E-nose for food fraud: Chinese researchers develop rapid method to detect adulterated beef

Meat adulteration is a serious issue in China, where manufacturers deceive consumers by replacing expensive meats with cheaper alternatives, such as replacing beef with pork.

This not only compromises safety and quality, but also hampers the development of the regional meat industry.

Currently, methods to detect meat adulteration include chromatography, chromatography-mass spectrometry, immunoassay and polymerase chain reaction (PCR).

“Although such techniques show a high repeatability, objectivity, and accuracy for a rapid processing situation, they tend not to be the most ideal options, owing to factors like being time-consuming, tiresome, and entailing complex laboratory protocols​,” researchers said.

In the current study, they developed an electronic nose (E-nose) technique which utilised colourimetric sensors and chemometrics. Researchers claimed this is the first time colourimetric sensors have been used, and believe there is great potential for its use in the rapid detection of meat adulteration.

The study was published in the journal, Foods​.

Sample preparation​

For this study, fresh beef rib steaks and streaky pork were obtained from an agricultural market in Suzhou, China, and minced.

Beef was adulterated by mixing minced pork with the minced beef at different levels of 0, 20, 40, 60, 80, 100% by weight. The sample were then minced again.

For each adulteration level, 14 samples of 40g each were prepared. In total, there were 84 samples prepared.

E-nose setup​

The E-nose system was made up of four parts, colourimetric sensor array, reaction chamber, image capturing instrument, and computer.

The colourimetric sensor array was used to convert the chemical information of the volatile organic compounds (VOCs) present in the meat to the electrical signals via its colour changes.

The main groups of VOCs released from fresh beef and pork meat include hydrocarbons, ketones, alcohols, aldehydes, acids, esters, sulfur, and heterocyclic compounds.

The reaction chamber provides an airtight space for the chromogenic agents reacting with meat VOCs.

The image capturing instrument was used for acquisition of colour images of the sensor array before and after exposure to the odour of sample, and the computer was used for pattern recognition and results representation.

Data in colour​

Each reaction would last for five minutes, and each image created would consist of a distinct, unique, colourful fingerprint for the meat samples.

The colours contain digital information of the VOCs emitted by meat samples.

There are differences in species and concentrations of the VOCs emitted by the minced beef and pork, caused by their different general chemical compositions, which is the basis of the determination of beef adulterated with pork according to VOCs.

According to a report by Fitch Solutions​, China is the world’s largest meat market, consuming 86 million tons per year, more than twice the US.

The report cited that while consumers globally were concerned about health, environmental, and ethical issues when it comes to meat products, consumers in China were most concerned about the safety of their meat.

Researchers said this presents an opportunity for the rapid, low-cost E-nose method to detect minced beef adulterated with pork.

This work was sponsored by the National Natural Science Foundation of China, the Anhui Provincial Natural Science Foundation, the provincial Natural Science Research Project of Anhui Colleges, and the Scientific Research Startup Foundation for Professors (or Doctors) of Suzhou University.

Source: Foods

https://doi.org/10.3390/foods9020193​

“Detection of Beef Adulterated with Pork Using a Low-Cost Electronic Nose Based on Colorimetric Sensors”​

Authors: Fangkai Han, et al​.