Life. Don’t talk to me about life.
–Marvin, the paranoid android, The Hitchhiker’s Guide to the Galaxy, by Douglas Adams
Unfortunately, life isn’t perfect. Once you’ve brewed, you aren’t really done. You have to check your beer to make sure it doesn’t have any problems. If it does, you should try to fix them, or at least learn from your mistakes so you can avoid them next time. This is the essence of troubleshooting, or trying to determine what went wrong when your beer didn’t turn out perfectly. It’s a problem-solving discipline that requires an in-depth knowledge of the system and processes.
Most faults for advanced brewers don’t present themselves like they do in a spiked beer on a BJCP exam. Faults don’t always pop up and ask to be noticed. Subtle things can be wrong; they are often hard to notice and may be more stylistic than technical but still have a technical (brewing process) issue as the source of the problem.
Beer judges don’t have recipe or process information, so they often guess at problems in beer. If you’re the brewer, you should be able to troubleshoot your own beer with perfect information. The only things you need to know are how to identify the faults and what you can do to address them. Can you fix the flaws on the fly during your brew day? What can you do after fermentation is complete? How do you know your beer is unsalvageable and should be dumped?
Your goal should be to be able to detect faults at various places in the brewing process. If you are able to fix (or at least partially mitigate) these faults, then your beer may still be drinkable or even quite good. If you aren’t able to fix the faults, you should consider them part of a learning experience, so that you can either adjust your recipe the next time you brew it, or investigate your equipment, ingredients, or processes to remediate the root cause of the problem.
I’ve categorized faults into two major groups: technical brewing faults and style-related faults. A list of common faults is provided, along with how they are perceived and what solutions might be applied. A proper diagnosis of the problem is critical to selecting the right approach for addressing the problem. Randomly applying “fixes” without knowing the source of the problem can often create more severe problems and rarely solves the original issue.
It bears repeating that most brewing faults can be avoided by using fresh, clean ingredients, following good wort production practices (proper level of free amino nitrogen and yeast nutrients, proper level of maltose), providing a sufficient quantity of fresh, high-quality yeast with proper aeration, controlling fermentation conditions, keeping oxygen out of the cold side of the brewing process, and following good sanitary practices. Those are the key control points in brewing; if you follow those practices, you are likely able to avoid most technical faults.
Before we delve into specific faults, know that some faults are temporary and others are permanent. Temporary faults will sometimes go away on their own or can be coerced into going away, while permanent faults often lead to dumping your beer. Be careful about writing off a batch of beer unless you know it contains an unrecoverable fault. If a beer is too bitter, too roasty, too estery, or too alcoholic, those features tend to fade with time, so simple aging under proper storage conditions will likely mellow those faults. Sour, medicinal, or oxidized flavors are usually there to stay; toss those.
Dealing with faults in a beer is similar to how a doctor treats an illness. You start with the symptoms (i.e., the faults in the beer), you diagnose the problem, and you prescribe treatment for the underlying problem. Anybody can “tell you where it hurts,” but a doctor goes to medical school to understand how to identify the important symptoms, understand what condition this represents, and decide what to do about it.
Fortunately, fixing a beer is much less complicated than healing a person, but knowledge and experience still are required. As the brewer, you have some inside information that will help; you know the ingredients and process used. If you can combine that with your beer style knowledge, sensory skills, and knowledge of common faults, you are well on the way to solving your brewing problems.
Common beer faults are identified using their perceptual characteristics; simply use structured evaluation (described in Chapter 5) to isolate the faults, then reference the fault list later in this chapter to help determine cause and effect. A complicating factor is that some faults can come from several different sources. Consider the most likely causes of faults rather than those that are rare, and look for multiple clues toward underlying problems. Again, think of those faults you perceive as symptoms of an underlying problem, and try to determine what went wrong. It can be somewhat of a detective game.
One problem with identifying faults and problems with beer is that some faults are confused with seemingly positive features. For example, if you detect caramel and fruitiness, you could be drinking an English beer, or you could be sensing early forms of oxidation. Heavy caramel (especially kettle caramelization) is sometimes confused with diacetyl. Be careful about jumping to conclusions prematurely, and look for confirming evidence of your diagnosis.
Some balance-related faults are temperature-dependent. If you serve a bitter beer too cold, it will seem even more bitter, since the balancing malt is suppressed. Warming it up might bring it into balance. Warm temperatures can exaggerate the impression of esters, alcohols, and other volatile aromatics. Try to assess the beer at proper serving temperature for the beer style in question.
You can simplify the diagnosis by leveraging your knowledge as the brewer. For example, if you know the fermentation was sluggish or that the target gravity wasn’t met, use that to prune the possible choices for the faults you detected. If you think the problem is ingredient-related, do you have any other beers made with the same ingredients? Do they have problems, too? Likewise for process. What are the common elements between different batches? Think of this as the “medical history” part of the investigation. If you made recent changes or have a recurring problem, see if that information can lead you to the source.
For subjective faults, broader input is often useful. Get feedback from other knowledgeable brewers, tasters, beer judges, etc. Are their observations consistent, or are they giving you widely varying opinions? Some beers can invoke love-it-or-hate-it responses from tasters.
Technical faults are what most people think of as flaws in beer; they are either single faults or a combination of faults that are derived from the brewing process, often from fermentation. These are more obvious faults that many people can find; basic tasting skills and quality control can often catch them. Sensory thresholds for the different chemical substances associated with the brewing faults can vary by individual, based on genetic or physical limitations, individual perceptual differences, and insensitivity to certain substances. It helps for you to know your own limitations.
Newer brewers often have beers that show multiple faults. The flavors I often detect in their beers are derived from weak fermentations; there are off-flavors of varying levels, poor attenuation, general unclean or muddy flavors, and vegetal notes. A slow start can allow spoilage bacteria to grow. Weak fermentations can cause the yeast to throw off many off-flavor by-products and not be able to clean them up. Stale extract has a tangy flavor. Oxidation of ingredients and the beer at various stages is frequently evident. Stale, dull flavors are common. Infections can exist in different forms. Some are from wild yeast and tend to be phenolic, others are tart, others are vegetal. General spoilage bacteria can take root after the wort is cooled and before the yeast starts active fermentation. Poor ingredients, inattention to oxidation, long lag times, weak fermentations, and poor handling of the finished beer all contribute to lame flavors and a poor drinking experience.
This discussion of faults is an elaboration on material I helped develop for the Beer Judge Certification Program’s instructional information for beer judges, and covers the most common technical flaws found in homebrewed beer.
Acetaldehyde. A fermentation-derived character perceived as an aroma and flavor of fresh-cut green apples, or as a grassy, rough, green, immature beer flavor. It is an intermediate fermentation compound and a precursor to alcohol. It is a common green beer flavor and a marker of beer maturity (it increases during fermentation, then decreases as the beer conditions).
It can be controlled by proper fermentation (pitching rate, oxygen, nutrients) and conditioning practices to allow the fermentation to finish and to let the yeast naturally reduce the acetaldehyde levels. Yeast must remain in contact during these phases to do their job. Ensure yeast remains healthy and in sufficient quantity to start fermentation quickly, then subsequently finish fermentation and achieve full attenuation. Allow sufficient conditioning time in contact with the yeast. Some yeast strains are known for producing higher levels of acetaldehyde, in which case selecting another strain is the solution.
Reducing head pressure during fermentation and conditioning can allow the aldehydes to blow off, as they are easily volatilized. Avoid oxygen during packaging; alcohol oxidizes back to aldehydes, which can then cause stale beer flavors. Light and heat can also catalyze this process.
Levels can be increased in primary fermentation by having an intense fermentation, increasing fermentation temperature, increasing pitching rate, increasing fermentation pressure, reducing aeration, and by stirring up the yeast. Levels can be reduced after fermentation by having an active secondary fermentation and conditioning, warm conditioning, increasing yeast concentration during conditioning, and reducing aeration.
Alcoholic/hot. A fermentation-derived character that can be perceived as an aroma, flavor, and mouthfeel. Although ethanol is relatively tasteless, it can be tasted (think of the flavor of vodka). It is often found with other higher alcohols and can have a spicy, vinous aroma and flavor and a warming sensation in the mouth and throat. At higher levels, the warming can seem hot or burning. Alcohol also adds bitterness to beer. Since ethanol is the primary objective of fermentation, it by itself is not a flaw unless it is unbalanced or insufficiently aged. However, it is often accompanied by other flavors from higher alcohols (see Solvent/fusel for more detail).
Conditions that favor development of ethyl alcohol also can lead to fusel alcohols being formed. Reducing the alcohol level can control this character, which can be accomplished by reducing the starting gravity of the recipe, reducing the fermentability of the wort (raising the mash temperature, using less sugary adjuncts), or using a less attenuative yeast strain.
Conducting a healthier fermentation can produce cleaner alcohols. Lower fermentation temperature, ensure proper fermentation conditions are met, check yeast health, and select a yeast strain that produces less alcohol character. Follow good sanitation practices to avoid infection, which can increase attenuation and alcohol production.
Finally, let the beer condition and age longer before consuming. Beers with a higher alcohol content often need considerable cellaring before they become smooth and drinkable.
Astringent. A mouth-puckering mouthfeel with a lingering, bitter harshness and a husklike, grainy flavor. Astringency is primarily a mouthfeel but is accompanied by telltale flavors. It is typically derived from a combination of the ingredients and brewing process. Astringency in beer is caused by tannins; controlling tannin extraction controls astringency.
Tannins can come from grain husks and can be extracted during the mash, sparge, and boil. Don’t oversparge; attempting to get every last bit of extract from the grain can cause a husky flavor. Don’t overcrush the grain; husk particles can carry over to the boil and have more surface area for tannin extraction. Don’t boil grain. Don’t sparge with water above 170° F (77° C) and with a high pH (above 6). Use a lower amount of dark grains (especially black malt).
The vegetal matter in hops is also a source of tannins. Use a lower quantity of whole hops (especially high-alpha hops). Use water with lower sulfate content, since sulfates can accentuate bitterness and harshness associated with tannins. Avoid the use of raw spices, fruit pith, and fruit skins, which are also sources of tannins.
Diacetyl. A fermentation-derived character that can be perceived as a flavor and an aroma. It has a flavor like butter, butterscotch, or movie theater popcorn (artificial butter uses diacetyl as a flavoring). It sometimes has a slick mouthfeel as well. It is an intermediate yeast by-product, typically reduced by yeast during fermentation. Warm fermentation temperatures and high levels of aeration can increase diacetyl but also can lead to later reduction, if enough healthy yeast is present.
Control diacetyl by following good fermentation practices (adequate pitching rate of healthy yeast, aeration, nutrients) and avoiding low nitrogen adjuncts (which can reduce available yeast nutrients). Removing the yeast prematurely can leave high diacetyl levels. Don’t crash-cool the yeast, or rack, filter, or fine too early. Allow the beer to rest on the yeast until fully attenuated. Avoid adding oxygen during fermentation. Reduce primary fermentation temperature to control the production.
Diacetyl can be removed by stimulating yeast activity in the absence of oxygen (i.e., a diacetyl rest, more commonly conducted for lagers), or by raising the temperature or extending secondary fermentation (warm conditioning). Bacteria, wild yeast, and mutated yeast can also produce diacetyl, so good sanitation and yeast-handling techniques are important for control. Some yeast strains are known diacetyl producers; avoid those if you wish to control this character. Bottle-conditioning beer at cellar temperatures also gives the yeast additional time to reduce the diacetyl.
DMS (dimethyl sulfide). Perceived as the flavor and aroma of creamed corn, cooked corn, cooked vegetables (often sulfury vegetables like cabbage). Derived from malt (S-methyl methionine, SMM) during germination. Highly kilned malts produce less SMM, so paler beers will have more DMS. Above 65 to 70° C (149-158° F), SMM is converted to DMS, but DMS is volatile and can blow off with rising heat (as in a proper boil).
Control at the source by reducing the amount of SMM (reduce Pilsner malt and other very pale malts). Drive off any DMS created from SMM by using a long, vigorous, rolling, open boil. When DMS has not been fully volatilized during the boil (nonvigorous boil, insufficient boiling time, covered boil), it will remain in the beer. DMS can also be created after the boil, unless the wort is cooled rapidly. Long whirlpool times or extended time before chilling can create DMS.
DMS can also come from infections. Make sure you use a healthy, vigorous yeast starter and follow good sanitation practices. Cool quickly, and pitch yeast shortly afterward.
Estery. Perceived as a fruity (strawberry, pear, banana, apple, grape, citrus) aroma and flavor, it is generally fermentation-derived (not counting esters that come directly from malt or hops). Esters are commonly associated with English and Belgian ales but are unwanted in most lagers. At excessive levels, esters can take on an unpleasant, solventy character.
Ester formation is quite complicated and depends on many factors. Esters are derived from an alcohol and a fatty acid. Not all esters are produced in the same way. Ester production is influenced by yeast strain, wort composition, and fermentation conditions. Contradictory evidence exists as to the effect of pitching rate on esterification. The optimal pitching rate to maximize esters may differ by strain.
When factors favoring growth (oxygen, lipids, stirring) are present, yeast tend to grow more and produce fewer esters. Fermenting at a high temperature and adding new wort to an active fermentation stimulate ester production. Conditions that stimulate fusel production (temperature, zinc) also contribute to esterification. Many esters are formed from fusel alcohols as well as esters.
Lager yeast produce fewer esters, but low fermentation temperatures may be the primary cause. Warm-fermented lagers will be quite estery. Many ale yeasts produce a significant amount of esters, particularly strains associated with English and Belgian beers.
Carbon dioxide pressure during fermentation is a common way of influencing ester production. High levels of carbon dioxide inhibit ester production. Tall, cylindrical tanks increase pressure on the yeast but also produce natural convection currents that limit esterification. Shallow fermenters tend to maximize ester production (e.g., in German weizenbiers and Belgian ales).
Ester production can be increased by selecting a yeast strain known for esters, using flocculent yeast, adjusting the pitching rate (high or low, depending on the strain), and from yeast mutations from generation to generation. Esters can also be increased by reducing oxygen in the wort, raising the gravity of the wort, reducing fatty acids present, and increasing zinc levels. Higher fermentation temperatures, decreased pressures, and decreased stirring can increase esters. In general, stressing the yeast during fermentation can increase esters.
Bottle conditioning and aging the beer longer at cellar temperatures on the yeast can reduce esters. Slow oxidation during storage can increase esters.
Grassy. Perceived as the flavor and aroma of fresh-cut grass or green leaves. Generally a hop-derived character produced by the prolonged contact of beer with the vegetal material in hops, or through contact with raw hops (as in dry hopping).
Control by reducing or eliminating dry hopping, possibly substituting another late-hop technique instead. Also can be controlled by reducing the quantity of whole hops used throughout the beer. Avoid post-fermentation oxygen pickup, which can give a harsher, grassy character to hops. Check hops and malt for freshness; stale, oxidized flavors can sometimes have a grassy component.
Light-struck. Perceived as a skunky or catty aroma and flavor. Certain wavelengths of visible light striking hop chemicals cause a physical change that produces mercaptans, the same chemical skunks produce to defend themselves. Humans are extremely sensitive to these sulfur compounds and can detect them in concentrations as little as parts per billion.
Since light-struck beer is caused by exposure to sunlight, avoid allowing direct sunlight to strike the beer after hops have been added. Store beer in brown bottles, since clear and green bottles are up to eight times less effective in blocking the critical wavelengths. Avoid extended exposure of packaged beer to sunlight or fluorescent light. Brown bottles can reduce the transmitted light but are not opaque; given enough time, beer in brown bottles can skunk, too.
Some hop varieties (such as Cluster) can have a catty aroma; avoid their use in late additions. This isn’t exactly the same as light-struck but can have a similar character.
Medicinal. Perceived as the flavor and aroma of Chloroseptic lozenges, disinfectant, or other harsh medicines or cleaners. Caused by chlorophenolic substances, derived from a combination of chlorine and phenols. One of the most offensive flavors in beer.
Control by removing chlorine from the water supply. Avoid water with chlorine or chloramines (use RO water, if necessary). Filter supply water with activated charcoal filters. Use Campden tablets to neutralize chloramines. Avoid chlorine bleach sanitizers.
Control by reducing sources of phenols. Reduce astringency/grain husk sources. Avoid excessive whole hop use. Practice good sanitation to reduce infections, particularly from wild yeast strains. Avoid yeasts that produce phenols, such as weizen strains and some Belgian yeast.
Metallic. Perceived primarily as the flavor of iron, copper, coins, or blood. Can be detected in the aroma in high enough concentrations. Typically caused by impurities in the water source or defects in equipment. Can also come through intentional or unintentional chemical additions.
To control, check your water supply for metallic ions, particularly iron. Get your water tested. Reduce salt additions to brewing liquor. Check the condition of your brewing equipment, looking in particular for rust. Make sure stainless steel equipment is properly passivated. Fully rinse any sanitizers. Try using RO water if your water supply is suspect, and only add the brewing salts necessary.
Musty. Perceived as the flavor and aroma reminiscent of a stale, moldy cellar. Carries the impression of age, filth, dirt, and general lack of cleanliness. Can be due to mold in the ingredients, stale ingredients, oxidation, or infection.
Avoid oxidation (see Oxidized). Follow proper sanitary practices. Avoid peat-smoked malt. Check water for freshness and taste; use an activated charcoal filter or use RO water. Use fresh ingredients (especially malt and hops); sometimes the staleness carries through from the source. Avoid the use of corks when bottling; the cork itself can cause off-flavors (a flavor known as “corked” in wine tasting). Check equipment or supplies (like bottle caps) for contamination and cleanliness.
Oxidized. A common problem, can be perceived as a stale, papery, or wet cardboard aroma and flavor; this form of oxidation is always bad and is not recoverable. Slow oxidation of alcohols are sometimes desirable, and can provide a pleasant sherrylike character in some styles, such as barley wines and old ales. Controlled oxidation of tannins can soften astringency in red wine and hoppy beers. Esterification of harsh fusel alcohols during aging can also lead to improved flavor and aroma.
Oxidation from slow aging can cause beer to take on sweeter or more caramelly flavors and can cause esters to increase. Not all oxidation will be like paper, cardboard, or sherry. Some might cause increases in these other flavors that take a beer out of balance before ultimately becoming dull, stale, and old-tasting.
To control, avoid introducing oxygen into the beer during the second half of fermentation or later. Don’t let airlocks run dry. Don’t splash the beer when racking or bottling; blanket the beer with carbon dioxide after racking. Check bottle caps and keg seals for good fit. Use oxygen-scavenging caps. Purge bottles and kegs with CO2 prior to filling. Bottle-condition beer; yeast will take up oxygen. Store beer cold to slow the rate of oxidation (and other chemical reactions). Drink beer when fresh.
Plastic (phenolic). Perceived as the flavor and aroma of adhesive bandages, electrical tape, or styrene plastic. Typically caused by a wild yeast infection but also can be produced by some yeast strains when fermented at very high temperatures.
Follow proper sanitary practices, avoiding infection by wild yeast. Use a different yeast strain or form. I’ve had off-flavors from some older dry yeast products. Make sure your yeast is healthy and active, and follow good fermentation practices. Avoid a long lag time at the start of fermentation. Reduce fermentation temperatures.
Solvent/fusel. Perceived as a hot burning sensation on the palate, and an alcoholic, spicy, hot, vinous, and solventlike aroma and flavor. Can cause headaches, especially in the temples. Fusel alcohols are fermentation-derived.
Ethanol is relatively tasteless. Fusel alcohols (or higher alcohols) are more aromatic than ethanol. In general, conditions that promote rapid yeast growth can foster fusel alcohol production. Fusels are produced when yeast growth stimulators create demands for amino acids beyond the quantity of amino acids in the wort.
Factors that favor increased fusel alcohol production include increased dissolved oxygen, stirring/convection currents (using tall fermenters), high fermentation temperature, high-gravity wort (greater than 13 °P, 1.052), low pitching rate, low-pressure fermentation, and yeast strain (certain strains, especially ale strains, produce more fusel alcohols).
If performing a higher-gravity or warmer fermentation, increasing pressure in the fermenter can inhibit fusel alcohol production (as well as esters). To control, take steps to reduce the rate of yeast growth. Lower fermentation temperature or use a different yeast strains. Using glucose adjuncts (no nitrogen) increases fusel production (hello, malt liquor). Follow proper sanitation practices, since infections can also cause fusels to be produced.
Sour/acidic. One of the five basic tastes, it can also be perceived as an aroma and a mouthfeel. Different acids have different aromas and flavors and a different overall balance. Lactic acid can have a clean sourness, citric acid a sharp sourness, and acetic acid a harsh, vinegary sourness (see Vinegary for a description).
Follow proper sanitation practices to reduce the chance for infection. Check your equipment for nicks or scratches that can harbor bacteria. If you make lambics or otherwise intentionally use acid-producing bacteria, segregate your equipment. Select a different yeast strain. Don’t mash for long periods of time at low temperatures (this is called a sour mash).
Smoky (phenolic). Perceived as a smokelike, charcoal, or burnt flavor and aroma. Can be caused by infections or by ingredients or processes that involved burning.
Follow proper sanitation practices to avoid infection. Select a yeast strain that produces fewer phenols. Adjust the fermentation temperature of your yeast (either up or down, depending on the strain). Check for a scorched mash or boil; clean equipment of residue from previous batches, stir decoctions constantly, control heat applied to kettles and tuns. Reduce the use of dark malts or rauchmalz.
Spicy (phenolic). Perceived as the flavor and aroma of spices, such as clove, pepper, vanilla, etc. These are often positive phenols, and are produced by yeast or are derived from ingredients or processes.
Certain yeast strains and hop varieties can produce spicy characteristics, such as clove and pepper. Adjust fermentation temperature (sometimes higher, sometimes lower, depending on yeast strain and beer style). Oak aging can increase the vanilla character in beer.
Sulfury. Perceived as the flavor and aroma of rotten eggs or burning matches. Sulfur dioxide (SO2) is the striking match aroma and flavor. It’s a common feature of many European lagers and has antioxidant and antimicrobial properties. Sulfur dioxide can reduce acetaldehyde production during storage. Winemakers often add sulfites for these positive purposes. Hydrogen sulfide (H2S) is the rotten-egg aroma and flavor, which comes from fermentation. Unhealthy yeast or nutrient deficiency can cause increased H2S levels. It is easily volatilized.
Lower SO2 with warmer conditioning and storage, increased lagering times, and reducing head pressure during lagering. Reduce its formation during fermentation by increasing yeast nutrients in wort, increasing lipids, increasing aeration, having healthy, active yeast, and removing hot and cold break and trub.
Reduce H2S by increasing lagering temperatures and fermenter height to cause it to be blown off faster. It can also be caused by an infection, so follow proper sanitation practices.
Sulfates in the water, or sulfate additions (Burton water salts, gypsum) can cause the flavor and aroma of sulfur. Some yeast strains produce more sulfur than others (typically lager strains), so choosing another yeast can be a control. Some copper in the boil can help take sulfur out of beer; simply having some copper equipment in contact with the wort during the boil is sufficient. I know some brewers who throw a small copper plate into the wort to achieve this effect; my false bottom is copper, so I naturally have this on my system. Note, however, that adding copper to finished beer is a mistake that can negatively impact its flavor and appearance.
Vegetal. Perceived as the flavor and aroma of cooked, canned, or rotten vegetables (cabbage, celery, onion, asparagus, parsnip). Can be caused by DMS (see DMS), an infection by wort spoilage bacteria, or oxidation of ingredients.
Encourage a fast, vigorous fermentation (use a healthy, active starter to reduce lag time; this is often due to bacterial contamination of wort before yeast becomes established). Follow proper sanitation practices. Check for aged, stale, or old ingredients (especially old liquid malt extract, which I perceive as a tangy vegetal flavor). Avoid oversparging at low temperatures.
Vinegary. Caused by acetic acid and perceived as vinegarlike sourness in the flavor and aroma. Acetobacter infection is the cause, but oxygen is necessary for vinegar to be produced, since the bacteria is aerobic.
Control sources of acetobacter and avoid oxygen uptake. Follow proper sanitation practices. Check your equipment for nicks or scratches that can harbor bacteria. If you make lambics or otherwise intentionally use acid-producing bacteria, segregate your equipment. Select a different yeast strain. Avoid using barrels or putting wood in your beer.
Yeasty. Perceived as a bready, sulfury, yeastlike, or glutamate flavor and, to a lesser extent, aroma. Some of these flavors are due to young, fresh yeast still in the beer, while others are caused by too long a contact with the yeast.
Young yeast character can be controlled by using a more flocculent yeast strain, allowing yeast sufficient time to flocculate, filtering the beer or using clarifying agents, and avoiding carrying over as much yeast during transfers. Aging the beer longer can also reduce the fresh yeast character.
Autolysis is a character that can come from beer being held on the yeast too long at too warm a temperature. I perceive it as an umami or glutamate flavor (like MSG). Glutamates can remind people of soy sauce, mushrooms, Parmesan cheese, or other similarly strongly flavored foods. Despite being termed “savoryness,” it’s not a desirable flavor in beer. I’ve heard it described as “rubbery”; I don’t perceive it that way at all. When a beer develops autolysis character, its pH rises after fermentation has completed; that’s one confirmation that it’s present.
To control autolysis, rack your fermented beer off the yeast as soon as the yeast has reduced the green fermentation flavors. Don’t store your beer on the yeast for a long time, particularly at warmer temperatures. If it needs additional conditioning, rack to a secondary fermenter to reduce the quantity of yeast in contact with the beer.
For the longest time, I thought autolysis was a myth, since I never tasted a rubbery flavor in beer. However, once Gary Spedding taught me that it was a glutamate flavor, I could then taste it in several beers (even a few of my own, unfortunately). It caused me to rethink my conditioning practices.
A beer can have no obvious technical flaws yet still not seem right. When this is the case, it is often a style-related fault—that is, one that has to do with the balance and drinkability of the beer, or how the beer compares subjectively against commercial examples, reference style guidelines, or simply the taster’s own expectations. These faults are often more difficult to identify and isolate, since they are necessarily based on a subjective assessment by a taster and are based on a comparison with a possibly arbitrary standard.
Let’s set aside any argument about beer styles; those are covered in Chapter 5. Assume the brewer accepts the reference style description, and that the beer has a noticeable difference when compared against the standard. Style knowledge and structured tasting skills are necessary to isolate and describe the problem in relation to the reference beer style description.
Style-related faults can often be traced back to recipe formulation, ingredient selection, or process selection. Correcting these faults may involve some of the same corrections as would be used to address technical faults.
A beer with a lower starting gravity than expected will often have the wrong malt-to-hop balance, with the bitterness seeming high. For stronger beers that have noticeable alcohol, lower gravity will make the beer seem more mundane. Lower gravity beers might also seem watery or lacking malt presence.
Gravity-related issues are usually traceable to poor efficiency or improper measurement of boil volumes. Start by checking the malt; is it slack (damp) or does it have any insect damage? Those can reduce the potential extract. Then check the crush of the grain; you’re looking for intact husks but flour the size of coarsely ground black pepper. A finer crush will convert faster and give a higher efficiency and vice versa; make sure you are leaving enough time for full conversion (do a starch test if unsure). Doughing-in (hydrating your malt before raising it to a mash temperature) can also improve efficiency. Stirring the mash improves efficiency.
Checking the mash chemistry is next on the list. Did you supply sufficient calcium? Did the mash pH settle in the 5.2 to 5.5 range? Consider step mashing to improve efficiency. Make sure your measuring tools (thermometer, pH meter, hydrometer) are calibrated. Add a mash-out step to increase efficiency. Cut a checkerboard pattern into your mash with a long, thin spatula prior to sparging. Slow the lauter flow and sparge longer.
Measure your starting volume and gravity accurately before beginning the boil. Use a calibrated measuring stick for your system. Determine your final boil volume to hit the target gravity before beginning the boil. If your volume is correct but the gravity is low, add more fermentables (malt extract or sugary adjuncts) to the boil. If your volume is low but the gravity is correct, shorten the boil. If your volume is low but the gravity is high, dilute the wort with water. Based on your system’s evaporation rate, decide on the length of the boil to hit the target volume. It’s much easier to correct these issues before the boil. Remember that you can adjust several variables (boil length, starting volume, starting gravity) to achieve the target result.
Attenuation affects how dry or sweet a beer tastes and, to a lesser extent, the amount of body present. Errors in attenuation can greatly impact the balance, drinkability, and style fidelity of a beer. Dryness accentuates bitterness, and sweetness masks bitterness, so a change in attenuation will alter the impression of bitterness even if the measured IBUs are the same.
Attenuation is driven more by wort composition than yeast strain, so first look to your grain selections and your mashing techniques. Yeast strain can play a secondary role, but most yeast will fully attenuate given the proper conditions. Less flocculent yeast strains and longer conditioning times can improve attenuation.
Try to determine the composition of the extract remaining in the beer. Does it have a malty or sugary sweetness, or is it dry? Sugary sweetness indicates unfermented sugars remain, while a dry beer suggests that dextrins are the cause. Sugary sweetness can be reduced by encouraging continued fermentation, while dextrins remain unfermentable by traditional beer yeast.
Dextrins can add body and raise finishing gravity but not add sweetness. The sweetness often clashes with bitterness, so aim for dextrins for body, not residual unfermented sugars. Too many dextrins make the body full and can hurt drinkability. Certain styles need some residual sweetness, but many are fully fermented.
If you did not get the attenuation you desired, lower your primary saccharification temperature or use a step mash. Adding sugar will increase the attenuation. Starting with a lower starting gravity will result in a lower finishing gravity, which may make the beer seem drier (and hence more attenuated) even if the degree of attenuation is the same.
If your beer attenuated too much, take the opposite steps. Mash higher, remove sugars from the recipe, increase the starting gravity, use more crystal malts, add starchy adjuncts, use dextrin malts, and shorten conditioning times.
The length of the boil can affect several factors in beer. If Pilsner malt or other malt with a significant amount of SMM is used, then a 90-minute boil should be used to reduce the DMS in the finished beer.
The strength of the boil affects the evaporation rate and the final volume. If the final volume target is missed, the original gravity and the BU:GU ratio are likely to be off, which will change the balance of the beer.
Long boils (more than 90 minutes) can extract more harshness from hops, in addition to more bitterness. If you use a long boil, don’t add the hops until the last 90 minutes or less. Long boils also can increase the color of the wort and add caramelized flavors; this is desirable in some styles, but not others. Don’t use a long boil unless you are looking for these side effects.
Harshness is a common problem with beers that use a lot of hops. In my experience, hop-derived harshness comes from four factors: the quantity of hops used, the amount of time the hops are boiled, the water chemistry, and the chemical makeup of the hop varieties used. The more hops you use and the longer they are boiled, the harsher your beer can be. Large amounts of hops can give vegetal flavors, and long boils can extract harsh compounds. Brew water with a high pH, high carbonates, or high sulfate content can lead to harshness in a pale, hoppy beer. Hops with low cohumulone (check the varieties against data from places like HopUnion, “low” is under 30 percent) are known to have a smoother flavor.
All-late hopping can reduce harshness. Avoid post-fermentation oxygen pickup, since oxidized hops can give a harsh bitterness. Sulfates accentuate bitterness but can lead to harshness (particularly if used with noble hops). Using lesser amounts of high alpha hops can cut the harshness by reducing the vegetal mass. Certain hops (such as Magnum) are prized for their clean bitterness without harshness.
Dark grains can also cause harshness when used in long mashes and boils. Using cold-steeped dark grains can reduce this, as can adding the dark grains only at mash-out.
Excessive alcohol can cause harshness. Reducing the gravity of the beer, and hence the alcohol level, can help, as can cellaring the beer for extended times to smooth out the alcohol that is present.
The aftertaste of beer is particularly important, since that’s the flavor left in the taster’s mouth after the beer has been tasted; it’s the lasting impression. Some of the issues previously discussed (harshness, attenuation) affect the aftertaste, but there are other potential problem areas as well.
A muddy, dull, or indistinct aftertaste can sometimes by caused by using too many ingredients (flavor clashes), using old or lower-quality ingredients, or by having a high pH (above 4.5).
Lingering grassy and vegetal flavors could come from dry hopping. Try adding hops at knockout, in the whirlpool, or in a hopback to reduce the raw character, or reduce the length of time dry hops are used to less than a week.
If the aftertaste doesn’t seem dry enough, the problem might not be attenuation alone. It could be the pH is too high, or that not enough sulfates were used. Some styles, such as Irish and Scottish ales, use a little bit of roasted barley to add dryness to the finish.
The relationship between attenuation, dryness/sweetness, and bitterness affects the overall balance and drinkability of the beer. Bitterness and sweetness give a bittersweet flavor, which tends to linger. Excessive sweetness in the finish makes a beer difficult to drink, as does a full body. The lack of a crisp finish tends to make beers more suitable to sipping than drinking.
A cloudy or hazy beer can be off-putting and can even affect body and flavor. First try to determine the source of the haze: starches, sugars, yeast, or proteins/tannins. Starch haze usually indicates a mashing problem. Sugar haze usually is due to an incomplete fermentation. Yeast haze is a flocculation problem. Proteins and tannins are usually caused by not having a good hot and cold break or by carrying over excessive break material to the fermenter.
Clarifying is discussed in more detail in Chapter 8, but keep in mind that avoiding cloudiness is preferred to removing it later. Adopt proper brewing practices to convert starches fully, have a good hot break and cold break, fully ferment the sugars, and to have the yeast settle properly. Finings can be used in the boil or after fermentation is complete. Cold temperatures and time tend to improve clarity as the particulates flocculate. Filtering is a rougher way of removing haze-causing particles. Removing haze becomes more difficult once the beer is carbonated, so it’s best to handle clarity issues prior to packaging.