| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 90 === Summary
Pear is an important economical fruit crop in Taiwan. Most of the pears grown in Taiwan belong to the group of sand pear (Pyrus pyrifolia Nakai.). This research focused on the major cultivars of sand pear grown in this country, studied their quality changes during cold storage and did some observation on the physiological disorders occurred during storage.
Results from two consecutive years’ experiments on the cold storage of ‘Sinseiki’ pear indicated: First, early crop pear fruits produced at low altitude via top-grafting of flower buds method had about 3 months of storage life at 0℃, and both firmness and total soluble solids declined at the 4th month. Second, late crop pear fruits produced at high altitude via regular cultivation method had about 4 months of storage life. It was also observed that with or without ethylene absorbent during cold storage had no effect on fruit quality; and the addition of lime as carbon dioxide absorbent might cause off-flavor in pear fruits.
The sensitivity of sand pears toward CO2 varies with cultivars. ‘Sinseiki’ and ‘Shinkou’ pears were virtually insensitive to CO2, because pears treated with 2% CO2 for 48 hours before storage showed no adverse effects either on the skin or in the flesh. On the other hand, similar treatment caused severe skin-blackening disorder in ‘Xin-xue’ pear.
A skin-blackening disorder was observed in ‘Xin-xue’ pear after stored at 0-2.7℃ for two weeks. This blackening disorder occurred only at the skin tissue, the flesh tissue remained normal throughout storage. Since the disorder was not observed when pears were stored at 5℃, this skin-blackening disorder may be regarded as a chilling injury of ‘Xin-xue’ pear. The occurrence of skin-blackening was higher in large size fruit, and was promoted by sealing the wrapping plastic bag of fruit as well as by pretreatment with high concentration of CO2. Treating fruits with 0.2% ethoxyquin, an antioxidant, before storage and addition of CO2 absorbent in the wrapping bag could reduce the occurrence of skin-blackening. Microscopic observation of the free-hand cross-section of blackened tissue showed partial collapse of cells in the sub-epidermal tissue and these cells turned into yellow and brown, which is considered as the direct cause of skin-blackening.
A skin cracking disorder was observed in ‘Shinkou’ pears after stored at 0-1℃for 2.5 months. Microscopic observation of the free-hand cross-section of skin tissue found that a cavity was first formed beneath the epidermis, which then lead to the slitting of epidermis.
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