It's the season for new and old potatoes to alternate. The market is filled not only with old and new potatoes, but also with refurbished old potatoes. It has been reported that unscrupulous merchants use bamboo skewers to remove the sprouted parts of old potatoes. After washing, soaking, and smoking, they are sold as new potatoes.
When old potatoes are refurbished, only their appearance is changed; solanine is not removed. Solanine is a toxin produced when potatoes sprout. Consuming 200 milligrams of solanine, which is roughly equivalent to half a liang (about 25 grams) of a sprouted and greened potato, can cause poisoning. A person poisoned by solanine will first feel a scratchy throat, followed by severe abdominal pain, vomiting, and diarrhea—a very unpleasant experience. During the refurbishment process, old potatoes may also be soaked in a solution of sodium metabisulfite, as it can make old potatoes look brighter and prevent spoilage. However, this solution has certain carcinogenic properties, and its residue, sulfur dioxide, can damage the respiratory system and cause various diseases.
New potatoes and old potatoes are actually quite easy to distinguish. The former have thinner skins, more moisture, and a fresh, bright color when cut, while the latter are the opposite: they have thick, spotted skins and a dull interior. However, how can you tell the difference between truly new potatoes and refurbished old ones?
Look at the eyes. New potatoes typically have shallower eyes, while old potatoes have deeper ones. Refurbishing cannot change the depth of these eyes. If a potato looks new but has deep eyes, be cautious.
Squeeze the flesh. When buying potatoes, you can gently pinch them. If juice seeps out, it means the potato is new. If no juice seeps out and the potato still looks new, you have likely encountered a refurbished old potato. Although refurbished old potatoes have been soaked in a special solution, they still contain little moisture. They feel hard and lack elasticity when pinched.
Rub the skin. The skin of a new potato rubs off easily, whereas the skin of a refurbished old potato does not.