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Title: GRADUAL POSTHARVEST COOLING REDUCES BLACKENING DISORDER IN ‘NIITAKA’ PEAR (PYRUS PYRIFOLIA) FRUIT

Author
item LIM, BYUNG SEON - RDA, KOREA
item KIM, JEAM KUK - RDA, KOREA
item Gross, Kenneth
item HWANG, YONG SOO - CHUNGNAM UNIV, KOREA
item KIM, JUNG HO - KOREA FRUIT GROWERS ASSOC

Submitted to: Korean Society of Horticulture Science Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2005
Publication Date: 10/31/2005
Citation: Lim, B.S., Kim, J.K., Gross, K.C., Hwang, Y.S., Kim, J.H. 2005. Gradual postharvest cooling reduces blackening disorder in ‘niitaka’ pear (pyrus pyrifolia) fruit. Korean Society of Horticulture Science Journal. 46:311-316.

Interpretive Summary: Asian pears have a skin blackening disorder that makes them unattractive and of low quality and marketability. We studied the disorder by slowly decreasing the cold storage temperature after harvesting the fruit and monitoring development of skin blackening. By decreasing the temperature by 1 degree Celsius per day, to 1 degree (storage temperature), we were able to almost completely prevent the development of skin blackening, resulting in higher quality fruit and greater revenue for fruit growers. Growers and consumers will benefit from this research because the growers will be able to market more high quality fruit, and consumers will have higher quality fruit to purchase.

Technical Abstract: The effect of temperature preconditioning on the skin-blackening disorder observed in Asian pears (Pyrus pyrifolia cv. ‘Nakai’) during low temperature storage was investigated. In addition to incidence and severity of blackening, mineral content, changes in fruit fresh weight, firmness, total soluble solids and titratable acidity were evaluated. Blackening was only observed on the epidermis, not lenticels, cuticle, or flesh. Skin blackening appeared after 15 days storage in more than 62% of pears stored below 1ºC, while both storage at 10ºC and storage at 1ºC after preconditioning at 10ºC for 10 days resulted in a low incidence, 0 and 3.7%, respectively. In addition to these treatments, pears were given a gradual cooling preconditioning in which the storage temperature was decreased from 15ºC to 1ºC at a rate of 1ºC day-1. This preconditioning resulted in a blackening incidence of only 0.2%. A high relative humidity (~ 92 to 95%) treatment at 1ºC resulted in greater severity of skin blackening than a lower relative humidity treatment (~ 62 to 82%) after 15 days storage. However, the effect of humidity on blackening was negligible after 30 days. Calcium content of non-blackened fruit flesh and peel were higher than that of fruit which showed blackening. The flesh weight and firmness of blackened fruit was lower compared to normal pear fruit controls. There were no significant differences in dry weight, soluble solids or total acidity among treatments. The results suggest that skin blackening of Asian pears (Pyrus pyrifolia cv. ‘Nakai’) during low temperature storage is a chilling injury symptom.