| Summary: | 碩士 === 國立屏東科技大學 === 農園生產系 === 94 === A series of studies were conducted to elucidate the physico-chemical changes during postharvest packagings : unpackage, sealed in polyethylene (PE) bag, sealed in PE bag containing ethylene absorbents, perforated PE bag, torsional PE bag containing polystyrene net sleeve (PNS), sealed in PE bag containing PNS, sealed in PE bag containing PNS and ethylene absorbents. Different thickness (0.03、0.05mm) of PE bag lining packaging treatments, heat treatments (8、12 and 16sec. at 46℃ and 8、12sec. at 48℃), PE (pectinesterase) and PG (polygalacturonase) activity of two cultivars of guava fruits (Psidium guajava L.), named ‘Jen-Ju Bar’ and ‘Shui-Jing Bar’ during storage were also investigated. Results showed that the ‘Jen-Ju Bar’ and ‘Shui-Jung Bar’ fruits were stored at different temperatures (0-25℃) , there were not appeared clearly climacteric respiration and ethylene peak.
After stored at 0-25℃, the weight loss of unpackaged fruits were significantly higher than other package, secondly were perforated PE bag packaged fruits, and the fruits packed with PE bags were significantly lower. The weight loss were reduced with the lowering the storage temperature. However, guava fruits storing at low temperatures exhibited surface pitting and browning symptoms of chilling injury (‘Jen-Ju Bar’ , 0℃10 days and 5℃20 days ; ‘Shui-Jing Bar’ , 0℃4 days and 5℃6 days). Fruits packed with sealed in PE bag containing PNS and sealed in PE bag containing PNS and ethylene absorbents would delay and alleviate the development of chilling injury. The rate of chilling injury of ‘Jen-Ju Bar’ fruits were lower than ‘Shui-Jing Bar’ fruits, and the time of chilling injury symptom appeared of ‘Jen-Ju Bar’ was also late. Therefore, guava fruits should be stored at 5℃during storage and transportation. In addition, different packaging methods affected storage life of fruits. The fruits of ‘Jen-Ju Bar’ packed with sealed PE bag containing PNS and sealed in PE bag containing PNS and ethylene absorbents at 5℃were significantly extended the storage life to 33-34 days；‘Shui-Jing Bar’ fruits were 20 days.
Using different thickness of PE bag lining in carton of ‘Jen-Ju Bar’ and ‘Shui-Jung Bar’ fruits, regardless of 0.03mm or 0.05mm of PE bag linings, fruits stored at 25℃with vacuum sealed in PE bag lining produced off-flavor and decay. But fruits stored at 5℃with vacuum sealed in PE bag lining had the longest storage life (‘Jen-Ju Bar’, 33 days and ‘Shui-Jing Bar’, 25-26days). Fruits quality among those of fruits, with it used regardless of thickness of PE bag lining or vacuum sealed treatments, were no significantly different.
Prestorage heat treatments of ‘Jen-Ju Bar’ and ‘Shui-Jung Bar’ fruits stored at 5、10℃, the respiration rate of two cultivars fruits were increased slowly compared to untreatment fruit, the respiration rate of fruits stored at 10℃ was higher than stored at 5℃. The lower ethylene production rate of ‘Shui-Jing Bar’ fruits with heat treatments (12sec. at 48℃) stored at 5℃ and (12sec. at 46℃) stored at 10℃. On the quality of guava fruits, the fruit
firmness and crispness retained after heat treatments, and did not affect total soluble solids, titratable acidity, pH value and Vit. C of the fruits, and delay yellowing of peel color. Moreover, could extend their storage life and delayed and alleviated chilling injury and decay incidence.
Two cultivars of guava fruits ‘Jen-Ju Bar’ and ‘Shui-Jing Bar’ during storage, the enzyme activity of PE and PG were higher at 25℃than those of fruits stored at 5℃and 10℃. Regardless of package, PE and PG activity of fruits increased during storage and the effect of packagings on both enzymes activity were smaller than its effects on weight loss and firmness.
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