Joe Casey has been working at Widmer Brothers Brewing Company in Portland, Oregon since 1995 and is currently Assistant Brewmaster. He has a B.S. in Biology from Portland State University and is a member of the American Society of Brewing Chemists (ASBC).
Some brewers choose or accept turbidity because certain beer styles mandate it. If we traced the origins of beer haze back to the beginnings of brewing history, I'd guess we would see that brewers didn't always fully understand beer haze or, more importantly, did not have the technology to overcome it.
Certain raw materials contribute more haze material than others. Wheat is a prime example of a haze-inducing raw material. Beers with large amounts of hops, like IPAs, also tend to be hazy. This is due to the polyphenolic material contributed by vegetative matter. These polyphenols react with the proteinaceous malt compounds to form haze.
There are no flavor benefits to beer haze. In fact, hazy beers tend to be less flavor stable because of the excessive protein and polyphenol
levels. High protein levels can give a beer what is known as a "protein bite," something I associate with bitterness. Likewise, high levels of polyphenols can lead to astringency.
Polyphenols are contributed by both malt and hops, though the chemistry of each is slightly different. Generally speaking, malt-derived polyphenols are more reactive and thus more detrimental than the polyphenols contributed by hops. Also, hops only contribute about 20–30% of the total polyphenols. Efforts to reduce protein and polyphenols via filtration or through the use of some additives reduce the amount of haze forming materials and, consequently, clean up the flavor.
An argument in support of turbid beer centers around the fact that it is less processed (unfiltered). Aggressive handling, exposure to oxygen and the iron contained in filter media can be detrimental to the quality of a final beer. This argument, however, ignores the fact that good filter technique prolongs beer shelf life.
Filtration extends shelf life in a number of ways. One way is limiting protein and polyphenol species that can eventually react and form undesirable haze. Filtration also helps remove most present bacteria that could persist into the finished beer. Yeast is also removed during filtration. If too much yeast exists in a finished beer, autolysis is a potential result — this causes a beer's pH to rise. High pH values lead to harsh flavors and hinder beer foam stability through the release of protease enzymes.
Beer does tend to clarify naturally, to a point. Aside from filtration, beer clarity is governed by Stoke's Law, which describes the settling rate of particles in a medium. The larger the particle, the faster it settles. The longer the time, the more particles will settle. The greater the difference in density between the particle and the medium, the quicker the settling.
Counteracting Stoke's law is the continual formation of more haze via proteins and polyphenols left in the finished product. Still, preventing clarification is not easy. Delaying it a bit is possible, but even Hefeweizens will clear up with time.
One avenue to create a turbid beer is to skip the addition of Irish moss, which helps clarify beer. Also, you can pick yeast that is non-flocculent. (Just make sure it has a flavor that fits the beer style).
For clear styles, the best fining agents for homebrewers are probably Irish moss and isinglass. At Widmer, we call Irish moss floc. Floc is great because it is simple to use and effective. The active ingredient in floc is kappa-carageenan. Make a slurry, boil it for at least 10 minutes — longer if you're using chunky floc instead of the granular stuff.
Usage rate depends widely on the particular beer in question and is heavily dependent on the wort pH. A wort pH of 5 will require almost twice the amount of floc as the same wort at a pH of 5.4. Homebrewers should be aware that, as a general rule of thumb, Irish moss fines protein and isinglass is mostly used to fine yeast. Isinglass however, is also capable of removing other proteins.
Isinglass is derived from dried swim bladders of fish such as catfish and sturgeon. The swim bladders are removed, washed, dried and eventually reduced into powder. Isinglass contains collagen in an insoluble form, which has a positive electrical charge. Its long molecular structure gives it a strong attraction to yeast cells and haze causing proteins. It also removes some polyphenol and lipid material, which improves beer foam, flavor and stability.Todd Ashman has been the head brewer at Flossmoor Station Brewery in Flossmoor, Illinois since 1996. He studied with the American Brewer's Guild and worked at Bison Brewing in Berkeley, California in 1995.
We are only doing 750 barrels each year on a 15-barrel system. That means about one brew every six days. We decided a long time ago that we weren't going to filter because we believe it strips the body and the character of the beer. We, like many breweries, put a lot of effort into getting these things into our beers and don't want to take them out just before reaching the tap.
At our brewery, yeast is mostly chosen for its flocculation characteristics. They should be at least medium, but we prefer high flocculation. It should not be so high, however, that we will need to rouse the yeast because it settles out so fast.
We use seven or eight strains in our brewery. These include the London Ale yeast (Wyeast 1318) and Belgian yeasts like Wyeast 3787 and White Labs WLP530. We also use Wyeast 3944 (Belgian Witbier), but we aren't as concerned with flocculation with this one — a cloudy beer is actually what we're shooting for in our wit beer.
We choose malt that has as low of a protein level as possible. This means 10.5–11% protein, and never above 12.5%. With protein levels beyond this, you're definitely going to run into clarity issues.
These days, malt has protein levels that run up to 14%. You will not be able to clarify beers made with this malt without having plenty of time to wait. Watching malt protein levels is a good way to recognize the importance of malt analysis.
I swear by a clarifying agent called Whirlfloc tablets. I use them religiously. We purchase Whirlfloc from Crosby and Baker, so homebrewers should be able to find it easily. Basically, it's similar to Irish Moss but powdered beyond belief and pressed into tablets. We use between 50–60 tablets in 500 gallons (1,900 L). Homebrewers should use 1–2 tablets in 5 gallons (19 L) versus 1–2 teaspoons of Irish moss.
Something else that works for us is to use top pressure when carbonating our beer. Essentially, this means the carbonation is pressing down on the beer in our Uni-tanks, which forces particulate to the bottom and lends to clarity. We apply the gas at 15 psi for about one week at 34–35 ºF (2 ºC).