Post harvest Management of Horticultural Crops (2+1)

Curing

Curing

When roots and tubers are to be stored for long periods, curing is necessary to extend the shelf life. It is an effective operation to reduce the water loss during storage from hardy root and tuber vegetables such as potato, sweet potato, yam and other tropical vegetables where cuticle are poorly developed. They are relatively susceptible to mechanical wounding during harvesting and handling. These problems can be minimized by the process of ‘curing’ at intermediate to high temperature and high relative humidity (RH). During curing it develops periderm over cut, broken or skinned surfaces and helps in wound restoration.
‘Curing is accomplished by holding the produce at high temperature and RH for several days, while harvesting wounds heals and new protective layers of cell forms around wound’.

Advantages

• It helps in wound healing of harvest and handling injuries through skin hardening
• Reduce water losses
• Prevent infection from pathogen

How curing happens?

• Curing is normally undertaken in the field, but in some case curing structure are employed.
• Produce can be cured in the field by piling them in a partially shaded area. Cut grass or straw can serve as insulating material, while, covering the pile with canvas, burlap, or woven grass matting. This covering will provide sufficient heat to reach high temperatures and high relative humidity. The stack can be left in this state for up to four days.
• Curing in potato starts with deposition of suberin in parenchymatous cell just below the damaged area of the tuber.
• Suberin (a waxy waterproof substance found in the cell walls of many plants, especially corky in nature ) is a group of fatty acids which provides initial protection to the tuber against water loss and infection.
• Subsequently, below the suberized cells a meristematic layer of cells is formed which is the periderm, also called as cork cambium (Fig.19). This produces new cells which seal off the damaged area. But these processes are temperature and humidity dependent.
Eg. Curing of potato takes place in 1 days at 21⁰C ;2 days at 15⁰C ;3 days at 10⁰C;5-8 days 5⁰C.

Table: Optimum condition for curing of vegetables

Commodity	Temp(0C)	RH (%)	Days for curing
Potato	13-17	>85	7- 15
Sweet potato	27-33	>90	5- 7
Yam	32-40	>90	1- 4
Cassava	30-35	>80	4- 7
Garlic and onion	35-45	60-75	0.5-1 warm forced air

When extreme conditions in the field exist, such as heavy rain or flooded terrain, and curing facilities are not available, a temporary tent must be constructed from large tarpaulins or plastic sheets to cure the produce and avoid heavy loss.




Curing citrus fruits – curing treatments facilitates

• The wound healing
• Reduce decay through lignifications
• Increase in the antifungal chemicals in the fruit peel in orange (300C), pomelo, lemons and grapefruit at 340C and 90-100 % RH for 2-3 days, not later than 48 hr after harvest.
• In pumpkins and other cucurbits, curing is the hardening of the skin.
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