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  • Author or Editor: W J Bramlage x
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Cuticle scraped from apple peel contained both free and bound phenolics, and cuticle enzymatically isolated from peel contained much greater amounts of them. Both free and bound phenolics inhibited linoleic acid oxidation, but free forms had ≈50% higher activity. Free and bound phenolics had ≈75% and 50%, respectively, of diphenylamine's antioxidant activity on a molar basis. Cuticle possessed little lipid-soluble antioxidant activity, but surface cells contained four to seven times the activity of cuticle. In a model system, free cuticular phenolics strongly inhibited farnesene oxidation in hexane during 4 months at 25 °C, but lipid-soluble antioxidants did not. Both free and bound cuticular phenolics increased during maturation. During 0 °C storage, free forms doubled during 15 weeks, then remained constant, while bound forms did not change. Cellular phenolics fell during maturation and storage, reducing browning potential in the cells. These changes all correlated with changes in C2H4 production. When C2H4 was inhibited by AVG spray and low-C2H4 storage, little or no change occurred; when promoted by ethephon spray or high-C2H4 storage, phenolic changes were accelerated. Farnesene and cuticular phenolics were positively correlated but conjugated trienes, cellular phenolics, and scald negatively correlated with C2H4. We believe that C2H4 effects on phenolics may be closely related to scald development.

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Abstract

Chilling of 8-day-old cucumber (Cucumis sativus L.) seedlings for 48 hours at 2°C caused reversible damage; chilled seedlings collapsed but regained turgor within 6 hours at 25°. Hypocotyl segments from chilled seedlings exhibited increased solute leakage, ethylene production, and O2 uptake after transfer to 25°. Pretreatment of seedlings with 10−4 m abscisic acid generally reduced symptoms of damage but did not prevent chilling injury. Pretreatment with 10−3 m CaCl2 was generally ineffective, and pretreatment with 10−3 m ascorbate generally intensified symptoms of injury. Oxygen uptake increased during the first 6 hours at 25° but returned to the level of unchilled seedlings within 24 hours. Chilled tissue was sensitive to 2,4-dinitrophenol during this period, although sensitivity was less than in controls during the first 12 hours after chilling. Unchilled tissue was insensitive to SHAM, but O2 uptake was inhibited by SHAM during the respiratory burst following chilling. Tissue was no longer SHAM-sensitive after 24 hours at 25°, by which time the respiratory burst had subsided. Thus, the alternative respiratory pathway was apparently operating only during the time of the respiratory burst, when the seedlings were recovering from chilling injury.

Open Access

Superficial scald development on apples is related to preharvest environmental conditions, perhaps through effects on endogenous antioxidant concentrations In 1989 we examined effects of maturity, light, and preharvest temperatures (< 10°C) on endogenous antioxidant levels in the fruit at harvest and on scald development after long-term storage in 0°C air. Cortland apple trees were sprayed with 500 ppm ethephon 1 month before normal harvest to create maturity differences. Fruit on other Cortland trees were bagged 1 month prior to harvest to reduce light interception. Samples also were harvested from other Cortland trees after exposures to different numbers of hours < 10°C, Hours < 10°C before harvest were negatively correlated to scald development. Ethephon treatment decreased scald incidence, and bagging increased it, The total lipid-soluble antioxidant activity increased with increasing hours < 10°C and with ethephon treatment, while bagging of fruit slightly decreased this antioxidant activity. To better understand the relationships between preharvest factors and antioxidant levels, individual antioxidants, including ascorbic acid, α tocopherol, anthocyanins and glutathione, are being analyzed.

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Superficial scald development on apples is related to preharvest environmental conditions, perhaps through effects on endogenous antioxidant concentrations In 1989 we examined effects of maturity, light, and preharvest temperatures (< 10°C) on endogenous antioxidant levels in the fruit at harvest and on scald development after long-term storage in 0°C air. Cortland apple trees were sprayed with 500 ppm ethephon 1 month before normal harvest to create maturity differences. Fruit on other Cortland trees were bagged 1 month prior to harvest to reduce light interception. Samples also were harvested from other Cortland trees after exposures to different numbers of hours < 10°C, Hours < 10°C before harvest were negatively correlated to scald development. Ethephon treatment decreased scald incidence, and bagging increased it, The total lipid-soluble antioxidant activity increased with increasing hours < 10°C and with ethephon treatment, while bagging of fruit slightly decreased this antioxidant activity. To better understand the relationships between preharvest factors and antioxidant levels, individual antioxidants, including ascorbic acid, α tocopherol, anthocyanins and glutathione, are being analyzed.

Free access

Abstract

Uptake of Ca by apples (Malus domestica Borkh.) from a postharvest dip in CaCl2 solutions increased as CaCl2 concentration in the dip solution increased up to 3-4%; a 4% solution increased flesh Ca level by 60 to 100 ppm after 3 months of storage. Uptake occurred primarily during storage, apparently as Ca from residues left by the dipping treatment diffused through openings in the fruit surface. Absorbed Ca remained largely near the fruit surface, although some deeper penetration occurred. Uptake from a 2% CaCl2 solution was not influenced significantly by thickener, surfactant, fungicide, or scald inhibitor in the dip solution, and was not consistently influenced by storage at relative humidities of from 90% to greater than 95%. When relative humidity had an effect, uptake was reduced at concentrations greater than 95%. A 4% CaCl2 dip treatment reduced softening and development of senescent breakdown in ‘McIntosh’, but did not significantly modify quality of ‘Cortland’ or ‘Baldwin’ apples.

Open Access
Authors: and

Abstract

‘Cortland’ apples (Malus domestica Borkh.) from both exterior and interior of large trees were harvested over a 25-day period, and samples were stored for 0 to 5.5 months in air at 0°C. Antioxidant activity of peel at harvest was assayed. Hexane extracts of whole fruit were used to estimate α-farnesene and conjugated trienes after 1 to 4 months of storage; these values were correlated with scald development after 3 to 5.5 months of storage, α-Famesene increased during the first 2 months of storage and then decreased, while conjugated trienes increased progressively with storage time. α-Famesene was not affected by harvest date, but conjugated trienes were decreased by later harvest. Conjugated trienes were positively correlated more strongly with scald than was α-farnesene. Antioxidant activity increased with later harvest in both exterior and interior fruit, even though exterior fruit ripened during this time, while interior fruit did not. Antioxidant activity at harvest was negatively correlated more strongly with scald development than was either α-farnesene or conjugated trienes, with r values as high as −0.83. A large optical density (OD) peak at ≈200 nm was detected in the hexane extracts of apples, and it was correlated with antioxidant activity (r = +0.63). OD200 values for harvest extracts were as strongly correlated with scald development after storage as were antioxidant assays. A large number of compounds absorbed at 200 nm, including many with antioxidant activity. We propose that OD200 of hexane extracts is an estimate of antioxidant activity at harvest and may represent a convenient and effective chemical index of scald susceptibility of apples after harvest.

Open Access

Abstract

Applications of (2-chloroethyl)phosphonic acid (ethephon) on ‘McIntosh’ apple trees (Malus domestica Borkh.) in early August at concentrations of 125 to 500 ppm promoted the climacteric rise in respiration, increased soluble solids, fruit abscission, and red color, and also reduced flesh firmness. Results from ethephon applications in July were variable; in 1974 July applications were more effective, and in 1975 less effective, than treatments applied in early August. The effects of ethephon were reduced when 1000 ppm succinic acid-2,2-dimethylhydrazide (daminozide) was combined with the ethephon. No treatment influenced repeat bloom or set the year following application.

Open Access

Abstract

Sprays of (2-chloroethyl)phosphonic acid (ethephon) applied to ‘Delicious’ apple trees (Malus domestica Borkh.) in July at concentrations of 500 to 1000 ppm shortly after the completion of June drop hastened the respiratory climacteric, and increased soluble solids, watercore and preharvest drop. These effects were diminished when 1000 ppm succinic acid-2,2-dimethyhydrazide (daminozide) was included with ethephon. All concentrations of ethephon increased flesh firmness. Two periods of fruit abscission occurred following ethephon application at high concentrations: shortly after application and immediately prior to harvest. After cold storage, fruit which had received 500 or 1000 ppm ethephon had less scald but a greater incidence of brown core. High ethephon concentrations increased bloom the following spring but had no influence on fruit set.

Open Access
Authors: and

Abstract

A simple technique for determining ion leakage from hardy woody tissues was applied to apple (Malus pumila Mill.) fruit tissue. Parameters for this application are presented. Leakage was unaffected by concentrations of 0.4 to 0.7 M sucrose in the incubating medium or by incubating time of 12 to 36 hours at 23°C but varied between samples taken from different areas of the same fruit. Preparatory procedure to obtain the smallest sample without excessive injury was determined. The technique reproducibly identified increases in ion leakage of 5% or more over the controls.

Open Access
Authors: and

Abstract

Intact, mature apple (Malus pumila, Mill. cv. Richared Delicious) fruit exhibited 2 exotherms, at −2.1 ± 0.1°C and at −4.7 ± 0.3° during freezing. Freezing only through Exotherm 1 caused fruit softening. Freezing to inception of Exotherm 2 caused increased softening, and also slightly increased ion leakage. Freezing to termination of Exotherm 2 produced a 3rd increment of softening, greatly increased ion leakage, and reduced respiration. Only with freezing through termination of Exotherm 2 did visual injury symptoms occur; these symptoms were evident several hours after thawing, and apparently reflected lethal injury to the fruit. Injury was no greater after 3 months than after 1 month of storage at 0° following freezing.

Open Access