Skip to main content

We have far more bitter receptors than we do salty, sweet or umami.Photography by Hamin Lee; prop styling by Christina Yan

You may have experienced the bitter taste test in science class – an experiment that involves putting a treated paper strip on your tongue to determine how sensitive your taste buds are. For me it was at a food writers’ workshop in the Okanagan. The speaker, while discussing the five basic tastes: sweet, sour, salty, bitter and umami, passed out small white strips of paper that could detect whether we were able to detect certain bitter compounds.

“To most of you, this will taste bitter and unpleasant,” she said. “But some of you will taste nothing – it will be like a plain piece of paper in your mouth.” The strips were treated with phenylthiocarbamide (PTC) or propylthiouracil (PROP), chemicals that either taste bitter or are tasteless depending on the genetic makeup of the taster.

We tentatively set the white strips on our tongues, scanning the room to read each others’ reactions. To me, the paper was very bitter – something I’d instinctively spit out. But a few others looked alarmed, as if they had just learned they were blind to certain colours. “But I love bitter things, and dark, bitter ale,” one argued, previously oblivious to the fact that she lacked this particular bitter receptor gene.

An estimated 25 per cent of the population lacks some of the taste receptors that influence how we experience dark chocolate.Photography by Hamin Lee; prop styling by Christina Yan

Later, I pondered what my gin and tonic would taste like to those who fell into that same genetic category. At a time when flavour is paramount – our favourite snack foods come in a myriad of options from low salt to extra spicy, tasting rooms at wineries and craft breweries have become popular hangouts and restaurants often offer special tasting menus – it’s surprising to learn that an estimated 25 per cent of the population is unable to detect certain bitter compounds. This group lacks the particular set of taste receptor genes that might be responsible for determining how we experience dark chocolate or hoppy beer.

The T2R38 gene is one of our 20 or so bitter taste receptors, controlling our ability to detect glucosinolates, a family of bitter compounds found in foods such as brassica vegetables – Brussels sprouts, broccoli, cauliflower and kale. We have far more bitter receptors than we do salty, sweet or umami; evolutionarily speaking, it was beneficial for our ancestors to be able to detect bitterness, which was often a sign that something was inedible or even poisonous.

Humans are hard-wired to not like bitter flavours, such as those found in artichokes.Photography by Hamin Lee; prop styling by Christina Yan

“We’re hard-wired to not like bitter,” says science writer and educator Bob Holmes, author of Flavor: The Science of our Most Neglected Sense. “Most bitter compounds are warnings of toxins of some sort.” Children are extra sensitive to bitter, as it often signals danger, but as we get used to it, as adults we often come to crave it. “Nobody likes coffee to start with,” Holmes says. “But as you experience that bitter jolt and realize it comes with a caffeine kick, you start to like it.” Of course, most of us are attracted to coffee through its aroma, and initially cut the bitterness with cream and sugar.

There are thousands of compounds that make up the taste we know as bitter, which isn’t as easily defined as sweet and salty and is sometimes confused with sour: Consider the difference between tasting the flesh of a citrus fruit (sour) versus chewing on a piece of its rind (bitter). There is bitterness in black coffee, hoppy beer and tea that has been steeped too long, which releases more tannins. It’s a taste we rarely seek out or crave, yet kale has become the vegetable of the decade, production of bottled bitters is on the rise and the Negroni – made with bitter Campari – is one of the trendiest cocktails going. Greens such as arugula, radicchio and rapini are sought out to add complexity to salads, pasta and pizza – an element we may not miss, but appreciate when it’s there.

The bitterness of dandelion greens can add complexity to salads.Photography by Hamin Lee; prop styling by Christina Yan

“Bitterness can add so much interest to food,” says Becky Selengut, author of How to Taste, a handbook that covers the underlying principles of taste and offers techniques designed to hone your palate and make you a more confident home cook. “When you think about it, most herbs have an element of bitterness. So do most cheeses, most coffee, all of these things we like – part of the reason we like them is because the bitterness makes them interesting.”

Selengut often demonstrates the role it plays by making two Manhattan cocktails, one with and one without a shot of bitters. “Without bitters, it’s sweet and cloying, and one-dimensional,” she says. “With bitters, it’s round, deep, complex – it’s more interesting. The sweetness and the booziness of the alcohol is tamped down. It’s hugely different.”

Sweet and bitter cross-inhibit, Holmes says, which is why people don’t realize how sweet tonic water is; if you look at the can, it contains more sugar than many sodas. Since the two tastes contradict each other, if you experience more bitterness, it also means you’ll detect less sweetness.

“The world of taste is subjective,” Selengut says. “What one person experiences when they taste a dish is not necessarily the same as someone else, which means that no one can contest what it is that you, yourself, are tasting.”

Sweetness and bitterness, both found in grapefruit, cross-inhibit each other.Photography by Hamin Lee; prop styling by Christina Yan

But you can fine tune food to suit your personal genetics and taste buds; she suggests adding salt to turn down the perception of bitter, or to caramelize vegetables (consider roasted versus raw Brussels sprouts) or add sweetness for balance, and says fat will coat the tongue, also taming bitterness – like cream in your coffee. As for those super hoppy IPAs? “I think hops are amazing and I love the smell and complexity of those beers. There’s so much going on, but the aftertaste kills me,” says Selengut, who suggests putting a little bit of salt into the neck of the bottle.

For those who can taste PTC or PROP, its perceived intensity is often used as a measure of how sensitive their taste apparatus is. Back in the early nineties, science determined that a quarter of the population are “supertasters” – people with a greater concentration of taste buds also have an intensified sense of taste. Selengut finds it more accurate to call them “sensitive” tasters. “There’s nothing super about being a supertaster,” she says. “It’s almost like they’re overwhelmed by the sensation of taste, and tend to be picky eaters.”

Half the population are average tasters, and another 25 per cent are considered “tolerant” tasters. Often referred to as nontasters, they, of course, still have the ability to taste, although with fewer taste buds to begin with, they might find food generally bland, or douse everything in hot sauce.

Bitter melon is widely-used in Chinese cuisine.Photography by Hamin Lee; prop styling by Christina Yan

But just because you don’t register bitterness, doesn’t mean you can’t also be a supertaster. Genetic ability to taste bitter runs across the spectrum. “There’s a funny confusion about the taste test for supertasting,” Holmes says of the PTC or PROP strips. “They use this one compound that’s detected by one specific receptor. So if you can’t taste it, that just means you have a broken version of that one receptor. It doesn’t tell you how acutely you taste everything else. If you can’t taste PTC, all that says is that it’s the wrong compound to use to test whether you’re a supertaster.” You’ll likely get a more accurate assessment by getting up close with the tip of your tongue to visually count your taste buds.

Although you may be born with genetic differences, they won’t determine your eating experience for life. In her award winning 2014 cookbook Bitter: A Taste of the World’s Most Dangerous Flavor, with Recipes, Jennifer McLagan notes that cultural, environmental and experimental factors play a role in our perception of bitterness. “These factors set up expectations about a food, so that we often dislike something even without tasting it because of it how it looks, or how we think it will taste.”

And Holmes emphasizes how our tastes can change. “There are genetic bases to taste perception, and they do affect what we eat, but they probably aren’t the biggest factor,” he says. “Experience makes a bigger difference. Most of the flavour of food comes from smell, there are about 400 different odour receptors in the human genome, and our best guess is that you and I probably differ in about 30 per cent of them. We have different sets of bitter receptors, and then there are genes that affect how many taste buds we have. So it seems clear that everyone lives in their own, somewhat unique, taste world.”

The bitterness of radicchio is tamed with four balancing methods in the recipe below.Photography by Hamin Lee; prop styling by Christina Yan

Warm Radicchio Salad with White Beans and Smoked Sea Salt

Serves 4.

Four bitterness-balancing methods are used in this recipe: dilution by having the radicchio comprise only a small part of the finished dish: caramelization of the radicchio to increase its natural sweetness, salting to turn down the perception of bitterness, and finally, sweetness in the form of honey for balance.

1 cup dried cannellini beans, or 2 14 oz (398 mL) cans cannellini beans, rinsed and drained

1 tablespoon kosher salt

1 tablespoon extra-virgin olive oil

¼ chopped shallot

1 head radicchio, cored and cut into bite-sized pieces

1 teaspoon honey

½ teaspoon finely chopped fresh rosemary

Smoked sea salt

1 cup croutons (bread cubed and toasted in a 300 F oven for 15 minutes)

1 cup Italian salsa verde (recipe follows)

If using dried beans, soak them in 1 quart of water with the kosher salt and refrigerate overnight. Drain, transfer to a medium pot, cover with fresh water by at least 3 inches, and add a pinch of salt. Bring to a boil and simmer over medium-low heat for 45-60 minutes or until the beans are tender. Set aside to cool in the cooking liquid.

Meanwhile, heat the olive oil in a medium sauté pan over medium-high heat. Add the shallot and cook for 5 minutes, or until tender. Add the radicchio, honey, rosemary and smoked sea salt to taste, and cook until the radicchio starts to lightly brown around the edges, 5 to 7 minutes.

Drain the beans and put them in a large bowl along with the radicchio mixture and croutons. Dress with half the salsa verde and toss gently to incorporate. Taste and add more if desired.

Italian Salsa Verde

1 cup loosely packed, roughly chopped Italian parsley (stems are fine)

½ cup extra-virgin olive oil, plus more as needed

1 medium or 2 small oil-packed anchovies

1 small garlic clove, roughly chopped

2 teaspoons raisins or zante currants

5 toasted whole almonds

¼ teaspoon red pepper flakes

¼ teaspoon fine sea salt

1 teaspoon capers

2-3 tablespoons sherry vinegar

Place the first eight ingredients (everything but the capers and vinegar) into a blender and process until the puree is vibrant green. If it’s too thick for the blender, add more olive oil a tablespoon at a time until it runs smoothly. Add the capers and sherry vinegar to taste. Makes 1 cup.

Excerpted from How to Taste by Becky Selengut (Sasquatch Books).