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  • Author or Editor: Giora Zauberman x
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Abstract

Reducing the atmospheric pressure in the refrigerated storage chamber at 6°C markedly retards avocado fruit ripening. This effect is more pronounced when the pressure is reduced below 100 mm Hg. Fruit stored at 760 and 200 mm Hg ripened after 35 and 50 days, respectively, while fruit stored at pressures below 100 mm Hg remained unripe for 70 days in storage. The best storage pressure tested for avocado fruits was found to be 60 mm Hg. The inhibition of ripening under these conditions is explained by the lower oxygen partial pressure which retards respiration and ethylene production, and by the acceleration of the outward diffusion of ethylene from the tissue which lowers its internal level.

Open Access

Abstract

Wounded mature ‘Fuerte’ fruit (Persea americana Mill.) ripened faster than non-wounded fruit when stored at 14°C. Significant differences were not observed in respiration or ethylene production between wounded and non-wounded fruit when stored at 20° but the former softened faster and showed greater polygalacturonase activity. Wounded and non-wounded fruit ripened at similar rates when stored after wounding for 10 days at 5° and thereafter transferred to either 14° or 20°. No “wound ethylene” could be detected immediately after wounding at any temperature and is not the earliest event occurring during ripening. Effects of wounding in metabolic processes of ripening are observed better at a moderate continuous storage temperature of 14° than at 20°.

Open Access

Abstract

Amylase activity in detached avocado fruit (Persea americana Mill. cv. Fuerte) was directly correlated with ripening processes such as the climacteric rise in respiration, ethylene evolution, and softening. The term amylase designates the total amylolytic activity of avocado fruit but its exact nature was not studied. Amylase activity was higher in young than in mature fruits. After harvest, amylase activity started to rise with the onset of the respiratory climacteric. Parallel to the increase in amylase, a decrease in the starch content of the fruit pulp was observed. The disappearance of starch during softening was also demonstrated by electron microscopy. The possible role of starch as substrate and that of amylolytic activity as energy supplier, for metabolic processes in the fruit, is discussed.

Open Access

Abstract

Ripening of mature avocado fruit was accelerated by 18- and 24-hr ethylene treatments which were applied beginning 1 hr after harvest. Exposure to ethylene for 12 hr or less, starting 1 hr after harvest, did not accelerate the respiration rate, ethylene evolution, or fruit softening. Ethylene treatment for 6 hr starting at 1, 6, 12, or 18 hr after harvest did not accelerate the onset of the ripening process. It is suggested that ethylene does not just “trigger” the ripening of avocado fruit but rather is involved in a relatively long (18 to 24 hr) process which requires its continuous presence.

Open Access

Abstract

Chilling injury (CI) developed on the peel of ‘Keitt’ mango (Mangifera indica L.) fruit that were stored at 5°C and consequently transferred to 20° for ripening. Peroxidase and cellulase activities in the peel of such fruit rose during the development of CI to much higher levels than in nonchilled fruit. The activity of these two enzymes started to increase before any changes in total soluble solids and acid contents of the pulp could be observed. We suggest that the increase in activity of the two enzymes is part of the CI syndrome that develops during storage of mango fruit at chilling temperatures.

Open Access

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.

Free access

Abstract

Internal atmosphere composition, respiration rate, ethylene production, weight loss, and firmness were monitored during the ripening of waxed and nonwaxed avocado fruit (Persea americana Mill.) during storage at 5°C, and ripening at 20°. Artificial waxing, which usually forms a uniform film over the closely packed platelet structure of the natural wax, was sometimes incomplete. Waxing caused a slight buildup of CO2 and possible reduction in internal O2 concentrations during the preclimacteric of stored fruit, and may have reduced ethylene synthesis during the climacteric. Waxing caused a 1-day delay in fruit softening under extended cold-storage conditions.

Open Access

Fluorescent products (lipofuscin-like compounds) of lipid peroxidation, which accumulate with age, were extracted from `Fuerte' avocado (Persea americana Mill.) peels during ripening. Fractionation and analysis of these fluorescent compounds (FCs) was carried out by an improved method, based on separation of FCs from-chlorophyll by Sep-Pak silica cartridges. A sharp rise in FCs content was found 2 days after harvest in avocado fruits stored at 22C, and ethylene enhanced this rise 3-fold on the 4th day. The accumulation of FCs preceded by at leasts days the onset of climacteric ethylene and respiration and by 2 days the decrease in fruit firmness. Moreover, a 6-foId increase in the FCs concentration occurred during 1 to 2 weeks of storage at SC, but the avocado fruits did not show any other detectable signs of ripening. These results suggest that lipid peroxidation may be regarded as one of the earliest detectable processes occurring during fruit ripening. Thus, an increase of FCs in peel may be employed as a horticultural characteristic for estimating initiation of ripening in avocado fruit.

Free access