Effects of Heat Treatments on Quality of Citrus and

• Main Authors: Yu-Han Yang, 楊雨涵
• Other Authors: Deng-Tsen Horng
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/72256279412887524219

碩士 === 國立中興大學 === 園藝學系 === 91 === First, we explored the effects of hot-air treatments on the spoilage of ‘Ponkan’ fruits. The results showed that the effective control of spoilage could be affected by subjecting the green mold spore inoculated fruits either to 40℃ hot air for more than one day or to 35℃ hot air for more than two days. No favorable results could be obtained when blue mold spore inoculated fruits were treated under the same conditions. The data indicated that heat treatments killed the spores of the mold rather than improve the resistant capability of the fruits. In addition, we studied the impacts of hot-air treatments on the sugar contents, titratable acids and sugar/acids of some of Citrus spp. fruits. Hot-air treatments were found ,with the exception of ‘Ponkan’ mandrin, to diminish the amount of titratable acids of ‘Minneola’ tangelo, ‘Sunburst’ tangelo, ‘Liu Cheng’ orange, ‘Navel’ orange, lemon and ‘Ruby’ grapefruit. Taking the 40℃, 3-days experiment for example, the titratable acids in ‘Minneola’ tangelo, ‘Sunburst’ tangelo, ‘Liu Cheng’ orange, ‘Navel’ orange, ‘Eureka’ Lemon and ‘Ruby’ grapefruit were lowered by 10%, 21%, 27%, 17%, 9% and 10% respectively. However, similar treatments only caused minimal changes in the sugar contents of these fruits. The sugar to acid ratio in the juices of the above said cultivars, therefore, could be upgraded simply by heat treatments. The drop of titratable acids might be the result of drastic elevation of their respiration rate, which consumed the acids as substrates in the process. The orange that was subjected to two-days, 35℃, hot-air treatments followed by storing at 25℃ for 30 days in an air room tended to be better off than that of the controls in terms of the damage caused by the green mold. But, on the other hand, the risk of getting stem-end rot was quite high. In general, as far as the total spoilage rate is concern, there is no much difference between the hot air treated sets and the controls. The objectives of this experiment were to investigate the mechanism of actions of inhibition of senescent spots of banana after hot water (53℃) treatment. Banana after treatment for 5 minutes inhibited the development of senescent spots significantly. However the treatment failed to stimulate but reduced the release of ethylene from the banana fruits. Thus it seemed unlikely that the 53℃ water treatment could enhance ethylene biosynthesis or lead to the inhibition of the spotting problem. Spotting is a physiological disorder of peel browning during ripening. Some of the enzymes related to the browning phenomenon such as polyphenol oxidase whose activity was not affected by the water treatment seemed to rule out the possibilities of involving in the browning process. But one other browning-related enzyme, peroxidase, which was reduced in activity by the warm water treatment served to show the likelihood of involving in the development of spotting and its role in the browning merit further investigation. According to the experiments of ion leakage, gas concentration in the fruit tissues and unltrastructure of fruits, the permeability of fruit peel was significantly increased after the water treatment. This may reduce the possibility of accumulation of brown pigments in the banana peel and prevent the senescent spots from occurring.