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Open access

W. M. Mellenthin and P. M. Chen

Abstract

‘d’Anjou’ pears (Pyrus communis L.) harvested at optimum maturity with flesh firmness of 6.4 kg were stored at -1.1°C for 3 months before being subjected to different intermittent and simulated transit temperatures. Fruit held for 3 days at 1.7 or 7.2°C did not soften significantly at transit temperature of -1.1°C for 4 weeks, whereas fruit held for 3 days at 12.8°C softened from 6.0 kg to 4.0 kg after 4 weeks at -1.1°C. After 4 weeks at 1.7°C, fruit held for 3 days at all intermittent temperatures softened 5.0-3.5 kg. Simulated transit temperatures above 7.2°C caused softening to less than 2.5 kg within 3 weeks. The additive effects of brief intermittent and 4-week simulated transit temperatures indicated that the higher the temperature, the more softening of ‘d’Anjou’ pears occurred. Fruit held for 3 days at 1.7, 7.2, or 12.8°C and 4 weeks at -1.1 or 1.7°C softened rapidly to 1 kg within 8 days in the ripening environment at 20°C, in conjunction with accelerated rates of respiration and ethylene production. However, softening preceded climacteric rises in ethylene and respiration of fruit kept 4 weeks at -1.1°C.

Open access

P. M. Chen and W. M. Mellenthin

Abstract

’D‘Anjou’ pears (Pyrus communis L.) were harvested at weekly intervals for a 3-week period beginning at the start of commercial harvest in the Hood River Valley, Oregon. Late-harvested fruit at flesh firmness of 5.9 to 5.4 kg ripened with fair to good quality following 30 days storage at -1.1°C. Fruit harvested at optimum flesh firmness of 6.4 to 6.1 kg required 60 days of postharvest chilling to ripen with quality. The development of ripening capacity corresponded to the increase in internal ethylene to 1.5—2.0 ppm during cold storage. Dessert quality of late-harvested fruit declined after 90 days of storage while quality of optimum-harvested fruit continued to improve until 150 days in storage. Flesh firmness and ethanol-soluble matters indicated that fruit harvested over the 3-week period were of different maturities. Concentrations of titratable acids and soluble solids varied among different harvest groups.

Open access

C. Y. Wang and W. M. Mellenthin

Abstract

Friction discoloration of ‘d'Anjou’ pears (Pyrus communis L.) was found to be associated with total phenol and chlorogenic acid content. Concentrations of these substances in the skin decreased during fruit development but increased during storage. Tendency for friction discoloration also increased with storage duration. Treatments with ascorbic acid and sodium bisulfite reduced the susceptibility of skin to friction discoloration.

Open access

W. M. Mellenthin and D. Bonney

Abstract

Portable limb enclosures allowing continuous modification of prevailing temp for tree fruits are described. Experimental programs to match temp conditions prevailing during the growing season in the fruit regions of the Pacific Northwest are possible.

Open access

C. Y. Wang and W. M. Mellenthin

Abstract

High chlorogenic acid level was associated with ‘d’Anjou' pear tissues affected with cork spot; tissues adjacent to the cork spot had next highest level. In fruit without cork spot symptoms, tissues on the sunlight exposed side had more chlorogenic acid than shaded tissue. Affected fruit had higher and accelerated rates of ethylene production and respiration than normal fruit.

Open access

W. M. Mellenthin and C. Y. Wang

Abstract

Quality and ripening capacity of ‘d’Anjou’ pears (Pyrus communis L.) after long-term storage were influenced by the daily-hourly average (DHA) temperatures during 6-week prior to harvest. Fruits of 17.2° and 13.9°C DHA temperatures ripened with high acid and sugar contents while samples of 20.0° and 11.7°C DHA temperature treatments failed to ripen properly and had lower quality. Failure to ripen after prolonged storage was associated with high protein nitrogen levels in the fruits. Samples of lower DHA temperature were more susceptible to friction discoloration, while fruits of higher DHA temperature had a higher percentage of superficial scald. Temperatures during this period did not appear to affect harvest maturity, size or soluble pectin content of the fruit.

Open access

W. M. Mellenthin and C. Y. Wang

Abstract

Small ‘d’Anjou’ pears (Pyrus communis L.) tend to be more susceptible to friction discoloration than the large fruits. Susceptibility to friction discoloration decreased with maturity but increased with duration of storage. Phenolic substances which are associated with friction discoloration and which serve as the substrate for polyphenoloxidase also declined with maturity and accumulated in storage. However, polyphenoloxidase activities increased with maturity and decreased during storage. The accumulation of phenolic compounds may be a result of the low polyphenoloxidase activities in storage.

Open access

C. Y. Wang and W. M. Mellenthin

Abstract

Treatment with 2-mercaptobenzothiazole (MBT) inhibited the friction discoloration of fruit of ‘d’Anjou’ pear (Pyrus communis L.). The inhibition was apparently due to inactivation of the pear polyphenoloxidase.

Open access

C. Y. Wang and W. M. Mellenthin

Abstract

High storage humidities, wax, and polyethylene film as bin-liners were compared for minimizing loss in storage life and preventing fruit shrivel during storage prior to packaging for market of pear (Pyrus communis L. cv. d’Anjou). Lining the sides and covering the top of bins with 1.25-mil polyethylene film was the most beneficial in preventing fruit shrivel without adversely delaying cooling. Enclosing pears in film bin bags also controlled moisture loss but was detrimental to rapid removal of field heat. Waxing the fruit or covering only the top of bins with film did not reduce the cooling rate but were ineffective in preventing excessive moisture loss. Introduction of water vapor to maintain high humidity markedly reduced moisture loss but caused ice formation on the fruit and storage room floor.

Open access

C. Y. Wang and W. M. Mellenthin

Abstract

Continuous exposure of pears to 7.2°C (night) - 21.1°C (day) for 2 days or 10°C - 21.1°C for 9 days or 7.2°C - 26.7°C for 21 days induced the physiological disorder, premature ripening, during the month immediately preceding normal harvest. During the same period, premature ripening did not develop with temp exposures of 12.8°C - 21.1°C or with 7.2°C - 32.2°C. Cool temp 6 to 9 weeks prior to harvest may also cause premature ripening to occur but the fruit will recover to normal behavior if subsequent temp are above the threshold level.