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Prestorage treatment of avocado fruit (Persea americana Mill. cv. Fuerte) with a low-O2 atmosphere (3% O2 + 97% N2) for 24 hours at 17C, significantly reduced chilling injury (CI) symptoms after storage at 2C for 3 weeks. Fruit softening was also delayed by this treatment. The treated fruit had lower respiration and ethylene production rates during storage at 2C and subsequently at 17C. Electrolyte leakage was significantly lower in peel disks from treated fruit. Reducing power, expressed as total sulfhydryl groups, was higher in the peel and pulp of low-O2-treated fruit. The amount of peel chlorophyll was inversely correlated with the severity of CI symptoms.

Summary Exposure of tomatoe fruits ( Lycopersicon esculentum Mill.) to 0.2–0.4 % acetaldehyde (AA) vapours for 24 h prior to storage caused inhibition of fruit ripening as expressed by less colour development. The endogenous levels of AA and ethanol found in the juice were positively correlated with the AA concentration applied. Application of 0.6% AA vapours for durations of 6 to 24 h also caused significant delay in colour development. Colour inhibition occurred with fruits harvested either at the breaker or turningpink stage. Application of a N 2 atmosphere or C0 2 at different concentrations (50–90%) for 48 h resulted in production of endogenous AA and ethanol. Inhibition of ripening was the highest after treatment with 98% N 2 or 90% CO 2 , which also led to the highest levels of AA and ethanol. Polygalacturonase (PG) activity was inhibited by AA as well as by CO 2 or N 2 pretreatments.

Application of acetaldehyde (AA) at 90 to 360 mM to intact grape berries (Vitis vinifera L. CV. Sultanina and Vitis vinifera L. CV. 103) caused an increase in CO 2 production rate and a reduction in ethylene evolution rate. The increase in CO 2 production rate was accompanied by a decrease in juice acidity without any change in the total soluble solids content. Addition of ACC to berry halves dramatically increased ethylene production, which was inhibited by AA. Ethanol, applied at the same concentrations as AA, neither caused a reduction in ethylene evolution nor inhibited the conversion of ACC to ethylene. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC). It is well established that under reduced 02 levels below 8% there is retardation of fruit senescence, generally by inhibition of fruit ripening processes, including respiration and ethylene production (Kader, 1986). The first metabolize formed under anaerobic conditions is AA, which is converted to ethanol by the enzyme alcohol dehydrogenase (Cossins, 1978; Kelly and Saltveit, 1988; Pesis and Avissar, 1989). However, application of AA vapors to various climacteric and nonclimacteric fruits like oranges (Citrus sinensis (L.) Osb.) (Fidler, 1968; Pesis and Avissar, 1989), figs (Ficus carica L.), blueberries (Vaccinium corymbosum L.), and strawberries (Fragaria × annanassa) (Janes et al., 1978) caused an increase in the CO 2 production. This increase was accompanied by a decrease in acidity in figs (Hirai et al., 1968) and oranges (Pesis and Avissar, 1989). Janes et al. (1979) found a stimulation of 0 2 uptake by potato (Solanurn tuberosum L.) tubers treated with AA and ethanol, but related this increase to a stimulation of the cyanide-resistant respiration. Grape is a nonclimacteric fruit (Biale, 1960) that is harvested preferably after it has reached minimum maturity standards since, after harvest, there is almost no change in quality indices (Nel- son et al., 1963). However; AA vapors influence the quality of grapes harvested early in the season by increasing their total soluble solids content (TSS) or decreasing their acidity (Pesis and Frenkel, 1989). In addition, AA vapors have a fungicidal effect on stored grapes, and AA-treated berries have been re- ported to remain firmer during storage, which may increase their resistance to fungal attack (Avissar et al., 1989). The purpose of this study was to investigate the effects of postharvest appli- cation of AA or ethanol on CO2 and ethylene production by grape berries.

Production of volatiles was stimulated by the infection of Penicillium digitatum in 'Shamouti oranges. During 7 days of disease development, there was a progressive increase in the emanations of the anaerobic metabolites acetaldehyde, ethanol and ethyl acetate. There was also an increase in other volatiles including methanol, acetone, and ethylene, accompanied by a high production of CO2. The production of acetaldehyde, ethanol and CO2 in cultures of P. digitatum was, highest on the first day after inoculation, and decreased as the fungus developed. Ethyl acetate and ethylene increased when sporulation had already begun. Neither acetone nor methanol was found in P. digitatum in vitro. The increase of the volatiles in the infected oranges was due to the host-pathogen interaction and peel lesion. ZusammenfassungDie Produktion von fluchtigen Verbindungen verursacht durch Penicillium digitatum in Orangen und in Kultur Nach einer Infektion mit Penicillium digitatum an 'ShamoutL'-Orangen wurde die Produktion von fluchtigen Verbindungen angeregt. Wahrend der ersten 7 Tage der Krankheitsentwicklung wurde eine progressive Steigerung der Ausstromung der anaeroben Metaboliten Acetaldehyd, Athanol und Athylacetat beobacbtet. Ermitteit wurde auserdem eine Vemiehrung anderer fluchtiger Verbindungen wie Methanol, Aceton und Athylen, gekoppeh mit einer erhohten CO2-Produktion. Die Bildung von Acetaldehyd, Athanol und CO2 in P. digitatum-Kuhuren war am ersten Tag nach der Inokulation am hochsten, mit der weiteren Entwicklung des Pilzes wurde sie niedriger. Die Athylacetat- und AUthylenproduktion verstarkte sich, nachdem die Konidienbildung schon angesetzt hatte. Weder Aceton noch Methanol wurde in vitro in P. digitatum festgestellt. Die Zunahme von fluchtigen Verbindungen in infizienen Orangen war mit Wirt-Pathogen-Wechselwirkungen sowie Schalen-lasionen gekoppelt.