Ultra-sensitive probe modernizes food safety

Everyone depends on food, and people in Hong Kong, in particular, love their food. In recent years, food safety risks have gradually increased mostly due to food spoilage, one of the oldest risk factors. Everyone remembers how elders warn of contamination due to the “disease from the mouth” and it continues to be a concern nowadays. In addition to food labels, integrated technology can help. An invention from the Education University of Hong Kong reminds you to consume food when it is fresh before it becomes spoiled.

The traditional testing method

Checking the freshness of food has been passed down over thousands of years through human experiences making it possible to distinguish between good and bad food in different environments.

Let’s go back to the basics and use folk wisdom to try and “check” the freshness of food with our sense of touch!

Question 1
What is the smell of meat going bad?

Stinky Sour Bitter Salty

Correct answer: Stinky。
The meat is spoiled because of the sulfur chemical, so it stinks.

Question 2:
What is the smell of spoilt fish?

Stinky Sour Fishy Salty

Correct answer: Fishy。
Fish becomes fishy due to the presence of nitrogen compounds.

Question 3:
When milk is spoiled, it will become...

Stinky Sour Fishy Salty

Correct answer: Sour。
Spoiled milk turns sour because organic acids

Question 4:
What happens to the smell of alcohol when it goes bad?

Stinky Sour Salty Bitter

Correct answer: Bitter。
Bitter. Alcohol becomes bitter due to an organic chemical called phenol.

The basic human instinct to distinguish good or bad food is by taste and smell. Nowadays, “food safety labels” are more commonly used to remind people to consume food early to avoid food safety risks, such as “Use by” and “Best before”. However, the freshness of chilled food is affected by many external factors and canned food is even more difficult to distinguish by its smell.

Solutions to prevent spoilage

Statistics tell us that bacteria in food is the primary cause of food poisoning.

Food spoilage is a troubling issue as it damages people’s health, the economy, and reputation in the food industry. The most direct way to deal with spoiled food is to throw it away, which creates more municipal solid waste. However, ordinary food safety tests are tedious and slow. Problems are usually identified after contamination or else following the sale or consumption of rotten food items.

To solve these problems, Chow Cheuk-Fai Stephen, Professor of the Department of Science and Environmental Studies at the Education University of Hong Kong, worked with a team of 13 researchers with professional backgrounds in chemistry, microbiology, engineering and materials science, to develop over the years a convenient, rapid, effective method, which utilises conventional wisdom and new technology to test the freshness of food.

Chow Cheuk-Fai Stephen, Professor of the Department of Science and Environmental Studies at the Education University of Hong Kong

Needle Taste Test
Combining traditional wisdom and innovative technology

Professor Chow got inspired by many scientific journals. The smell released from food can be a key indicator of food spoilage meaning meat spoilage is closely related to smell. However, people can’t use their smell to detect the condition of well-packaged food such as canned food and packed fresh food stored in the fridge. Therefore, a food sensor is needed to check for the freshness of food in the container.

The team created a “food sensor”using supramolecular chemistry. The team developed chemical sensing technology that allows the sensor to dissociate and exchange its constituents to identify the freshness of food in a targeted and sensitive manner.

Common meat such as chicken, pork, beef, and seafood generates biogenic sulfides when it is spoilt. Therefore these biogenic sulfides can be used to indicate food quality. The sensor invented by the team will only react to sulfides. Thus, users can identify whether the food is rotten through the colour change in the sensor.

A short video of this research project

The development of the food sensor is still a work in progress. When completed, the food sensor will become a chip. Users can put the food sensor on a special food container and it can dectect biogenic sulphides in the headspace of the container. Colour of the food sensor will be changed to reflect the the freshness of meat or food.

Supported by the Innovation and Technology Fund (HKSAR) and a private technological company, the research team filed 3 patents, and their work was referred in international journals on more than 100 occasions. The team currently collaborates with sushi factories and restaurants that stock large quantities of fresh ingredients. After trial, it will be launched in the industry. The team has also begun work on the next generation of food sensor that can identify the freshness of dairy and alcohol products.

The prototype of the food sensor

The prototype of a food container carrying a food sensor

Since Professor Chow began his research career, his work has been inextricably linked to food safety. As one of the committee members of the Environmental and Conservation Fund Waste Reduction Project Vetting Subcommittee, EPD, HKSAR, he is delighted to see his work go from the laboratory to the real world.

He added that the motivation behind the research is due to food waste. Also, the F&B industry faces the challenge of curbing food poisoning caused by food spoilage. Therefore, he was inspired to improve the situation with his inventions. “Research is not a distant thing, it is inspired by daily life. Knowledge, chemical tools and even creativity can solve problems large and small.”

He also advised the new generation of researchers that although the road of research in Hong Kong is difficult, it is like a long-distance race, which may not be smooth in the middle. Yet, with the accumulation of experience and momentum, the run will become smoother to reach the destination.

Hong Kong Research Portal