An unwanted chemical on the bucket list

As if collecting the sap of maple trees and transforming it into syrup were not challenging enough, sugar bush operators can find all their hard work ruined in its final stages by an off-flavour that goes by the ironic name of “buddy”. Although the suspected cause is some organic constituent absorbed by sap as it makes its way through the inner recesses of the tree, this problem has remained unexplained and unpredictable.

Each spring, as days lengthen and it gets warmer, the chemistry of the sap change to allows tree buds to break and form leaves. This change had not previously been studied, explains Ray Bonenberg, who runs a maple syrup operation in the Ottawa Valley. It was known that alkyl-pyrazines are formed when boiling the sap to make maple syrup, as well as dimethyl disulfide and dimethyl trisulfide. When present in food, the pyrazines that show up in late season “buddy sap” have an aftertaste characterized as “malty” or “astringent”. Compounds such as dimethyl disulfide and dimethyl trisulfide yield flavours described as “peppery” or “brassica”. The effect may not be obvious until it is too late.

“It’s like over-date orange juice or Kool Aid gone bad,” adds Bonenberg. “You get a fizzy mouth feel. We call it micro-bile.”

As a member of the executive of the Ontario Maple Syrup Producers Association, (OMSPA), which represents some 3,000 maple tree farms in Ontario that annually yield millions of litres of syrup worth upward of $70 million, he notes that the industry has typically relied on little more than tradition and experience to avoid buddy. Since the presence of the unknown agent appears to be linked with warming, for example, many operators will wind up their sap collection as soon as overnight temperatures rise to the point where frogs begin singing. Apart from such subjective insights, however, there has been little formal investigation of what might be responsible for this unwanted effect on the sap and how to deal with it.

Now one of the first-ever scientific examinations of buddy is shedding light on what might be causing this contamination and, more importantly, how it might be prevented. Eloy Jose Torres Garcia, a student at Fanshawe College in London, Ontario, has completed a comprehensive analysis by LC MS-MS of hundreds of maple sap samples from across the province, which has yielded important chemical clues. He has identified some two dozen distinct biomarkers as candidate precursors to the formation of buddy syrup.

Garcia, a microbiologist who is originally from Colombia, notes that the sugary makeup of the sap is generally well known and straightforward, but the more subtle chemical features that supply the unique qualities that make up the taste of maple syrup are still being explored.

“They have their own chemical signature and no one knows what it is,” he says. “It is a complicated problem, but that is the beauty, that is the challenge.”

The study revealed likely precursors of the off flavours to be the amino acids asparagine and methionine. Concentrations of these agents can increase by a full order of magnitude from early in the season to later. The next phase of the research is to develop a test, perhaps based on aptamers, to detect high concentrations of the two suspect chemicals. Such progress has been made possible OMSPA’s help; the organization coordinated with a dozen of its members in southern and Northern Ontario, who sent specifically selected samples from their trees to Garcia’s lab.

OMSPA also collaborated with the research agency Mitacs to create a paid internship for Garcia to conduct his ground-breaking work. Mitacs, a non-profit agency supported by the federal and provincial governments, matched OMSPA’s financial contribution as part of an ongoing partnership with Fanshawe. The Mitacs internship program seeks out private sector partners to provide this kind of employment opportunity for students, which greatly improves their ability to find future careers in research and development.

For Garcia, who formerly studied cell biology in humans when he was in Colombia, this shift into the intricacies of arboreal biochemistry has been demanding, but it has been made all the more satisfying by the prospect of helping an iconic Canadian enterprise. “It has been a big jump, but it has been a nice journey,” he concludes.