A crystal-clear beer glowing in afternoon light can be a showstopper, but for certain styles, haziness holds its own joys. Like most things in beer, haze is a lot more complicated than it appears. A beer’s clarity depends on many factors: ingredients, process, yeast, fermentation, the traditional practices that define a style, as well as the brewer’s preference. Haze is essential for certain styles and a disqualifier for others, or it may depend on preference or whim. Brewers may go to great lengths to get rid of it or conversely take special steps to encourage it.
The earliest beers must have been muddy affairs, consumed within days and containing lots of undigested starch left by primitive brewing methods. By the time the Sumerians were building cities, they valued some beers for their transparent, well-aged character. Medieval drinkers almost certainly knew many clear beers, but during that age, a new “white beer” emerged, pale, hazy, and employing a good proportion of wheat and sometimes other grains such as oats, rich in gums and other complex carbohydrates. Delightfully creamy and richly hazy, white beer remains an important family of styles today. Then around 1500 lager rolled in. With its long, cold aging allowing plenty of time for everything to settle out, lagers, with their shimmering transparency, came to dominate the world of beer.
Haze comes in many forms, each with its own characteristics. The most obvious haze-maker is yeast. Before fermenting, yeast multiplies tremendously, so fermenting beer resembles a living milkshake—restlessly swirling with yeasty activity. Today, a yeasty haze is desirable in just a few styles of beer, most characteristically in hefeweizen, whose name literally translates as “yeasty-wheat,” as witnessed by the ritualistic rousing of the yeast from the bottom of the bottle and drizzling it atop the beer after pouring. Yeast is also present in a lager variation known as a kellerbier, lagers served unfiltered, typically in a brewery’s own bierkeller, or tap room, but occasionally packaged.
Yeast haze can be problematic, though. The cells pack a wide variety of chemistry. When they’re alive, they have a familiar bread-dough aroma, but like any living thing, when they die they begin to decompose. Even in something as tiny and innocuous as a yeast cell, the aroma of death is not pleasant. Dead yeast can smell like soap, garbage or even sewage. Also as a practical matter, yeast settles out fairly quickly, so unless you’re prepared to swirl the yeast with every pour—something not possible with keg beer—it is not the best way to achieve a stable haze in beer.
Protein is another haze found in beer. Proteins are large, nitrogen-bearing molecules that are partly broken up into smaller pieces during brewing. Brewers use the term “colloidal stability” to describe the harmonious state where the proteins do what we want them to, which is to create body and foam without precipitating and forming haze. While the small pieces are important for yeast nutrition and the medium ones contribute to beer’s body and foam, the larger chunks combine with polyphenols (tannins) to throw a haze, especially when the beer is chilled. A barley protein called hordein, rich in the amino acid proline, is responsible for most of the mischief. It is perfectly configured to attach to the polyphenols and form stable complexes that are too large to remain invisibly dissolved in beer, so given enough time, they may settle out.
As chill haze is considered unsightly, brewers of clear, chilled styles like lagers and Rhine Valley ales take great pains to reduce it, either through careful control of raw materials and the brewing process or by the use of certain clarifying agents. If a beer is well past its code date, protein doesn’t need the assistance of cold and will spontaneously precipitate out of the beer in flakes that can turn a beer into a snow globe. It’s unsightly, but at this point in the beer’s dotage, protein haze is the least of its problems, and it is apt to be dull of flavor, with cardboard and honey overtones.
In styles like Belgian wit, Berliner weisse and gose, their haze may be largely due to starch and other carbohydrates such as beta-glucan and related compounds. Witbier was traditionally brewed using a large proportion of unmalted wheat and a little oats, along with a “turbid” mashing procedure that destroyed some of the mash’s starch-busting enzymes, leaving lots of residual starches in the beer. This starchy haze was often described as an “opalescent sheen,” something you can’t really get from a yeasty cloudiness. This is why wheat and oats, especially in unmalted form, are just about mandatory in hazy styles. Some old books suggest adding regular wheat flour to the kettle for an added boost of starchy haze.
Because of the importance of clarity in the vast majority of beer sold throughout the world, brewers have invested heavily in research and have developed many tools for controlling and eliminating haze. But the brewing process, established by centuries of trial (and maybe a little error now and then) is the best place to start. Ripe barley, properly malted, has reduced levels of gums that cause haze. During the brewing process, haze-forming starches and proteins are broken down by malt enzymes, and larger starch particles are held back during the lautering process when the sugary wort is drained away from the remaining spent grains. Excess large proteins are coagulated into clumps during the boil by kettle finings—usually a derivative of an algae called Irish moss—so they can be separated from the boiled wort, along with the hops.
After fermentation and conditioning, the temperature is lowered, which “crashes” the yeast to the bottom of the tanks. After that, the beer may be filtered—or sometimes not. Although there are many types of filtration, it’s basically what it sounds like: pushing beer through some type of membrane or media that restricts the size of particles that can pass through. While it seems harmless enough, it’s important to know that the things that you might want to remove—yeast, protein, particulates—are fairly similar in size to things like color compounds and proteins that give beer its body and head, so there is a danger in over-filtering. Filtration often must walk a tightrope between these conflicting goals.
Chemicals called finings can also clarify, and they can work through a variety of mechanisms. Some, like isinglass, are naturally derived (in this case from fish swim bladders) and have a long history in brewing. Others are more high-tech. One newer enzyme called Clarity Ferm targets the barley protein mentioned above, disrupting proline amino acids that also happen to be the culprit in gluten, and as a side benefit renders the treated beer virtually gluten-free. An alternate strategy is to go for the tannins that pair with proteins to form haze. Finings like isinglass and gelatin create a net that drags particulates to the bottom of the tank.
The appropriateness of haze used to be pretty clear-cut: OK in wheats and wits, and clear for just about everything else. Of course, it’s a little more complicated in craft beer. While many breweries filter, few do it as intensely as mass-market producers. Many don’t filter at all, and many beers are packaged with some live yeast in the bottle as it provides some protection against oxidation. So, a little haze is seen as a sign of hand-crafted products.
And now, with the new crop of IPAs coming from the Northeast (and soon everywhere), haze is being interpreted as a visual manifestation of the level of hopping, something to which it is only loosely tied, if at all. The best of these use wheat, oats and/or spelt to achieve a creamy “milkshake” body and a dense, but flavorless haze. Others use flour in the kettle or even fruit puree containing pectin, another carbohydrate capable of throwing an attractive and durable haze. Most brewers skip the usual kettle finings or any other normal procedures that would clarify the beer. Some brewers use yeasts with genetic connections to hefeweizen strains, which are notoriously difficult to persuade to settle out.
So whether you’re an old-school purist or hop-throwing anarchist, there’s plenty to ponder as every sip takes you further into your own happy haze.
Randy Mosher is the author of Tasting Beer and is a senior instructor at the Siebel Institute.