Search Results

You are looking at 1 - 10 of 12 items for

  • Author or Editor: Irving L. Eaks x
  • Refine by Access: All x
Clear All Modify Search
Open access

Irving L. Eaks

Abstract

The respiratory rate, ethylene production and ripening of mature ‘Hass’ avocado fruits (Persea americana Mill.) were determined at 20° to 40°C. Typical climacteric patterns occurred at 20°, 25°, 30° and 35° with the climacteric maximum increasing with temperature, but only a decreasing respiratory rate with time was observed at 40°. Maximum ethylene production decreased as the temperature increased, with a significant decrease between 25° and 30°, only trace amounts were produced at 35° and essentially no ethylene production was detected at 40°. The ripened fruit quality was excellent at 20°, 25° and 30°, fair at 35° and abnormal and unacceptable at 40°. Fruit held at 40° for up to 2 days resumed ripening when transferred to 20°. The exposure to exogenous ethylene or propylene hastened the ripening response up to 35°, however at 40° the respiratory rate was increased, but ethylene production and normal ripening did not occur.

Open access

Irving L. Eaks

Abstract

The respiratory rate, ethylene production and softening of untreated and treated (propylene or ethylene) avocado fruit (Persea americana Mill, cv Hass) were determined during growth and maturation using fruit harvested monthly from August to July. Untreated immature fruit harvested in August exhibited a climacteric, produced ethylene and softened after 18, 21 and 18.5 days, respectively. Treatment of these immature fruit for 1 to 3 days beginning 1 day after harvest stimulated respiration during the treatment, but the respiratory rate decreased to the level of the untreated fruit within 1 day after the treatment was terminated and they subsequently paralleled the response of the untreated fruit. Ethylene production was not induced by the treatment in immature fruit, but was in mature fruit. The climacteric peak rate and the peak rate of ethylene production increased as the fruit matured. The days to the climacteric peak and days to soften decreased as the season progressed. The ethylene or propylene treated fruit had a progressively shorter time to the climacteric and to softening as they matured compared to the untreated fruit.

Open access

Irving L. Eaks

Abstract

The ripening, chilling injury and respiratory responses of ‘Hass’ and ‘Fuerte’ avocado fruit (Persea americana L.) were determined at 20°C subsequent to 0 to 5 weeks storage at 10°, 5° and 0°. Fruit held at 10° showed no chilling injury symptoms and were ripe by the third week. No softening or chilling injury symptoms occurred during the 5 weeks at 5° or 0°. However, after transfer to 20° fruit held at 5° and 0° longer than 1 week developed chilling injury and the severity increased as the exposure period increased. Short exposures to 5° and 0° tended to hasten ripening at 20° compared with fruit placed directly at 20°, but fruit held 5 weeks at 5° and 0° took longer to ripen at 20° than control fruit. Fruit placed directly at 20° showed a typical climacteric respiratory pattern which was associated with ripening. Chilling at 5° and 0° for more than 1 week resulted in high initial respiratory rates at 20°, followed by decreasing respiratory rates with no climacteric pattern associated with ripening.

Open access

Irving L. Eaks

Abstract

The effect of Ca between 0.05 and 5.0 m on days to ripen, respiratory rates, rates of ethylene evolution, and external and internal quality of ‘Fuerte’ and ‘Hass’ avocado fruit at 20°C when placed directly at 20° or at 20° after 1, 3, and 5 weeks storage at 0° and 5° was determined. Dipping fruit in Ca solutions had no significant effect on these responses. The results discussed are for vacuum-infiltrated fruit. Days to ripen was increased and respiratory rates and rates of ethylene evolution were reduced as the Ca concentration increased. At 0.4 and 0.5 m Ca, no detectable climacteric occurred, essentially no ethylene was produced and the fruit failed to ripen. Exogenous ethylene or propylene exposure for 2 days resulted in typical stimulation of respiratory rates, ethylene production, and ripening of untreated fruit. Treatment with Ca reduced each response. Storage experiments indicated that Ca reduced internal chilling injury symptoms and increased external symptoms. Commercial Ca treatment of avocados to delay ripening and reduce chilling injury symptoms does not seem practical, because of the necessity to vacuum-infiltrate the Ca solution into the fruit and the adverse effect on external quality when ripened after storage.

Open access

Irving L. Eaks

Abstract

The respiration, ethylene production and ethylene, ethyl alcohol, and acetaldehyde content of the internal atmosphere of citrus fruit increased at 20°C following exposures to chilling temperatures (0° and 5°) compared with fruit placed directly at 20°C. The increases were greater the longer the exposure and greater following exposure to 0° than following exposure to 5°. Exposure to 12.8°, a nonchilling temperature, did not elicit a stimulation of these attributes when transferred to 20°. Ethylene, ethyl alcohol, and acetaldehyde in the internal atmosphere of fruit remained at the same levels during the chilling exposures. During storage at 12.8° the acetaldehyde content in the internal atmosphere increased, but the ethylene and ethyl alcohol content did not. The chilling injury sustained by citrus fruit during storage could be evaluated by transferring samples to 20° and determining the respiratory rate, ethylene production or the volatile content in the internal atmosphere 24 hours after transfer to 20°.

Open access

Irving L. Eaks

Abstract

Avocado fruits of cvs. Bacon, Fuerte, Hass, and Zutano were harvested by clipping (stem in) or snapping (stem removed) and placed directly at 20°C. The 2 harvest methods showed no significant differences within each cultivar in the percentage wt loss or ripening rate. Clipped and snapped ‘Fuerte’ avocados stored at 5°C for 2, 3, or 4 weeks and transferred to 20°C showed similar rates of wt loss, ripening and respiration for the respective storage periods. Storage at 5°C tended to reduce the rate of ripening at 20°C. The respiratory patterns at 20°C for snapped and clipped ‘Fuerte’ placed directly at 20°C or held at 5°C for 2, 3, or 4 weeks were similar within each storage treatment. ‘Fuerte’ stored at 5°C displayed peak respiration rates 18 to 24 hr after transfer to 20°C and then a decreasing rate without a subsequent rise associated with ripening.

Open access

Irving L. Eaks

Abstract

The effects of chilling ‘Hass’ avocado fruit at 0° or 5°C on the respiratory rates, rates of ethylene production, ripening, and chilling injury symptoms at 20° were compared with the same responses of fruit exposed to a nonchilling temperature (10°) and fruit placed directly at 20°. Fruit held at 10° for 2 weeks were beginning the climacteric and ripened after about 4 days at 20°. Longer exposures at 10° resulted in ripe or overripe fruit. Fruit held for 2 weeks at 0° or 5° displayed normal climacteric patterns and ethylene production at 20°, and developed no significant chilling injury symptoms. Exposures of 4 and 6 weeks at 0° or 5° resulted in the development of chilling injury symptoms, abnormal ripening, atypical respiratory rate patterns, and reduced ethylene production rates which peaked after 2 days at 20° and showed a declining rate thereafter, with no increase in the rate of ethylene production associated with fruit softening.

Open access

Irving L. Eaks and Walton B. Sinclair

Abstract

Pectic substances in 4 avocado cultivars were determined as anhydrouronic acid (AUA) during ontogeny and related to fruit maturity, alcohol-insoluble solids (AIS), alcohol-soluble solids (ASS), ASS minus oil, total oil, fresh weight and dry weight. The concentration of pectic substances in avocado pulp varied among different cultivars and increases during growth and maturation. AUA varied between 0.7 to 1.5% on a fresh weight basis. However, values on a dry weight basis are relatively constant at about 5.0% and independent of the state of maturity or cultivar. AIS, ASS, alcohol-soluble acid and oil increase as the fruit mature, ASS minus oil and water content decreased during the growth and maturation periods. Changes in oil content during ontogeny was the only constituent of those examined which was related to maturity.

Open access

Irving L. Eaks and Arthur J. Dawson

Abstract

The influence of vegetative ground cover which lowers soil temperature was evaluated on regreening of fruit of ‘Valencia’ [Citrus sinensis (L.) Osbeck] orange. Carotenoid content of the rind increased to a maximum in March and then declined at each subsequent sampling. Chlorophyll content declined to a minimum in February, then increased slightly through May and increased markedly during June and July. Cartenoid content was higher and the chlorophyll content lower in the rind of fruit from the ground cover plots than in fruit from the bare-ground plots. Ethylene degreening for 5 days improved color index values of regreened ‘Valencia’ oranges; however, the color of fruit direct from the ground cover plots was superior to the color of fruit from the bare ground plots after degreening. Postharvest, regreened ‘Valencias’ showed no significant loss of chlorophyll or changes in carotenoids in air at 20°C. Exposure to ethylene caused a loss in chlorophyll, but the rate of loss was slower and the final chlorophyll levels after 8 days degreening with ethylene were relatively high compared with other citrus cultivars given similar treatment.

Free access

Steven J.R. Underhill, Richard L. McLauchlan, and Irving L. Eaks

In accordance with the currently approved Australian citrus disinfestation protocol for export to Japan, degreened `Eureka' lemons [Citrus limon (L.) Burm.] were cold-stored for 2 weeks at 1C. Following cold treatment, fruit were stored at 5C for 3 weeks, then transferred to 20C for an additional week to simulate transportation and handling. Fruit harvested early in the season were more susceptible to chilling injury than fruit harvested later, with 62% having lesions >1 cm2 after 2 weeks at 1C. Most of the chilling injury occurred after subsequent storage (at 5C) rather than immediately after the 1C treatment. Injury was different from surface pitting or oleocellosis, manifesting as large uniform surface lesions 2 to 3 cm in diameter that rapidly discolored following storage at 20C. Although the oil glands were flattened, the collenchyma layer immediately above the oil gland remained intact. Cellular discoloration was localized around the oil gland, possibly indicating a lateral release of oil gland contents. Nondegreened late-season fruit developed substantially lower levels of chilling injury.