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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Means for Maintaining Host Resistance 131
lesion development, and the inhibition was closely related to the decrease
in the O2 level from 8% to 2% (Sommer et al., 1981). The development of
the CO-sensitive Monilinia fructicola in peaches was completely inhibited
in cold storage by the addition of CO to a I0W-O2 atmosphere (4%);
however, a normal rate of rot development was resumed once the fruits
were transferred to air at 20°C (Kader et al., 1982).
In spite of the efficiency of CO combined with I0W-O2 atmospheres in
decay suppression, the use of this gas is limited, mainly because of its
high toxicity to humans and the fear of inhalation of the poisonous gas by
workers. The use of CO is additionally limited by its tendency to mimic
ethylene effects, as has been found in tomatoes, strawberries, sweet
cherries and peaches (Barkai-Golan, 1990).
3. MODIFIED ATMOSPHERE PACKAGING
Sealing certain commodities in polymeric film packages promotes the
extension of their storage life as a result of the formation of a modified
atmosphere (MA) within the package. This practice is referred to as
modified atmosphere packaging (MAP). The method is based on the
alteration in the composition of the gases around the commodity within
the sealed package. Elevation in the CO2 level along with the decrease in
the O2 level in the package result in a decreased respiration rate of the
stored fruits or vegetables, and the extension of their physiological life.
The levels of the gases accumulated in the sealed package are
determined by the respiration rate of the commodity, the storage
temperature, the permeability of the film material to the atmospheric
gases, the ratio of the produce weight or surface area to the area of
semi-permeable film, among other factors (Smock, 1979).
In looking for suitable wrapping for strawberries exported from Israel
to Europe by sea, it was found that polyethylene or polyvinyl chloride
(PVC) film enabled fruit to be stored at 0-2°C for 10 days, followed by two
additional days at 20°C (Barkai-Golan, 1990). The prolongation of the
storage life was evident in the firmness and the fresh appearance of the
fruit and the calyx, and the considerable reduction of decay, caused
mainly by Botrytis cinerea. The incidence of decay was correlated with
the level of CO2 accumulated in the atmosphere around the fruit. During
cold storage the level of CO2 ranged between 1.5 and 2.5%, but the low
temperature controlled decay. Following transfer to 20°C, CO2 levels rose
up to 7.5-12%; under these conditions, the suppressive effect of CO2 on
decay development is attributed mainly to its effect of delaying the
http://arab2000.forumpro.fr