Several crops, such as potatoes and sweet potatoes are easily injured during harvest
because they have to be dug from the ground, and therefore need to be cured. Curing
immediately after harvest is a simple and effective method to reduce water loss
and decay during postharvest storage of root, tuber, and bulb crops. Curing is a
process that involves the synthesis of new tissue, commonly through lignification
or periderm formation. This process is essential to cure cuts and reduce water loss,
fungal infestation, and hence reduce losses during postharvest handling. Curing is
commonly done at high temperatures and high relative humidites. Curing in sweet
potato roots heals the wounds by promoting epiderm formation, and makes the roots
less likely to ‘skin’ during further handling (Blankenship and Boyette, 2002).
Sweet potato roots are commonly cured at 30 °C and 85% relative humidity (RH)
for about one week (Blankenship and Boyette, 2002). However, curing at near 100%
RH was found to be best for avoidance of weight loss due to root injuries (Kushman,
1975). In root and tuber crops, curing refers to the process of wound healing with
the development and suberization of new epidermal tissue called wound periderm.
The type of wound affects periderm formation. Abrasions result in the formation
of deep, irregular periderm, while cuts result in a thin periderm, and compressions
and impacts may entirely prevent periderm formation. In bulb crops, curing refers
to the process of drying (some water loss takes place) of the neck tissues and of
the outer leaves to form dry scales. Onions and garlic can be cured in the field where
they are undercut, then hand pulled, the roots and tops are trimmed and the bulbs
then are allowed to dry in field racks or bins from 2 to 7 days or longer (depending
on ambient conditions). Where ambient conditions are unfavorable, curing may be
done in rooms with warm forced air. Onions develop the best scale color if cured
at temperatures of 25 ° to 32 °C. Citrus fruit may also be conditioned by exposing
to high temperatures and RH to reduce skin injury and decay, however the fruit
can be sealed in plastic film to reduce weight loss (Ben Yehoshua et al., 1989).