You’ve likely encountered beers that incorporate everything from fruit purées to Italian rainbow cookies. But this trend is far from the only method of creating desirable flavors and aromas.
In fact, conjuring a flavor with its natural source is a tactic that plenty of producers forgo entirely. For centuries brewers have achieved complex flavors in their brews—from caramel to lemon to coffee—without actually using those ingredients.
When maltsters heat or roast malt, it triggers the Maillard reaction. This is when sugars and proteins bond to create new molecules called melanoidins. (This reaction is also responsible for the charred flavors of grilled meat and the toasted notes in baked bread.)
“Talking about Maillard flavors in beer can be tricky because there is a lot of overlap with caramelization flavors,” says Max Finnance, an Advanced Cicerone and senior manager of education and training for Artisanal Brewing Ventures. “The words are even used interchangeably, incorrectly, sometimes. They are distinctly different chemical reactions.”
Melanoidin flavors are “most commonly developed in the malting process before the brewer gets their hands on the grains, such as with Munich malt, but can also be developed in a decoction mash or in the boil,” Finnance adds.
Generally, the darker the malt, the more melanoidin character in the finished beer. Specific kinds of character can vary. The melanoidins in Munich and Vienna malts, for example, often create amber and red hues. They also add notes of graham cracker, toast and caramel.
Meanwhile, chocolate or Carafa malts, stouts and porters, contain melanoidins that contribute coffee, espresso and roasted flavor notes.
Hops are a key ingredient in beer production. One reason is that they contain terpenes, which are chemical compounds that help determine how beer tastes and smells.
Here are eight terpene types and derivatives:
Alpha acids: These are the major bittering compounds in hops, also known as humulones. Alpha acids are found in varying degrees in almost every beer.
Myrcene: This is one of the most common types of terpene, also found in cannabis. It creates that dank character common to both hops and marijuana. Myrcene gives certain beers pungent, earthy, grassy and vegetal characteristics. It’s commonly found in IPAs, especially dry-hopped versions.
Beta-pinene: Beta-pinene is woody, spicy, earthy and herbal. It will make you think of everything from basil and parsley to cedar and pine. The latter of which is a key characteristic for West Coast IPAs.
Caryophyllene: Similar to beta-pinene, this terpene is also spicy and woody, but it has some sweetness, too. It’s evocative of black pepper, cinnamon, rosemary and figs.
Humulene: This complements beta-pinene and caryophyllene well. It’s also herbal and spicy, like ginger.
Geraniol: On the lighter side of the spectrum, this contributes a floral character. It has notes of rose, brightened by citrus, like lime and orange. It’s found commonly in IPAs, pilsners and farmhouse ales.
Linalool: This terpene takes the floral component a step further with a bit of sweetness. It includes notes of lavender, mint and citrus.
Limonene: With a bright, bitter contribution of citrus—like orange and grapefruit peel—this terpene also has some spice to it, like caraway and fennel seed.
Esters are chemical compounds that create the fruity flavors found in beer. They are the result of the interaction of alcohol and acid, often driven by yeast during fermentation, a process called esterification.
There are plenty of ways to and which types are present. Different yeast strains produce different levels. Ale strains, or saccharomyces cerevisiae, are thought to produce more esters than lager strains, or saccharomyces pastorianus.
But fermentation temperature impacts esters the most. The warmer the fermentation, the more esters produced.
Here are common esters:
Isoamyl acetate: Isoamyl acetate contributes to a beer’s fruity aromas and flavors. According to Natalya Watson, an Advanced Cicerone, author and educator, its presence in Belgian Golden Strong Ale is often perceived as a pear-drop note. However, in German Weissbier, it’s more banana-like.
Ethyl octanoate (aka ethyl caprylate): Fruity and floral, this ester has notes of apricot.
Ethyl acetate: This fruity compound is the most abundant ester found in beer. It’s created when ethanol, the primary alcohol in beer, reacts with acetic acid.
Ethyl caproate: It has an anise-like character.
Phenylethyl acetate: This ester is sweet and floral, with notes of rose and honey.
Isoamyl formate: It represents the darker-fruit end of the spectrum, with plum notes.
Heptanol butyrate: Also dark-fruity, this has a blackcurrant character.
Phenols are compounds that consist of hydroxyl (oxygen and hydrogen) and an “aromatic hydrocarbon ring” of hydrogen and carbon molecules. They’re prevalent in nature, and their presence in beer can be attributed to hops, malt, water and/or yeast.
“There are a range of phenolic flavors found in beer, some of which are considered favorable, such as white pepper, clove and allspice,” says Jen Blair, an Advanced Cicerone, beer judge and educator. “And some are considered unfavorable, such as cough medicine, [bandages] and chlorine. Phenols are also responsible for the barnyard, horse blanket and ‘funky’ flavors found in wild beers.”
Desirable phenols are mainly yeast-derived. Certain yeast strains produce phenols as a byproduct of fermentation, much like esters, and they can also yield them at higher temperatures. Esters impact the perception of phenols, says Blair. “[The phenol level] stays the same in beer, but their perception varies based on the esters created.”
Here are some common types of phenols:
4-Vinyl Guaiacol: According to Blair this is the most common phenol in beer and it imparts a clove flavor. If you’ve had a Hefeweizen, you’ve experienced it.
4-Ethyl Phenol: Though some perceive it as pleasant, most consider 4-Ethyl Phenol an off-flavor. It comes from the wild yeast brettanomyces and helps shape beers with a barnyard characteristic, like that of Belgian lambics. But 4-Ethyl Phenol can also be medicinal and is unwelcome in other beer styles.
Guaiacol and syringol: These give smoked beers their characteristic campfire aroma. They come from smoked malts like rauchmalt, used to make German rauchbier.
Tannins, also found in wine, are polyphenol compounds in a brew’s malt and hops. It’s important for brewers to take care when sparging or rinsing the mash grain bed. Otherwise, tannins can seep into the beer and cause an unpleasant astringency.
However, the polyphenols found in hops are sometimes welcome at low levels. These can give certain IPAs their classic bitter bite. As their presence climbs, so does a beer’s harshness and green, vegetal character.
So, Why Bother Learning All This Science?
Understanding the origins of a beer’s flavors and aromas can help drinkers better recognize the styles they enjoy. It can also help identify inappropriate notes that might signal that a beer isn’t the best example of its style. For instance, a pilsner should never have fruity esters or spicy phenols.
It also helps to build appreciation for the wide array of flavors and aromas brewers can create with seemingly so few ingredients.
Last Updated: June 5, 2023