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- Author or Editor: R. W. Buescher x
Abstract
Organic acid and sugar levels were determined quantitatively by gas-liquid chromatography in tomatoes (Lycopersicon esculentum Mill.) stored up to 21 days at 2°C and subsequently ripened at 20°. The concentration of malic acid in the pericarp declined during chilling, but citric acid accumulated. Citric acid was considerably higher after ripening of fruit chilled for 21 days than in non-chilled fruit. Sucrose and fructose levels declined during storage while the concentration of glucose remained fairly constant. Both glucose and fructose levels were lower in fruit ripened after 4 and 21 days of low temperature storage than in non-chilled fruit.
Abstract
Hardcore in sweet potato roots (Ipomoea batatas (L.) Lam) is induced by chilling and subsequent exposure to nonchilling temperatures prior to cooking. The defect is detected only after cooking and could adversely affect consumer acceptance and utilization. Of seven cultivars tested, ‘Red Jewel’ and ‘Jewel’ were the least susceptible to hardcore, while ‘Georgia Jet’ and ‘Jasper’ were the most susceptible. Cured roots were more susceptible than those freshly harvested in all cultivars except ‘Centennial’. Exposure to ethylene during the post-chilling induction period did not reduce the incidence of hardcore but significantly reduced its severity.
Abstract
The effects of ethephon concentration, maturity, and length of storage before treatment on red color development were determined in harvested rin tomatoes. Red color development was greater in fruits treated with 1% ethephon than in fruits treated with higher or lower concentrations. Ethephon-induced color was greater in fruits treated 42 days from anthesis than in fruits treated at 35, 49, 56, and 63 days. Less red color developed as time in storage before treatment increased. It is suggested that ethephon (ethylene) directs red color formation in rin fruits if it is applied prior to the onset of predetermined pathways which result in the expression of the yellow color.
Abstract
Turning tomatoes (Lycopersicon esculentum Mill.) were held at 20°C and exposed to ambient, 5, 10, 20, 40 and 60% CO2 with 21 ± 1% O2. C2H4 evolution was rapidly reduced when fruits were exposed to CO2. In 5, 10 and 20% CO2, C2H4 evolution continued to decline with increasing duration of exposure but after 4 days in 40 and 60% CO2, C2H4 evolution increased probably because of injury. Maximum retardation of color development occurred while exposed to between 10 and 20% CO2. After removal of CO2, color development advanced rapidly and after 4 days in air, color of fruits that had been exposed to 5 and 10% CO2 was indistinguishable from that of fruit held continually in air. Color of fruits exposed to 20, 40, and 60% CO2 never reached color of fruits held only in air, in addition, exposure to these concentrations reduced subsequent salability due to enhanced mold growth, uneven ripening, and watersoaking. Intermittent exposures to 20% CO2 and air caused rapid fluctuation of C2H4 evolution and retarded color development. CO2 was not effective in inhibiting wound induced C2H4 evolution.
Abstract
Electrolyte leakage from tissue discs and internal conductivity of intact fruit of peach (Prunus persica (L.) Batsch) were determined during storage at 1°C and after transferring to 21°. Both methods produced similar results, however, the method used for measuring internal conductivity was rapid, nondestructive, and seemed to be more sensitive. Electrolyte leakage remained fairly constant while internal conductivity tended to decline during 5 weeks of chilling. Electrolyte leakage and internal conductivity increased when fruits were transferred to 21°. At 21° fruits which had been chilled for 2 weeks had enhanced leakage while conductivity was enhanced in fruits chilled for 1 and 2 weeks. In fruits transferred to 21° after 3 or more weeks of chilling, leakage and internal conductance declined and woolliness was concomitantly detected. The binding of free ions appears to be closely associated with woolliness in peaches.
Abstract
Snap beans (Phaseolus vulgaris L.), when broken during harvesting and handling, develop a brown discoloration on the broken ends which is not removed by processing and is detrimental to the appearance and processed grade. Broken-end discoloration (BED) was controlled when samples were treated before storage with 7500 to 10,000 ppm SO2 for 30 seconds or when samples were stored in controlled atmospheres containing 20 or 30% CO2 for 24 hours. Processed quality attributes of color, flavor, texture, and sloughing were not affected by these treatments. Oxygen levels of 5% or less also controlled BED but caused off-flavors in the canned product. Elevated CO2 levels were not injurious to snap bean quality as long as O2 was maintained at 10% or higher.
Controlled atmospheres (CA) have been used as auxiliary to refrigeration for the storage and transportation of food crops. Commodities sensitive to high levels of CO2 experience fermentation. This study was focused upon the effects of CO2-enriched atmospheres on ethanol (ETOH) accumulation as an indicator of the sensitivity of 22 different produce to short-term exposure to 30% CO2 in air for 2 days at 7C. Commodities were obtained from a wholesale or grocer supermarket. ETOH was determined by gas chromatography (GC). Differences in response to 30% CO2 in air were observed among commodities. Kiwi fruit and broccoli had initial low levels of ETOH, which greatly increased after the first day of storage. Cherries and spinach maintained approximately a constant increase in ETOH accumulation during the whole period of storage. Pickling cucumber and zucchini squash had high ETOH accumulation at the early period of storage, which was even higher by the second day of exposure to 30% CO2 in air. In most of the commodities under study ETOH accumulation increased as a response to 30% CO2 levels in air. There was no apparent influence of plant organ on ETOH accumulation.
Abstract
Postharvest exposure of snap beans to elevated CO2 (40%), but not reduced O2 (2.5%), enhanced softening when the pods were subsequently heated. Softening and solubilization of pectic substances induced by CO2 were related to lowered hydrogen ion concentrations, which were caused by the depletion of malic acid. In contrast, high CO2 stimulated succinic acid accumulation but did not alter citric acid levels. Blanching and boiling reduced the content of both succinic and malic acids in pods. Transelimination was effective in depolymerizing and solubilizing pectic substances in snap bean pods. The shift in pH induced by CO2 increased the transelimination reaction and thus increased pod softening.
Abstract
Hardcore was apparent in cooked sweet potatoes (Ipomoea batatas Lam.) which had been chilled and transferred to nonchilling temperatures prior to cooking. The severity increased with duration of chilling at 2°C. Hardcore was not observed in roots boiled immediately after chilling, although these roots were firmer than those not chilled. Enhanced levels of pectic substances, soluble in sodium hexametaphosphate, were associated with hardcore tissue, while starch, protopectin, and hemicellulose were related to enhanced firmness of continuously chilled roots. No differences in pectinmethylesterase activity were observed between storage treatments. Reduced levels of alpha amylase activity in continuously chilled roots probably accounted for the enhanced levels of starch after the roots were processed. From data on U.V. absorption, phenolic levels, and electrolyte leakage, we believe that hardcore develops when phenolics or related substances, and possibly cations, bind with cell wall materials.
Abstract
Brown-end discoloration (BED) of broken snap beans (Phaseolus vulgaris L.) occurs whenever pods are held for several hours before processing. Increases in phenylalanine ammonia lyase (PAL), catecholase, and peroxidase activities as well as total phenolic content coincided with the development of BED. The intensity of BED and catecholase activity declined with increasing incubation temperatures (40 to 70°C). Perosidase activity did not decline until after 60° and PAL activity was stable through 70°. We therefore believe that catecholase oxidation of phenolic substances are directly associated with BED of snap beans.