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D. Mark Hodges, Charles F. Forney, and Wendy Wismer

The degree of damage that may occur through harvesting and packing represents one of the major factors that can affect quality of fresh-cut produce. The purpose of this study was to examine the effects of different steps in a representative fresh-cut processing line on storage quality of spinach (Spinacia oleracea L.). To this end, spinach leaves were removed at successive points on the line: 1) before entry into the line (control); 2) after a shaking procedure but before initial rinsing with 10 °C water + 5 mg·L-1 chlorine dioxide; 3) after centrifugal drying; and 4) after commercial packaging. After removal from the different points in the line, the spinach samples were stored at 10 °C for 16 days, during which time malondialdehyde (MDA) concentration (lipid peroxidation assay), electrolyte leakage (membrane leakiness), chlorophyll content (a, b, and total), and color attributes (L, saturation, hue angle) were measured. Both lipid peroxidation and electrolyte leakage increased with time of storage and with stage of procesing. Electrolyte leakage increased most in material removed after the shaking procedure, but prior to hydrocooling. Overall total chlorophyll loss during storage did not change with time of removal from the processing line, although overall chlorophyll b content decreased in stored material 8 days following centrifugal drying and packaging. A more rapid loss in chlorophyll a relative to chlorophyll b over the first 8 days of storage was reflected in hue angle measurements regardless of the point of removal. The processing line under study, thus had both beneficial and detrimental effects on storage quality of spinach. Detrimental effects associated with centrifugal drying and packaging procedures could be modified to improve quality.

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D. Gerasopoulos and D.G. Richardson

Mature `Anjou' pears (Pyrus communis L.) continuously stored at 20 °C or -1 °C before transfer to 20 °C exhibited differences in the sequence of ripening events up to 100 days. Pears continuously held at 20 °C showed little change in ripening characteristics (chlorophyll, firmness, titratable acidity) for 14 to 28 days, then these characteristics decreased at a daily rate of 1.4% thereafter. A 40% increase in soluble polyuronides paralleled the firmness loss, while ACC did not exceed 0.5 nmol·g-1 until the 84th day, and internal ethylene did not exceed 0.2 μL·L-1 until after 90 days, whereas ACC oxidase activity (and total protein) peaked after 63 days. `Anjou' pears stored at -1 °C showed no changes in chlorophyll, firmness, protein, or total polyuronides for at least 84 d. Despite essentially no change in firmness during -1 °C storage, there was a slow but steady increase (≈15 %) in soluble polyuronides. ACC oxidase activity, expressed as ethylene production, rose to 71 nL·g-1·h-1 and the ACC content increased to almost 1.0 nmol·g-1 by the 84th day. Internal ethylene slowly increased and levelled to 1 μL·L-1 by the 56th day. Satisfaction of a chilling requirement thus appears to favor the development of ethylene synthesis capacity, which on transfer from cold storage to higher temperatures results in enough internal ethylene to rapidly drive the associated ripening mechanisms. Fruit for which the chilling requirement (≥70 days at -1 °C) was met softened in response to accelerated internal ethylene production on transfer to 20 °C for 7 days. However, pears that were not chilled or partially chilled did not sustain the increased ACC levels or ACC oxidase activity. Chemical name used: 1-aminocyclopropane-1-carboxylate (ACC).

Open access

Priyanka Sharad Mahangade, Indra Mani, Randolph Beaudry, Norbert Müller, and Sangeeta Chopra

the evaluation of the performance of imperfect storages. We studied parameters of senescence (leaf abscission, leaf yellowing, and chlorophyll loss) as they related to an estimate of the total metabolic activity experienced by amaranth stems for four

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Shimon Meir, Sonia Philosoph-Hadas, and Nehemia Aharoni

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.

Open access

Mikal E. Saltveit Jr. and Fabio Mencarelli

Abstract

Exposure of whole fruit, slices, or pericarp disks of tomato (Lycopersicon esculentum Mill.) to 0.5 to 3.0 ml absolute ethanol vaporized in a 4-Iiter container for 3 hr significantly reduced the climacteric rise in CO2 and C2H4 production, lycopene synthesis, and chlorophyll loss. Inhibition of ripening occurred whether fruit were at the mature-green or breaker-turning stage. Whole fruit recovered and ripened normally after a delay that was related to the tissue ethanol concentration. Treated slices did not ripen normally, and exposure to 16 μl C2H4/liter did not promote ripening. The level of ACC was 14-fold higher in treated slices, while C2H4 production was reduced 70%. Treatments with AVG and ACC indicated that ethanol inhibited ACC conversion to C2H4. Chemical names used: 1-aminocyclopropane-1-carboxylic acid (ACC); [S-(E)]-2-amino-4-(2-aminoethoxy)-3-butyric acid (AVG).

Open access

E. F. Poenicke, S. J. Kays, D. A. Smittle, and R. E. Williamson

Abstract

Ethylene is produced by cucumber fruits (Cucumis sativus L.), at a rate which is size dependent. Small fruits (<2.6 cm diam) produced substantially more ethylene/kg fruit than did large fruits (2.6-3.8 and 3.8-5.1 cm diameter). Respiration was similarly affected. Mechanically harvested fruits produced 2 to 3 times more ethylene than did hand-harvested fruits. Texture profile analysis (TPA) of cross-sections of fruits treated 48 hr with 0, 0.1, 0.5, 1.0, 5.0 and 10.0 µl/liter ethylene indicated little change in textural parameters at concentrations below 10.0 µl/liter. Ethylene treatment, especially high concentrations, decreased fruit chlorophyll content. Greatest chlorophyll loss was at the stem-end of the fruit. Ambient concentrations of ethylene in well-ventilated trucks of cucumbers were not great enough to present a quality problem for processing cucumbers.

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Barry J. Pogson and Stephen C. Morris

In most broccoli (Brassica oleracea L. var. italica) cultivars studied, the loss of chlorophyll was marginal after 5 weeks cool storage (1 °C) + 2 days at 20 °C, but there was significant loss of chlorophyll from some poor-storing cultivars, particularly after 10 weeks cool storage (+2 days at 20 °C). Soluble sugars were depleted rapidly during cool storage (especially sucrose) and were essentially exhausted after 10 weeks at 1 °C. Losses of total proteins were only 20% after 10 weeks cool storage. There is preferential catabolism of carbohydrates (sucrose, glucose, and fructose) at low temperatures, whereas, at 20 °C, protein and carbohydrate levels decline concomitantly. The patterns of sugar and protein depletion suggest that all soluble sugar is potentially accessible for metabolism, but protein catabolism is targeted to specific tissues or organs. After 5 weeks at 1 °C and placing at 20 °C, ethylene production and respiration increased to steady-state levels. Peak production of wound ethylene usually occurs 4 to 6 hours after harvest at 20 °C. After 5 or 10 weeks cool storage, this peak of production was not detected at 20 °C. After 10 weeks at 1 °C, recovery of ethylene production was delayed and the respiration rate only partially recovered to the steady level. However, chlorophyll loss is the major determinant of marketable life without cool storage, and, after 5 weeks at 1 °C, postharvest decay is the major determinant of marketable life after cool storage, particularly after 10 weeks at 1 °C.

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J.D. Fry, N.S. Lang, and R.G.P. Clifton

`Floratam' St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] stolons were sampled from the field between October and March to determine potential changes in lethal low temperatures and nonstructural carbohydrate composition. Lethal temperatures determined by electrolyte leakage ranged from – 6.1 to – 5.3C. Little variability in lethal temperatures over sampling dates indicated that `Floratam' St. Augustinegrass did not readily acclimate to cold temperatures. Starch was the carbohydrate present in highest concentration in `Floratam' stolons, with levels ranging from 7.7 to 12.4 mg/100 mg dry weight. Sucrose concentrations varied from 2.4 to 5.7 mg/100 mg dry weight. Glucose and fructose were also present in `Floratam' stolons at lower concentrations. A slight increase in sucrose and decrease in starch were observed between November and December, when low temperatures resulted in chlorophyll loss and turf was <25% green. On all other sampling dates, changes in sucrose and starch were variable. Changes in concentration of total nonstructural carbohydrates or soluble sugars did not seem to influence the freezing resistance of `Floratam' St. Augustinegrass.

Open access

Joseph Makhlouf, Claude Willemot, Joseph Arul, François Castaigne, and Jean-Pierre Emond

Abstract

The effect of controlled atmospheres on the regulation of ethylene biosynthesis during the senescence of broccoli flower buds (Brassica oleracea, L. Italica group cv. Green Valiant) was assessed. The broccoli buds wee stored in the dark at 25C under a continuous stream of nitrogen containing the following percentages of CO2-O2 : 0-20 (air), 0-2.5, 6-20, and 10-20. Generally, respiration, ethylene production, and ethylene-forming enzyme (EFE) activity followed a climacteric like pattern in all atmospheres. The ACC content changed little during the “climacteric”, but increased dramatically during the “post-climacteric” period, when ethylene production and EFE activity decreased. Under high CO2, respiration was reduced, but ethylene production and EFE activity were temporarily stimulated early during treatment. Under low O2, respiration, ethylene production, EFE activity, and ACC content were reduced, and the “climacteric” and chlorophyll losses were delayed to a greater extent than under high CO2. Whatever the treatment, ACC level was not the limiting factor in ethylene biosynthesis in broccoli; the reduction in ethylene production during senescence resulted from the degradation of the system that converts ACC to ethylene. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

Free access

R.S. Mueller, D.P. Murr, and L.J. Skog

1-Methylcyclopropene (1-MCP), a gaseous synthetic cyclic hydrocarbon, has been shown to have potential to become an important new tool in controlling the response of plants sensitive to ethylene. Due to its irreversible binding to the ethylene receptor(s) and its subsequent prevention of the physiological action of ethylene for extended periods, 1-MCP may prove also to have effective commercial application in the control of ethylene effects in detached organs such as fruit. Our objective was to investigate the effectiveness of 1-MCP in controlling ripening in pear. Two commercial cultivars (Bosc, Anjou) and one numbered cultivar from Agriculture and Agri-Food Canada's breeding program (Harrow 607) were harvested at commercial maturity. Immediately after harvest, fruit were exposed for 24 h at 20 °C to 1-MCP ranging from 0 to 100 μL•L-1 then placed in air at 0 °C and 90% relative humidity for 5 and 10 weeks. Following treatment and after 5 weeks storage plus a 7- or 14-day post-storage ripening period, fruit softening and ethylene evolution were inhibited and fruit volatile evolution was reduced significantly by exposure to 1-MCP at or above 1.0 μL•L-1 in all three cultivars. Concentrations exceeding 1.0 μL•L-1 were required to maintain initial firmness and inhibit ethylene production after 10 weeks storage in air. Evolution of alpha-farnesene and 6-methyl-5-hepten-2-one was related to low temperature stress and chlorophyll loss as a result of ripening, respectively, and were affected by 1-MCP exposure. The pattern of evolution and amounts of other volatiles was also affected by 1-MCP treatment. These results indicate a huge potential for commercial use and application of 1-MCP in controlling fruit ripening and senescence.