It is believed that some bleaching agents widely used in flour production contain as much as 30 percent pulverised lime, an inedible substance that has been linked to health problems, said China Daily.
Bleaching agents, usually made from cornstarch, are added to flour to shorten the time needed for whitening. Substituting cheaper and heavier lime for cornstarch cuts the cost of producing the bleaching agent, which is sold by weight.
Consumption of pulverised lime can lead to gradual damage to the lungs and eventually the entire respiratory system.
In 2008, it was revealed that Chinese milk powder manufacturers were employing identical methods by substituting melamine into their product in order to boost its apparent protein content. An estimated six people died and 300,000 were sickened as a result of the practice, which also sparked global concern over the laxity of food safety in China.
Yuzhong Food Additive Company in Rugao in East China's Jiangsu province is alleged to have added 500g (1.1 lbs) of pulverized lime to every 2 kg of bleaching agent, according to sources in the company. Legal Weekend, a publication run by the official Legal Daily, said the workers turned whistleblowers on fears the practice could cause a major health scare.
The report cited the company owner, Chen, as saying his company was able to undercut rival bleaching agent prices by almost 20 per cent as a result of the adulteration practice. Yuzhong sold bleaching agents to big flour mills in Jiangsu and neighbouring Shandong and Anhui provinces.
Flour is mostly used to make noodles, dumplings and steamed buns in China, especially in the north.
China media reports said domestic bleaching agents used in flour production are usually a blend of benzoyl peroxide (BPO) and corn flour. Using pulverised lime instead of corn flour reduces costs because the tainting substance is cheaper weighs more than the edible ingredient.
No regulations were found expressly prohibiting use of pulverised lime as a food additive. However, experts are reported to have said its use was “definitely forbidden”.
Chen Junshi, a leading researcher with the national food safety and risk assessment committee, said adding the compound is unlawful.
"I don't think it's a hidden rule in the industry," he said