Chinese researchers unmask toxic 'gutter oil' used in cooking

Date: Aug-27-2014 There is a growing public health problem in China due to the illegal use of waste cooking

oil - also known as "gutter oil." To tackle it effectively, the authorities need better ways to

rapidly distinguish the dangerous oil from safe, edible cooking oil.

In their paper, the authors describe how investigations show gutter oil contains toxic substances ranging from harmful bacteria to heavy metal, and fatty acids.

Now a team led by Professor Hongbin Ding at the Dalian University of Technology, in

northeastern China, has developed a new method, using laser-induced breakdown spectroscopy

(LIBS), to differentiate safe cooking oil from toxic gutter oil.

Prof. Ding and colleagues at the university's School of Physics and Optoelectronic

Engineering, describe how they developed and tested the new technique in the Chinese Science

Bulletin.

Gutter oil - which the Chinese call "di-gou-you" - is leftover oil from restaurants, and is

widely used in China. In their paper, the authors describe how investigations show gutter oil -

which they refer to as trench oil - contains toxic substances ranging from harmful bacteria to

heavy metals and fatty acids.

In the long term, consumption of gutter oil can lead to serious liver problems, including

cancer, and it can cause developmental disabilities in children and newborn babies.

Trade in gutter oil persists as authorities lack effective detection tools

However, despite punitive measures by the Chinese government, the lucrative trade in gutter

oil persists. The situation is further hampered by a lack of tools that rapidly distinguish

illegal gutter oil from legitimate edible cooking oil.

Illegal traders use various techniques to make gutter oil look like genuine edible cooking

oil: they bleach it to make it lighter in color, and they add alkalis to neutralize the acidity

caused by the high levels of animal fats.

Based on stories in the Chinese press, if you eat out in China, you are likely to be

unwittingly consuming gutter oil at a rate of one in every ten restaurant visits.

In their study, Prof. Ding and his team show how a technique called laser-induced breakdown

spectroscopy (LIBS), which is used in the quantitative and qualitative analysis of solids,

liquids and gases, can be used to rapidly differentiate between gutter oil and legitimate edible

cooking oil.

LIBS is one of the technologies that the ChemCam on NASA's Curiosity rover is using to analyze

rocks.

First study to show successful use of LIBS to detect gutter oil

In this study, the device uses a high-energy laser beam to vaporize and excite a sample of the

oil into a plasma that emits a unique spectrum characteristic of the chemical composition of the

oil.

By analyzing the spectrum using principal component analysis (PCA) combined with an Artificial

Neural Network (ANN) model, the team created a new approach that uniquely identifies the elements

in the gutter oil, and allows it to be quickly and efficiently differentiated from genuine

cooking oil.

The LIBS technique is viewed a big step forward in chemical analysis because it has many

advantages over current methods such as requiring little or no sample preparation, its fast

analysis time, and the fact it can sense substances remotely - on Mars some of the rocks LIBS is

sampling are up to seven meters away from the rover.

The study is the first to report successful use of LIBS to detect gutter oil. Prof. Ding and

colleagues have developed software that allows rapid analysis from a single shot LIBS spectrum.

They conclude:

"The achieved identification accuracy based on PCA and ANN was 94.2%, 98.1%, respectively.

This indicates that LIBS detecting technique based on PCA and ANN statistical analysis brings a

new possible approach to identify trench oil efficiently and quickly."

In May 2014, Medical News

Today reported how researchers in Canada are developing a new forensic tool that detects ethnicity and gender in a single hair. The method, which uses spectroscopy, takes only 85 seconds to complete.

Written by Catharine Paddock PhD

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Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.