Monday, January 9, 2012

Curing Sweet Potatoes

Freshly dug sweet potatoes are not always as sweet due to the large amounts of starch in the tubers. Besides, they may not last long enough especially if they are not stored in very good conditions.

Curing sweet potatoes is the next most important after harvesting and before consumption. Always, when harvesting, keep the sweet potatoes in a shade and ensure that sweet potatoes are not bruised. In curing, the sweet potato should be placed under some controlled environment to ensure some important physiological changes occur.

The curing process should begin immediately after the sweet potato has been dug, while they are still fresh.

During the sweet potato curing process, the starch is converted to sugar to give the tubers a very sweet taste. Also, the curing process heals the cuts and bruises sustained during harvesting enabling the tubers to develop a layer of suberin on the skin of the fleshy root which encloses each sweet potato tuber in its own "organic plastic bag." This new tough outer covering will be impermeable to moisture.

An improvised kiln for curing sweet potatoes: Image courtesy
 The process that happens during curing is called suberization. During suberization, starch is converted to unsaturated fatty acids which combine with oxygen to make suberin, a remarkable mixture of waxy substances which allows the tuber to breathe but which holds in almost all of the tuber’s moisture. Suberin, in combination with wound priderm (which forms a corky layer over wounds), seals in  moisture and seals out rot-producing organisms, thereby protecting against infection. Cured sweet potatoes do lose moisture but the loss is very slow. A properly cured sweet potato can sit at room temperature in the open air for several months and lose scarcely any weight."

Cure sweet potatoes in a warm, humid room for five to ten days. Temperatures of 80F to 85F and a relative humidity of 80% to 90% are ideal for curing. Since these conditions are hard to maintain inside the home, many small scale farmers develop small kilns that come close to these conditions for curing the sweet potatoes.

After curing, the sweet potatoes should be stored at 55F to 60F for six to eiight weeks. This storage  has been found to develop the sugars and the maltose sugar-creating enzyme. This enzyme will really kick in while baking at 350 F to 375 F to develop the sweet, syrupy sugars. An ideal place for storing could be a warm cabinet in your kitchen. A good example is shown below:

Sweet potato storage after curing. Image courtesy
Cured sweet potatoes can last several months without compromising the quality. The length of time normally varies depend on the conditions of storage. Following the above "optimum" curing procedures will ensure your sweet potatoes last as long as possible for the sweetest potato meal!

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