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- Author or Editor: Patrick E. Brecht x
Abstract
Various postharvest temperature-time combinations on nitrate-nitrite conversion in fresh spinach (Spinacia oleracea L.) were investigated. At 0°C spinach could be held as long as 40 days without significant changes in these nitrogen components. Substantial loss of nitrate-N and accumulation of nitrite-N occurred in spinach held for 3 to 7 days at 20°. Simulated transit periods of 2 weeks at 0 and 5° and simulated marketing periods of 3 days at 10° were imposed separately and in sequence to spinach in pretransit storage for 15 hours at 21° or to spinach without a pretransit storage period. Accumulations of nitrite-N exceeding 2 ppm fresh weight were found only if the simulated transit period was 5°. In this instance pre- and posttransit storage further increased nitrite accumulation. Nitrite-N levels exceeding 10 ppm were found only in visibly decayed samples.
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.
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.
Abstract
Brown stain on crisphead lettuce (Lactuca sativa L. cv. Calmar) was increased by exposure to carbon monoxide (CO) combined with elevated CO2 (1, 2 or 5%) regardless of the O2 level (2, 5, 10, or 21%). Carbon monoxide at 1, 3, or 5% added to air without added CO2 did not induce brown stain. Holding under 5 or 10% O2 in combination with 1% CO2 and with or without 1% CO for 20 days followed by a 4-day period in air at 10°C resulted in better overall visual quality compared with air or 2% O2 controls. Carbon monoxide in combination with air or 2% O2 reduced the respiration rate of lettuce during a 10-day period at 2.5°C. Lettuce previously subjected to CO had higher respiration rates, relative to controls, during the subsequent 4-day period in air at 10°C.