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Abstract

Fumigation with 2-aminobutane (2-AB) provides effective and convenient decay control for citrus fruits, but the temporary residue tolerance of 20 ppm can easily be exceeded. Factors found to control residues were the cultivar, concentration of 2-AB, temperature, duration of fumigation, and load (as a percentage of maximum capacity) in the fumigation chamber. The simplest procedure was to evaporate the entire charge of 2-AB as rapidly as possible. Residues in ‘Dancy’ tangerines and ‘Temples’ were higher than in oranges. Safe dosages for waxed fruit in poly bags and master cartons fumigated for 3 hr in full cabinets at various temperatures were (in ml/100 cu ft): 80 ml at 85° F, 110 ml at 70°, and in excess of 150 ml at 50° and below. Risk of exceeding tolerance at 40° and lower was minimal. Use of a chlorinated hydrocarbon, Quick Color, to eliminate explosion hazard had no consistent effect upon 2-AB residues.

Controlled atmospheres have been proven an effective postharvest disease deterrent for strawberries both in transport and storage. However, these treatments do not provide residual protection once the commodity is removed from the atmosphere, and the atmospheres can cause off-flavors in the fruit. Elevated oxygen atmospheres are a novel addition to this technology and could potentially provide better decay control without the harmful effects on fruit flavor aspects. Elevated oxygen will potentially discourage microbial growth, as anaerobes grow best under very low oxygen levels and aerobes grow best under atmospheric oxygen. Threshold elevated oxygen levels to prevent Botrytis cinerea growth in vitro and in vivo on strawberry were assessed. Botrytis cultures (mycelial plugs and spores) and fresh strawberry fruit were exposed to 21%, 40%, 60%, and 80% oxygen atmospheres at 5 °C for 5, 7, and 14 d. Growth of cultures from mycelial plugs was evaluated after treatment and during post-treatment incubation by measuring the diameter of the fungus. Spore germination and germ tube elongation were evaluated every 24 h for 3 days after treatment by counting the number of germinated spores and measuring elongation, respectively. Strawberry quality including firmness, color, soluble solids, titratable acidity, ethylene production and respiration rates, and presence of defects were evaluated upon removal from the elevated oxygen atmospheres as well as after 1, 3, and 5 d storage in air at 20 °C simulating market conditions.

Fruit of table grape cvs. Black Monukka, Flame Seedless, Thompson Seedless and Himrod were fumigated with 2, 4 and 6 Deccodione tablets for 30 minutes in a fumigation chamber. Fruit was brought to the cold rooms and stored at 32 F and high relative humidity for upto 10 weeks. Decay control index, freshness of stems and bleaching around the capstem were recorded at 2, 4, 6, 8 and 10 weeks of storage. Size of the smoke particles was determined using an electrical aerosol analyzer.

Fruit was kept in good condition by fumigation with 6 smoke tablets upto 10 weeks. Lower doses failed to control the decay. No bleaching around the capstems commonly associated with sulfur dioxide fumigation was noticed. Majority of the smoke particles were between 0.18 and 0.32 micrometers. Fumigation with Deccodione tablets could be a viable alternative to sulfur dioxide fumigation.

Abstract

Decay of apples (Malus sylvestris Mill.) inoculated with Penicillium expansum was controlled by acetaldehyde vapor concentrations (v/v) of 0.5% for 180 min, 1% for 120 min, 2% for 60 min, and 3% for 30 min. The above treatments did not produce lenticel or skin injury. Fumigated conidia did not germinate in 21 days at 21°C on artificial media and failed to induce decay in stem-punctured apples. The pathogen could not be re-isolated from fumigated inoculated punctures, however, the pathogen was obtained from inoculated punctures not exposed to acetaldehyde vapor. Fungicidal action of acetaldehyde vapor was a function of concentration and exposure period. Objectional off-flavors were not detected in fumigated apples, although appreciable amounts of acetaldehyde vapor were absorbed.

Abstract

The effects of 10% carbon monoxide (CO) added to air or controlled atmospheres (2% O₂ with or without 5% CO₂) on quality and storage life of grapes (Vitis vinifera L. cv. Thompson Seedless) were compared with those of the conventional SO₂ fumigation treatments for decay control. CO in air reduced respiration and C₂H₄ production rates, and retarded berry browning and softening, but was only partially effective in retarding decay beyond 2 months at 0°C. SO₂ treatments were very effective in controlling the spread of decay, but brown discoloration of the berries increased, especially after 2 months at 0° or 1°. When combined with 2% O₂ with or without 5% CO₂, CO inhibited C₂H₄ production and retarded decay development, but the presence of CO₂ increased brown discoloration of the berries. A combination of 2% O₂ + 10% CO was as effective as SO₂ in controlling decay of grapes held at 0° for up to 4 months and caused less browning and bleaching than SO₂.

Abstract

Moist air heat treatment at 52C for 15 min prevented decay in individually plastic-wrapped or naked nectarine [Prunus persica (L.) Batsch var. nectarina (Ait.) Maxim.] fruit puncture-inoculated with Monilinia fructicola (Wint.) Honey. Heat treatment for 5 or 10 min slowed decay development, but did not prevent it. In treatments where decay occurred, the wrap increased decay. Heat treatment tests at 52C for 15, 30, 45 min slowed softening and ethylene production of fruit. Wrapping alone reduced ethylene production 75% and respiration 12%, but did not significantly influence softening. The wrap reduced or eliminated undesirable skin browning associated with heat treatments.

Abstract

Decay of peaches [Prunus persica (L.) Batch] and nectarines [P. persica var nectarina (Ait.) Maxim.] held 6 days at 18.3°C was considerably higher on fruits previously stored 6 weeks in air or in 1% O₂ + 5% CO₂ (CA) at 0° than on those freshly harvested and held 6 days at 18.3°. Monilinia fructicola (Wint.) Honey) caused most of the decay of freshly harvested fruits, whereas Monillinia, Botrytis, Penicillium, and Alternaria species caused decay of stored fruits. Treatment in 46°C water containing 100 ppm benomyl (methyl-1-(butylcarbamoyl)-2-benzimidazole carbamate) effectively controlled decay during storage at 0° and during ripening at 18.3° without injuring the fruits. Treatment in 46° water alone partially controlled decay. Treatment in 52° water controlled decay of peaches during storage but not during ripening. This treatment severely injured peaches but not nectarines.

Abstract

Healing of minor injuries to ‘Valencia’ orange (Citrus sinensis (L) osbeck) occurs rapidly at 30°C and 96-98% relative humidity. It is manifested by a marked increase in the activity of phenylalanine ammonia-lyase (PAL) and deposition of lignin. PAL activity is confined mainly to injured flavedo while uninjured peel and albedo tissues exhibit very little activity. Inoculation of injured flavedo, immediately after injury, with P. digitatum sacc. disrupts the increase in PAL activity. When acetone powder from decayed peel was mixed with that of healed injured fruit and enzyme preparation was made from the mixture, there was no apparent reduction in phenylalanine ammonia-lyase activity, except that cuased by dilution. The synthesis of both PAL and lignin in mature fruit is strongly inhibited by cycloheximide, but not by actinomycin D.

Abstract

The time required to degreen Florida ‘Bearss’ lemons can be greatly reduced by the use of 1 to 10 ppm ethylene at 25 or 30°C. Degreening was accomplished in 2 to 3 days instead of the 2 to 3 weeks required with the current commercial practice of cool coloring at 15° without ethylene. Applications of a benzimidazole fungicide (thiabendazole, benomyl) prior to degreening adequately controlled decay. Rapid degreening with ethylene at higher temperatures (25° or 30°) eliminates the need for cool coloring storage and brings lemon availability more nearly in phase with consumer demand.

Abstract

The long voyage of Florida grapefruit (Citrus paradisi Macf.) to Japan and extended marketing periods on arrival were associated with a problem with excess diphenyl (biphenyl) residues. Japanese food additive regulations have necessitated reliance on the vapor-phase fungistat diphenyl, for which residues in the fruit increase with time after packing. Residues in some shipments unexpectedly exceeded the Japanese tolerance of 70 ppm. Experiments designed to identify the effect of various factors on diphenyl residues are reported. The amount of diphenyl, temperature before refrigerated transit and exposure time, especially before refrigeration, affected diphenyl residues. Air filtration had little effect. Very early season grapefruit (harvest started before legal maturity) in August and September 1978 absorbed excessive diphenyl residues. Excessive absorption of diphenyl by grapefruit is apparently characteristic of very early fruit.