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- Author or Editor: Donald J. Huber x
The present study was conducted to explore the process of watersoaking seen previously in beit alpha-type cucumber fruit treated with ethylene. Fruit were harvested at four levels of maturity: Immature (4 to 8 days after anthesis, DAA), Mature (10 to 14 DAA), Breaker (16 to 20 DAA), and Yellow (35 to 40 DAA). Fruit were then stored at 13 °C in the presence of air (control) or either 10 μL·L-1 ethylene or 1300 μL·L-1 propylene for up to 12 days. The physiological response to ethylene treatment varied with fruit maturity. Immature-stage fruit treated with ethylene for 9 days had mesocarp watersoaking, epidermal sloughing, and lower hue (118°, control 124°), endocarp pH (4.4, control 5.4), and whole fruit firmness (23 N, control 46 N). Mature-stage fruit behaved similarly to Immature-stage fruit, but lacked mesocarp watersoaking. In contrast, after 9 days of ethylene exposure, the Breaker- and Yellow-stage fruit exhibited no watersoaking, accumulated beta-carotene in peel tissue (13.6 μg·g-1 F.W, control 0.35 μg·g-1 F.W.) and had a “melon”-like aroma. Ethylene exposure for all maturities increased respiration rate and decay incidence compared to air-treated fruit. Ethylene evolution was only detectable in fruit with visible decay. Decay incidence in response to ethylene treatment was inversely proportional to maturity at harvest. Watersoaking, exhibited exclusively in Immature fruit, spread inward from the epidermis starting after about 6 days of ethylene treatment. Cells in watersoaked tissue stained negatively for viability with fluorescein diacetate and cells proximal to watersoaked cells stained weakly compared to air-treated controls. Current work is focused on identifying the mechanism of cell death.
Grape tomatoes (Lycopersicon esculentum Mill. `Santa') harvested at light-red (>90% color) and full-red stages were treated with 1 μL·L–1 1-methylcyclopropene (1-MCP) for 24 hours at 20 °C and stored at 20 °C. After 1 day of storage, fruit harvested at light-red stage treated with 1-MCP had a 56% lower respiration rate than untreated fruit. By day 7, respiration rates of the two treatments had converged at about 2 mL·kg–1·h–1. Ethylene production of light-red stage tomatoes treated with 1-MPC was 24% lower than untreated during storage, with rates converging by day 11. For fruit harvested full-red, 1-MCP had similar effects on respiration and ethylene production, although convergence occurred earlier, by day 5. Subsequent tests were conducted only with fruit harvested at full-red stage, since fruit harvested at the light-red stage had lower soluble solids content (4.3%) than fruit harvested at the full-red stage (5.5%). Several combinations of 1-MCP concentrations and exposure times were applied at 20 °C: 1 μL·L–1 for 24 h, 5 μL·L–1 for 6 or 12 h, 25 μL·L–1 for 6 or 12 h, and 50 μL·L–1 for 6 or 12 h; following the respective pretreatment fruits were stored at 20 °C. 1-MCP pretreatment extended marketable life by 1 d, irrespective of pretreatment regime, where untreated and pretreated fruit remained marketable (<15% of fruit soft, decayed and/or shriveled) for 6 and 7 d, respectively. However, 1-MCP did not affect whole fruit firmness, epidermal color, internal color, soluble solids content (6.5%), total titratable acidity (0.64%), or pH (4.3). In a third test simulating commercial handling procedures, full-red harvested tomatoes were treated with 1 μL·L–1 1-MCP for 24 h at either 13 or 20 °C, stored for 4 d at 13 °C, and then transferred to 20 °C. Under these conditions, marketable life for untreated and 1-MCP-treated tomatoes was 7 and 8 d, respectively.
The purpose of the present study was to investigate the role of ethylene action, via use of the ethylene antagonist 1-methylcyclopropene (1-MCP), on the senescence and quality of fresh-cut ripe papaya (Carica papaya L. `Sunrise Solo') fruit. Ripe papaya fruit were treated with 2.5 μL·L-1 1-MCP and immediately processed into fresh-cut slices or left intact. At 2-day intervals over 10 days at 5 °C, continuously stored slices were monitored for ethylene production, firmness, electrolyte leakage, color, sensory changes, and pathogen incidence. Slices freshly prepared from intact fruit stored under identical conditions were measured similarly. Ethylene production did not differ significantly between the treatments, although production rates were slightly but consistently higher in slices from intact control compared with intact 1-MCP-treated fruit. Mesocarp firmness of continuously stored slices and slices from fruit stored intact was significantly retained by 1-MCP. Firmness of continuously stored slices from 1-MCP-treated fruit declined 50% compared with 75% for control slices. Firmness of fresh-cut slices prepared from intact control and 1-MCP-treated fruit at each sampling interval declined 26% and 15%, respectively. Electrolyte leakage remained low and changed little in slices freshly prepared from fruit stored intact. Leakage from continuously stored papaya slices increased after 4 days, and after 6 days controls increased significantly compared with stored slices derived from papaya fruit initially treated with the ethylene antagonist. The flesh color of continuously stored slices or slices prepared from fruit stored intact was influenced by 1-MCP only during the later periods of storage. Microbial counts in stored slices or slices prepared at each sampling were generally unaffected by 1-MCP. Informal sensory analysis indicated that the edible shelf life was 6 days in stored slices from 1-MCP-treated fruit compared with 2 to 3 days for stored slices from control fruit.
Mature green and pink tomato (Lycopersicon esculentum Mill.) fruit were subjected to ionizing irradiation in the range of 0.7 to 2.2 kGy from gamma-or X-ray sources. Firmness of whole fruit and pericarp tissue, pericarp electrolyte leakage, and pericarp cell wall hydrolase activities were measured following irradiation and during postirradiation ripening at 20 °C. Irradiation-induced softening was evident in mature-green and pink fruit within hours following irradiation, and differences between irradiated and control fruit persisted throughout postirradiation storage. Trends of firmness loss were much more consistent and showed much greater dose dependency in pericarp tissue than whole fruit. Irradiation enhanced electrolyte efflux in fruit of both maturity classes. Fruit irradiated at the mature-green stage softened during postirradiation storage but exhibited an apparently irreversible suppression in polygalacturonase activity, with levels remaining <10% of those of nonirradiated fruit. Polygalacturonase activity was less strongly affected in irradiated pink fruit than in mature-green fruit, but activity remained reduced relative to the controls. Pectinmethylesterase and β-galactosidase activities were significantly enhanced in irradiated fruit of both ripening stages in the early period following irradiation, but reductions were noted after prolonged storage.
Abstract
The postharvest behavior of watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] fruit harvested at selected stages of development and stored in air or exposed to 50 μl ethylene/liter or 6500 μl propylene/liter was investigated. Characteristics measured included the effects of ethylene or propylene on ripening, respiration, ethylene production, and fruit firmness. Ethylene treatment induced a rapid deterioration of fruit at all maturation stages, as evidenced by the acute placental tissue softening and watersoaking. Melons of all maturation stages held in air showed little textural change throughout storage and produced only trace quantities of ethylene. Respiratory activity of fruit at each maturation stage was enhanced in the presence of ethylene or propylene and returned to normal rates upon removal of the gases. Ethylene production was not initiated by exposure of fruit to propylene, and was detected only in fruit exhibiting symptoms of decay. The results support the conclusion that watermelon fruit exhibit a nonclimacteric pattern of ripening.
Abstract
In the article “Respiration and Ethylene Production in Harvested Watermelon Fruit: Evidence for Nonclimacteric Respiratory Behavior,” by Mohamed E. Elkashif, Donald J. Huber, and Jeffrey K. Brecht [J. Amer. Soc. Hort. Sci. 114(1):81–85, January, 1989], the respiratory drifts in Fig. 1 were not clearly visible. An improved figure is printed below.
Bell pepper (Capsicum annuum L., var. `Jupiter') fruit stored in 1.5%, 5%, or 10% O2, or in air at 20C for24 hours were compared to determine the residual effect of low-O, storage on respiration after transfer to air. The lowest O2 concentration (1.5%) exerted the greatest residual effect on bell pepper fruit CO2 production and O2, uptake. No ethanol was detected in the headspace gas of fruit stored in 1.5% O2. Carbon dioxide production continued to be suppressed for ≈ 24 hours after transfer from 1.5% O2 to air. Exposure to 5% O2, for 24 hours resulted in less suppression of CO, production and O2 uptake upon transfer to air, while 10% O2 exerted no residual effect. Extending the storage period in 1.5% O2 to 72 hours extended the residual effect from 24 to 48 hours. Ethylene production was not affected by storage in 1.5% or 4% O2 for 24 or 72 hours. The residual effect exhibited in whole fruit was not apparent in mitochondria isolated from bell pepper stored in 1.5% or 4% O2.
Ethylene production by locule gel tissue excised from full-size immature- and mature-green tomato fruit was inhibited by exposure to l00μl·l-1 C2H4, and ACC content was reduced. In contrast, CO2 production, EFE activity, red color development, and tissue liquefaction were stimulated by C2H4, and, in immature gel, the onset of autocatalytic C2H4 production was hastened. The autoinhibition of C2H4 production required continuous exposure to C2H4, as transfer to air and then back to C2H4 resulted in C2H4 production first increasing to control levels, then decreasing again. Locule tissue from pink fruit responded to C2H4 treatment with increased production of both C2H4 and CO2, but ACC levels were unchanged. Inhibition of C2H4 action by pretreatment with STS inhibited both autoinhibition of C2H4 production in immature gel and autocatalytic C2H4 production in mature tissue. These results indicate that there is a transition from a negative to a positive feedback mechanism of C2H4 on C2H4 biosynthesis in locule gel during ripening. Additionally, this feedback mechanism, which involves ACC synthase, is apparently under separate control from the other manifestations of C2H4 action.
In this study, ripening characteristics, including color change and softening, were determined for tomato (Lycopersicon esculentum `Florida 47') fruit at immature-green through light red stages of development and subsequently treated with 1 μL·L–1 1-methylcyclopropene (1-MCP). Special attention was directed at comparing the responses of immature and mature-green fruit. Surface color and whole fruit firmness were measured every other day. 1-MCP delayed or slowed color changes and softening in fruit of every maturity class, with differences between control and treated fruit evident immediately following 1-MCP application for 24 h at 20 °C. Fruit treated with 1-MCP at early maturity stages (immature-green, mature-green, and breaker) exhibited an extended delay in external red pigment accumulation compared with control fruit. Fruit of all maturity classes developed acceptable final hue values (hue angle ≤55°), and the time required to reach these values declined with advancing fruit maturity. Immature-green fruit treated with 1-MCP did not attain an acceptable degree of softening during the specified storage periods examined before deteriorating due to shriveling and pathogen proliferation. 1-MCP-treated mature-green and breaker stage fruit did recover to acceptable firmness (5–10 N) and hue values but exhibited a severely reduced storage life thereafter compared with untreated fruit of equal maturity. Fruit at turning and more advanced stages exhibited reduced rates of softening and color development when treated with 1-MCP, yet they attained firmness and color values within the range of acceptability for commercial use. Fruit treated with 1-MCP at pink and light-red stages of ripening developed normal external color and exhibited significantly extended postharvest life due largely to a significant retention in firmness when compared to control fruit. Based on the studies described for `Florida 47' tomato fruit, 1-MCP would appear to be of little benefit and possibly detrimental if applied to early maturity fruit, most notably greens and breakers, due to irreversible limitations in the capacity of these fruit to soften to acceptable values. In sharp contrast, more advanced stage fruit, particularly pink and light red, responded to 1-MCP with significantly extended shelf-life due to retention of firmness.
Growth and development were characterised in two compound tropical fruit, soursop, Annona muricata L., and breadfruit, Artocarpus altilis (Park.) Fosb. The growth curves of both fruit were typically sigmoidal as determined by length, diameter, fresh weight and dry weight measurements. Soursop showed biphasic development with the flower/fruit remaining in an apparent resting state for some 12 weeks post anthesis before entering the second or true phase of growth leading to maturity. For both fruit, size increase extended over a 3 month period. Maturity indices were derived for each fruit and simple post harvest changes in texture, respiration and ethylene evolution investigated. storing either fruit under refrigeration down to 14°C significantly extended storage life though at temperatures below this chilling injury was evident.