Experts say nation's current tests fail to detect all illegally produced samples

BEIJING - The country's food safety and health watchdogs are working jointly on finding an accurate scientific method to identify "gutter oil", as the current national standard for the content of edible oil fails to disqualify the illegal sort.

Gutter oil, or illegally recycled cooking oil, is often scooped up from sewage drains and gutters behind cooking establishments and then sold to small restaurants. More broadly, it also refers to oil refined from low-quality pork and animal offal as well as oil overused for fried food.