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- Author or Editor: Sharon J. Peterson x
Abstract
Methods for mixing various concentrations of O2, CO2, N2, and C2H4 in high-pressure cylinders are described. The concentrations are mixed by partial pressure or partial volume and then are verified by gas chromatography. The procedures generally allow for a precision of ±5% when either 1.0% O2 or CO2 or higher concentrations are mixed with N2 or when C2H4 at 100 µl·liter-1, or more, is added. For lower concentrations, or when both O2 and CO2 are combined with N2, then the precision is ±10%.
Abstract
Zucchini squash (Cucurbita pepo L.) was stored 2 weeks at 2.5°, 5°, or 10°C and with 1%, 2%, 4%, 8%, or 21% O2 and then was aerated 2 days at 10°. Low O2 levels inhibited the rates of CO2 and ethylene production, particularly at 5° and 10°. Both rates increased during aeration, but much more in samples held previously at 2.5° or 5° than in those from 10°. About 75% and 55%, respectively, of the burst in CO2 production in samples from 2.5° and 5° was due to exposure to low temperature; the remainder was attributed to the effect of exposure to low O2 levels. For ethylene production, the corresponding values were about 95% and 70%. Zucchini squash stored at 5° for 2 weeks was virtually free of chilling injury (Cl), surface mold, decay, or off-flavors; almost all of the fruit still was rated good to excellent in appearance. About ¾ of the squash was still in this category after 2 additional days at 10°. At 5°, squash did not benefit from storage in low-O2 atmospheres. Storage at 2.5° induced severe Cl, which was ameliorated by holding the squash in 4%, 2%, or 1% O2 instead of in 21% or 8% O2. However, amelioration was no longer evident after 2 days of aeration at 10°. Defects not related to Cl—especially off-flavors—developed most noticeably in squash held at 10°; the benefit from low O2 levels was slight. Storing zucchini squash at 6° ± 2° likely would be optimal if it must be held longer than a few days.
Abstract
‘Honey Dew’ melon fruits (Cucumis melo L.) matured under filters that transmitted between 1% and 100% of total solar and between 2% and 100% of ultraviolet (UV) radiation. Solar yellowing (SY) developed predominantly on top of the melons and increased as their exposure to direct solar radiation increased. Degree of exposure to solar radiation during maturation and susceptibility to postharvest development of chilling injury (Cl) during 17 days at 2.5°C were inversely related. SY and Cl also were inversely related. Levels of ACC in the skin were low at harvest and unaffected by degree of exposure to solar radiation. Reducing the exposure to the sun by half nearly doubled the concentration of ACC during chilling; complete shading resulted in little additional increase in ACC. After chilling, the skin from the bottom of the melons consistently contained slightly more ACC than that from the top. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).
Callus tissue grown from `Marsh' grapefruit (Citrus paradisi Macf.) albedo tissue was grown at 30C for ≈ 40 days. Calli were preconditioned in normal air for 5 days at 10 or 30C before being fumigated for 2 hr with 0, 32, or 48 g of methyl bromide (MB)/m 3. Calli were then held at 10C and K+ leakage was measured after 1, 10, 20, and 30 days. The amount of K+ leaked from MB-fumigated calli was greater than that for nonfumigated calli and increased with higher MB dose. Leakage also increased with time following fumigation. Leakage of calli preconditioned at 30C and fumigated with 48 g MB/m3 was 140%, 196%, and 260% greater than leakage from nonfumigated calli 10, 20, and 30 days after fumigation, respectively. Leakage from calli preconditioned at 10C for 5 days before MB fumigation was less than that from calli held at 30C. MB doses of 32 and 48 g·m-3 increased leakage of calli preconditioned at 10C by 6% and 43% and for those preconditioned at 30C by 99% and 140%, respectively, 10 days after fumigation. In addition to K+ leakage, MB induced the development of a tan to orangish-brown discoloration.