Last month you planned and brewed what should be your best beer yet, and today is the first pour. This time, your recipe used a new brand of malt extract, or a new specialty grain or adjunct, and you also added some dry hops, or fruit or spices, to the secondary fermentor to give it that extra flavor you were looking for. The guys at the homebrew shop had tried pulling your leg when you told them the recipe, suggesting that you add seaweed to the boil, and put fish guts and gelatin in the fermentor. What a bunch of kidders, you didn’t believe a word of it!
And now you pour your best beer and, and … it’s cloudy! What happened?!
There are several possible causes of cloudy, or hazy, beer. Maybe it’s simply that your yeast has not flocculated (settled out) yet. You could try cold conditioning the beer for a few days to see if that helps. You might have wild yeast or bacterial contamination; it could be haze due to unconverted or insoluble starch, or fruit pectin; or it could be a protein-polyphenol haze. How can you tell? What should you do about it? Contamination is an issue unto itself and needs to be evaluated as such. Hazes due to starches represent a food source to many wild yeasts and bacteria, and can cause flatulence as the starches are broken down in your gut. Fruit pectin haze can be combated by the use of pectic enzymes (pectinase) or by changing how you prepare your fruit for the fermentor. Finally, proteins and polyphenols from the malt and hops can combine to form both temporary and permanent hazes, although these can often be mitigated by fining agents that will clarify the beer.
Those of us used to seeing crystal clear American light lagers may assume that this is how clear every beer should be. Wrong! In fact, the low-protein, high-adjunct beers of the US are some of the clearest beers in the world, if not the clearest. The ingredients have a lot to do with it, but the other half of the equation is the filtering capability that large commercial breweries have available to them. Filtering systems for homebrewers are available, but require that you keg the beer and force carbonate, because the yeast is filtered out too.
But other than aesthetics, why should you care about cloudy beer? You can’t taste haze … or can you? Haze can often be an indicator of another problem, such as bacterial contamination. Bacteria often cause clouding of the beer and characteristic off-flavors. For instance, Pediococcus damnosus is a commonly feared brewery contaminant that generates high amounts of diacetyl. In addition to the tartness of lactic acid, Lactobacillus can produce a variety of flavors, some of which are pleasant, as in lambic beers. Other strains of lactobacilli will produce excessive amounts of diacetyl, much like Pediococcus. A third type of haze-causing bacteria are coliforms, and these bacteria will often produce vegetal off-flavors, reminiscent of parsnips and old celery. Hazes due to bacterial contamination will most likely develop in the bottle after fermentation, and the sudden appearance of haze can be an indicator that something has gone wrong.
What is beer haze? Beer haze, including chill haze, is a combination of haze-active proteins and haze-active polyphenols, which complex together via hydrogen bonding to create large molecules suspended in the beer that create a visible haze. Hydrogen bonding is strongest at colder temperatures. At warm temperatures, the component molecules are vibrating too much for the weak hydrogen bonds to hold the protein-polyphenol complex together. That’s why chill haze behaves the way it does. With time, the protein-polyphenol complexes can oxidize and polymerize into permanent haze, but it all starts with haze-active protein and haze-active polyphenols.
Why do we say, “haze-active”? What does that mean? Basically it refers to the type and size of the proteins and polyphenols, both of which are large, complex molecules that come in many forms. Haze-active proteins are of the same size class as foam-active proteins, but haze-active proteins happen to be rich in the amino acid proline, which appears to be the site where haze-active polyphenols can attach.1 Haze-active proteins can be broken down into non-haze-active proteins by proteolytic enzymes, but those enzymes also break down the foam-active proteins, which is obviously a problem.
Millions of dollars are spent annually researching and combating beer haze. Why? Because in addition to the aesthetic appeal of a clear beer, the polyphenols that contribute to haze are part of a chemical equilibrium that contributes to oxidative staling reactions. You may be wondering just what a polyphenol is. You may have heard of them in terms of being an off-flavor in beer—compounds that have spicy, plastic, or medicinal flavors. No, actually those compounds that have characteristic off-flavors are phenols. Polyphenols are polymers of phenol compounds. You may have heard that polyphenols are tannins. Actually it’s the other way around—tannins are a type of large polyphenol molecule. And you have probably heard that oversparging or having the wrong mash pH will leach tannins into your wort. This is indeed true, because tannins (and other polyphenols) will be extracted from the malt husks and papery hop cones under such conditions.
There will always be some level of polyphenols in the beer, but it’s like complaining about having sand in the desert. Unless there is a sandstorm, you just accept it and work around it. If you think of phenols as being like Lego® blocks, you will get an idea of the possible variations in size and how small polyphenols can link up to form large polyphenols, including tannins. The most common manifestation of protein-polyphenol haze is “chill haze,” which is formed by small polyphenols cross-linking with haze-active proteins. These complexes are insoluble when the beer is chilled, but don’t have enough mass to settle out effectively and so remain suspended in the beer. These chill haze complexes break up when the beer is warmed to room temperature.
Larger polyphenols form larger protein-polyphenol complexes that can settle out as hot and cold break material, while the smaller polyphenols are carried over into the final beer. As mentioned earlier, these small polyphenols can grow by polymerization, especially in the presence of oxygen. If a beer with chill haze was poorly handled during bottling, the oxygen can cause the chill haze to become permanent haze.
It is interesting to note that, while searching abstracts in the professional brewing journals, haze seems to have become a bigger problem since the late 1990s. While this increase could simply be attributed to growth in the craft brewing industry and a tighter focus on quality, a better explanation might be that there is also more awareness and control of oxidation in the wort production process. A reduction in wort oxidation will result in less polymerization of the smaller polyphenols, such that less polyphenols and tannins are precipitated in the break material during boiling and cooling. Thus, more polyphenols survive into the packaged beer where they contribute to chill haze. In other words, a beer produced 50 years ago with little regard to wort oxidation before fermentation (not aeration for yeast growth) may have been more prone to staling and had a shorter shelf life, but it was probably clearer than comparable beers today.
To reduce the chances of haze forming in your beer, you can take steps during your brewing process to try to reduce the haze-active protein levels, reduce the polyphenols, or a bit of both. You can make these reductions by tweaking the recipe or by using clarifiers and finings. Each option has its pros and cons. To reduce the level of haze-active proteins and polyphenols in the recipe, you can change from an all-malt recipe to one that uses a percentage of low-protein adjunct, such as corn, rice, or refined sugar. This approach is exemplified by American light lager, Belgian tripel and Belgian golden strong ale. Using wheat, or wheat extract, in a recipe to reduce polyphenols (because wheat doesn’t have a husk) can be a double-edged sword. At low levels, 5%–12% of the grain bill, the high protein levels in wheat can cause extensive haze, but as the percentage of wheat increases to 40% the total polyphenol levels are substantially decreased and the beer is very clear.
Hops are another source of polyphenols. Many brewers swear by the exclusive use of low-alpha-acid aroma hops for bittering, justly claiming a more refined hop character in the beer. The downside to this is a greater proportion (up to four times) of hop cone material in the wort, and the large amount of polyphenols that will be extracted from this material during the boil. I brew an American wheat extract beer that tends to be hazy due to the wheat gluten, but last time I brewed it I switched from using Nugget (12% AA) as my bittering hop to using all Liberty (3.5% AA). That batch had a superb hop character that was as rich as royalty, and a creamy head that needed a spoon to clean the glass, but it was hazier than previous batches.
It has been shown that 70% of malt polyphenols can survive the hot and cold break, while only 20% of hop polyphenols do.2 The message here for reducing haze-active polyphenols and proteins is to achieve a good hot break and cold break to minimize the excess protein that will bind with the polyphenols to cause haze. Dry hopping after the boil will introduce more hop polyphenols, which is why you often see hazy IPAs.
If you are an all-grain brewer, your malts and the way you mash and sparge can affect your polyphenol levels too. New barley varieties have been developed to have less polyphenol than current varieties, and while test batches have been promising for reduced haze, these new malts haven’t really caught on in the market. Your sparging method can also affect the total level of polyphenols. While the first runnings generate the highest concentration of the small polyphenols, the last runnings of a continuous sparge contain the highest proportion of tannin-type polyphenols extracted from the husks. This is due to the rise in mash pH as the buffering power of the malt acids is rinsed away from the grain bed. This problem can be mitigated by either calcium additions to or acidification of the sparge water (see chapter 21). Using a batch sparge (where the final runnings typically don’t fall below 1.020) or a no-sparge technique (where there is no rinsing), can also minimize pH rise and prevent excessive tannin extraction into your wort.
Now we come to the seaweed, fish guts, and gelatin. You can add clarifiers to your wort and beer that will bond with haze-forming molecules and allow them to settle to the bottom. Irish moss, isinglass, and gelatin are the most common clarifiers used by homebrewers. Polyvinylpolypyrrolidone and silica gel products are most commonly used by commercial brewers, because they cost less in bulk and are generally more effective than carrageen and collagen. However, they are not digestible and need to be physically separated from the beer before packaging. Proline-specific enzymes are also now available, and these have proven to be very effective at eliminating haze while preserving beer foam.
Irish moss, or carrageen moss, is a type of red seaweed containing a certain class of long-chain polysaccharides called carrageenans, which preferentially attracts and binds to large proteins. Irish moss is the only clarifier that you add to your boil. All other clarifiers are added after fermentation. Irish moss is added during the last 5–20 min. of the boil, where it greatly enhances the clumping and precipitation of proteins that would otherwise contribute to haze and staling reactions.
In the past, it was generally accepted that haze-active proteins were different from the proteins responsible for head retention (i.e., foam-active proteins). However, more recent studies3 have shown that the two groups of proteins are similar enough that any attempt to eliminate haze-forming proteins using either enzymes or non-specific protein-absorbing additives (e.g., bentonite) will also affect the head retention and body of the beer. What this means to you is that either adding a protein rest to your mash schedule or enzyme clarifiers to your wort is probably not a good idea. In addition, misuse of the right clarifiers can also be trouble. If too much Irish moss is used in the boil, not only can the proteins responsible for head retention be affected, but it could also reduce the free amino nitrogen (FAN) that the yeast need for nutrition. For this reason, Irish moss is not recommended for use with malt extract or adjunct worts.
Irish moss is commonly available as dry flakes that are rehydrated before use. A typical dose is 1 teaspoon of flakes for 5 gal. of boil volume (125 mg/L). Another form of Irish moss is a product called Whirlfloc® from Australia, consisting of a large tablet that you simply drop into your wort. Each tablet is good for a 5 gal. (19 L) batch. People have reported excellent results using Whirlfloc.
The other popular fining agent is isinglass, commonly used in English cask ales. Composed almost entirely of the protein collagen, isinglass is obtained by cleaning and drying the swim bladders of the sturgeon, cod, hake, and other fishes. It is an excellent clarifier for yeast and haze, but expensive given its source.
Isinglass is sold as dehydrated powder to be used at a dosage of 30–60 mg/L, but it is most commonly available for homebrewers as a ready-to-use liquid. To use, add isinglass to the fermentor after fermentation has finished, or to the bottling bucket when you add your priming sugar solution. Do not attempt to heat up isinglass, because it is easily denatured. Two ounces of the liquid product will treat five gallons of beer (3 mL/L). Isinglass is considered to be better than gelatin for use in cask conditioned ales, because it settles readily at cask serving temperatures after being disturbed. Gelatin typically requires coolers temperatures to resettle after movement.
(Seriously, you have to wonder whose idea this was. “Igor, go get me some fish guts to add to the beer. What! Nothing fresh? Well just scrape some of that dried stuff off the cutting board there…”)
Gelatin is a byproduct of the collagen extraction process from cow hooves and pigskin. It is not as effective as isinglass at settling the yeast mass, needing about three times as much to do the same job, but it is less expensive. The recommended dosage rate is about 0.2–0.4 g/L (or 0.75–1.5 g/gal.), although brewers have reported good results with dosage as low as 0.08 g/L (0.3 g/gal.). As with any fining agent, the exact dosage depends on the yeast and haze content of the particular beer. Too much of any fining agent can cause residual haze and a condition commonly referred to as “fluffy bottoms,” where the sediment is easily disturbed and pours out with the beer.
Gelatin can be added to the beer in the fermentor before racking to the bottling bucket or keg, or it can be added directly to the keg. The clarifying action of gelatin does not depend on the gelling action that it is known for. Instead, gelatin acts as a bridge between haze active proteins and polyphenols, attracting and hydrogen bonding them together into clumps with enough mass to settle to the bottom. The beer should be cold, between 35°F and 45°F (2–7°C), in order to strengthen the hydrogen bonds and facilitate clumping.
To prepare gelatin, it only needs to be thoroughly dissolved in a small amount of water. Powdered gelatin acts a lot like dry malt extract when it is added to water. It will hydrate without clumping in cold water, but needs to be heated to about 150°F (65°C) to fully dissolve. Adding powdered gelatin directly to hot or boiling water tends to result in clumps that take a lot of stirring to dissolve. Once dissolved, the hot solution of gelatin can be poured directly into chilled beer and typically clarifies the beer within 24 hours. Swirling the beer to distribute the gelatin solution will help but is not usually necessary. Best results are obtained when the clarified beer is racked away from the settled haze and trub before bottling or kegging. There is typically enough yeast in suspension to support priming and natural carbonation, although adding a small pitch of fresh yeast will speed the process.
Polyvinylpolypyrrolidone (PVPP), also known as crospovidone, is a micronized white powder with a high surface-area-to-volume ratio that readily adsorbs polyphenols, including tannins. The necessary contact time is only a few hours. Commercially, PVPP is the most popular clarifier and stabilizer (a common brand is Polyclar®). For homebrewing, about 6–10 g per 5 gal. (19 L) is added after fermentation but prior to bottling. The powder is commonly combined with cooled boiled water to form a slurry that is then added gently to the fermentor. The PVPP slurry needs to be mixed thoroughly with the beer and allowed to settle out, which should take less than a day. Then the beer should be carefully racked off the sediment and bottled or kegged. This material is not approved by the FDA for ingestion. Commercial breweries remove PVPP by filtration.
Silica hydrogels and xerogels are the other half of the one-two punch that commercial brewers use to control haze and improve shelf life. Where PVPP works to bind polyphenols, silica gel binds to proteins. In fact, silica gel binds preferentially to haze-active proteins, because chemically it reacts with the same proline sites that polyphenols do. Like PVPP, silica gel is used at the same rate of 6–10 g per 5 gal. (19 L), and added using the same procedure. Silica gel and PVPP work synergistically to reduce haze more than each would alone. A combined product called Polyclar Plus™ is available to commercial breweries; at time of writing I don’t know if it has been packaged for use at a homebrewing scale. Silica gel is not approved by the FDA for ingestion. Commercial breweries remove it by filtration. Allowing the material to settle and carefully racking away from the sediment should be sufficient.
Proline-specific endoproteases, such as Clarity Ferm from Whitelabs, act by cleaving the haze-active proteins where a proline amino acid is accessible in the protein chain. This cleavage reduces them to smaller, non-haze-active proteins. The proline sites will still bond with haze-active polyphenols, but the size of the complex can’t grow to form a haze. This type of enzyme has the bonus benefit of breaking up the proteins that form gluten. Industry studies have shown that beer treated with this enzyme measured less than 20 ppm gluten based on the R5 Mendez Competitive ELISA assay.4 However, even though the current benchmark for considering a food to be gluten-free is <20 ppm gluten, there is enough variation among people with gluten-related allergies that marketing a beer as gluten-free may be impossible from a legal liability standpoint. For more information, see appendix I, “The Trouble with Producing Gluten-Free Beer.”
The dosage rate for Clarity Ferm is listed as being 12 mL per barrel for both gluten and haze reduction. This translates to 0.4 mL/gal. (about 0.11 mL/L). The enzyme must be stored cold (39–46°F [4–8°C]) to ensure viability, but has the convenience of being able to be added to the fermentor at pitching time.
Beer haze can have many possible causes, but a hazy beer that still tastes good is probably suffering from protein-polyphenol haze. Haze is usually treatable by the use of different ingredients, including malt and hop varieties, as well as by additives like clarifiers and finings (table C.1). I hope this discussion will help you understand how these hazes form and how to best address the cause and solution when making your own homebrews.
Table C.1—Clarifier Summary Table
| Clarifier | Purpose | Amount | Comments |
|---|---|---|---|
|
Irish moss |
Protein coagulant |
1 teaspoon/5 gal. (125 mg/L) |
A good clarifier for almost all worts, though not recommended for high-adjunct or extract-based worts. |
|
Whirlfloc |
Protein coagulant |
1 tablet/5 gal. (19 L) |
A good clarifier for almost all worts, though not recommended for high-adjunct or extract-based worts. |
|
Isinglass |
Yeast and haze flocculent |
30–60 mg/L, or 2 fl. oz./5 gal. (3 mL/L) in liquid preparation |
Most effective for settling yeast. Will also settle some protein haze. |
|
Gelatin |
Yeast and haze flocculent |
0.3–0.6 g/gal. (80–160 mg/L) |
Generally, the most economical and effective clarifier for homebrewing. Suggested dosage is 0.75–1.5 g/gal. (0.2–0.4 g/L).a Typically clarifies in 1 day. |
|
Polyvinylpoly-pyrrolidone (PVPP) / Polyclar® |
Polyphenol binder |
6–10 g/5 gal. (0.30–0.52 g/L) |
A non-aerated slurry should be mixed into the beer before bottling and allowed to settle out. Typically clarifies in 1 day. |
|
Silica gel |
Haze- active protein binder |
6–10 g/5 gal. (0.30–0.52 g/L) |
A non-aerated slurry should be mixed into the beer before bottling and allowed to settle out. Typically clarifies in 1 day. |
|
Proline-specific endoproteases (e.g., Clarity Ferm) |
Haze- active protein reducer |
12 mL/bbl., or 0.4 mL/gal. (0.1 mL/L) |
A proteolytic enzyme that breaks up haze-active protein molecules (typically hordeins), reducing both haze and gluten content. Added to fermentor at pitching. |
a Dosage based on Siebert and Lynn (1997).
Portions of this work were originally published as a feature article in Zymurgy, vol. 26, September–October, 2003. Gelatin and Clarity Ferm notes revised 2015.