Post harvest Management of Horticultural Crops (2+1)

Categories of Physiological disorders

Physiological disorders can be divided into five general categories:

1. Nutritional – Eg. bitter pit in apple, blossom end rot in water melon and tomato.
2. Temperature (low and high) – Eg. sunburn on the shoulders of tomato and mango,(high-temperature injury occurred prior to harvest).
3. Respiratory - low oxygen and or high carbon dioxide concentrations in and/or around harvested produce in CAS and MAP. Eg. black heart of potato (low-oxygen injury).
4. Senescent – Eg. mealiness in apples, are due to harvesting over-mature produce and/or overstoring produce.
5. Miscellaneous - disorders which are product-specific in terms of symptoms expressed.
Eg. a) Bitterness (isocoumarin accumulation) in carrot.
b) Greening of potatoes exposed to light
c) Rooting of onions exposed to high humidity
d) Russet spotting on the midrib of lettuce leaves (exposure to ethylene)

Nutritional and low-temperature disorders are more problematic than others.

The cellular, biochemical and biophysical mechanisms that give rise to physiological disorders in produce are extremely complex. Moreover, they often involve elusive interactions with the pre-and postharvest conditions.