Post harvest diseases fruits and vegetables - Xavier University ...

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FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE Means for Maintaining Host Resistance 129 by decreasing the O2 concentration from 21% to 2.5% or raising the CO2 level from 0.03% to 10% (Biale, 1946; Young et al., 1962). Storing Florida avocados for 45-60 days at lO'^C in an atmosphere of 2% O2 and 10% CO2 resulted in a remarkable reduction in anthracnose (Colletotrichum gloeosporioides), the main cause of spoilage during storage and marketing, and at the same time prevented chilling injury, which is generally accompanied by increased susceptibility to fungal attack (Spalding and Reeder, 1975). Since such concentrations of O2 and CO2 have only a slight inhibitory effect on the growth of C. gloeosporioides, decay control in this atmosphere was attributed to maintenance of the fruits in the firm mature-green stage and thus to the maintenance of the quiescence of the fungus. In contrast to avocados, CA was only slightly, or not at all beneficial to papayas, for which, similarly, decay is the chief limiting factor in storage extension (Spalding and Reeder, 1974). Atmospheres of 10-20% CO2 or more reduce the incidence of decay caused by S. cinerea and Rhizopus stolonifer in several cultivars of strawberries, as exhibited, not only during cold storage but also after removal of the fruit to shelf-life conditions, without causing objectionable off-flavors (Harris and Harvey, 1973). Under these conditions decay suppression may be attributed both to the direct effect of the CA on the pathogens and to its effect on the physiological deterioration of the fruit. The resistance of the fruit to Botrytis and Rhizopus decay in a C02-enriched atmosphere was hypothesized to be the result of the high levels of acetaldehyde and ethyl acetate produced by fruit under such conditions (Shaw, 1969). An atmosphere enriched with CO2, at 10, 15 or 20%, retarded storage decay of blueberries by 1-2 days after the berries had been removed from the CA and held at 21°C, whereas an atmosphere of 2% O2 was ineffective on its own in suppressing decay, and did not enhance the effect of the CO2 atmosphere (Ceponis and Cappellini, 1985). Decay suppression by high CO2 (20%) has also been recorded in muskmelons after 14 days at 5°C followed by shelf-life conditions (Stewart, 1979), while CA (10-20% CO2 + 10% O2) along with ethylene absorbance prolonged the storage life of Galia melons, through the maintenance of tissue firmness and decay suppression (Aharoni et al., 1993a). CA had considerable benefits over air for the long-term refrigerated storage of white cabbage (Geeson and Browne, 1980): storing cabbage in an atmosphere of 5-6% CO2 + 3% O2 at 0-2''C resulted in the retardation of general senescence effects, such as yellowing, toughening and loss of flavor, and in the inhibition of physiological disorders and the repression of decay development during prolonged storage. http://arab2000.forumpro.fr
FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE 130 Postharvest Diseases of Fruits and Vegetables One of the beneficial effects of CA storage is its ability to reduce chilling injury in certain sensitive crops. Several studies indicated that prestorage treatments of grapefruits with high concentrations of CO2 were effective in inhibiting the development of pitting in cold storage (Hatton and Cubbedge, 1982). However, no reduction in chilling injury was induced by CA in other citrus fruits, such as limes and lemons (Spalding and Reeder, 1983; McDonald, 1986). Intermittent exposure of unripe avocado fruits to 20% CO2 reduced chilling injury during storage at 4°C (Marcellin and Chaves, 1983). An atmosphere of 2% O2 and 10% CO2 prevented the development of anthracnose {Colletotrichum gloeosporioides) at 7.5°C and reduced chilling injury at 4.4°C in Fuchs avocados (Spalding and Reeder, 1975). Low-oxygen atmospheres were found to delay the development of chilling injury symptoms while reducing their severity, in peaches stored at 5°C (Ke et al., 1991), and to ameliorate chilling-induced pitting in zucchini squash (Mencarelli et al., 1983; Wang and Ji, 1989). 2. CONTROLLED ATMOSPHERE WITH CARBON MONOXIDE The addition of CO to the atmosphere results in the suppression of various fungi sensitive to the gas, such as Penicillium digitatum, P. italicum and Monilinia fructicola. The effectiveness of this fungistatic gas is pathogen dependent and is greatly enhanced in combination with a I0W-O2 atmosphere (2.3%). The addition of high CO2 to this atmosphere further enhanced fungal growth inhibition, because of the additive effects of CO and CO2 (El Goorani and Sommer, 1979, 1981). The possibility of using CO atmosphere for decay suppression during storage has been studied for various commodities. Kader et al. (1978) showed that the addition of CO (5 or 10%) to a I0W-O2 atmosphere (4%) reduced the incidence and severity of the gray mold decay in Botrytis cmerea-inoculated tomatoes at their mature-green or pink stage. When added to air, CO increased the CO2 and ethylene production rates and, in parallel, hastened the ripening of mature-green tomatoes, while the addition of CO to a I0W-O2 atmosphere had no or very little effect on these physiological responses. Studying the effects of various atmospheres on the severity of watery soft rot of celery caused by Sclerotinia sclerotiorium, Reyes (1988) found that whereas a I0W-O2 CA (1.5%), with or without high CO2 (16%), reduced decay development only slightly, a combination of 7.5% CO + 1.5% O2 suppressed disease significantly without causing undesirable effects on celery quality. Applying mixtures of O2 and CO to B. cmerea-inoculated apples inhibited http://arab2000.forumpro.fr
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