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What Determines the Color of Beer?

What Determines the Color of Beer?
What Determines the Color of Beer? (Photo Courtesy Flickr/Danielle Griscti)

Did you know all beer is red? We don’t perceive all beer as red, of course, but deep down in its molecules, it is. Since all beer is red, what determines the color of beer?

Grain is by far the strongest coloring agent in beer, and grains are colored by melanin, a rust-red pigment that drives the color of beer. But what about Pale Ales and Imperial Stouts, you say? Some beers don’t appear red at all. As with most questions about beer, the answer involves chemistry – in fact, a number of factors can affect color, and we’ll take a closer look at all of them. We’ll also examine what beer color can (and can’t) cue us to expect in terms of flavor, as well as how beer color is measured and described.  

The Chemistry of Color

Two chemical reactions make grains go from pale yellow to jet black: Maillard reactions and caramelization.

Maillard reactions are what you get when you start linking amino acids to sugars, usually prompted by the introduction of heat. The resulting combinations create a wide range of flavors and aromas and are associated with darkening color. Know it or not, you’ve been chasing and enjoying these flavors your whole life: the “browning” of grains in a kiln (and wort, in the boil) is the same process that steak or toast undergoes when heated. In beer, these Maillard reactions express most often as toasty flavors, but that’s far from exclusive: literally hundreds of perceptible flavors can be created in this process. Since the reactions generally occur at lower temperatures (100-200⁰ F, depending on the malt we’re developing), time becomes an important factor. Length and temperature of kilning can vary and create malts of the same color, but they may have different properties relevant to brewers (whether they can be converted in the mash, for example).

The second process – caramelization – is much simpler. Caramelization is what happens when you heat a sugar until it breaks apart. Grains don’t naturally contain sugar, though: we need to convert the starch in the grain into sugar, so the first step in the process is getting the grain wet and heating it to about 160⁰ F. At that temperature, you’re developing sugars inside the grain. The maltster will then ramp up the temperature to 220⁰ F or higher, and at that temperature you’re baking the sugars apart. The flavor compounds are exactly what you’d expect if you’ve ever tasted caramel: burnt sugar, butter, dark fruit and toffee. The longer the malts are caramelized, the darker they’ll get. All caramel malts contain also non-fermentable sugars, which will add flavor but not potential alcohol.

Finally, we have roasted or chocolate malts. Nothing complicated here: these are non-caramelized malts that are simply kilned at high temperatures until they’re roasted black. They add deep colors, and usually impart coffee, chocolate and even acrid/burnt notes.

Far and away, the malts chosen and their ratios within the recipe are the most important aspect of beer color. The darker the malts used, or the more pale malts used (the color builds, making the aggregate color darker), the darker the beer will be. Even small amounts of chocolate (roasted) malt will bring on rapid color shifts, while pale malts in sufficient quantities can still make for a very dark beer.

Time is Color

An underappreciated contributor to beer color isn’t even an ingredient: it’s time. As beer ages, particles in suspension within the beer – yeast, polyphenols, etc. – begin to fall to the bottom of the vessel. The remaining beer will reflect less light, making it appear darker. In this way, age all by itself will darken beer over time. Aging also creates new flavor perceptions, the most notable of which is that beers become less bitter as the isomerized alpha acids that make the beer bitter break down over time, and the malts are emphasized. The aging process can be accelerated by something we often associate with age in beer: oxidation.

Oxygen is a key component in the degradation of organic products and can have pronounced effects on beer color. The oxidative process that turns bananas brown has the same basic effect on your beer, and just like with stale fruit or bread, you’ll notice flavor differences. Flavors will first become muted, and if oxidation is more severe, off-flavors like cardboard or wet paper can develop. Not all aged, oxidative flavors are bad, of course. The sherry or vinous flavors that result from oxidized melanoidins can be very pleasant in amber or dark beers. By and large, though, oxygen is the enemy, and if you see a beer that’s darker than it should be (a deep red IPA, for example), be on the lookout for off-flavors from age or oxidation.

The Usual (and Unusual) Suspects

So far it’s been malts (and how kilned/toasted/roasted they are, and the amount used) and time that predict beer color. A host of other factors contribute as well, just to lesser degrees. In no particular order:

  • Boil Length: The longer a beer is boiled, the more Maillard browning occurs.
  • pH Level: A more acidic mash results in a paler beer thanks to the chemistry of water. It’s also possible for some molecules in fermenting beer to lose their color as the pH lowers, causing the color of the beer to lighten slightly.
  • Yeast Strain: “Low-flocculating” yeasts stay in suspension longer, catching more light, whereas “high-flocculating” yeasts drop clear more quickly.
  • Hops Usage: Hops – especially as the amount used increases – leave behind polyphenols and acids. Depending on the beer, this can create haze that lightens the perceived color of the beer.
  • Specialty Ingredients: This should be obvious but adding new ingredients with different colors of their own can skew the color of your beer! I still remember the blood-red cranberry ale my wife made; it was a beautifully unusual color in beer. Many fruited sours take on exotic colors thanks to fruit or syrup additions, adding to their visual and flavor interest.

What Color Tells Us – and What It Doesn’t

Color tells us surprisingly little about what a beer will taste like. It gives us probabilities, not certainties. A lighter beer is more likely to feature light grainy flavors: biscuit, bread, very light toast. As a beer moves towards amber and copper, we’re more likely to perceive caramel and toffee flavors. And, naturally, dark brown or black beer is more likely to showcase cocoa and coffee flavors. These are not conclusive, though: since color can be so easily shifted down the color scale by even minute amounts of roasted malts, it’s perfectly possible to use a relatively low-flavor-impact chocolate malt (Midnight Wheat, for example) and adjust color without adding flavor. Color can be misleading. A good flavor wheel can give you approximations, but take it with a grain of… grain!

Probably the most common misperception is that color predicts alcohol content. If beer were brewed using only a single type of malt, it would: as grain was added to the grist and more sugar added to the wort, the color would darken at a generally linear rate. However, it’s perfectly possible to make a double-digit ABV Belgian Tripel that’s pale gold by using only pale malts and simple sugars (which may add no color at all). By the same token, it’s possible to produce a German Schwarzbier (black lager) under 4 percent ABV by using small doses of roasted malts. Assume nothing about ABV based on color – doing so can be, frankly, dangerous.

Defining Color

Finally, we turn to measuring color in beer. Believe it or not, there’s a lot of science that went into developing the scale we use!

Beer color is measured on the Standard Reference Method (SRM) scale. SRM is calculated by passing light of a specific wavelength through a specific “thickness” of beer (one centimeter) and measuring the amount of light absorbed by the beer. Beers at 2-5 on the SRM scale are considered pale/gold and include styles like Pilsner and light lagers. Beer in the 7-15 range is considered amber, and styles include Oktoberfests, American Amber Ales and (paradoxically) English Pale Ales. At 16-25, we reach copper and brown, with styles like Bock and English Brown Ales. Above 25, we’re parsing shades of deep brown and black, topping out (in practical terms) at about 40, though the SRM scale theoretically runs well into the 70s and 80s in the most-roasted beers like Imperial Stout! Above 40, though, the beer is effectively black and opaque.

Enough of just looking at beer though – maybe it’s about time we go and taste one!