So far we’ve investigated the role that acidity and sugar play in the creation of craft cocktails. While sugar predates acidity in cocktail history, these building blocks can be thought of as a pair – acidity and sugar directly oppose each other. When sugar overpowers acidity, drinks become cloying and heavy. With the reverse, drinks are tart, thin, and unpleasant. It is only when sweetness and acidity balance each other that a cocktail takes on a savory deliciousness that I call tension.
The sweet-sour balance is not the only way to create a craft cocktail. Before the invention of the sour family, cocktails were merely spirit, sugar, water and bitters. This category of drinks, now best exemplified by the Old Fashioned derives their deliciousness through the mitigating effects of sugar on the bitterness of wood-aged spirits and bitters.
The previous articles have stayed clear of any serious chemistry. Unfortunately, bitter and alcohol have a lot going on that needs some explanations, and chemistry provides the language. [editor: Nerd warning. Suck it up.]
Bitterness is one of the five basic tastes. It is sensed by nearly every part of the mouth, but particularly the gums and along the jaw. Bitterness is a drying, numbing sensation that is vital from an evolutionary standpoint, as many plant toxins are bitter. The evolved high sensitivity to bitterness (i.e. low threshold detection) ensured that poisonous plants were not eaten, and if they were, so little was consumed that toxicity was avoided. Even today, bitter things are a learned love – most people drink their first coffee with lots of cream and sugar in an attempt to mask its bitterness. Over time and repeated introduction, bitter flavors become palatable.
The taste threshold for bitter is .000008 M (Moles), and the reference compound is quinine, which is derived from cinchona bark. Humans detect quinine when exposed to merely 0.0026 grams of it. Quinine has been a frontline treatment for malaria since the 17th century, and is fluorescent. In cocktails, quinine is commonly found in tonic water, and a family of aperitifs known as Kina, which includes:
- Lillet Blanc (although it was reformulated in the 1980’s to remove the quinine),
- the defunct Rinquinqin (peach + quinine), and
- today's Cocchi Americano.
Bitterness is mediated by the interaction of the G protein gustducin and a family of taste receptors known as TAS2R. One of these, TAS2R38, is fascinating, as it seems to not only control the number of fungiform papillae (taste buds), but also determine whether or not a person is a non-taster, a normal taster, or a supertaster. These tests date back to the early 1930’s, when Dow chemist Arthur L. Fox realized that he could not taste the bitter chemical phenylthiocarbamide (PTC), but a colleague could. Today, the chemical used is 6-n-propylthiouracil (PROP), and people are divided into those who taste nothing (nontasters), those for whom it is moderately bitter (normal tasters), and those for whom is it intensely bitter (supertasters). [editor: Nerd part’s over. Exhale.]
Supertasters may also find other tastes magnified, such as the salinity of olives, or the heat of chilies. They also may have aversions to coffee, chocolate and vegetables in the Brassica family (cabbage, Brussels sprouts, kale, rutabaga).
But while quinine is interesting as a reference bitter, there are certainly other sources of bitterness in cocktails. One of the most prevalent is spirits aged in new wood barrels, such as Bourbon or Cognac. The bitter compounds in new wood (tannins and phenols mainly) leach into the spirit, which also slowly oxidizes. If given enough time, other compounds like hemicelluloses and the aldehydes (wine geeks out there, think of the rancio of Sherry) formed through the oxidation of alcohol contribute to “roundness” or “softness” in a wood aged spirit. New wood/short aged bitterness is different than old wood/long aged bitterness!
In wines (remember: vermouth is a wine), most of the bitterness comes from phenolic compounds (mainly catechin and epicatechin) found in grape stems, skins and seeds. These are more prevalent in red wines than white, as white wines are rarely fermented with the skins, seeds and stems present. In wood, these bitter compounds polymerize, forming complex chemicals that are not well understood. [editor: Okay, I lied a little. Now it’s really over.]
Then there are Amari, a class of aperitifs or digestifs that contain strong, bitter flavors. Some common examples of Amari are Campari, Fernet Branca, and Averna. While these liqueurs can have anywhere from dozens to hundreds of components – and some are bittered in a minor fashion by vegetables (Cynar with artichoke; Zucca with rhubarb) – they are mainly bitter due to only four.
- Quinine – already discussed – has a cedary, powerful bitter character.
- Gentian root is incredibly earthy and root-like, and moderately bitter. It appears in Suze, Amer Picon, and Angostura bitters. Bonal Gentiane-Quina (a.k.a Bonal) contains both gentian root and quinine.
- Quassia bark is in Amaro Nonino, and has an interesting coumarin-like hay and vanilla flavor, with low bitterness.
- Finally, wormwood (Absinthe and vermouth, but a lot of other things) is weirdly minty, foresty and a bit numbing.
Cocktail bitters are theoretically so bitter they’re non-potable, though that doesn’t stop intrepid cocktail creators from utilizing them. For more information on this topic, read Bitters Non-potable? Pshaw. It is fairly safe to think of them as concentrated, much less sweet, higher alcohol versions of amari.
Looking at some specific cocktails can help determine what effects bitterness has on the various other components in a drink. For example, in the Bonal & Rye, disparate sources of bitterness (wood aged spirit, cocktail bitters, Amaro) are mitigated by the softening effects of sugar in the form of Cointreau.
Bitterness and acidity is a more difficult topic. Look at something like the Golden Gate Swizzle, where a massive amount of bitter from Fernet Branca, Angostura and Angostura orange coexists with a “sour” base made from lemon and orgeat. In his seminal work on taste “The Taste of Wine”, Emile Peynaud says that “Bitterness is easier to perceive in a less acid milieu”. I would say that bitter and sour together is like trying to push the water in a full bucket. You’ll be able to affect a temporary lowering of the water in the bucket, but the water has to go somewhere, and it does – it pushes out sideways. Acid seems to decrease bitterness, but it also lengthens its stay on the palate.
Finally, bitterness and alcohol work synergistically to increase each other’s effects. A minimalist example of this would be a simple Pink Gin – 4 dashes of Angostura in 3 ounces of Plymouth gin. With no sugar and no acidity to buffer the alcohol + bitter combination, both the bitterness and alcohol are front and center.
From being a vegetative warning to early humans to becoming essential in 19th and early 20th century cocktails to its modern day renaissance in volumes not thought possible, bitterness is incredibly important to the craft cocktail maker.
Editors Note: This is the third in a 4-part series on cocktail construction by Kindred Cocktails editor, Zachary Pearson.