There is a famous snack in Changsha, Hunan, named strong-smelling preserved bean curd. Lot of visitors in Changsha would like to try this snack. One of my friends interests in it very much. We'll go to the most famous street to eat once she comes to Changsha.
But presently, it's not so easy for us to eat, because some of street pedlars put something harmful to health into preserved bean curd, like iron vitriol (industrial ferrous sulfate). These make us very worry, some pedlars use ferrous sulfate and sodium sulfured to make preserved delicious.
In fact, ferrous sulfate is divided into industry grade and food grade, but the price of food grade ferrous sulfate is very high, and will cut the benefit of pedlars. So they choose industry grade ferrous sulfate to replace.
It will harm people’s health seriously, it will thrill pneogaster and will occur the cough and hard breath, and also harms to eyes, skins and mucous membrane, what’s the worst, it will occur shock and stupefaction even die.