Just when you’d dodged or denied every doubt about your favorite roadside stir fry, another palate spoiler has made its way to the dinner table.

A recent student investigation in Wuhan led by tireless food crusader Professor He Dongping has revealed 2-3 million tons of ‘swill oil’ makes its way back to our rice boxes and meals out each year. It is usually sold as pig feed.

And we’re not talking recycled cooking oil (as in the proper way), but stuff from the country's drains and gutters treated to look like edible cooking oil in a lucrative night-time operation. One of the components of this swill oil is aflatoxin, a potent carcinogen. Yummy.

This 'distilled sewage' is then sold on, and the study estimates one in 10 of China's restaurants use it to cook their food. Diners might be torn on what to find more disturbing -- the thought of consuming swill oil or the fact that this illicit practice has been an ‘open secret’ in the food industry for some time. ChinaSmack even reported on the practice last year, with some pretty unappetizing pics.

Kind of makes the other bad-food story to have emerged recently, that of a dodgy dealer in White Rabbit Creamy Candy selling tons of product that was five years past its expiry date, look rather tame and fluffy in comparison.