Methods for differentiating recycled cooking oil needed in China

By Qian Ye and Xiaofang Pei

In This Section

February 2012

Chinese consumers have been repeatedly impacted by food safety events over the past few years. Recently, recycled cooking oil has emerged as a food safety issue that challenges government authorities and consumers alike.

Recycled cooking oil, or “gutter oil,” is refined from kitchen waste, gutters, drains, and animal fat, as well as oil that has been repeatedly used to fry foods. By using a series of simple processes that include collection, preliminary filtration and boiling, refining, and the removal of adulterants, illegal gutter oil can be cleaned up enough to meet the sanitation standards of cooking oil and sold to low-end restaurants and small canteens. As a result, low-income people are major consumers of recycled cooking oil.

Although contamination with pathogenic microorganisms is not likely to be a problem in such recycled cooking oil, significant levels of toxic substances that remain in the oil, such as aflatoxins, polycyclic aromatic hydrocarbons, and 4-hydroxy-trans-2-nonenal (HNE), among others, might be harmful and could even cause cancers. So, the reuse of the gutter oil has caused great concern.

Why does recycled cooking oil make it back to the table? Significant profits are the major reason. Since the price of edible oils surged three years ago, a processor can easily sell one short ton of recycled cooking oil at half the price of fresh oil at a huge profit. For example, waste cooking oil can be purchased for about 3,000 renminbi (RMB), or $470 per ton. After a preliminary extraction, including deodorization, dehydration, and decolorization, the raw oil can then be re-sold at a price of 5,000 RMB per ton, while the retail market price of the end product is about 8,000–10,000 RMB per ton. Such huge profits lure greedy people to take part in this illegal practice, making it difficult to manage and control. Inadequate inspection, difficulties in identifying recycled cooking oil, and consumer habits, such as over-ordering at restaurants to show respect to guests, might also contribute to this phenomenon.

The Chinese government is taking several steps to address these problems and eliminate recycled cooking oil from people’s dining tables. It has launched a plan to cut off the source of the recycled cooking oil by uniformly collecting kitchen waste and gutter oil. Harsh punishments have been introduced in an effort to deter unscrupulous traders and manufacturers. Restaurants that are found to purchase and use the harmful oils will be immediately shut down and subjected to heavy fines in accordance with the Food Safety Law of China.

Eradicating the marketing and use of recycled cooking oil is not an easy task. There are too many small restaurants for the public health authority to oversee. Recycled cooking oil is also extremely challenging to identify, so the Chinese government has made national and global appeals to scientists to develop new analytical methods that can be used to differentiate gutter oil quickly and easily. No satisfactory suggestions have been obtained thus far. Meanwhile, some people may think that forbidding the use of recycled cooking oil is not based on risk analysis. So, assessing the risks of gutter oil in the kitchen could be a tough task for professionals.

Xiaofang Pei is an associate dean and professor in the West China School of Public Health at Sichuan University in Chengdu, China. She is also vice general secretary of the Association of Preventive Medicine in Sichuan, associate editor of Modern Preventive Medicine, and a member of the editor’s committee for the Chinese Journal of Health Laboratory Technology. She has been engaged in teaching and research in the fields of public health and microbiology, especially as they relate to food safety, since 1983 and has published more than 90 articles at home and abroad. Qian Ye is one of her students. They can be contacted at

More on China

Gutter oil is just one of many recent food scandals that have plagued China. In 2007, thousands of pets in the United States and Canada fell ill after eating pet food containing ingredients from China that had been illegally adulterated with melamine and cyanuric acid. A year later, 300,000 people in China became sick, and at least six babies died, after consuming milk powder—again, laced with melamine. Then, in April 2011, three children in China died and an additional 35 were hospitalized after drinking milk contaminated with nitrite.

According to a New Scientist article that appeared online at on August 2, 2011, China’s Food Safety Commission (FSC) has responded by ramping up its law enforcement. About 2,000 people have been arrested, and nearly 5,000 businesses shut down. Since the incident in April 2011, nearly six million food businesses have been inspected.

The central government has also strengthened food safety laws. The penalty for some infringements that formerly carried fines have been increased and now carry the possibility of imprisonment. In July 2011, the Chinese state-run news agency Xinhua reported that one man was given a suspended death sentence for producing and distributing clenbuterol, which speeds muscle growth in pigs but is poisonous to humans.

Yet, an article that appeared in Food ( on November 23, 2011, pointed out that while China has revamped its food safety laws, inconsistent methods, procedures, equipment, and resources as well as poor coordination between provincial and national governments make enforcement extremely challenging.

Interestingly, the December 2011 issue of the The Atlantic included an extensive feature article by Orville Schell ( about how the world’s largest retailer, Walmart Stores, Inc., is improving safety and the environment in China—by insisting that the companies it does business with implement higher standards.

Meanwhile, Food Production reported on December 5, 2011, that 5,575 International Organization for Standardization (ISO) 22000: 2005 food safety management systems standard certifications were awarded to food sector businesses in China in 2010—more than doubling the certifications awarded to Chinese food sector businesses in 2009, and accounting for almost a third of the 18,630 certificates issued worldwide in 2010 (see