Search Results

You are looking at 1 - 10 of 12 items for

  • Author or Editor: Chaim Frenkel x
Clear All Modify Search
Authors: and

Abstract

‘Sultanina’ and ‘Perlette’ grapes (Vitis vinifera L.), with initially low sugar concentrations (13% to 14% total soluble solids content; TSS) and high acidity received postharvest application of 0.2% to 0.9% acetaldehyde vapors for 24 hr. This treatment increased TSS, decreased acidity of the juice, and enhanced the sensory preference by judges in a test panel. However, the response was limited to early picked fruit with low TSS and high acidity and the treatment damaged the berries of ‘Sultanina’ grapes and left some off-flavor. The levels of acetaldehyde and ethanol in the juice were positively correlated with the amount of applied acetaldehyde, the level of ethanol being 20 times higher than that of acetaldehyde. After 4 days of shelf life, the levels of both acetaldehyde and ethanol declined in the juice.

Open Access
Authors: and

Five-day-old etiolated cucumber (Cucumis sativus L. cv. Marketmore) seedlings held at 2C for 72 hours develop chilling injury resulting in desiccation and collapse of the hypocotyl tissues and eventual plant death. Hypoxia-induced accumulation of ethanol and acetaldehyde led to tolerance to subsequent chilling as evidenced by continued hypocotyl growth and freedom from injury. Arrest of volatile accumulation by applied bisulfite negated the development of hypoxia-induced chilling tolerance in seedlings. In seedlings held in normoxia, cold tolerance was induced by applied ethanol vapors, whereas acetaldehyde had a marginal effect, suggesting that hypoxia-induced cold tolerance may arise from the accumulation and activity of ethanol. Cold tolerance was induced by exposure to gaseous n-propanol and n-butanol vapors and other volatile anesthetics, including chloroform and halothane, indicating that ethanol activity may stem in part from an anesthetic effect that causes disorder of membrane lipids. However, development of cold tolerance in ethanol-enriched tissues was time-dependent, suggesting an association with biosynthetic event(s). Ethanol did not change the fatty acid composition in cucumber hypocotyl membranes.

Free access

Abstract

Following harvest, fruit of peach (Prunus persica (L.) Batsch) allowed to soften at room temperature for 48 hours and then placed in ice-cold water, underwent a rapid increase in firmness. The fruit rapidly lost firmness upon transfer to warm water (20°C). The changes in firmness were inversely correlated to the temperature changes in the fruit flesh. Solutions containing soluble pectin fraction extracted from the fruit similarly showed changes in viscosity in inverse proportion to the changes in the temperature. The changes in firmness of intact fruit as influenced by temperature may, in part, reflect the gelling behavior of pectin fractions.

Open Access

Abstract

Hydroperoxide levels were determined in aqueous and lipid extracts from fruit of tomato (Lycopersicon esculentum Mill.) at 6 different stages of ripening. An increase in the levels of peroxides in both the aqueous and the lipid fractions was associated with the upsurge in ethylene evolution. The changes in peroxides in the lipid fraction corresponded to the changes in the activity of lypoxygenase. Peroxides may constitute some of the active oxygen forms occurring in vivo which are required for the synthesis of ethylene in fruit.

Open Access

Abstract

Detached fruits of the rin mutant in tomato (Lycopersicon esculentum Mill.) synthesized little or no lycopene in the presence of 10, 100, or 1000 ppm ethylene in air. However, lycopene synthesis was initiated in fruits kept in 60% or 100% O2 (elevated tensions of oxygen) in the presence of 10 ppm ethylene.

Open Access

Abstract

‘Bartlett’ pears (Pyrus communis L.) were kept in cold storage in air, and at CO2 concentrations of 5, 10, 15, and 20%. The mitochondrial fraction from the fruit pulp was extracted periodically, made into acetone powder and assayed for activity of succinic dehydrogenase. Progressive decreases in activity of the enzyme were observed with increases in CO2 concentration in the storage atmosphere.

Open Access

Abstract

‘Barttett’ pears (Pyrus communis L.) were stored in air or 10% CO2 at 0°C for 90 days. Electronmicroscopy study of the core, representing the ovary tissue confined by the inner concentric vascular bundles, revealed extensive ultrastructural alterations of various membranous systems in CO2-treated fruit, including the mitochondria, the plastids, the tonoplast and the cytoplasm. These alterations in protoplasmic membranes accompanying CO2 treatment suggest loss in cellular organization and may explain the injurious effect of CO2 in fruit.

Open Access

Abstract

Various concentrations of salicylhydroxamic acid and alpha, alpha-dipyridyl (reported inhibitors of cyanide-insensitive respiration) applied to fruit of ‘Bose’ pear (Pyrus communis L.) reduced fruit softening. The application of silver ions, reported to inhibit ethylene action, delayed ripening.

Open Access

Abstract

Acetaldehyde is produced in fruit of pear (Pyrus communis L.) and can stimulate ripening. The action of selective inhibitors indicates that acetaldehyde operates independently of ethylene.

Open Access

Abstract

The compositional changes occurring in the cell wall of maturing and ripening pear fruits (Pyrus communis L. cv. Spadona) were examined in relation to the activity of pectolytic enzymes and cellulase. Fruit softening was accompanied by a rise in water and EDTA-soluble pectic fractions, and in free galacturonic acid. The latter reached peak levels after 15 weeks of cold storage and thereafter declined. Simultaneously with the degradation of pectin there was a 4 to 5 fold increase in polygalacturonase activity, but pectin-methyl-esterase activity declined as it did throughout the harvest and storage seasons. Cellulase activity which was present also in immature fruit increased 2 to 3 fold as the fruit softened, but in the last stages of softening it decreased. Treatment of the firm fruit with partially purified preparations of cellulase and polygalacturonase both caused a dissolution of insoluble pectin material.

Open Access