Why does it matter if your beer is clear? Sometimes it doesn't matter at all: Hefeweizen, for example, is an outstanding German wheat beer that's supposed to be cloudy; its haze is due to the high protein content of the wheat and the poorly-flocculating yeast that hefe brewers traditionally use. But another thing that can make beer hazy is organic contamination. Haze can also indicate an old beer. Without any other visual cues, someone might judge your beer strictly on its clarity. Many other people probably prefer clear beer because that's what they're used to. As the saying goes, "the first taste is with the eye."
Evaluating Beer Clarity
The first step to making your beer clear is to learn how to judge clarity. You don't need to rush out and buy a turbidity meter (unless your wife will let you!). One simple test is simply to hold the beer up to an outside window. What can you see? If all you see is a golden glow, you probably have hazy beer. If you can read the sign across the street, you probably have very clear beer. Another method is to look up at the underside of the foam. Can you see the details of the bubbles on the far side of the glass? Or can you only see the bubbles on the near side? Your eye is the final judge. If you need a reference, open a Bud and pour it into a glass. Bud is as bright as it gets. Like most other big breweries, Anheuser-Busch has scrutinized every operation in its breweries with an eye to clarity and shelf life.
If you want your beer to be bright, you have to focus on clarity during every step of the brewing process. This article will show you how.
Types of Beer Haze
Basically, beer haze is very small particles of stuff that are either floating or partially dissolved in your beer, depending on the temperature, with an average size about one-quarter the size of a yeast cell. Beer haze particles are generally divided into two broad categories: hazes with a biological origin and hazes with a non-biological origin. There's also a special kind of non-biological haze, called a chill haze. Chill haze is essentially a small particle comprised of proteins and polyphenols. While the ingredients are always in the beer, it is only when it gets cold that the protein and polyphenol combine to make a particle large enough to be seen (or filtered). As your beer warms up, the haze disappears.
Biological particles that can throw a haze include brewer's yeast, wild yeast and bacteria. Normally, brewer's yeast flocculates into small bundles and drops to the bottom of the fermenter. What is left drops out during cold storage, leaving a naturally yeast-free beer. For this to happen, you need to pitch plenty of healthy yeast and make sure it has enough oxygen. This combination ensures a healthy fermentation, one that's unlikely to be bothered by contaminating bacteria and "wild" yeast (non-brewing strains) that may invade a weak ferment.
Before yeast can start to consume the sugars we have made, it must first do some preparation. This time is called the "lag" and it is a very vulnerable period. This is the time when wild yeast and bacteria can get an unwanted headstart on the brewer's yeast. That's why it is so important to pitch healthy yeast and have good oxygen levels in your wort. The best "pitches" are 10 to 14 days old for an ale yeast (meaning it has been 10 to 14 days since the last time it was pitched) and about 3 to 4 weeks for a lager yeast. When collecting the pitch, also called slurry, it is common to discard the early and late flocculators (the top and bottom layer) and collect only the center layer of the yeast. The pitch should smell and taste clean. It is traditional in English breweries to pitch one pound per barrel of active yeast, which translates to about 2.5 ounces by weight for a five-gallon batch. In large breweries it is common to perform a cell count to ensure accurate pitching rates. Homebrewers often just use a fresh culture every time they pitch.
If you are fermenting a normal-gravity beer (1.048 or so), then it is fine to use sterile air for oxygenation. Many homebrewing suppliers carry small filters to place in-line with an aquarium pump. These filter out all sources of contamination in the air. If you're using sterile air, it is practically impossible to over-oxygenate your wort. For higher-gravity beers, it is better to use pure oxygen, since 02 becomes increasingly important with increasing gravity. Medical-grade O2 can be purchased at welding supply houses or from homebrewing supply shops. You know you have used the proper amount of O2 for your beer when you harvest the next generation of yeast and the pitch has tripled or quadrupled in size. A good starting point is to add 45 seconds of O2 through an air stone. For a high-gravity brew do this twice.
Sometimes the brewer can cause "selective pressures" by changing the flocculation characteristics of a yeast strain. If we look at a population of yeast, some cells are better suited to different extremes of living conditions. Some cells will be better flocculators and some will be better attenuators. Some will perform better warm, others like it cold. "Selective pressures" (whether intentionally or accidentally caused by the brewer) can make a whole strain behave differently than the original strain.
A good example of "selective pressure" would be to ferment an ale yeast cold and have a slow fermentation. In a ferment like this, sometimes the only yeast to survive are the least-flocculating cells. After they have replicated and finished fermenting the beer, they are reluctant to flocculate, which causes a yeast haze. In this case we have created a "selective pressure" by killing the more-flocculent yeast and rewarding the less-flocculent yeast. This can happen in one generation or slowly over several generations. This is why most brewers return to a fresh culture every 10 or so generations, or after an unusual ferment. If your yeast strain becomes non-flocculating over time, it will not settle out of your beer and will need to be filtered. In a nutshell, it's important to use a strain with good flocculation properties.
Wild yeast is any yeast the brewer did not intend to pitch into the beer. Yeast and bacteria are everywhere, and on every surface, unless it has been sterilized. Since homebrewers only sanitize, not sterilize, wild yeast are always present in the brewing environment, including on your hands.
Wild yeast can have very poor flocculation characteristics, which means they will never settle out and will make your beer downright cloudy! The best way to eliminate wild yeast from your beer is to sanitize everything very carefully and ensure there are no unfermentable sugars remaining in the beer. Once you have completed the boil, everything that comes into contact with the wort or beer should be sanitized. That means every valve, line, tool and vessel. It is up to the brewer to look at every item and undertake the best sanitation method for each object.
Bacteria are small living cells (less than 1 micron) that would like to contaminate our wort and beer if given the chance. Bacteria are difficult to eliminate from the brewing process, because they are everywhere: drifting in the air, on every surface and on your hands. Fortunately, most bacteria are killed by the combination of the acidity of wort, the alcohol content and the hops in beer, leaving us with a short list of possible bacterial contaminates. It is important to realize that none of them are pathogenic. You cannot make anyone sick with beer. (Well, we all probably have had a hangover!)
Many species of bacteria can replicate at 36 times the rate of yeast. By the time your yeast has eaten all of the O2 and finished replicating, the bacteria can have raised 36 families and ruined your beer. Since each generation doubles the bacteria count, 36 generations is a lot of cells. Obviously this would make the beer taste incredibly off, but a milder infection can be just enough to throw a haze.
This is a good time to introduce something I call the crumb theory: Beer can get contaminated with small amounts of bacteria at any point in its lifetime. Bacteria need food to survive, so brewers try to eliminate any excess food that bacteria may use to survive. For example, when yeast gets old and dies, it decomposes (this is called autolysis) and releases its proteins into the beer. This is a potential food source for bacteria (especially lactic-acid bacteria), so most of the lactic-acid bacteria risk can easily be eliminated by properly separating the beer from the yeast after fermentation. Making sure your beer has fermented completely is another critical tool for eliminating residual food supplies.
Let's review. Brew clean and pitch healthy yeast into a wort with plenty of O2 and you will eliminate the sources for biological haze. It is important to eliminate sources of biological haze because filtering biological hazes is time-consuming and not very effective. A heavy biological haze will have too much material to filter. The result is often a clogged filter; or worse, a torn filter that lets unfiltered beer through. If your beer is in this sorry state, usually the flavor damage is permanent.
A final note: Some biological hazes slowly gain intensity in beer that has been filtered. As the beer begins to clear, "dust" slowly collects on the bottom of the bottle. Usually, the entire bottle is clear except for the bottom — when the beer is poured into a glass the "dust" stirs and the beer is hazy. The only solution is to identify the source of the contamination and remove it before your next brew. If you are lucky, you can drink some of your "dusty" brew before it begins to taste odd.
Non-biological hazes are not as simple to handle. Non-biological hazes fall into these categories: particulate, proteinaceous, protein-polyphenolic, carbohydrate-starch, beta-glucan, lipids or addition-related. Wow, that's a lot of causes. Which one is making my beer hazy? Good question. It may not be possible for us to tell without a lab, but by exploring the possibilities, we can learn what we do in the brewing process to "throw a haze." With experience all of the sources of non-biological haze can be eliminated from the process, but protein-polyphenol hazes require constant vigilance.
Instead of detailing every particle and its contributions to beer haze, let's review the brewing process with an eye to clarity. All throughout the brewing process particles are created and removed. It is important to remove the particles as early in the brewing process as possible.
It is important to eliminate all tin and iron from the brewhouse. Tin and iron can cause hazes. Most homebrewers do not use tin or iron, but if you are boiling in your grandma's cast-iron kettle, I would suggest finding a stainless-steel brewpot. Water sources that are high in iron should be avoided. If you get your water from a municipal supply, you are probably okay, as they have limits on the allowable iron content.
Next we mill the grain and create particles of starch and husks (extract brewers skip this step and go straight to the kettle). Over-milling your grain can make this task more difficult, for two reasons: You make more husk particles to filter out, and the smaller husks compact and require more force to push the sweet wort through the grain bed. This greater force can push small particles through the mash bed or cause a stuck mash. So do not over-handle your grain. This can pulverize the husks, creating small husk particles that will be difficult to filter out during lautering. Any residual husk in the boil will be detrimental to beer clarity. When I crack grain I look for the husks to be complete and separated from the starch, with 25% of the starch as powder. This is a fine mill; it probably is safer to have less of the starch powdered and the kernels opened, but the husks not completely stripped off.
In the mash we must cooperate with the maltster to degrade beta-glucans, protein and starch, since all of these things can cause problems later on. Most malts we use are very highly modified, which means most of the protein has been degraded for us, and a single starch rest (mash profiles are discussed below) is all that is needed. If you are using an under-modified malt, like Budvar, most homebrewers will have to "step mash" in order to further break down the beta-glucans and the proteins to avoid a haze. With most highly modified modern malts, however, a protein rest lowers head retention and really does not help clarity.
Here is a breakdown of the various mash rests and their uses.
Beta-glucans are a gum derived mostly from grain husks. The standard rest to break down beta-glucans is 100° F for 15 minutes. Excess beta-glucans can thicken our beer enough to create problems with filtration, and in extreme cases can cause a haze.
Proteins are present in malted barley and some adjuncts are high in protein. Proteins can combine with phenols to cause a haze in beer. Most protein degradation is performed by the maltster; homebrewers can further degrade the proteins by holding the mash at 120-130° F for 15 minutes. Another tip: If you use adjuncts to boost the alcohol content of your beer or to lower the malt content, avoid high-protein adjuncts like raw wheat. Instead, go with low-protein adjuncts like rice or corn. A healthy boil is beneficial because it helps ensure good "break" or precipitation of the protein/polyphenol trub.
The conversion of starch to sugar is accomplished by holding the wort at 142 to 158° F. It is in this temperature range that alpha and beta amylase enyzmes, which are present in malted barley, can work together to convert the barley starch to sugar. Alpha amylase works at the upper end of this range and leaves more unfermentable sugars behind, making a sweeter, malty beer. Beta amylase works at the lower end of this temperature range, and will make less unfermentable sugars, leaving us with a dryer beer. If you want to rest at the low end of this range, then the mash must be longer (about 90 minutes). Most people choose a warmer temperature for their mash, at about 154° F. This results in quicker conversion (about 60 minutes) and contributes to a "maltier" beer. A rest that's conducted at an improper temperature, or a rest that's too short, will leave residual starch in suspension and throw a haze into our beer.
To ensure you have converted all of the starch to sugar, it is useful to perform a iodine test. Take a few drops of wort and place it on a white plate. Add one drop of iodine from your local drugstore. If the solution turns blue, you still have residual starch.
The best place to filter out husk particles is in the mash. We accomplish this by re-circulating the wort through the mash bed. As I mentioned earlier, over-milling your grain can make this task more difficult, and you may wind up with tiny husk particles in your wort. Since husks contribute to the phenol levels it is important to keep them from the boil kettle. Phenols combine with proteins and cause a haze.
A simple method is to place a bowl upside-down on top of the mash. Because we are pre-boil, it is not necessary to sanitize this bowl. Draw about a pint of sweet wort off the bottom and gently pour it over the bowl. If we hydraulically cut through the mash it ruins our filter bed, so go slowly. As my personal rule of thumb, I like to re-circulate the entire volume of the mash in about 30 minutes.
When we have clear sweet wort, it is time to run off into the boil kettle. This is called sparging. Sparging is simply pushing the sweet wort down with hot water and rinsing the rest of the grain free of sugar. We must be careful not to over-sparge. The last runnings of the sparge have very little sugar and increasing levels of polyphenol and lipids. Polyphenols and lipids can cause haze and instabilities in your beer so it is best to keep them out.
You should stop sparging when you can start to taste tannins in the final runnings. Tannins are the astringency in tea and taste like weak tea. Tannins are a polyphenol that indicate over-sparging. You can also use a hydrometer or a pH meter to decide when to stop sparging. If you are using a hydrometer, chill a sample and stop your sparge at 1.008. If you are using a pH meter, chill a sample and stop sparging when the run-off pH increases to 5.8. If you are like me, you have stopped the run-off before you have filled your boil kettle. To get your final boil volume just add liquor (water) from your hot-liquor tank.
Homebrewers often will put a bag of specialty grains into the boil kettle if they are not mashing. The usual method is to place about 1.5 pounds or less (for a 5-gallon batch) of cracked crystal or dark malts into a fine mesh bag. The sweet wort is warmed up to 170° F and then the heat is switched off. The bag is placed in the sweet wort for 30 minutes. The heat of the 170° F water destroys the enzymes that break down the malt, so very little starch is converted to sugar.
Because the enzymes are inactivated and therefore are not converting the starch, steeped grains add various levels of starch to the sweet wort. Crystal malt has already been "mashed" and roasted grains are so burnt that little starch remains, so these specialty grains don't contribute enough starch to worry about. The lightest specialty grains are the ones to consider; I save malts like Vienna or Munich for my mash tun. Either way, remove all grain when the sweet wort is below 178° F. The over-use of steeped grain can cause hazes, so sticking to less than 1.5 pounds for 5 gallons works well.
The Hot Break
Just before the kettle comes to a boil, the hot break starts to form on the kettle. It is formed mostly from protein. This break looks like a foamy, eggy substance. When the break is at its maximum, skim it off. If you wait until the boil begins, the break will sink back into your sweet wort and you will have to whirlpool it later.
What makes a good boil? A boil should be as hot as you can get it (215° F is recommended, but not possible for many homebrewers), long (at least 60 minutes) and vigorous (it is recommended to boil off about 8 to 10% per hour). Simply simmering will not be enough to coagulate protein into a good hot break and will result in a cloudy wort. If you have done this correctly, the boil will contain large pieces of what looks like egg white. This is trub.
Trub is coagulated protein compounds, and it can be addressed by adding finings to the wort. There are many choices. The most common is probably Irish moss, a refined seaweed that helps precipitate protein into the hot break. Use one to three teaspoons of Irish moss flakes for 5 gallons of beer, and add the moss 15 minutes before the end of the boil. Kettle finings improve the break and reduce protein levels, which results in a clearer beer.
Once you have completed the boil, the kettle is a good place to separate out some of the larger particles. This can be accomplished by giving the wort a good stir; be sure to get the entire volume spinning in one direction. Let this settle for about 20 minutes (longer if you have a very deep kettle). Spinning the wort creates lower pressure in the center of the kettle. This starts a vertical circulation, with the wort running down the sides of the kettle and up the center, pulling the trub towards the center. Gravity drops the trub and hop matter down against the flow of wort and deposits it in the center, away from your valve, allowing for an easier rack from the boil kettle. You can alternatively run your wort through a hopback and use the whole hops to filter the trub from your wort.
The Cold Break
Cold break is the solids that begin to fall from solution as the wort drops below 140° F (by definition). It is very similar but not identical to the composition of hot break. The colder you take your wort after the boil, the more trub you will precipitate. This is because warmer wort can hold more dissolved trub than cold wort.
Now that we have made the best food for our yeast, it is time to give them their chance. When I learned to brew in a microbrewery, the master brewer told me that "brewers are only yeast farmers; if we are good to them, they give us beer." There is a great deal of wisdom in this sentence. Be clean, control your temperature and give your yeast oxygen. Healthy yeast are tough; in the right environment, they will out-compete the organisms that can cause haze.
From this point on, it is extremely important to eliminate all sources of oxygen from your beer. Even the tiniest amounts of O2 will cause stability problems. Flush everything with CO2 before you transfer and don't splash.
The homebrewer often leaves the cold break (trub) in the vessel during fermentation. Some of it will settle before the yeast and can be seen on the bottom of the carboy. It is wise to rack off this trub after a day or so, as it is another food source for bacteria.
At the end of fermentation, transfer your beer off the yeast. Make sure to leave as much of the sediment behind as possible. If you are coming out of a carboy, place the racking cane about 1 inch from the top of the yeast. When the beer level starts to get to the end of the cane, gently tip the carboy, allowing the yeast to settle into the corner. Stop racking just as you start to take the top of the yeast.
It should be noted that dry hopping can cause a haze. If you choose to dry hop, you can fine with silica gel and then filter. Or you could use Polyclar AT to remove the tannins introduced by the hops. This is usually successful in removing dry-hop haze. If clarity is your final concern, then no hops after the hopback.
The Bright Tank
The next chance we have to "filter" our beer is by aging. Some people do this in a second carboy; others use an aging vessel that can be pressurized like a keg, so it is easier to rack off the sediment without introducing oxygen. Gravity pulls the large particles to the bottom of the aging vessel. It is best to chill this vessel — three weeks at 32° F is recommended. Cold helps the particles to precipitate.
There are three finings we can add to the bright tank, depending on what we want to remove. Isinglass, which is made from the swim bladders of certain fish, will help to settle the yeast. Polyclar AT (also called PVPP) will adsorb polyphenols. And silica gel will adsorb haze-forming proteins, leaving head-retention proteins behind. To add isinglass, hydrate one quarter to 1 gram of isinglass in one quarter to 1 pint of sterile distilled water for a 5-gallon batch. Polyclar AT and silica gel are best used together, because together you can use less than either of them alone, making it easier to filter. Add between 5 and 10 grams each of Polyclar AT and silica gel in a 5-gallon batch. Be sure to keep everything sanitized. Polyclar AT and silica gel should be followed by filtration or the finings can remain in the beer.
I like to sample the beer one month after brew day and evaluate it for clarity. If it is up to my standards I rack off the sediment into a keg or bottle. If it's not, I start to think about filtration. Many beers do not need filtration and will be very bright at this point.
The mega-breweries would take the beer to 29° F, centrifuge to remove all of the yeast, run it through a filter small enough to remove all of the haze particles, bottle the beer, and then pasteurize the whole package with the cap on to kill any bacteria. The craft brewers I have met can be divided into two groups: the ones who choose either no filtration or coarse filtration; and the craft brewers who bottle their beer and often filter with a small-pore filter that traps all bacteria (this is called sterile filtration). Many craft brewers use sterile filters because they can't afford pasteurization. Sterile filtration alters the chemical composition of the beer (Fix and Fix, "An Analysis of Brewing Techniques," 1997) and, in my opinion, adversely affects its flavor.
So we look at our beer and decide it looks like pea soup. Well, a filter is probably not going to help. It will make the beer clear, but we have created a problem earlier in the brewhouse, and it is likely to have affected the flavor. If we look through our beer and decide it is almost clear enough, but could use a little polishing, then a filter may be just the ticket.
What filter do we use? There are three methods in common usage.
Diatomaceous Earth Filter
In a large brewery, the economics dictate using a diatomaceous earth (DE) filter. DE is the skeletal remains of algae. It is very small and has jagged edges that lock it together. A DE filter is a vertical plate that has coarse pores. You start pumping the beer through the filter while you "dose" the beer with DE. This initial beer has a considerable amount of DE that escapes through the coarse screen and is re-circulated. After a few minutes, the DE will have bridged the holes in the screen, making a fine filter. Once the beer is clear, the output is diverted to a tank. If the transfer is interrupted, the DE falls off the screen and the process must be started over. Since the beer must re-circulate through the filter, the transfer is usually accomplished with a pump. If this sounds complicated, it is, and it's not suitable if you have less than 200 gallons.
Another filter that is useful but not commonly used is a pad filter, originally designed for home winemakers. It is two plates that spread out the beer and push it through a filter pad. These are available from mail-order houses. They work just the same as the cartridge filters many homebrewers have.
A cartridge filter is a plastic or metal housing that is designed to hold a cartridge. There are many sizes, but 6" and 10" are the most common. There are many cartridges to choose from, and it is important not to choose one with charcoal or carbon. They will remove all of the flavor from your beer and you may end up with Zima.
A good choice for beer filtration is spun polypropylene. Spun filters come rated by the smallest particle they will let through. Common filter sizes are 10 micron, 5 micron, 1 micron and 0.5 micron. Yeast is about 7-8 microns. Bacteria ranges widely but is about 1.5 microns. One micron is .00004 inches, or much smaller than the naked eye can see. If you're thinking, "I'll just use the 0.5," not so fast. Smaller is not always better. If you were to run a really cloudy beer through a 0.5 micron filter it would likely clog before you had finished filtration. So it is common to step through a few filters. I use 10 micron, then 1 micron or 0.5 micron, depending on how cloudy the beer is and how clear I want the beer to be.
I did an informal tasting of some hoppy beers filtered to different sizes. Every taster had noticed a difference by 1 micron; they all perceived a loss of bitterness. At 0.2 micron the hop flavor was completely changed.
While it is possible to filter beer without CO2, it is best to use a keg-to-keg transfer with the filter in-between. Any time we move the beer after fermentation, we must be vigilant about eliminating O2 pickup and a keg-to-keg transfer is the easiest method. The set-up goes like this: Connect your gas to the unfiltered keg gas-in line. Connect the product out line to the filter. Connect the output side of the filter to the beverage side of the fresh keg. Connect a bleed valve to the gas-in of the fresh keg (see photo on page 28).
Make sure to sanitize all of the parts with your usual method before assembly. The filter can be used fresh out of the package. I have heard of homebrewers reusing filters by boiling them, but I have never tried. The cheap ones are not rated for 212° F.
It makes sense to flush out the filter system before using it. I like to run sterile water through all of the hoses and the housing and filter. Most cartridges have a bleed valve on the top. On the housing I use, there is a red button. If you see a pocket of air on the top of your filter, press this button until the fluid level rises to the top. When I am sure I have gotten all of the air out, I push the water out with CO2.
After everything is hooked up, open the valve to the CO2 tank and crack the bleed valve. It is critical to resist the temptation to filter too quickly or at too great a differential pressure, especially with the spun poly cartridges. While it is easier to filter pre-carbonation, it is possible to filter post-carbonation if necessary. When filtering post-carbonation, it is important to control the bleed valve so the transfer goes very slowly. CO2 is dissolved into the beer. As long as the beer after filtration is cold and under enough pressure we will not lose any carbonation. It is important to pre-chill the receiving keg to avoid carbonation loss.
If you would like to use the two- or three-step method, you can either transfer to another keg, changing cartridges before you do so, or use two or more housings in a row. If you are trying to remove a chill haze it is important to filter the beer as cold as possible. A chill haze must be visible to be filtered, because when a particle is dissolved, it is in solution and does not contribute to a haze. A common number is 29° F, but it is probably safer to try about 32° F until you know your set-up. (You don't want to freeze any water left in your system.)
So now you have a keg of bright beer. It will stay that way forever, right? Well, not really. Over time, even the clearest beer can get hazy. Package stability is a huge problem even for the mega-breweries, and they have spent considerable time devoted to keeping the beer as fresh and clear as the day it was "born." But if you've followed the recommendations above, you have a good headstart.
We were careful to control many of the precursors to aging haze. We stopped sparging just in time to prevent polyphenols from getting into our wort. We were careful not to add any oxygen after fermentation.
I have tasted low-gravity, lightly hopped beers after six months and found them as bright as the day they were bottled. With practice and attention to detail, you can brew crystal-clear beer!Colin Kaminski is a brewer at Downtown Joe's in Napa, California. He also works as a product developer at Beer, Beer and More Beer. Colin attended a presentation by Ian Ward at the Northern California chapter of the Master Brewers Association. The presentation was based on a research paper, "The Nature, Formation and Prevention of Beer Hazes," that Ward wrote for Savilles in Aldrich, England. Savilles is a leading fining manufacturer for the beer and wine industries; Ward works for Savilles from Napa.