each group was not significantly diffierent. The respiration rate reduced 69.87%, soluble sugar content increased 29.14%, reducing sugar content increased 25.42%, and starch content decreased 11.80%, soluble pretain content decreased 40.61% compared with the control group of sweet corn treatment by microwave (750W,50s) after storaged 15 days.3. After storaged 15 days, sucrose phosphate synthase (SPS) activity of microwave treatment sweet corn increased 39.54%, and phosphate activity increased 57.94% compared with the control group, which were effective to reduce the loss of sugar; catalase (CAT) and lipoxygenase (LOX) activity of microwave treatment group increased 35.29% and 37.91% respectively, which were significantly reducing the free radicals, enhanced the ability of free radical scavenging, delayed the organisms aging of postharvested sweet corn. Peroxidase (POD) activity of microwave treatment group has always been lower 29% than the control samples, and significantly delayed the lignification of sweet corn, slow the aging process during storage.4. After storaged 15 days, pectinase activity of microwave treatment sweet corn increased 19.01%, promoted the decomposition of pectin substances. The ethylene of microwave treatment is higher than the control group, the peak of ethylene appeared about 3 days earlier, promoted the ripening process of aging, which were disadvantageous for sweet corn storage.5. The thermal effects of microwave will affect the hardness of sweet corn, but the microwave treatment reduce the transformation of pectin and the original pectin to make sweet corn hardness decreased delay. The sensory quality of sweet corn continued to decline during storage, but the microwave treatment was significantly better than the control group after storaged 9 days.6.45 species flavor were detected in the fresh sweet corn, and there is not significantly reduce after storaged 15 days. Microwave treatment had no significant effect on the sweet corn flavor during storage.7. The indicators of microbial colony count is in line with commercial standards of fresh food. The total number of colonies of microwave treatment group is lower than the control group, but in the same order of magnitude, so microwave treatment had no significant effect to reduce the microbial colony count of sweet corn during storage.Therefore, the microwave with modified atmosphere fresh sweet corn on the significant effect of storage after 15 days still has good eating quality, and easy to operate, easy-to-industry promotion.