Step 2: Dry these dried sweet potato skins, store them, take them out and dry them again in about 5 days. At this time, dried sweet potatoes will have a slight frost.
Step 3: After drying and storing for half a month, the dried sweet potatoes are basically covered with a layer of natural frost. The longer the storage time, the thicker the frost and the higher the sweetness.
Extended data:
The frost on the surface of dried sweet potatoes is caused by the washing out of sugar inside.
Fresh dry sweet potato contains a lot of water, glucose and fructose. After drying, the water gradually evaporates, and the glucose and fructose contained in the pulp penetrate into the epidermis. These two kinds of sugar have different properties. Fructose tastes sweet and absorbs water easily. When it permeates the surface, it will catch the moisture in the air and attach to the epidermis, similar to the syrup outside the preserves. Glucose is not as sweet as fructose.
References:
Dried sweet potatoes _ Baidu Encyclopedia