Gold nanoparticles used to test the quality of maple syrup

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Producing the maple syrup we pour on our pancakes requires enormous precision and its quality is scrupulously inspected before it is made available for sale.

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But sometimes, undesirable flavours can make their way into the syrup and ruin its quality, to the dismay of maple syrup producers.

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Happily, researchers at the Université de Montréal, in collaboration with Federation of Quebec Maple Syrup Producers and producers in the field have developed a simple way of testing the sap with gold particles and nanotechnology.

Particles of gold “one one-100th the width of a hair” generally take on a red tint in the liquid in which they are placed. But when maple sap is added, the liquid turns blue.

“It’s like a test of the pH, or chlorine in swimming pools, explained Université de Montréal chemistry professor Jean-François Masson, co-creator of what is known as the COLORI test. The more drops one must add before the colour changes, the greater the chances that the syrup will be of good quality, he said.

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A total of 250 kits have been distributed this year as a pilot project, and researchers expect to invest more broadly in the market in 2024.

That way, producers can test for quality before “putting a lot of energy and time in making their syrup,” said Joël Vaudeville, director of corporate communications for the Federation of Quebec Maple Syrup Producers, and they can also compare the sap coming from different spots on their maple grove, which often extends over a wide area.

He welcomed the fact the test is “very simple to use” on site in the maple grove and that producers have access to an analysis grid to be able to interpret the results themselves. “This allows them to make business decisions,” Vaudeville said.

The Canadian Food Inspection Agency says that “defects in flavour … can be a trace of caramel, found most frequently in amber or dark syrup, or a trace of sap or bud found mostly in syrups of the end of the season,” among others. These defects can mean that the syrup can be used only in processing plants and not sold as is in stores.

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Besides unwanted tastes, there are four classes of syrup. Golden, with a delicate flavour, is produced at the beginning of the season and, as the season advances, the colour of the syrup darkens and the flavour becomes more pronounced.

With climate change, fluctuations in spring weather have become more pronounced, said Masson; over the past decade, “atypical flavour profiles” have been found in maple syrup, mostly at the end of the season.

The research to develop the test, supported by the Consortium de recherche et innovations en bioprocédés industriels au Québec, was published in the scientific journal ACS Food Science & Technology.