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Judith Zambrano and Juan Manzano

The effect of applying Ca++ in two forms: infiltration and dipping on mango fruit cv `Haden' was investigated. This effect was evaluated by measuring some quality parameters in the flesh and in the skin of the fruit. It was found that postharvest application of Ca++ extent the storage life of the fruit by a week. This fact, together with the results obtained from the quantification of sugars, ascorbic acid, total soluble solids alcohol. insoluble solids, starch and titrable acidity seem to indicate that the application of Ca++ delays slightly the process associated with ripeness. Furthermore, no significant difference between the two forms of Ca++ applied was found, except for the amount of ascorbic acid and total sugar. Finally, dipping application of Ca++ is easier than infiltration and it is therefore suggested.

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Gene E. Lester

Plasma membrane (PM) from hypodermal-mesocarp tissues of muskmelon fruits (Cucumis melo L. var. reticulatus Naud.) were compared to the electrolyte leakage changes of the same tissue during maturation and storage at 4 or 24C. During fruit maturity and storage, leakage of the hypodermal-mesocarp tissue increased, which is coincident with increased total sterol: total phospholipid ratios and increased phospholipid fatty acid saturation index of the PM. ATPase activity, a marker for the PM, indicated that the PM increased in buoyant density from 1.13 g.cm-3 to 1.14 g.cm-3 during maturity and ATPase activity peaked with fruit maturation. ATPase activity decreased with 10 days postharvest storage and was less at 24C vs. 4C, which was coincident with increased hypodermal-mesocarp electrolyte leakage. Biochemical changes within the sterol and phospholipid matrix of the PM are suggested to contain the processes capable of altering fruit membrane permeability and subsequent muskmelon fruit storage life.

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Diana L. Lange

Several leading Eastern muskmelon varieties were evaluated for their postharvest characteristics. The varieties evaluated were `All Star', `Athena', `Eclipse', `Legend', `Quasar', `Starship', and `Superstar'. The fruit were harvested in multiple harvests from 1 July through 10 Aug. 1996. Postharvest measurements taken included soluble solids (%), firmness, rind and flesh color, respiration, flavor quality, damage after drop tests, storage life, and shipping ability. The fruit of each cultivar were harvested at “half-slip” and “full-slip” and fully evaluated at each level of maturity. Most of the cultivars had similar postharvest characteristics, except `Superstar', which had the lowest overall ratings. Firmness ratings were highest for `All-Star', `Athena', and `Legend' and were lowest for `Superstar'. The flavor quality was similar for most cultivars and lowest for `Superstar' fruit. This trial will be repeated in 1996 and promising cultivars will be recommended for midwestern Unites States production.

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George D. Nanos and F. Gordon Mitchell

Storage at 0C of `O'Henry' and `Fairtime' peaches and `Red Jim' and `September Grand' nectarines (Prunus persica L. Batsch) resulted in significantly longer postharvest life than did storage at 5C, due to differences in the development of internal breakdown (IB) symptoms. Conditioning at 20C for 2 days before storage at 0 or 5C generally prolonged the storage life of fruit of these cultivars. The use of elevated CO2 during conditioning helped maintain fruit firmness. Addition of 5% CO2 to air gave the best results in maintaining fruit firmness and freedom from IB symptoms for up to 6 weeks. Reducing the O2 content kept flesh firmness high after storage but did not delay the appearance of IB. Conditioning at 30C using various atmospheres was less effective than conditioning at 20C.

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Dana F. Faubion, Mary Lu Arpaia, F. Gordon Mitchell, and Gene Mayer

Optimum controlled atmosphere (CA) storage conditions were evaluated over a two year period for California-grown `Hass' avocado (Persea americana). Fruit harvests corresponded to early, middle and late season commercial harvests. Various temperatures and CA conditions were tested. The results indicate that the storage life of `Hass' can be extended from 3 to 4 weeks in 5C air, to 9 weeks in 5C CA if they are held in 2% oxygen and 2 to 5% carbon dioxide. Loss of quality as determined by chilling injury expression and flesh softening was greatly reduced in these conditions. Fruit maturity influenced the response to CA storage. Late season fruit had greater loss of quality in storage than earlier fruit. In 2% oxygen and 2.5% carbon dioxide, continuous exposure to ethylene levels as low as 0.1 ppm significantly increased quality loss. Delays in cooling and CA atmosphere establishment of up to three days after harvest did not effect quality.

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Wolfgang Schuch, Janos Kanczler, Duncan Robertson, Graeme Hobson, Greg Tucker, Don Grierson, Simon Bright, and Colin Bird

We have analyzed the quality and composition of transgenic tomato fruit (Lycopersicon esculentum Mill.) cultivar Ailsa Craig modified by the expression of antisense RNA to polygalacturonase (PG). Tomato plants with <1% of normal PG activity in the fruit were grown under commercial glasshouse conditions and shown to have reduced levels of PG activity throughout ripening compared with untransformed lines. The firmness of fruit, as measured by vertical compression throughout ripening, was not altered in the transgenic samples when compared with controls. However, storage life and ability to withstand transport without damage were improved in the transgenic tomatoes. Tomato juice made from the PG antisense fruit by a cold-break method had significantly higher consistency (distance flowed per unit time) than juice from control fruit.

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Jennifer R. DeEll, Clément Vigneault, Frédérique Favre, Timothy J. Rennie, and Shahrokh Khanizadeh

The objective of this research was to evaluate the effects of vacuum cooling and temperature on the quality and storage life of mung bean sprouts (Vigna radiata L. Wilczek). Sprouts in micro-perforated bags were either not precooled or vacuum cooled to 9, 6, or 3 °C, and stored for 7 days at 1, 3, or 6 °C. Vacuum-cooled bean sprouts lost more weight than sprouts not precooled, and the weight loss was greater when the sprouts were cooled to lower temperatures. However, the total loss never exceeded 5% and no apparent signs of shrivel were observed. Vacuum cooling resulted in greater product freshness after 4 days of storage, but the effect was nonsignificant after 7 days. Storage temperature had greater influence on bean sprout quality than did cooling temperature, with greater freshness and whiter hypocotyls at the lower temperatures. However, blackening of cotyledons increased as the storage temperature decreased.

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Deirdre M. Holcroft, Maria I. Gil, and Adel A. Kader

`Wonderful' Pomegranates (Punica granatum L.) were placed in jars ventilated continuously with air or air enriched with 10 or 20 kPa CO2 at 10 °C for 6 weeks. Samples were taken initially and after 1, 2, 4, and 6 weeks, and postharvest quality attributes were measured. The arils of the pomegranates stored in air were deeper red than the initial controls and than those stored in CO2-enriched atmospheres. This increased color was associated with increased anthocyanin concentration. Arils from fruit stored in air enriched with 10 kPa CO2 had a lower anthocyanin concentration than air-stored fruit, and atmospheres enriched with 20 kPa CO2 had even lower levels, possibly from suppressed anthocyanin biosynthesis. Anthocyanin concentration correlated well with the activity of phenylalanine ammonia lyase but not with glucosyltransferase activity. Moderate CO2 atmospheres (10 kPa) prolong the storage life and maintain quality of pomegranates, including adequate red color intensity of the arils.

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Alfred Jones

Sweetpotato [Ipomoea batatas (L.) Lam.] cultivars with high levels of resistance to root damaging insects have been developed through the collaborative efforts of a multidisciplinary research team. These resistances were combined with other traits necessary for a successful cultivar such as: disease resistances; high yield; long storage life; prolific sprout production; marketable root size, shape and skin at tributes; and culinary excellence. Adpotion of quantitative genetic principles, development of a wide gene base, sequential selection schemes, use of effective selection criteria and appropriate susceptible standards contributed to the program's success. These achievements were made with, little prior knowledge about inheritance patterns, gene action, mechanisms of resistance or a complete knowledge of the insects concerned. The value of insect resistant cultivars has become better appreciated with the recent decrease in chemical alternatives.

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K.S. Mayberry and T.K. Hartz

Trials were conducted in California to evaluate techniques to extend storage life of netted muskmelons (Cucumis melo L.). The use of polyethylene bags, either as individual melon wraps or as liners for 18-kg commercial cartons, minimized water loss and associated deterioration of the fruit. Individual bags and carton liners were equally effective. A 3-minute dip in 60C water effectively checked surface mold development on wrapped fruits. Lower temperature and/or shorter exposure treatments were less effective. When applied in addition to hot water treatment, imazalil fungicide did not confer significant additional benefit. The combination of polyethylene bags and hot water treatment maintained high quality, marketable fruit for at least 28 days of storage at 3C,