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  • Author or Editor: Leonard L. Morris x
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Abstract

A reflectance spectrophotometer (Agtron E5-W) was found to be a useful laboratory tool for nondestructive determination of tomato fruit color as an indicator of ripeness classes and changes in ripeness in postharvest studies. Values obtained represent the average green and red color hues of the whole fruit which is rotated dueing the measurement.

Open Access

Abstract

Mushrooms [Agaricus bisporus, (Lange) Sing.] stored at 10° and 20°C showed a sigmoid pattern of growth while at 0°C growth was retarded. The postharvest growth exhibited at 10° and 20°C could be related to a decrease in free a-amino N while at 0°C there was a significant increase in the level of free a-amino N during storage. Protease activity in the tissue increased at all 3 temperatures. It is suggested that postharvest maturation of mushrooms is supported by utilization of low molecular weight nitrogenous compounds formed through increased protein degradation. Mushrooms stored at 20°C toughened and matured faster than those stored at 10° or 0°C. Increases in discoloration during storage appeared to be correlated with decreases in total phenols and with increases in o-diphenol oxidase (o-DPO) activity. The relationship of these biochemical changes to postharvest maturation of mushrooms is discussed.

Open Access

Abstract

Controlled atmosphere (CA) storage prolonged the shelf life of mushrooms (Agaricus bisporus, [Lange] Sing.) if the O2 concentration was 9% or the CO2 concentration was 25 or 50%. Concentrations of 2 to 10% O2 stimulated pileus expansion and stipe elongation with maximal stimulation of growth occurring at 5% O2. Levels of CO2 above 5% markedly inhibited growth, even after air was substituted for the CO2 treatment. Five percent CO2 stimulated stipe elongation and suppressed pileus expansion. Protein degradation, as indicated by protease activity and the level of a-amino N in the tissue, increased during postharvest maturation of mushrooms. As in starving bacteria, it is suggested that the main physiological function of proteolysis in the postharvest maturation of mushrooms is as a source of C and N.

Open Access

Abstract

Postharvest discoloration of cultivated mushrooms (Agaricus.bisporus [Lange] Sing., ‘tan strain’) was significantly retarded by treatment with succinic acid-2,2-dimethylhydrazide (SADH). The optimum SADH concn was 100 ppm. The effect, however, lasted no longer than 3 days after which time all SADH treatments discolored at rates equal to or greater than controls. The decrease in discoloration was correlated with a decrease in o-diphenol oxidase (o-DPO) activity. Protease activity was higher in SADH treated mushrooms suggesting that reduction in browning was due to degradation of o-DPO rather than direct inhibition of o-DPO by SADH. In vitro SADH competes with proline for quinones produced by enzymatic or non-enzymatic oxidation of diphenols. It is proposed that in vivo SADH exerts a dual effect in reducing mushroom discoloration: first SADH induces degradation of o-DPO through an increase in proteolytic activity, and second it binds to quinones thereby removing intermediates which lead to pigment formation.

Open Access

Abstract

Storage of mushrooms (Agaricus bisporus, [Lange] Sing.) in 0% O2 reduced discoloration and o-diphenol oxidase (o-DPO) activity for up to 7 days. Levels of O2 above 0% had little or no effect in reducing discoloration and o–DPO activity compared to air controls. Concentrations of CO2 above 5% appeared to increase surface discoloration while markedly inhibiting o-DPO activity. After transfer to air, the effectiveness of the increased CO2 treatments in reducing o-DPO activity in mushrooms depended on storage time in CO2.

In vitro CO2 markedly inhibited o-DPO activity, with 50% inhibition at 25% CO2. Complete inhibition was never attained. The inhibition by CO2 was found to be competitive with respect to catechol and could not be overcome by increasing the O2 concentration above 20%. The action of CO2 in vivo in reducing o-DPO activity could be through a direct competitive inhibition or through the inhibitory effect of CO2 on mushroom maturation.

Open Access

Abstract

Growth-regulating substances have been used extensively on horticultural crops to increase fruit set and prevent fruit drop. Several investigators have observed that preharvest application of growth regulators such as 2,4,5-trichlorophenoxyacetic acid may affect fruit maturity and ripening (Stewart, 4). This raised the question about the effects of the postharvest treatment of fruits with grbwth regulators.

Open Access

Abstract

Numerical rating scales and their descriptive equivalents for firmness, visual quality, decay, butt discoloration, wilting, and other defects of lettuce (Lactuca sativa L.) are described. Also presented are scoring systems for brown stain, russet spotting, and rusty-brown discoloration of crisphead lettuce that consider severity of lesions, proportion of leaf affected and number of leaves affected in a head.

Open Access

Abstract

Parthenocarpic cucumber fruit (Cucumis sativus L. cv. Deliva) of marketable maturity (10 to 14 days after anthesis) were held at 12.5° or 20°C in reduced O2 levels for 5 or 18 days before transfer to air. Carbon dioxide production at reduced O2 levels was generally less than in air; however, at O2 levels < 0.5%, anaerobic respiration resulted in increased rates of CO2 production. Upon transfer to air after 18 days, all samples from reduced O2 showed increased CO2 production rates that equalled or exceeded that of the air controls. Except at 0.0% and 0.25% O2 levels, ethylene production was increased in reduced O2. After transfer to air, ethylene production increased and the increase was inversely related to the previous O2 level. Ethanol and acetaldehyde production were measureable for fruit held in 1% O2 after 18 days at 12.5° and showed dramatic increases at lower O2 levels. Low-O2 injury (pitting) developed on most fruit held at 0.0% O2 and on many fruit held at 0.25% O2. Only minima! commercial benefits are likely to be realized from storage of 1 to 3 weeks in 0.5% to 2.0% O2 at 12.5°.

Open Access

Abstract

The incidence of brown stain on crisphead type lettuce (Lactuca sativa L. cv. Calmar) was highly dependent on postharvest temperature. Following exposure to 2% O2 + 5% CO2 for 5 days at constant temperatures from 0° to 20°C, brown stain decreased as simulated transit temperature increased and was negligible at 10°C and above. Simulated market temperatures following exposure to 2% O2 + 5% CO2 at 0°C markedly influenced brown stain expression with near maximum expression present after a 3-day period in air at 10°C. Low O2 (2%) was more effective in reducing respiration (CO2 production) of lettuce at temperatures above 5°C than at 5°C, or lower.

Open Access

Abstract

The severity of brown stain on crisphead lettuce (Lactuca sativa L., cvs. Calmar and Great Lakes 118) held at 0° or 2.5°C for 10 days increased with increasing CO2 (1 to 5%) and decreasing O2 (21 to 1%) levels. Very slight or no brown stain developed on lettuce subjected to 0, 1, or 2% CO2 in combination with 10 or 21% O2 for 10 days or on that held in 2.5 or 5% CO2 + 2% O2 for 4 days at 2.5°C. In 2.5 or 5% CO2 + 2% O2, brown stain intensified with duration of exposure (2 to 30 days) at 0° or 2.5°C.

Open Access