Optical Sensor for Food Safety

Molecular laser spots potential carcinogen in food.

01 July 2017

A molecular laser spectroscopy technique developed at VUB B-PHOT, the Photonics Team at Vrije Universiteit Brussels, could help spot early signs of elevated acrylamide levels in potatoes, tackling a current concern in food safety.

Acrylamide is formed when bread, potatoes, and other foods rich in starch are cooked for too long or at very high temperatures. The International Agency for Research on Cancer (IARC) classifies acrylamide as a “probable human carcinogen” based on data showing it can increase the risk of some types of cancer in lab animals. The chemical is the subject of a campaign by the UK Food Standards Agency to raise awareness of the dangers of overcooked toast and other staples.

Photonics 21 logo The nondestructive scanning technique developed by SPIE member Lien Smeesters, a post-doctoral researcher at B-PHOT, earned the 2017 Photonics21 Student Innovation Award, which is sponsored by SPIE and Hamamatsu. Smeesters’ innovation scans peeled potatoes before they move into the food manufacturing process, weeding out those that may cause high levels of acrylamide when subsequently cooked.

In collaboration with Tomra Sorting Solutions, her technique will be incorporated into a sorting operation for French fries, identifying the items to be removed while they are in free fall, and doing so without the need for added chemicals or dyes.

An infrared laser scans the falling chip from both the front and rear sides and detects the characteristic molecular fingerprint of elevated levels of acrylamide precursors in the light that emerges from the potato after internal scattering. Having been identified in mid-air, a directed jet of air removes the sub-standard item from the food stream.

“Not all potatoes result in excessive acrylamide formation during frying,” Smeesters says. “We have sought to spot the undesirable potatoes when they are in their raw, peeled stage. After scanning with laser beams, the good potatoes will emit a different light signal than the unsuited ones leading to an unambiguous detection.”

The potatoes with acrylamide precursors do not have to be thrown away, however. Smeesters noted that they may still be suitable for low-temperature processes, such as in making mashed potatoes or soup.

SPIE CEO Eugene Arthurs (left) and Lien Smeesters at the Photonics21 meeting earlier this year.

Previous research by B-PHOT in this area, including Smeesters’ doctoral thesis, demonstrated the potential value of molecular spectroscopy in identifying food contaminants such as mycotoxins, poisons produced by toxic fungi. A case study investigated the use of fluorescence techniques, in particular one- and two-photon-induced fluorescence spectroscopy, as a means to spot aflatoxin in individual kernels of maize. The technique accounts for the natural fluorescence of proteins in maize as well as the variations in density and texture of the material under analysis.

The new contactless operation for potatoes could ultimately lead to an operation suitable for domestic use, making it available to users in the kitchen.

“Although we are a long way off, the miniaturization of the technology would enable a compact potato quality test tool in your home,” Smeesters says. “A hand-held device indicating whether a potato would be unsuited for frying could reduce our exposure to acrylamide.”

Smeesters, a member of SPIE Fellow Hugo Thienpont’s research group, was an active member of the SPIE VUB Student Chapter, the largest SPIE Student Chapter in Western Europe.

Smeesters said the Photonics21 award shows the importance of applied scientific research and the ability of optical technologies to solve real-life problems.

“I want to thank B-PHOT and Tomra Sorting for the opportunity to work on this exciting research topic,” she said, “and for enabling the integration of the technologies I developed into the state-of-the-art optical sorting machines.”


A recorded presentation from the 2017 SPIE Defense + Commercial Sensing event on optical tools for food quality and safety is freely available on SPIE.org.

Richard Crocombe, cochair of the next-generation spectroscopic technologies conference, discussed recent advances in optical tools to meet food safety challenges such as chemical contamination and food fraud.

Crocombe, a consultant in handheld and portable spectroscopy, delivered his talk at a photonics industry session and covered the way portable analytical instruments can detect melamine in powdered milk, horsemeat sold as ground beef, and “chicken” eggs that have not come from chickens.

View the presentation: Photonics and Food: Optical Tools Tackle Food Safety Challenges

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