Search Results

You are looking at 1 - 6 of 6 items for

  • Author or Editor: Shimon Meir x
Clear All Modify Search
Authors: and

Abstract

Stored ‘Jonathan’ apple (Malus domestica Borkh) fruit from poorly aerated trickle-irrigated plots had a high incidence of “Jonathan breakdown” (starting as flesh browning beneath the peel) and, from sprinkle-irrigated plots, “Senescent breakdown” (starting from the core area). The flesh of such fruit was high in ethanol at picking time and in acetaldehyde after several months of storage. High ethanol levels in the fruit after 4 months of storage were related to a high ethylene production of the fruit. High soluble solid levels were characteristic of fruit prone to Jonathan breakdown but not to senescent breakdown. The acid content of the fruit flesh was directly correlated with the acetaldehyde content after several months of storage. The acetaldehyde content of the flesh of fruit from plots suffering from root hypoxia rose after 3 months of storage at 1°C. In contrast, the ethanol content of healthy fruit decreased gradually during storage. Fruit from plots suffering from root hypoxia, and particularly their peel, were low in Ca, Β, and Fe, but high in K. Low fruit Ca was related to high acid, acetaldehyde, and sorbitol levels. Fruit low in Ca softened rapidly in storage.

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

Various combinations of preharvest ethephon sprays were applied to ‘Granny Smith’ apples (Malus domestica Borkh). The fruit were harvested twice the first year with selective picking from the interior and exterior of the tree and three times the second year. Scald incidence was measured after storage at 0°C in air for 3 or 6 months plus 1 week at 20°. There was a correlation between scald after storage and fruit soluble solids concentration and firmness at harvest and with conjugated triene levels at harvest or after storage. Ethephon sprays reduced scald incidence between 20% to 75% depending on treatment and storage length.

Open Access

A newly developed rapid and convenient method was used for fractionation and analysis of fluorescent compounds (FCs) formed during lipid peroxidation in parsley (Petroselinum crispum Mill.) leaves. These lipofuscin-like FCs [which arise in vivo from reaction of malondialdehyde (MDA) with amino acids] were found to increase during the senescence of detached parsley leaves, following the commencement of chlorophyll degradation and proteolysis. However, accumulation of FCs in response to exogenous ethylene coincided with the onset of chlorophyll loss and proteolysis on day 2 and was accelerated markedly later. Unlike FC accumulation, levels of aldehydes and MDA in control leaves increased more drastically during senescence, but were not affected significantly by exogenous ethylene. The results suggest that the accumulation of FCs in detached parsley leaves exposed to exogenous ethylene is an early senescence-associated process.

Free access

Jasmonic acid (JA) and methyl jasmonate (MJ), collectively referred to as jasmonates, are naturally occurring plant growth regulators involved in various aspects of plant development and responses to biotic and abiotic stresses. In this study, we found that postharvest application of jasmonates reduced decay caused by the green mold Penicillium digitatum (Pers.: Fr.) Sacc. after either natural or artificial inoculation of grapefruit (Citrus paradisi `Marsh Seedless'). These treatments also effectively reduced chilling injury incidence after cold storage. The most effective concentration of jasmonates for reducing decay in cold-stored fruit or after artificial inoculation of wounded fruit at 24 °C was 10 μmol·L-1. Higher and lower jasmonate concentrations were less effective at both temperatures. MJ at 10 μmol·L-1 also most effectively reduced the percentage of fruit displaying chilling injury symptoms after 6 weeks of storage at 2 °C and 4 additional d at 20 °C. When tested in vitro, neither JA nor MJ had any direct antifungal effect on P. digitatum spore germination or germ tube elongation. Therefore, it is suggested that jasmonates probably reduced green mold decay in grapefruit indirectly by enhancing the natural resistance of the fruit to P. digitatum at high and low temperatures.

Free 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