Just unearthed sweet potatoes.
By Terra Brockman
As soon as frost threatens here in Illinois, my brother Henry drops everything and calls all hands to come help dig the sweet potatoes.
As I walk the rolling hills to his rich bottomland fields, my footsteps prompt the plaintive call of the Japanese yaki-imo man whose refrain -- "yaki-imo, ishi yaki-imo " (roasted sweet potatoes, stone-roasted sweet potatoes) -- resonates in my head.
This East meets Midwest moment is not so strange since both Henry and I spent the better part of the 1980s in Japan, and since sweet potatoes were grown all over the warm zones of the Americas for some 5,000 years before they were "discovered" by Europeans and disseminated throughout the rest of the world. China now produces most of the world's sweet potatoes.
In temperate zones like Illinois, we need to balance keeping the tubers in the ground as long as possible, with getting them out as quickly as possible when the temperatures fall. It's during those last weeks when the sweet potatoes enter an exponential growth phase, but as soon as the soil temperature falls below 55 degrees, the tubers will begin to rot.
Meats are often cured with smoke or a mixture of salt, sugar and nitrate. Some vegetables, such as garlic and onions, are cured by dry air, and others by high temperature and humidity. Sweet potatoes need this latter cure, which causes the periderm, the skin and layer underneath it, to thicken and reform, healing any bruises or cuts, and triggering the development of enzymes that convert some of the starch in the roots to sugar.
After curing, sweet potatoes can last up to six months if they are stored between 55 and 60 degrees. Any temperature lower than that, like in your refrigerator, will lead to the same problems caused by the cool autumn soil, namely, rot.
Storage at the proper temperature improves sweet potatoes, as the maltose sugar-creating enzymes continue to work. Some years, our family has had perfect sweet potatoes clear into May, bringing us full circle to when the new slips are in the hoophouse getting ready to be transplanted for the next season's sweet potatoes.
Here is his method, which is very similar to that used by me and the yaki-imo man.
If you don't have a fire handy, simply roast the potatoes in a heavy roasting pan at 375 F until they can be easily pierced with a fork. In this method, the sweetness and piquancy of the potato is brought out in a manner hardly obtainable in any other way. Cover them with warm ashes to a depth of 4 inches. On top of the ashes, place live coals and hot cinders. Let the sweet potatoes bake slowly for at least two hours.
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