The Herbs And Molecules That Make Up Bitter Flavors

In ‘Flavorama,’ plants, scents, and science come together in a recipe for deliciously bitter walnut-amaro cake.

The following is an excerpt from Flavorama: A Guide to Unlocking the Art and Science of Flavor, by Arielle Johnson.

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Flavorama: A Guide to Unlocking the Art and Science Of Flavor


Bitter herbs are so old-school, they’re in the Old Testament (and the Torah). Where vegetables have a kind of fresh and juicy-green bitterness, bitter herbs like wormwood, yarrow, and alpine genepi— or more common thyme or sage in large amounts— are layered over with resiny, piney, even spiced flavors.

Bitter herbs have the biggest overlap of molecules that are both bitter-tasting and perform other biological actions in the body. So they’re also one of the biggest overlaps of culinary recipes and products and medicinal ones. Traditional Chinese medicine has many of these, including kudingcha, a tea made from extremely bitter, saponin- and polyphenol-rich Ilex kaushue leaves, which are in the holly family and can reduce blood glucose and help kill cancer cells.

Herbal- bitter alcoholic infusions and liqueurs, most notably Italian amaro, can include dozens of bitter herbs like wormwood, gentian, and quassia alongside other layers of botanicals. As a digestivo, a kind of vestigial herbal medicine, a glass of amaro is an important finish to meals for many Italians, taking advantage of the effects many of its bitter ingredients (some triggered by the perception of bitterness, some locally by bitter molecules) have on indigestion. Postprandial needs aside, amari are also an amazing playground for different moods of herbal- bitter flavor combinations. Aroma profile can really change the vibe of the bitterness in these drinks: the more resiny and piney, the more deeply bitter and dry they taste. The more citrus, sweet herbs, and spices, the more buoyant and balanced. The unforgiving aroma profile of fernet makes it taste all the more bitter than the clove-anise flavors of (still very bitter) Underberg. Some great places to start for herbal bitterness are Campari, spicy, citrusy, colaesque Ramazzotti, and earthy Cynar, which famously includes bitter artichoke leaves.

If you’re not a big amaro drinker, your reference for herbal-bitter might be hops. Technically flowers, these beer seasonings have resiny, floral, citrusy aromas, and when you boil them for a while, the heat flips a couple of chemical bonds in a molecule called humulone, creating the much more bitter isohumulone. The humulones protect the beer from spoiling, which is why hopped beer is so ubiquitous. Up until the fifteenth or sixteenth century, instead of hops, beers often had a mix of bitter herbs called gruit, which often included heather, horehound, mugwort, yarrow, bog myrtle, and juniper. Some craft brewers still use gruit in special herbal brews; many of these herbs are more commonplace now as ingredients in herbal cough drops.

Walnuts have tannic, herbal bitterness, which comes from antioxidant phenolic molecules (unlike
bitter almonds, which get their bitterness from cyanide- containing amygdalin), offset by a buttery-sweet, almost mapley flavor. They’re as rich-tasting as any other nut, but made into butter, or a nut crust, or into cookies, they bring much more heft, with a more bitter edge, compared with hazelnuts, pecans, and otherwise similar nuts.

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Walnut-Amaro Cake

Walnut is noticeably bitter-herbal and tannic compared with many other nuts, so this recipe leans into the bitter by adding some bitter-sweet amaro, tempered with a little extra salt. The amaro has the added benefit of essentially spicing the cake, too.

Preheat the oven to 350ºF and butter a 9-inch cake pan.

In a food processor, pulse 3 and 1/3 cups (400 g) walnuts and 3 tablespoons (30 g) cornstarch until they’re the texture of bread crumbs but not pasty. Set aside.

In a large bowl with a hand mixer or with a stand mixer, combine:

  • 5 large eggs
  • 1 packed cup (200 g) light brown sugar
  • 3 tablespoons (45 ml) Ramazotti (or another sweet and brown amaro, like Averna or Nonino)
  • 1½ teaspoons (8 g) baking powder
  • ½ teaspoon (3 g) salt

Beat until the eggs are very pale yellow and rather fluffy, 6 to 8 minutes.

In a second bowl, fold the ground walnuts together with one-third of the egg mixture. (It will seem like it doesn’t want to combine, but be patient and gentle so as not to deflate the whipped egg.) Continue folding in the egg mixture to the lightened nut mixture one-third at a time until fully combined.

Scrape the batter into the buttered pan and bake for 45 minutes, until the cake is puffy and somewhat matte-looking on top. A toothpick inserted in the middle should come out with wet crumbs on it, but not goop. Remove from the oven and cool for 10 to 15 minutes in the pan. Gently invert onto a rack to continue cooling.

Serve as is or with whipped crème fraîche and a sprinkle of flaky salt. Stores, well wrapped, for 3 to 4 days.

Serves 4 to 8 as dessert.

Reprinted from Flavorama by arrangement with Harvest, an imprint of HarperCollins Publishers. Copyright © 2024, Arielle Johnson.

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About Arielle Johnson

Arielle Johnson is the author of Flavorama: A Guide to Unlocking the Art and Science of Flavor. She’s based in New York, New York.

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