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Randolph M. Beaudry and Sylvia M. Blankenship

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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Christopher D. Gran and Randolph M. Beaudry

The oxygen partial pressure associated with the respiratory quotient (RQ) breakpoint (ie., lower oxygen limit) was determined for fruits of several apple cultivars stored at 0°C. Fruits were sealed in low density polyethylene pouches of various thicknesses and known permeability to determine O2 uptake, CO2 production, and respiratory quotients (RQ) at various O2 partial pressures. There were differences in the shape of O2 uptake versus steady state O2 curves between cultivars. While some cultivars showed steady declines in respiration rate from 8 kPa O2 to < 1 kPa, other cultivars showed no decline in respiration until O2 levels fell below 3 to 4 kPa. Fruits having elevated RQ values had greater levels of headspace ethanol in the polyethylene pouches, which confirmed anaerobic respiration. The lower oxygen limit ranged from a low of approximately 0.75 kPa for cultivars Northern Spy and Law Rome to high of 1.5 kPa for McIntosh.

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Eric W. Gay and Randolph M. Beaudry

O2 and CO2 permeabilities were determined for experimental polyethylene polymers (Dow Plastics, Freeport, Texas) in relation to low-density polyethylene (LDPE) films for the packaging of horticultural commodities. A stainless steel flow-through permeability cell was used to determine O2 and CO2 permeabilities at 0, 5, 10, 15, 20 and 25C for the polymers. Data were fitted to the Arrhenius' relationship and the Arrhenius' constant and energy of activation were determined. In addition, flow-through containers of sealed cherry tomatoes at room temperature were used to determine ethylene permeability of the polymers. The new polymers were several times more permeable than LDPE to O2, CO2, and ethylene. The results were incorporated into a model for predicting O2 concentrations over a temperature range for sliced apple fruit. The greater permeability of the new polymers will improve control of O2 and CO2 in modified atmosphere packages and enhance flexibility of package design.

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Randolph M. Beaudry, Jun Song, and Weimin Deng

Apple scald (peel browning) is hypothesized to involve a chilling disorder. Numerous studies have linked chloroplast fluorescence changes with chilling injury before symptom development. Therefore, chloroplast fluorescence was used for the prediction of scald in apples. `Red Delicious' apple fruit were harvested at three maturities and stored at 1 to 2C. They were removed from storage weekly and placed at ambient temperature (22C). Chloroplast fluorescence was measured at 0, 3, and 7 days after removal. A significant decline in quantum yield response (Fv/Fm), which indicates a reduction of chloroplast function, was recorded after 30 days in first-harvest fruit and 40 to 50 days in the second- and third-harvest fruit. The decline in Fv/Fm preceded scald development by ≈30 days in first-harvest fruit and 20 to 30 days in second- and third-harvest fruit. The data suggest that fluorescence changes and scald development may be related physiologically. Fruit firmness and other fruit ripening phenomena were also measured and their relationship to the fluorescence and scald development were investigated. The results indicated that the chloroplast fluorescence may be used as a predictive tool for scald development in stored apple fruit.

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Diana Dostal Lange and Randolph M. Beaudry

Low O2 and high CO2 concentrations can be used effectively to slow respiration and retard decay, but anaerobic and C02-injurious conditions must be avoided. The objective of this research was to: 1) determine the effects of low O2 and very high-C02 on flavor quality and accumulation of fermentation products. Strawberries and blueberries were stored in 2% O2/0% CO2, 20% 02/50% CO2, 2% O2/50% CO2, and 20% 02/0% CO2 for 0, 2, 4, 6, and 8 days at 20C. A taste panel evaluated the berries at the end of each storage period and again after 2 days under ambient conditions. Ethanol was the primary fermentation product that accumulated in response to low O2 and high CO2 concentrations. However, acetaldehyde was produced preferentially in response to elevated C02 levels. The flavor quality of the strawberries and blueberries was only acceptable for 2 days for treatments containing 50% CO2. The most intense off-flavors were detected in the 2% 02/50% CO2 and 20% O2/50% CO2 samples. 50% CO2 was highly effective in preventing decay, but this concentration was too high for acceptable flavor quality for storage periods greater than 2 days.

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Weimin Deng, Jun Song, and Randolph M. Beaudry

The effect of polymers used in packaging on the aroma of the packaged product has been little explored. Using a package-in-a-jar system, we are able to simultaneously measure volatile production by plant organ (Malus domestica Borkh. cv. Golden Delicious) and the permeability of the packaging film to those volatiles. In this system, apple fruit were placed into a glass container or sealed in a low-density polyethylene(LDPE) package and subsequently placed into a glass container. Air or a modified atmosphere was slowly passed through the glass containers such that the O2 level in the package was similar to that in containers with no package. The package and jar head spaces were sampled for CO2, O2, ethylene, and aroma volatile analysis by gas chromatography/mass spectrometry. The effect of temperature, atmosphere and film presence to some major volatile compounds was determined. When storage temperature increased from 0°C to 22°C the production rate of hexylacetate and 2-methyl butylacetate increased 11.27- and 17.15-fold, respectively. At 0°C, as O2 decreased in concentration from 10% to 5% (v/v), hexylacetate and butylacetate declined significantly; however, 2-methyl butylacetate was not affected. This can be taken to indicate the production of 2-methyl butanol for 2-methyl butylacetate formation is not as O2 concentration dependent as straight-chain alcohols. At the same O2 concentration, non-packaged fruit evolved greater amounts of all volatiles than packaged fruit. The flux of α-farnesene, hexylacetate and 2-methyl butylacetate was 26.6-, 1.7-, and 1.4-fold higher, respectively, for fruit in glass container. The sorption of α-farnesene and some other volatiles into LDPE film is evidently considerable, altering the aroma profile of packaged produce relative to a flow-through system.

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Nazir Mir, Rufino Perez, and Randolph M. Beaudry

`Cortland' apples (Malus ×domestica Borkh.), either untreated or treated with diphenylamine (DPA), were stored for 120 days in air at 0 °C. Peel samples were taken from these fruit immediately after storage, placed in glass vials and incubated for 48 hours, or were isolated from fruit held 2 to 72 hours at 22 °C and incubated in the vials for 2 hours. Emission of 3,7,11-trimethyldodeca-1,3(E),6(E),10-tetraene, known as trans,trans-α-farnesene, or simply α-farnesene, and its oxidation product, MHO, were measured in the vial headspace. α-Farnesene content in the gas phase of vials with peel samples reached a maximal level 2 hours after vials were sealed and was higher in DPA-treated than untreated fruit. The content of α-farnesene in the vial headspace remained unchanged for DPA-treated fruit peel during the 2-day holding period. However, α-farnesene declined rapidly after 10 hours incubation for control samples. Incubating peel samples of control fruit under N2 atmosphere prevented the decline in α-farnesene. The MHO release by the peel of control fruit was rapid during the first 2 hours and continued to increase for 24 hours. In contrast, the MHO released from DPA-treated fruit peels was 8000-fold lower than from peel samples of control fruit. The increase in vapor phase MHO was concomitant with peel browning in controls. For whole fruit held at 22 °C for 2 to 72 hours, cumulative MHO release from fruit peels followed a pattern that was similar to the pattern of superficial scald development in these fruit.

Open access

Alejandra Ferenczi, Nobuko Sugimoto, and Randolph M. Beaudry

The volatile profile of ‘Redchief Delicious’ apple (Malus ×domestica Borkh.) fruit was evaluated at 18 time points from 3 weeks before to 8 weeks after onset of autocatalytic ethylene production to capture the dynamics associated with development from mature green to senescent fruit. Minor amounts of ester production began several days before the onset of ethylene production. Ester production rose rapidly as internal ethylene levels increased beyond 22 nmol·L−1 (0.5 µL·L−1). Peak ester production roughly coincided with maximum ethylene synthesis, declining thereafter. Ester production was further evaluated according to the acid- (alkanoate) and alcohol- (alkyl) derived portions of the ester. The maximum rate of production for a given ester tended to occur later in development as the chain length of the alcohol-derived portion declined. The production rate for many esters paralleled the rate of emanation of their respective alcohol substrates, suggesting that availability of the alcohols limits ester production more than availability of the acid substrates. Combining production rates with sensory descriptors and human sensitivity to individual volatiles permitted approximations of aroma sensations likely engendered by the fruit throughout ripening. Overripe and alcoholic sensations are predicted to increase 2 weeks after the initiation of ripening in response to an increase in the production of ethyl esters. Acetate esters predominated, comprising 50% to 80% of esters throughout maturation and ripening, indicating that the substrate acetyl-CoA may be at saturating levels for alcohol acyl transferase (AAT) at the final step of ester formation. Acetate feeding did not enhance ester production, although label from 13C-acetate was extensively incorporated into esters. The data are consistent with the action of multiple AAT isozymes differing in activity and substrate preference. Incorporation of labeled 13C-acetate into precursors of esters, alcohols, and acids, reflected ester biosynthesis via 1- and 2-carbon chain elongation pathways in ripening ‘Redchief Delicious’ apple fruit.

Free access

M. Helena Gomes, Randolph M. Beaudry, and Domingos P.F. Almeida

The respiratory behavior of fresh-cut melon under modified atmosphere packaging at various temperatures was characterized to assess the potential for shelf life extension through low-oxygen and to generate information for the development of appropriate packaging conditions. Cantaloupe melon (Cucumis melo var. cantalupensis ‘Olympic Gold’) cubes were packaged and stored at 0, 5, 10, and 15 °C. Packages attained gas equilibrium after 5 days at 10 °C, 6 days at 5 °C, and 10 days at 0 °C. In cubes stored at 15 °C, decay started before steady-state gas levels were reached. Respiration rates were measured and respiratory quotient calculated once steady-state O2 and CO2 partial pressures were achieved inside the packages. O2 uptake increased with temperature and O2 partial pressure (pO2 pkg), according to a Michaelis-Menten kinetics described by = [( × pO2 pkg)/( + pO2 pkg)]. Respiratory parameters were modeled as an exponential function of temperature: = {[1.34 × 10−17 × e(0.131 × T) × pO2 pkg]/[1.15 × 10−24 × e(0.193 × T) + pO2 pkg]} (R 2 = 0.95), Q 10 = 3.7, and Ea = 84 kJ·mol−1. A good fit to the experimental data was also obtained considering as constant: RO2 = {[4.36 × 10−14 × e(0.102 × T) × pO2 pkg]/[0.358 + pO2 pkg]} (R 2 = 0.93), Q 10 = 2.8, and Ea = 66 kJ·mol−1. These results provide fundamental information to predict package permeability and steady-state pO2 pkg required to prevent anaerobic conditions and maximize shelf life of fresh-cut cantaloupe. The kinetics of respiration as a function of pO2 suggests that no significant reductions in respiration rate of fresh-cut cantaloupe can be achieved by lowering O2 levels.

Free access

Michael Wendorf, Nazir A. Mir, and Randolph M. Beaudry

Broccoli tissue, ranging in weight from 7 to 21 g, was sealed in packages made from low-density polyethylene (LDPE) of various thickness and permeability to establish a range of O2 levels in the package headspace. A pouch containing either hydrogen peroxide (H2O2) or water as a control was also sealed in the package. For packages that developed anaerobic atmospheres, inclusion of H2O2 permitted the maintenance of aerobic conditions for up to 3 days at ambient room temperature. These results suggest that the plant tissue is able to actively metabolize the H2O2 vapor to generate O2, which will prevent the development of low-O2 conditions in packaged produce, even under conditions of elevated storage temperature.