Gold Medal Kung Fu Century Eggs Claimed to Be Lead-Free, but Pulled from Shelves After Copper Levels Found to Be Double the Limit

The Taichung City Government recently conducted random inspections of century eggs, candied fruits and young ginger, testing for heavy metals such as lead and copper as well as preservatives, additives and colorants. A total of 108 items were sampled, and 1 century egg product failed: the "Gold Medal Kung Fu Century Eggs (110 per box)" sold at a 7-Eleven in East District, Taichung, which was found to contain "heavy metal: copper 11.9 ppm" (standard: 5 ppm or below). The source was Hongliang Foods Co. in Pingtung City. The sampled store has been notified to remove the product from its shelves, and the case has been transferred to the Pingtung County Government Health Bureau for follow-up handling.

Century Eggs Are Set by Alkali Penetrating the Egg Liquid, and Added Heavy Metals Easily Exceed Limits

The Taichung City Health Bureau stated that "century eggs" are made by allowing alkali to penetrate the egg and set the egg white, which gradually turns transparent, giving the product a soft, springy and elastic texture. To raise the production yield, some operators may add "copper sulfate" or "copper oxide," resulting in excessive addition and levels above the limit. If the human body takes in too much of the heavy metal copper, it may cause physical discomfort, such as gastrointestinal symptoms and effects on liver and kidney function. The century eggs that exceeded the limit this time were labeled "lead-free" on the packaging, but testing found that their "copper" level was above the limit.

Chen Ming-ju, head of the Department of Animal Science and Technology at National Taiwan University, previously told News&Market that during the process of making raw eggs into century eggs and salted eggs, alkali penetrates the egg, so metallic lead or copper is needed to set the egg. Lead-free and copper-free production methods are currently under development, but the taste differs from that of ordinary egg products.