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  • Author or Editor: James Mattheis x
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Carrots, broccoli, and lettuce were treated with air, continuous ethylene, 1-methylcyclopropene (MCP), or a combination of MCP before continuous ethylene. The respiration rate of ethylene-treated carrots reached a maximum 4 days after treatment and remained higher compared to controls through 16 days at 10 °C. Ethylene treatment also resulted in an accumulation of isocoumarin. Treating carrots with MCP before ethylene exposure inhibited the increase in respiration rate and accumulation of isocoumarin. MCP treatment reduced broccoli respiration and yellowing compared to controls, indicating that ethylene is involved in the senescence of broccoli. Ethylene exposure stimulated respiration and yellowing of broccoli. Treatment with MCP before continuous ethylene exposure negated the ethylene effects. MCP also inhibited respiration and russet spotting of lettuce stored in ethylene-containing atmospheres. The results indicate MCP can be used to block ethylene-induced isocoumarin accumulation (associated with bitterness) in carrots, yellowing in broccoli, and russet spotting in lettuce.

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Metabolism of peel constituents was assessed during ripening of `Delicious' and `Golden Delicious' apples. The ethylene action inhibitor 1-methylcyclopropene (1-MCP) and/or controlled atmosphere storage (CA) were used to limit ethylene activity during and after storage at 1 °C. `Delicious' apples not exposed to 1-MCP developed a brownish discoloration (not superficial scald) during the initial 2 months of storage in air. LC/MS analyses of peel components indicated 1-MCP and/or CA inhibited the degradation of compounds responsible for red peel color (i.e., idaein) as well as other flavonoids. Ethylene regulation of metabolism of other phenolic and related constituents including (-)epicatechin and chlorogenic acid appears to be compound specific. The (-)epicatechin content is not impacted by 1-MCP or CA, while chlorogenic acid accumulation is reduced in fruit exposed to 1-MCP and/or stored in CA. β-carotene and lutein content in peel of `Delicious' fruit stored in air was lower compared with untreated controls. Chlorophyll degradation was enhanced in air-stored fruit previously exposed to 1-MCP; however, this result was not observed in 1-MCP exposed fruit from CA. Results for `Golden Delicious' apples also indicated that exposure to 1-MCP and CA, as well as storage duration, impacts metabolism of peel constituents. Chlorophyll degradation was delayed in fruit previously exposed to 1-MCP and then stored in CA. Impacts of 1-MCP and storage environment on concentrations of other `Golden Delicious' peel constituents increased with storage duration. The results indicate metabolism of apple fruit peel constituents during fruit ripening is differentially regulated by ethylene.

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Commercialization of 1-methylcyclopropene (1-MCP) has provided a new tool to storage operators for management of fruit quality in the postharvest environment. For apple as an example, availability of the commercial 1-MCP product SmartFresh has brought an additional dimension to decisions regarding postharvest chemical treatments, storage temperature regimes, storage atmospheres, and planned storage duration based on fruit maturity at harvest. Poststorage impacts of 1-MCP use at harvest on handling and packing procedures have also become apparent with commercial use. Marketing programs have also been impacted because the “tails of the manifest” (large/small sizes, lower color grades) can be held longer in cold storage after packing primarily as a result of slower loss of firmness in many cultivars. Although some quality issues, primarily related to physiological disorders occurring on specific cultivars, are yet to be fully resolved, continuing widespread use of 1-MCP is indicative of its commercial usefulness.

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Ripening and development of physiological disorders and decay were assessed in ‘d’Anjou’ pear fruit after 1-methylcyclopropene (1-MCP) treatment and cold storage in air or controlled atmosphere (CA). Fruit were exposed after harvest to 0 or 12.6 μmol·L−1 1-MCP and then stored at 0.5 °C in air or 1, 3, or 5 kPa O2 with 0.5 kPa CO2. Pears were held poststorage at 20 °C for 7 days before analysis. 1-MCP fruit usually had higher hue compared with controls. Softening after removal from storage was delayed in 1-MCP fruit regardless of storage atmosphere; however, control fruit stored in air or CA ripened to below 23 N, a minimum value for consumer acceptance, after all storage durations. 1-MCP fruit stored in air, 3, or 5 kPa O2 softened in the outer cortex (fruit surface to 8 mm into the cortex) to below 23 N only after 9 m, however, only fruit stored in air softened to less than 23 N in the inner cortex (8 mm to coreline). 1-MCP treatment also delayed deformation in cortex tissue tensile strength (TTS); after six or more months, 1-MCP fruit TTS was lower compared with those for control fruit. After 9 m, 1-MCP fruit stored in air had TTS values similar to those of controls whereas values for fruit stored in CA increased with CA O2 concentration. Titratable acidity was higher in 1-MCP-treated fruit stored in air (6 m only) or 3 or 5 kPa O2 compared with controls. Superficial scald developed after 6 m on control fruit stored in air or 5 kPa O2 and on control CA fruit regardless of O2 concentration after 9 m. No 1-MCP fruit developed scald. The results indicate ‘d’Anjou’ pear ripening in response to 1-MCP is influenced by storage pO2 as well as storage duration, and at the 1-MCP treatment concentration used, softening to a consumer standard for firmness occurred only in fruit cold stored in air for 9 months plus a 7-day poststorage ripening period. These fruit had peel hue less than 100, and the yellow peel color may not be consistent with current market expectations.

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Broccoli (Brassica oleracea L. var. italica Plen) was held for 12 days at 10 °C in air or in ethylene (1 μL·L–1), with or without prior exposure to MCP (1 μL·L–1) for 12 hours. In a second experiment, the effects of concentration of MCP, prior to exposure to ethylene, were evaluated. Treatment with MCP reduced whereas exposure to ethylene stimulated respiration and yellowing. Treatment with MCP before continuous exposure to ethylene negated the effects of ethylene. The inhibitory effect of MCP on respiration of broccoli exposed to 1 μL·L–1 ethylene was concentration-dependent, while the effect on yellowing was not. The results indicate that the yellowing of broccoli is mediated by ethylene action, and that MCP treatment inhibits yellowing and reduces respiration, even when broccoli is exposed to ethylene. Chemical name used: 1-methylcyclopropene (MCP).

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`Bartlett' and `d'Anjou' pear fruit were treated after harvest with MCP at 0, 0.01, 0.1 or 1 mL•L-1 and then stored at 1 °C. After storage, half of the fruit was continuously exposed to 10 mL•L-1 ethylene for 7 days in a flow-through system at 20 °C. A treatment concentration effect was evident for both respiration and ethylene production, all MCP concentrations reduced respiration and ethylene production by `d'Anjou' and `Bartlett' fruit compared to controls. Fruit quality changes in `d'Anjou' and `Bartlett' fruit were delayed by MCP treatment. Firmness and titratable acidity were higher through 4 months storage for `Bartlett' fruit treated at the two higher MCP rates. After 2 months, `Bartlett' fruit treated at the two higher MCP rates remained green, but, after 4 months, all fruit were yellow. Loss of firmness and titratable acidity was also reduced following MCP treatment of `d'Anjou' fruit. Yellowing of `d'Anjou' fruit was prevented by MCP treatment, even when fruit were exposed to ethylene after removal from storage. Poststorage ethylene exposure did not overcome the effects of MCP. Development of superficial and senescent scald was prevented by MCP treatment.

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Airborne methyl jasmonate (MJ) can modulate apple fruit ripening, including the degreening process. Degreening of `Fuji' and `Golden Delicious' apples by jasmonates [jasmonic acid (JA) and MJ] in aqueous solution was investigated. JA and MJ applied by dipping apples in solutions of jasmonates for 2 min enhanced degreening during ripening at 20C. MJ was more effective at promoting degreening compared to JA. The minimum concentration of jasmonates required to promote significant degreening during the 2-week ripening period was 1 mM. Degreening of jasmonate-treated apples ripened at 4C progressed slower compared to apples ripened at 20°C. JA stimulated apple fruit ethylene production at concentrations as low as 10 μM. Jasmonates at 1 or 10 mM were more effective at accelerating the degreening process compared to 0.35 or 3.5 mM ethephon. Firmness, soluble solids content, and titratable acidity of `Fuji' apples were not significantly affected by jasmonate treatments. Peel injury occurred on apples treated with 10 mM JA or 3.5 mM ethephon.

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Enclosing `Fuji' apple (Malus ×domestica Borkh.) fruit in paper bags 2 months after full bloom delayed the increase in internal ethylene concentration at the onset of fruit ripening, and increased the respiration rate early in the bagging period. Bagging delayed and reduced red color development, especially on the blush side, but did not affect fruit resistance to gas diffusion. External surface color changed significantly within the first 4 days after bags were removed. Exclusion of UV-B from sunlight by Mylar film after paper bag removal impaired red color development. Bagging during fruit development increased superficial scald but eliminated stain during cold storage. Exposure to sunlight for 19 or 20 days before harvest reduced scald incidence in comparison with leaving bags on until harvest.

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`Golden Delicious' apple [Malus sylvestris var. domestica (Borkh.)] cortex disks suspended in solutions containing a nitric oxide (•NO) donor [S-nitrosoglutathione (GSNO) or sodium nitroprusside (SNP)], •NO gas, or nitrite (KNO2) were used to identify impacts of •NO on ethylene production and NO2 on •NO and ethylene production. Treatment with GSNO or SNP reduced ethylene biosynthesis compared with control treatments containing equimolar concentrations of oxidized glutathione (GSSG) or Na4(CN)6 respectively. Apple disk exposure to •NO gas did not impact ethylene production. Treatment with NO2 resulted in increased •NO production and decreased ethylene biosynthesis. Generation of •NO increased linearly whereas ethylene generation decreased exponentially with increasing NO2 treatment concentration. •NO was enhanced in autoclaved tissue disks treated with NO2 , suggesting that its production is produced at least in part by nonenzymatic means. Although this evidence shows •NO is readily generated in apple fruit disks by NO2 treatment, and ethylene synthesis is reduced by •NO/NO2 generated in solution, the exact nature of •NO generation from NO2 and ethylene synthesis modulation in apple fruit disks remains to be elucidated.

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The efficacy of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) applied in water to slow ripening of `Golden Delicious' [Malus sylvestris var. domestica (Borkh.) Mansf.] apples was evaluated in comparison with 1-MCP applied as a gas in air. The material was applied by dipping fruit in 1-MCP water solutions (0, 0.03, 0.3 or 3 μM) for 4 min, or by exposing fruit to 1-MCP gas (0, 0.01, 0.1 or 1 μL·L-1) in air for 12 h. Fruit were held in air at 20 °C for 25 days after treatment or stored at 0.5 °C in air for up to 6 months followed by 7 days in air at 20 °C. Application of 1-MCP in water or air delayed the increase in respiration and ethylene production associated with fruit ripening, and reduced the amount of fruit softening, loss of acidity and change in peel color. Treatments applied in water required a concentration 700-fold higher compared to those applied in air to induce similar physiological responses. Fruit responses to 1-MCP varied with treatment concentration, and the maximum effects were obtained at concentrations of 0.1 or 1 μL·L-1 in air and 3 μM in water. Peel color change was impacted less than retention of firmness and titratable acidity for some 1-MCP treatments. Treatment with 1-MCP was less effective for slowing peel degreening when treated fruit were stored at 0.5 °C compared to storage at 20 °C. In 1 of the 3 years of this study, fruit treated with 1-MCP and stored in air at 0.5 °C developed a peel disorder typified by a gray-brown discoloration that is unlike other disorders previously reported for this cultivar.

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