There's something fishy about the shark-fin soup found at various restaurants in Beijing, Zhengzhou and Nanjing, and not in a good way. It might not actually contain shark and could be toxic, according to an exposé by a state broadcaster yesterday. The revelation came after a reporter with CCTV went undercover as an apprentice at a high-end restaurant in Zhengzhou, the capital of Henan province, and became an assistant to an unidentified chef responsible for making dishes containing abalone and shark's fin, the report said. "It's commonplace for high-end restaurants to mix real shark fins with fake ones in the soup to serve to customers, while those we make are largely counterfeit ones," the chef was quoted as saying, adding that "ordinary customers have no way of differentiating real shark fins from fake ones". And the chef said that if a customer did raise questions about whether the shark fins in their pricey soup were genuine, the restaurant offered them an alternate complimentary dish to appease them. The broadcaster said it found similar problems involving fake shark-fin soup in restaurants in Beijing and Nanjing. Zhu Yi, an associate professor of food science at China Agricultural University in Beijing, said that after examining samples collected from some of the restaurants, he found the supposed shark fins being used for soup were mostly made of edible gelatin and sodium alginate, with a bit of calcium chloride. He also said that a dish made with fake shark fins contained almost no nutritional value at all, but was basically safe for people to eat. However, Zhu also found excessive amounts of a toxic and pungent chemical compound called trichloroacetone in a shark-fin-soup sample sold in Tongzhou district, in the outskirts of Beijing. The report said the chemical was toxic to the reproductive system, kidneys and liver.