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Quiet in the Peanut Gallery!

EuroPhotonics
Jun 2015

If you have a peanut allergy, you’re in for a bad time. A constant state of alert is status quo, with typical culprits (like peanut butter, peanut flour and peanut oil) on the blacklist and other, more subtle threats (like chocolate, pastries and candy) flirting with the prohibition. Even lawn fertilizer has been known to contain peanut hulls. Being the watchdog for this kind of danger is not easy, especially when vague warnings of “May contain peanuts” abound. Recent developments, however, might make the job a bit easier.

A team of researchers at Universidad Politécnica de Madrid (UPM) in Spain and the Institut national de recherche en sciences et technologies pour l’environnement et l’agriculture (IRSTEA) in France have adapted near-infrared (NIR) hyperspectral imaging (HSI) to measure peanut contamination in powdered foodstuffs.

“These results show the feasibility

of using HSI systems for detecting traces of peanut and similar products that are present in low percentages in powder foods with contrasting spectra,” said Puneet Mishra, graduate research assistant at UPM.

Any food product may contain traces of peanut if made with powdered foodstuffs, such as wheat flour, that were ground up in a facility that also grinds peanuts. Contamination can be impossible to prevent, since even trace levels of the legume represent a life-threatening problem for those who are allergic.

Several techniques already exist for detecting peanut contamination, such as enzyme-linked immunosorbent assay and real-time polymerase chain reaction. However, these techniques are destructive, tend to be time-consuming and work only with small samples.

Peanut GalleryNIR spectroscopy detects specific molecules based on their absorption and reflection of light. Peanut powder generates a NIR spectrum that is distinctive from those for wheat flour, powdered milk and cocoa. The problem with conventional NIR spectroscopy is that it collects an average NIR spectrum over a large area, allowing trace peanut contamination to be missed.

NIR-HSI, on the other hand, produces images with spectral data from every pixel. The researchers developed a scoring system to determine whether specific pixels in an image of wheat flour contained peanut powder, allowing them to estimate the contamination level.

Samples of wheat flour were spiked with powder from four types of peanut, including raw, blanched and roasted. The system detected peanut concentrations as low as 0.01 percent, though it could only accurately determine the level of contamination between 0.1 and 10 percent. Mishra and his colleagues are now looking to apply the same technique to other nuts.

“Although peanut is the most common cause of nut allergy, peanut-allergic patients are frequently also sensitive to tree nuts,” he said. “We are presently sampling different tree nut mixtures of almond, walnut and hazelnut to check the feasibility of HSI for detecting them.”

The research was published in the Journal of Near Infrared Spectroscopy (doi: 10.1255/jnirs.1141).



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