Cold storage of fruit & vegetables
Practical Action
Storage conditions
Temperature
All fruits and vegetables have a 'critical temperature' below which undesirable and irreversible
reactions or 'chill damage' takes place. Carrots for example blacken and become soft, and the
cell structure of potatoes is destroyed. The storage temperature always has to be above this
critical temperature. One has to be careful that even though the thermostat is set at a
temperature above the critical temperature, the thermostatic oscillation in temperature does not
result in storage temperature falling below the critical temperature. Even 0.5°C below the
critical temperature can result in chill damage. Table 1 gives the critical temperatures for
various fruits and vegetables.
Temperature
°C
Relative
humidity
%
Maximum storage time
recommended
(ASHRAE handbook
1982)
Storage time in cold
stores for vegetables
in tropical countries
Apple
0-4
90-95
2-6m
Beetroot
0
95-99
Cabbage
0
95-99
5-6m
2m
Carrots
0
98-99
5-9m
2m
Cauliflower 0
95 2-4w
1w
Cucumber
10-13
90-95
Eggplant
8-10
90-95
Lettuce
1
95-99
Leeks
0
95 1-3m
1m
Oranges
0-4
85-90
3-4m
Pears
0
Pumpkin
10-13
Spinach
0
Tomatoes
13-21
Table 1: Storage conditions
90-95
70-75
95
85-90
2-5m
1-2w
1w
It can be seen from the table that there are basically three groups of fruit and vegetables:
those stored at 0 - 4°C; those stored at 4 - 8°C; and those that require a storage temperature
above 8°C. It is often more convenient to concentrate on one of these groups.
Relative humidity
For most produce, a high but not saturated, relative humidity is required, eg 85 - 95%.
Table 1 shows specific relative humidities for fruits and vegetables. There is always some
moisture loss during cold storage but excessive moisture loss is a problem. It is essential that
the relative humidity is kept above 85%. This can be done by:
allowing the produce to reach storage temperature and then covering in plastic
sprinkling the produce with water, this should be done before storage since if the
vegetables are sprinkled during storage condensation occurs at the refrigeration unit.