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  • Author or Editor: Sylvia M. Blankenship x
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Banana fruit respiration rates and quality parameters such as peel color, pulp pH and soluble solids content were examined at 14°C under a number of controlled atmosphere (CA) environments. CA conditions were 1%, 2%, 4%, or 8% oxygen with or without 5% carbon dioxide. Each treatment combination was also done with or without 50 μL·L–1 ethylene added to the atmospheres. Green banana fruit were either gassed with ethylene (triggered) or ungassed. One percent oxygen was too low to consistently give undamaged bananas. The addition of 5% carbon dioxide to the controlled atmosphere increased fruit respiration rate whereas air plus 5% carbon dioxide showed decreased respiration when compared to air control fruits. Green, triggered fruit partially ripened under the CA conditions. Pulp pH and soluble solids content changed in a normal ripening pattern, however peel color was poor. Addition of ethylene to the atmospheres advanced fruit ripening somewhat in all fruit. When green, ungassed bananas were placed under CA, the presence of ethylene in the atmosphere did not cause the bananas to turn yellow, although some changes in pH and soluble solids were detectable. In triggered fruit the presence of ethylene in the storage advanced ripening with higher oxygen concentrations promoting faster ripening. Bananas that have ripened under CA conditions are not as high quality as those ripened in air in terms of visual appearance.

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The reasons for knowing the maturity of fruit center around controlling fruit quality after harvest. Farmers are usually concerned with trying to determine harvest date to fit their labor, storage, and marketing needs, whereas research scientists are typically trying to account for the effects of maturity as a variable in experiments. Specific goals for farmer and researcher will, in part, govern what maturity indices are used and what values are acceptable. Restrictions in time and equipment will also affect choice of maturity assessment methods. In some instances, internal or external characteristics might be more important. Because changes in a number of characteristics comprise ripening, there is no single criteria or method that can be termed “best.” However, for each situation, an optimal choice of criteria or method may exist. The logic and information necessary to reach those optimal choices, from the perspective of the researcher and the commercial horticulture operation, is presented and contrasted.

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Fraser fir [Abies fraseri (Pursh) Poir.] branches were held at 5C for 4 to 6 weeks in the following atmospheres: 1% or 3% in nitrogen; 0%, 1%, 5%, 10%, 20%, 40%, or 50% CO2 in air; or air only. Experiments were conducted in two. years during the fall, winter, and early spring. In general, CO2 ≥ 5% accelerated needle loss. There was considerable tree-to-tree variation in tolerance to elevated CO2. Oxygen at 1% killed branches, and 3% O2 showed no benefit compared to air. The initial dark respiration rate at 21C was about four times higher than at SC. Respiration decreased for ≈ 10 days and stabilized at 14% to 20% of the initial values. Respiration increased exponentially with increasing temperature between 5 and 27C. Short-term controlled or modified atmosphere storage would probably not be useful in improving the postharvest handling of Fraser fir.

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Cut branches of Fraser fir [Abies fraseri (Pursh) Poir.] were subjected to solutions with different molarity, pH, and solutes. Citrate-phosphate and Na-phosphate buffers induced heavy needle loss at concentrations as low as 10 mm, whereas needle loss was negligible for MES buffer, sucrose solutions, and distilled water. Needle drop increased in response to higher solute concentration and/or greater duration of exposure. Needle loss was almost 100% at pH 3.0 and 9.0, but minimal at pH 6.0 and 7.0. Chemical name used: 2-(N-morpholino) ethanesulfonic acid (MES).

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A problem facing the peach industry is the ability to harvest field-ripened peaches and get them to market without significant softening or damage. However, getting mature peaches into marketing channels before significant softening occurs is a challenge. Our objectives were to evaluate two growth regulators to determine the effect on fruit quality and softening at harvest and after 1, 2, or 3 weeks in cold storage and to evaluate the effect on harvest date. The two products evaluated in this study were ReTain (aminoethoxyvinylglycine (AVG)—Abbott Labs) and EthylBloc (1-methylcyclopropene (MCP)—Biotechnologies for Horticulture). ReTain is a growth regulator that inhibits ethylene production and is used in commercial apple production to delay harvest. EthylBloc is applied as a gas and attaches to ethylene receptor sites which inhibits ethylene effects. A trial with preharvest foliar applications of ReTain and postharvest gassing with EthylBloc was initiated in July 1998 on `Contender' peaches. ReTain applications were made at 3-day intervals beginning 19 days before first harvest at the rate of 50 g a.i./acre. Applications 3 days before harvest resulted in increased flesh firmness at harvest and decreased ethylene evolution, which continued for up to 3 weeks in cold storage. Fruit were also gassed with 1 μl•L-1 (1ppm) EthylBloc in the laboratory the day following harvest for 24 h. Fruit treated with ReTain and EthylBloc had twice the flesh firmness of peaches that were not treated after 1 week in storage. ReTain applied 3 days before harvest delayed maturity. Further evaluation will be conducted in 1999.

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`Beauregard', `Jewel', `Hernandez', `Carolina Rose', and `White Delight' sweetpotato [Ipomoea batatas (L.) Lam.] roots were placed in chambers for curing at 30 °C and 50%, 70%, or 85% relative humidity (RH) for 1 week. Uncured roots were held at 15 °C and 90% RH. After curing, roots were removed temporarily from the chambers, and chamber conditions were reset for the following storage treatments: 15 °C/85% RH; 18 °C/70% RH; and 18 °C/50% RH. Roots were stored 3 to 4 weeks. Experiments were in factorial arrangements so all combinations of curing and storage conditions were present. Experiments were conducted in two seasons. Roots were subjected to a pressurized water jet and the amount of skinning that occurred was visually rated several times during curing and storage. Weight loss was measured in `Beauregard'. Susceptibility to skinning changed over time and with the temperature and humidity conditions. Curing at 30 °C and any humidity between 50% and 85% generally improved epidermal adhesion, but there were exceptions. Lower humidities promoted greater weight loss. Epidermal adhesion changed during storage, becoming both stronger and weaker, indicating that sweetpotato epidermis is in an active state even after curing. The standard curing and storage conditions of 30 °C/85% RH and 15 °C/85% RH, respectively, are still a reasonable practice.

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Abstract

‘Starkrimson Delicious’ and ‘Golden Delicious’ apples (Malus domestica Borkh.) were harvested weekly in 1983, 1984, and 1985; sealed in containers; and measured daily for ethylene accumulation over a 6-day period (or until ethylene reached ≥2.0 μl·liter−1). The number of hours to accumulate minimums of 0.2, 0.5, 1.0, or 2.0 μl·liter−1 were calculated from daily readings and were regressed against date of sample harvest. When the number of hours required to accumulate a selected ethylene level began to decline, a linear equation using the first declining point and previous point was generated and used to predict a harvest date for immediate fresh-market use. Predicted harvest dates were compared to harvest dates selected by a taste panel. Out of 12 predictions made over a 3-year period using an ethylene level of 0.2 μl·liter−1, predicted harvest dates for ‘Golden Delicious’ were within 4 days of the taste panel harvest date on three occasions. In ‘Starkrimson Delicious’ there were five accurate predictions out of 12; however no single minimum level of ethylene gave successful predictions. Overall, it does not appear that this method accurately predicts harvest dates for ‘Starkrimson Delicious’ or ‘Golden Delicious’ destined for immediate sale on the fresh market.

Open Access

Abstract

2,5-NBD, a compound which competes with ethylene for binding sites and inhibits ethylene action in plant tissues, was applied to ‘Delicious’ apples (Malus domestica Borkh.) as a gas in either a closed or flowing system. Apples held in the closed system for 30 days at 25C in either 2000 or 4000 µl 2,5-NBD/liter were as firm as fruit held equally long at 5C; apples held in air at 25C were 19 N softer. Softening appeared to be mediated by ethylene. Soluble solids content and starch loss were similar for fruit held in air or in 2,5-NBD at 25C. The fruit’s internal ethylene concentration showed that 500 or 2500 µl 2,5-NBD/liter suppressed, but did not completely inhibit, autocatalytic ethylene production. The preserving effect of 2,5-NBD diminished after 50 days at 25C. Chemical names used: Bicyclo [2-2-l]-hepta-2,5-diene (2,5-norbornadiene; 2,5-NBD).

Open Access

Abstract

Gaseous mixtures of O2 + CO2 in N2 or ethylene in air were held in glass or plastic syringes for up to 30 hr under different temperatures and conditions. Concentration changes in the gases were followed over time to determine the best method to hold gas samples until analyses. At 25°C, ethylene loss was less from glass than plastic syringes. Twenty minutes at 25° was the maximum holding time before a statistically significant change in concentration occurred for 10 μl·liter−1 ethylene samples in plastic syringes. Plastic syringes absorbed ethylene. Ethylene loss from plastic syringes at 25° was linear within the constraints of the experiment over 30 hr, with the loss of 10 μl·liter−1 ethylene being more rapid than loss from 1 μl·liter−1. Carbon dioxide and O2 levels changed less from glass than plastic syringes at 25°. Holding ethylene or CO2 + O2-filled syringes under saturated NaCl or MgSO4, respectively, did not influence the change in CO2 or ethylene level from the syringes. The change in O2 concentration was less in plastic syringes held in a MgSO4 solution than plastic syringes held in air.

Open Access