Flavor Modulation in the 21st Century

Pulling off the mask

Sobel is quick to distinguish tactics of taste blocking from the process of flavor masking. “The term ‘blocking’ refers to an actual physical interaction on the palate where you have chemicals that are blocking the taste receptors on the tongue,” he says. In masking, “you’re not using something that’s going to physically bind to the taste bud to block that perception. What you’re doing is using more of a psychological impact of competing responses from both the nose and tongue—because the flavor attribute is really coming from the nose; the taste attribute is really coming from the tongue.”

In other words, you’re playing head games. “Masking really takes advantage of understanding that psychological response in the brain,” Sobel says. “All signals going from the tongue, and also from the olfactory bulb, compete for time within the brain,” he explains. To mask caffeine’s bitterness, he says, “you could go ahead and put a flavor in there—something like a vanilla flavor, for instance—at a very low level. This confuses the brain to preferentially perceive the vanilla flavor, because the brain, from a very early age, is trained to like vanilla flavor.”

Flavor modifiers “have little or no taste of their own,” says Gascon. They are “chemicals or extractives or substances that have proven to have an effect on the way you perceive food. They complement, enhance or modify the flavor of what you use them in,” he says. They do so through mechanisms such as adaptation (fatiguing the palate on a particular taste or flavor), cross-adaptation (raising or lowering the perception threshold for one substance by fatiguing the palate on another), taste-blocking (literally blocking the ability to perceive certain flavors or tastes), and taste modification (completely changing a taste or flavor perception from what’s expected).

Sometimes a stealth flavor modifier needs help. Flavor chemists may start with a silent base and accessorize it with identifiable flavors. Ray Hartman, senior flavorist, FONA, calls this flavor pairing. “A good example would be if you’re trying to block bitterness in some type of product,” he says. “So you use a masking agent to mask or offset your bitterness, and then you pair it with a grapefruit flavor to meet consumers’ expectations for bitterness, because grapefruit actually has its own bitterness.”

Similarly, Sobel worked on a product that “had a sulfurous off note,” he says. Mango flavor solved the problem. Because mango carries a slight sulfuric note of its own, it piggybacks onto the undesirable sulfur and brings it over to the acceptable side.

Matching like with like isn’t the only option, says Jean Gallagher, technical solutions manager, FONA. “It may be something where you want to pair known and unknown so that you’re sending something of a confusing signal, if you will,” she says. “It’s disruptive, and yet pleasant.”

Sometimes, masking may not be the biggest obstacle. “I think the hardest challenges aren’t so much covering up off notes,” Sobel says, but “matching the temporal width of a flavor perception.” Consider the example of a caffeinated chewing gum. While a masking system based on cinnamon is a common solution, “the issue then is that the cinnamon flavoring doesn’t last long enough,” he says. “So what happens is the caffeine starts to come through after you start chewing for a while, and then you have to start exploring other options of how you get flavor duration to occur.”

Modifying from the ground up

Matching the desired profile with the starting base is the only way flavor modification works. “We always look at the end product and keep that in mind throughout the process,” Sobel says. “By understanding the overall complexity of the finished product, that gives us a better strategy for how to approach it.”

Processing and storage are always important. “Heat, preservatives and so on will influence the off-note formation in the finished product,” says Yep. “Also, you don’t want the processing conditions to cause unnecessary reactions. Sometimes off notes don’t really get pronounced until the product has been on the shelf or exposed to light. So a masking system may need to be developed to handle future off notes—not necessarily just the taste of the product right off the line.”

The take-home message is nothing new: Flavor modulation is best pursued on a case-by-case basis. “There’s no one silver bullet that’s going to address the issue of difficult ingredients, nor is there any one flavor that is going to do the job adequately,” Gallagher says.

“That’s why there are a lot of different approaches,” adds Hartman. “There’s masking, there’s flavor enhancement, there are modifiers—there’s just not one pathway to success on these projects. You could use compounds that block taste on the tongue. You could use ingredients that work synergistically with other compounds or other basic tastes. There are multiple ways to tackle the problem. At the end of the day, what’s going to define success is whether or not this product is preferred.”

Kimberly J. Decker, a California-based technical writer, has a B.S. in Consumer Food Science with a minor in English from the University of California, Davis. She lives in the San Francisco Bay area, where she enjoys eating and writing about food. You can reach her atkim@decker.net.