Researchers develop artificial ‘tongue’ for more accurate taste testing

In a study published in Analytical Methods​, the researchers detailed how they used an artificial 'tongue' with gold taste buds to test maple syrup.

The 'tongue' is a colorimetric test that detects changes in colour to show how a sample of maple syrup tastes. The result is visible to the naked eye in a matter of seconds.

"The artificial tongue is simpler than a human tongue: it can't distinguish the complex flavour profiles that we can detect,​" said UdeM chemistry professor Jean-François Masson, who led the study. "Our device works specifically to detect flavour differences in maple syrup as it's being produced."​

Masson told FoodNavigator that the ‘tongue’ is a solution of gold nanoparticles, which is bright red in colour and similar to a pH test for swimming pools. You simply pour a few drops of syrup into the gold nanoparticle reagent and wait about 10 seconds, he explained. The colour of the solution changes from red to blue in presence of different tastes profiles.

If the result stays in the red spectrum, it has the characteristics of a premium quality syrup, the kind best loved by consumers and sold in grocery stores or exported.

If, on the other hand, the test turns blue, the syrup may have a flavour "defect", which may be treated as an industrial syrup for use in processing.

"It doesn't mean the syrup is not good for consumption or that it has a different sugar level,​" Masson said of the "blue" type syrup, which the food industry uses as a natural sweetener in other products. "It just may not have the usual desired characteristics, and so can't be sold directly in bottles to consumers."​

60 categories of taste

According to the researchers, the taste of maple syrup has as many as 60 categories to fit into including caramelized, woody, green, smoked, salty -- burnt maple syrup is essentially a concentrated sugar solution of 66% sucrose and 33% water; the remaining 1% of other compounds determines the taste.

Like wine, the taste of maple syrup changes according to a variety of factors, including the harvest period, the region, production and storage methods and, of course, the weather. Too much variation in temperature over a weekend, for instance, can greatly affect the taste profile of the product.

The artificial tongue developed at UdeM could someday be adapted for tasting wine or fruit juice, Masson said, as well as be useful in a number of other agrifood contexts.

“We anticipate that the test could be used to test other sugary foods, such as honey or juices and other products that the taste profile changes throughout the harvest season. Of course, the test would need to be adapted to the molecular complexity of these other applications,”​ Mason told us.

He said he envisages the test enhancing areas such as wine tasting, sensory panel and consumer tests. “The test will not replace tasting, as the human tongue can detect more subtle changes in flavour. In addition, wine is meant to be consumed, such as is for maple syrup, so sensory panels are still highly relevant. However, the test removes subjectivity in some contexts, as reported in our study for the detection of a buddy flavour in maple syrup, which can be interpreted differently by some expert panel. So, it must be seen as a supplementary tool to properly categorise food.”​

The artificial tongue was validated by analysing 1,818 samples of maple syrup from different regions of Quebec. Masson and his team plan to increase the number of samples tested, as 1,800 tests ‘only represent 0.6% of the production in Quebec’. “We are working on ramping up the test capability to have a larger fraction of the production tested to further validate the test," ​he said. "We are also interested in understanding the molecular changes in the taste profile change of maple syrup, to provide a scientific explanation of the change in maple syrup taste.”​

Source​​

A high-throughput plasmonic tongue using an aggregation assay and nonspecific interactions: classification of taste profiles in maple syrup​

Analytical Methods​

Authors: Simon Forest, Trevor Théorêt, Julien Coutu, Jean-Francois Masson

DOI: 10.1039/C9AY01942A​