Does your maple syrup actually contain maple?

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Different grades of syrup are lined up along a window inside of the Marvin's sugarhouse in Johnson, Vermont last April.Ian Thomas Jansen-Lonnquist for The Boston Globe

There are dozens in any grocery store, labels that claim maple flavor, carrying the promise of woodsy, intense sweetness, often with an illustrated flourish of a maple leaf.

Too many of those goodies, maple producers say, have no maple at all inside. Oatmeal, cookies, agave syrup — familiar brands and products of all kinds, they say — are made with artificial flavors, not the real thing.

"You're talking about an inferior product both in terms of quality and price," said Roger Brown, a co-owner of Slopeside Syrup in Richmond, Vt. "Marketing it as something it's not — that's why we have rules against that."

Some 31 US senators and congressional representatives have now gotten behind maple producers across the region and are demanding action. In a letter delivered last month to the Food and Drug Administration, the lawmakers asked the agency to "investigate and take action against misbranded products in interstate commerce."

"These practices seem to intentionally mislead consumers who get cheap, industrially produced sweeteners and artificial flavors rather than the pure and genuine natural product they believed they have purchased," the letter stated.

An FDA spokeswoman, Lauren Kotwicki, said in an e-mail, "The FDA is reviewing the petition and will respond directly to the petitioner."

Like few other products, maple syrup comes with a ready-made and compelling marketing message. From its earliest days, it has been touted as a pure product, with its light golden color that runs clear and amber, like sunlight. It is produced with hard, backwoods work, bearing the stamp of authenticity. For a time, in the 19th century, it was held up as a symbol of morality — a product made by free men rather then the slave-produced sugar of the West Indies and elsewhere.

Protecting the sweetener's image is key for the industry, which has seen lucrative crops in recent years. Revenue from maple syrup in the United States totaled $100 million in 2015.

The issue has been especially inflaming in Vermont, where some 4.5 million maple trees yielded 1.4 million gallons of maple syrup in 2015 — 40.7 percent of the nation's total, according to US Department of Agriculture data.

Massachusetts produced 75,000 gallons, Maine 553,000 gallons, and New Hampshire 154,000.

"False claims are meant to fool and cheat consumers, and they erode the well-earned reputation for quality of pure maple syrup," said David Carle, spokesman for Vermont Senator Patrick Leahy, one of the lead signatories on the FDA letter. "It's clear-cut theft, directly stealing income from maple producers in Vermont."

Carle noted that the labeling effort comes as Vermont prepares to enforce a bill requiring that all genetically engineered food be labeled. The bill takes effect in July. The push for greater transparency about maple products is part of the same focus, he said.

"It's about consumers' right to know," Carle said.

In a separate letter, maple syrup producer associations across the region highlighted several companies they said wrongly claimed maple ingredients. One was Quaker Oats and its "maple & brown sugar" flavor instant oatmeal. The ingredient list does not show maple sugar or syrup, mentioning only "natural and artificial flavors" among the other ingredients.

The company did not respond to requests for comment.

At Nature's Path, which makes organic breakfast foods, spokeswoman Wendy Kubota said that after a 2015 inquiry from Vermont's maple syrup makers, "we reformulated our Maple Nut Hot Oatmeal to include real organic maple sugar in the recipe. All the other products we make with maple in the name already contained real maple ingredients."

The push to keep maple syrup's image pure coincides with technological changes in the industry. Largely gone are days of buckets attached to trees and sap hauled away with yoked beasts. Today, the process involves tubes threaded through the woods to draw sap to a central location — a method that has helped US producers nearly triple output since 2000.

The increase has also been driven by healthy prices, said Mark L. Isselhardt, a maple specialist at the University of Vermont Extension's Proctor Maple Research Center.

"People are using it for more than their pancakes and waffles," he said. "And producers are happy to meet the demand."

Growth in the industry, with more large commercial outfits jumping in, has been steady, he said. United States maple syrup makers tapped 500,000 more trees in 2015 than in 2013, according to Department of Agriculture numbers.

Efforts to imitate the taste of maple syrup with imposter ingredients is not new. In the early part of the last century, shelves filled with syrup diluted by "glucose, sorghum, or corn; some purveyors added decoctions of maple wood, hickory, or even of corn cobs," according to the Atlantic Monthly. Producers and consumers alike cried foul, and the result was the passage of the Pure Food and Drug Act in 1906, the magazine noted.

For Brown, whose family in 2010 began making syrup from 20,000 maple trees on the property his grandparents used for a local ski area, the issue of falsely claiming maple as an ingredient means lost sales.

"When I offer samples of syrup at farmers market, one of the most common complaints I hear is, 'I don't like how it tastes.' But it turns out they have never tried real, pure maple syrup. People have an incorrect perception of maple flavor as this weird chemical taste," Brown said.