The court case against those convicted of profiting from the manufacture of gutter oil involves a huge amount of money and covers many provinces in China. So what are the dangers of eating so-called "gutter oil" and how can it be distinguished from oil that’s safe to consume.

Gutter oil is oil that’s been recycled from waste cooking oil. In some cases it’s produced using discarded animal parts, animal fat and skins, internal organs, and expired or otherwise low-quality meat which is then cooked in large vats in order to extract the oil.

Experts say gutter oil has been shown to be very toxic, able to cause diarrhea and abdominal pain and other serious health effects.

Fan Hongzhi, associate professor of China Agricultural University, said, "It can increase the chances of heart disease and diabetes. It also has implications for Alzheimer’s disease and has adverse effects on children’s development. It can also stimulate an increase of inner organ fat."

Deadly toxins found in gutter oil are aflatoxin and benzopyrene, which are among the most carcinogenic substances known.

Foods fried in gutter oil may contain large amounts of benzopyrene. Gutter oil processing techniques are also poor. So the amount of these toxins may be higher. If you eat such food over a long period, it can do considerable damage to your health.

According to the report, two or three million tons of gutter oil has made it onto China’s dining tables. But gutter oil can be distinguished from safe cooking oil.

Gutter oil usually is less transparent, and has an abnormal colour and bad smell.