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  • Author or Editor: Sylvia M. Blankenship x
  • Journal of the American Society for Horticultural Science x
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Scatchard plots for ethylene binding in apples (Malus domestica Borkh.), which were harvested weekly for 5 weeks to include the ethylene climacteric rise, showed C50 values (concentration of ethylene needed to occupy 50% of the ethylene binding sites) of 0.10, 0.11, 0.34, 0.40, and 0.57 μl ethylene/liter-1, respectively, for each of the 5 weeks. Higher ethylene concentrations were required to saturate the binding sites during the climacteric rise than at other times. Diffusion of 14C-ethylene from the binding sites was curvilinear and did not show any indication of multiple binding sites. Ethylene was not metabolized by apple tissue.

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Abstract

Internal ethylene levels, fruit firmness, soluble solids content, and starch–iodine reaction in ‘Delicious’ and ‘Golden Delicious’ apples (Malus domestica Borkh.) were measured weekly for 6 to 8 weeks during fruit maturation for 3 years. Internal ethylene level did not consistently correlate with minimum maturity as judged by agricultural inspection or optimum maturity as judged by a taste panel in either cultivar. Internal ethylene levels ranged from 0 to 26 μl·liter−1 in ‘Delicious’ and 0 to 41 μl·liter−1 in ‘Golden Delicious’ on taste panel harvest dates. Decreases in fruit firmness and increases in starch conversion and soluble solids content were observed prior to any increase in internal ethylene in both ‘Delicious’ and ‘Golden Delicious’. Thus, internal ethylene concentration is not a reliable index of maturity for harvest determination for immediate sale on the fresh market. The combination of fruit firmness decrease, soluble solids increase, and conversion of starch seem to be more closely tied to perception of maturity by both the agricultural inspectors and taste panel.

Open Access

Abstract

High performance liquid chromatography of mature ‘Beurre d'Anjou’ and ‘Beurre Bosc’ pear (Pyrus communis L.) fruit flesh showed that the major phenolics at harvest were chlorogenic acid, catechin, and arbutin. Neither cultivar contained epicatechin nor p-coumaroyl quinate. During 160 days at –1°C the chlorogenic acid content of d'Anjou increased significantly. In ‘Bosc’, chlorogenic acid levels decreased during storage. Catechin content increased linearly while arbutin levels remained nearly constant in both cultivars. Coincident with the completion of the cold requirement for initiation of ripening and endogenous ethylene production, i.e., 20 days for ‘Bosc’ and 50 days for ‘d'Anjou’, there was an appearance of low levels of a p-coumaric acid derivative and trace amounts of epicatechin/p-coumaroyl quinate. At 120 days epicatechin/p-coumaroyl quinate increased in ‘d'Anjou’ but not in ‘Bosc’. There is a coincidence, and perhaps relationship, between ethylene production and the quantity as well as the composition of phenolics present during storage. Bruising pear fruit after 120 days of storage caused a 30% increase in chlorogenic acid and a 50% increase in catechin, but no increase in p-coumaric acid derivatives.

Open Access

Abstract

Forty-six days at –1°C were required to stimulate ethylene synthesis in harvested ‘d'Anjou’ pears (Pyrus communis L.). The effect of exogenous ethylene on changes in quality parameters and organoleptic properties, and the effect of cold temperature on the development of ethylene production, were studied during the 46 days at –1°. Pears were held in 10 or 50 ppm exogenous ethylene at 20° after 30 or less days at –1°. Respiration increased from 8 to about 19 mg CO2·kg-1·hr-1 in fruit held in ethylene over a 12-day period, whereas fruit held in air showed only a slight increase. Firmness of fruit held in ethylene decreased from 66 to 12 N over 12 days at 20°. No significant change in firmness occurred in fruit held in air at 20°. The volume of extractable juice was unchanged in fruit held in air, but declined in fruit held in ethylene. The soluble solids content was not affected by ethylene treatment. Taste panel evaluation determined that fruit held 30 days at –1° then held 10 days in ethylene at 20° were ripe, sweet, and juicy, but fruit held in air were comparable to fruit never held at 20°. Pear flesh disks cut from fruit held 21 days at –1° did not convert exogenous 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, but did so when cut from fruit held 41 or 50 days at –1°. Only with the onset of ethylene production was endogenous ACC detectable in pear flesh. During the 46 days at –1° required for initiation of ethylene production, the capacity to convert ACC to ethylene developed first, followed by production of ACC and ethylene.

Open Access

An ethylene action inhibitor, MCP, was applied to preclimacteric and climacteric apple [Malus sylvestris L. (Mill.) var. domestica Borkh. Mansf.] fruit. Experiments were conducted in North Carolina and Washington State utilizing the following cultivars: Fuji, Gala, Ginger Gold, Jonagold, and Delicious. MCP inhibited loss of fruit firmness and titratable acidity when fruit were held in storage at 0 °C up to 6 months and when fruit were held at 20 to 24 °C for up to 60 days. For all cultivars except `Fuji', differences in firmness between treated and nontreated fruit exceeded 10 N after 6 months storage. These beneficial effects were seen in both preclimacteric and climacteric fruit. Ethylene production and respiration were reduced substantially by MCP treatment. MCP-treated fruit had soluble solids equal to or greater than those in nontreated fruit. Storage and shelf life were extended for all cultivars tested. Chemical name used: 1-methylcyclopropene (MCP).

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Bell peppers (Capsicum annuum L.) are classified as nonclimacteric fruits while some hot peppers have been reported as climacteric. Responses of peppers to exogenously applied ethylene-releasing compounds suggest ethylene involvement in the ripening process. Ethylene production and respiration rates in 13 cultivars of pepper: `Camelot', `Cherry Bomb', `Chiltepin', `Cubanelle', `Banana Supreme', `Habanero', `Hungarian Wax', `Mesilla', `Mitla', `Savory', `Sure Fire', `Tabasco', and `King Arthur' were studied under greenhouse and field conditions. Fruit from each cultivar were harvested at different maturity stages determined by color, ranging from mature-green to full red-ripe. Carbon dioxide and ethylene production were measured by gas chromatography. Both variables were significantly different among maturity stages for all cultivars. Respiration rates were between 16.5 and 440.3 mg·kg-1·h-1 CO2. Ethylene production ranged from 0.002 to 1.1 μL·kg-1·h-1. Two patterns of CO2 production were identified: higher CO2 production for mature-green fruit with successive decreases for the rest of the maturity stages or lower respiration rates for mature-green fruit with an increase in CO2 production either when fruit were changing color or once fruit were almost totally red. A rise in CO2 production was present for most cultivars. Ethylene evolution increased significantly at maturity or before maturity in all cultivars except `Cubanelle' and `Hungarian Wax'. Respiration rates and ethylene production were significantly different among cultivars at the mature-green and red stages.

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Variation in amount and composition of epicuticular wax among several apple (Malus ×domestica Borkh.) cultivars was characterized by gas chromatography, thin-layer chromatography, and gas chromatography-mass spectroscopy. Across cultivars, wax mass ranged from 366 to 1038 μg·cm-2. Wax mass decreased during the 30 days before harvest. Ursolic acid accounted for 32% to 70% of the hydrocarbons that make up the epicuticular wax. Alkanes, predominantly 29-carbon nonacosane, comprised 16.6% to 49%. Primary alcohols of the hydrocarbons ranged from 0% to 14.6% of the epicuticular wax. Secondary alcohols of the hydrocarbons were the most cultivar specific, making up 20.4% of the epicuticular wax in `Delicious' and only 1.9% `Golden Delicious' strains. Aldehydes and ketones of the hydrocarbons represented a small amount of total wax, ranging from 0% and 6.0%. Percentage of primary alcohol in the epicuticular wax increased as fruit developed. Other components showed no distinct trends with fruit development. Examination of the ultrastructure of cuticular wax using scanning electron microscopy revealed structural differences among cultivars.

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Mature green `Grande Naine' bananas (Musa AAA) were harvested 13 weeks after flowering in June and Sept. 1993 and Feb. and Mar. 1994 and were sent air freight to Raleigh, N.C. Fruit were held under 1) storage (36 days at 14 C and 80% to 90% relative humidity) or 2) ripening (8 days storage, followed by ethylene treatment on day 8 and subsequent storage at 17 °C and 80% to 90% relative humidity). Despite of similar grade and age, length of the preclimacteric phase (green life) was different between fruit harvested at different times of the year. Fruit harvested in February and March had a longer green life than those harvested in June and September. Rate of respiration best described changes that occurred during the postharvest life of bananas; however, variables such as pulp pH and soluble solids could be commercially useful measures. Once gassed with ethylene, ripening rates were similar between all four lots of fruit, indicating that seasonal variation probably doesn't contribute much to variability seen during ripening. Hand position in the bunch did not have a large influence on variability during ripening or storage.

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