Getting sweet on bitterness with America's Test Kitchen

When it comes to flavors, bitterness can be one of the more divisive. Most people either love it or hate it. But learning to use bitterness in the kitchen is an empowering tool for home cooks. To learn about more about the science behind bitterness -- and how to skillfully wrangle it -- we talked with Molly Birnbaum and Dan Souza, executive editors of Cook’s Science for America’s Test Kitchen.

Lynne Rossetto Kasper: Can we talk about bitter tastes? Because it's curious that fast food is so popular, and its appeal is salt, fat and sugar. Yet, people are really taking to these bitter foods: dark chocolate, bitter greens, and hoppy beers.

Dan Souza and Molly Birnbaum Photo: Steve Klise

Molly Birnbaum: Bitterness is an incredibly complex flavor which, as humans, we have a very complex relationship with. It’s very individual, we all taste it different, and we feel very different about it.

Dan Souza: At Cook’s Science, we're very interested in it. We sent reporter Courtney Humphreys out to Colorado. She visited a place called MycoTechnology that is making bitter blockers that you can add to food. She also visited a place where they're brewing beer that's very bitter and very hoppy. We have a clip from her:

Courtney Humphreys: I felt like I had to go there just to try this thing because I couldn't quite believe it. I didn't know what it would be like to taste something that would block bitterness. They had me try the bitter blocker in beer, which is something I don't like the bitterness of. That was helpful for me. It was interesting because they put some of it -- diluted in water -- and added it to this beer. It was an India Pale Ale, a bitter beer. I have to say, it really changed the taste dramatically. As soon as they put it in, it was milder. It was almost like drinking a lager. I was like “Wow, this craft IPA has become basically Budweiser.”

LRK: What's the science behind this bitter blocker?

Chocolate Financiers Photo: Daniel J. van Ackere

MB: This bitter blocker, which is called ClearTaste, is made from mycelia on mushrooms. It's all-natural and organic because it is made from these mushrooms that grow in the forest. These mycelia are made into a powder that can be put into liquid. It contains molecules that temporarily stick to the taste receptors on the tongue and in your mouth to block the perception of bitter.

DS: A lot of bitter foods can be very good for you. You mentioned bitter greens. A lot of the compounds like the phenols in bitter greens -- or in coffee or chocolate -- can be very good for you. But a lot of people don't like that bitter flavor. So, bitter blockers are becoming quite popular. One of the interesting things about this is you find people who really like bitter things, and those who don't. When you look into why we do or don't like bitter, it's a much more complex taste than something like sweetness. We have 25 genes that code for bitter receptors on our taste buds. Whereas, for sweetness we only have two genes that code for them. Sweet is really simple: if it's sweet, we know it has calories, and evolutionarily, that would be helpful for us. Bitterness, on the other hand, often indicates toxicity. It's something that we learn to like; some people learn to like it better than others.

MB: For example, I love good brussels sprouts or dark chocolate. These foods with nice, bitter edges add a lot of complexity. The other interesting thing about having all of these genes that code bitter taste receptors in your mouth, it shows that we all taste bitter differently. It’s another reason some people like it and some people don't: there are so many differences in our taste receptors. There are a lot of differences in how we actually taste a grapefruit or those brussels sprouts that you get at the restaurant covered in bacon and maple syrup.

LRK: That's what makes them more attractive? The sweetness counteracts?

MB: Right. It's a natural mask. You don't actually have to go to mushrooms to mask some of that bitterness.

LRK: What are some of your thoughts about using bitter in our daily cooking?

Seared Flank Steak with Charred Broccoli Chimichurri Photo: Kevin White

DS: It's interesting to see a lot of restaurants and chefs are incorporating things that don't sound good on the surface, like burnt vegetables or vegetable ash. When we burn foods, we think that's generally a bad thing. They definitely become really bitter, but chefs are using it as an extra layer of seasoning. Having bitterness in there can add a lot more complexity to food. We've been playing around with that a lot at America’s Test Kitchen and for Cook’s Science. We recently developed a recipe that uses charred -- almost burnt -- broccoli in a couple of interesting ways. The first is that we take some of the top of the broccoli, the little florets, and we char them in a dry cast iron skillet until they are dark. We blend that into a classic chimichurri sauce, an Argentinian herb sauce we use a lot on steak. It's got olive oil, herbs, and fresh garlic. It normally doesn't have a lot of bitterness, just a little bit from the herbs. But this charred broccoli adds a ton of flavor to it. You get a rounder, more interesting sauce. We also char some broccoli to serve on the side.

MB: It's a really delicious dish. We serve it with flanked steak. It all can be done in under an hour, and that bitter char gives it this complexity and interesting kind of flavor aspect to it. It's super good.

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To learn more about bitter flavors in everything from vegetables to beer, read the Cook's Science article "Building a Better Bitter," then test out their recipes for Seared Flank Steak with Charred Broccoli Chimichurri and Chocolate Financiers. We also suggest this recipe from the aptly-named Mark Bitterman for Tangerine-Fennel Salad with Bitter Celery Vinaigrette.