Today, the refined sweet potato starch sold in the market is refined from the starch contained in the sweet potato. Most of the adulterated are mixed with dried sweet potato and milled into fine powder.

It can be identified by the following two aspects:

Sound: use a pinch of starch powder between your thumb and forefinger to rub and twist. Pure starch is smooth and delicate and squeaks; the starch is rough and sluggish.

Water test: take a small amount of starch, put into a cup of water, stirring for a moment, pure starch will soon precipitate, the above water is still clear; and adulterated starch above the water is cloudy.