The Maillard reaction is arguably the world’s most beloved chemical process. Cooks learned long ago that raw, unappetizing ingredients such as potatoes and grains can be turned into toasty treats with the addition of heat and a bit of time.
Chemists know our enjoyment is due to the magic that happens when amino acids meet sugars to produce mouthwatering organic compounds such as pyrazines, pyrroles, and furanones.
But in 2002 the food world learned that this browning reaction has a dark side. It turns out that one of those Maillard products is acrylamide, a chemical long known to cause cancer in animal studies. In humans, it is considered likely to be carcinogenic and has been identified as a cancer-causing agent in tobacco smoke.
Acrylamide is used industrially to make polyacrylamides–water-soluble thickeners widely used in grouts and water treatment facilities. Because of acrylamide’s human health effects, regulators including the US Environmental Protection Agency have set very low limits for exposure in drinking water, similar to the levels for benzene.
The discovery of acrylamide in foods like crackers, cookies, potato chips, and french fries rattled food makers and health regulators around the world. Scientists learned that acrylamide is formed from the reaction of the amino acid asparagine with reducing sugars like fructose. But hundreds of variables—how crops are grown, cooking times, and even the type of leavening agent used—can affect the amount of acrylamide in a given food.
It is not possible to have the foods we enjoy while completely eliminating acrylamide, so reduction is the name of the game, experts tell C&EN. Moreover, no single approach will reduce acrylamide in all product types and manufacturing methods, say guidelines published by the trade group FoodDrinkEurope.
Ingredient suppliers have been working in their own labs and with customers to develop both customized and off-the-shelf solutions. Novozymes, Kerry, and DSM have products based on the enzyme asparaginase and say they are now popular tools to reduce acrylamide. When added to uncooked foods, the enzyme converts asparagine to the amino acid aspartic acid, preventing it from forming acrylamide.
Such products may look more appealing to food manufacturers now that new European Union voluntary targets are in effect. Under those guidelines, companies have to prove their foods’ acrylamide levels are as low as reasonably achievable, a principle known by the acronym ALARA. In California, activist groups commonly sue brands and retailers, claiming acrylamide levels in common products violate labeling requirements under the state’s Proposition 65.
“I would put acrylamide at the top of the list of priority chemicals for the food industry,” says Gina Reo, president of Quality Assurance Strategies, a food and beverage consulting firm. She says acrylamide is the leading chemical subject to Proposition 65 lawsuits against food companies and retailers. “Especially in the baking industry it is very problematic.”
Reo advises companies to follow the ALARA principle because there are currently no acrylamide levels that regulators have deemed safe. And, she points out, it is easy for a baked or fried product to exceed the EU’s voluntary target. For example, many common sweetened biscuits contain acrylamide near the target of 350 µg/kg.
“If you have a plan to consistently review and reduce acrylamide, that is your best weapon,” Reo says.
Those reductions are often hard won. Because the Maillard reaction adds aroma and flavor to foods, short-circuiting it can change the very attributes that consumers find appealing. Another problem is that healthier, whole-grain-based toasted foods can contain more acrylamide than products made with highly processed flour.
At the same time, food companies want to avoid ingredients that might turn off wary consumers. An enzyme like asparaginase is appealing because it is considered a processing aid and thus doesn’t need to be listed as an ingredient.
When the asparagine-to-acrylamide pathway first came to light, Novozymes saw an opportunity. “As an enzyme company you quickly think how you have these two reactions and they make this product—how do we stop that reaction?” recalls Fiona Becker, Novozymes’s R&D director for food and beverage.
“We had a lot of enzymes to try out,” Becker says. “We were positively surprised that asparaginase, one of the first enzymes we tested, worked very well and reduced acrylamide significantly.” Testing confirmed that the enzyme did not get in the way of other amino acid–sugar reactions in baked goods. But the company had to figure out how to make a lot of asparaginase at a price that would attract the food industry.
That was a pioneering application of new tools at Novozymes, Becker says. “We used a combination of gene sequencing, bioinformatics, and an in-house genome library” to find the right gene to use in the fermentation organism.
Food makers continue to evaluate a wide range of foods for acrylamide, and some find they need special versions of asparaginase. Becker says her research background in microbe discovery suggested to her that extreme environments would be a good place to look. Indeed, one organism Novozymes recruited is an archaea microbe first discovered in an undersea hydrothermal vent. Called Pyrococcus, it makes asparaginase and has an optimum growth temperature of 100 °C.
Similarly, DSM’s range of enzymes includes an asparaginase for high-pH foods such as masa-style corn chips and baked goods containing certain leavening agents, according to Man-Yee Chung, a global business manager for food specialties at DSM.
Customers of the ingredient firm Kerry get their asparaginase by chucking in a whole organism. In 2018 the company licensed a nongenetically modified yeast from the Canadian specialty yeast provider Renaissance BioScience. Its sole role is to reduce acrylamide.
Mike Woulfe, head of business development for enzymes at Kerry, says a target market is organic food brands. He says the firm has already had a fantastic response to the product. “It is the only truly non-GMO solution available in the market.”
Manufacturers of potato-based foods can reduce acrylamide by selecting potato varieties genetically modified to have low levels of asparagine and reducing sugars. The Idaho potato giant J. R. Simplot introduced the Innate potato in 2015. It was developed using RNA interference to silence a gene called Asn1 involved in asparagine biosynthesis and two genes, PhL and R1, that control the formation of sugars. Doug Cole, the company’s biotech affairs specialist, says Simplot is supplying the potato to more than a dozen potato chip processors in the US.
Food firms contacted by C&EN say they have put years of effort into meeting current guidelines on acrylamide, and they continue to seek reductions. Reo, the consultant, says Nestlé has been a leader in tracking and reducing acrylamide levels. A Nestlé spokesperson confirms that the firm has successfully reduced acrylamide in cereals, jar foods, and biscuits aimed at infants, considered a vulnerable population.
Experts tell C&EN that the food industry expects more stringent regulations within the next 2 years. That has inspired more work on acrylamide reduction. Last summer, Simplot licensed CRISPR-Cas9 and related gene-editing technologies for use in a future generation of low-acrylamide potatoes.
Unfortunately for food firms, researchers continue to find unhealthy substances that arise during cooking and frying. For example, reheating cooking oils results in potentially harmful lipids that may accelerate cancer progression. And in 2014, the EPA found that furfuryl alcohol, another product of the Maillard reaction, is likely to be carcinogenic to humans. It was added to California’s Proposition 65 list in 2016.
Ingredient companies don’t have a solution for furfuryl alcohol yet, but given the business opportunity, they are definitely on the case.