I remember my first attempt at homebrew. It was an IPA. It tasted like garbage but I drank it because I made it and I didn’t want to tip it out. I also spent a lot of time researching what could have gone wrong. Understanding the off flavour is the main key. From there you can figure out where you went wrong and how to avoid it again. The list below is 21 common off flavours in brewing. Maybe you’ll be lucky enough and you won’t ever encounter these issues, but if you do, this guide should help you out.
Acetaldehyde
Tastes/Smells Like:
Bruised apples, Green apples, rotten-apples, freshly cut pumpkin, squash-like or latex paint. Often sweet apple esters and sourness is mistaken for this off-flavour.
Green apple or cider-like characteristics can be tricky. To the untrained palate, you may think this is just an interesting fermentation by-product that gives your beer a little fruity zing, but the reality is it is rarely an intended characteristic in beer. This off-flavour is caused by acetaldehyde, which is a compound formed during fermentation as a precursor to alcohol. It typically increases in amount during fermentation and then decreases as beer conditions and ages.
Possible Causes:
Acetaldehyde is a naturally occurring chemical produced by yeast during fermentation. It is usually converted into Ethanol alcohol, although this process may take longer in beers with high alcohol content or when not enough yeast is pitched. Some bacteria can cause green apple flavours as well. It can also be caused by oxidation, where too much O2 exists in packaged beer, it can change ethanol’s back to acetaldehyde.
Acetaldehyde is a key signifier of young “green” beer, so often times the issue is remedied by simply allowing the beer to condition longer.
How to Avoid:
Let the beer age and condition over a couple of months time. This will give the yeast time to convert the Acetaldehyde into Ethanol. Always use high quality yeast and make sure you are pitching the correct amount of healthy yeast for the gravity of the wort or make a yeast starter.
Krausening, a traditional German technique, can also help clean up acetaldehyde in beer. If additional conditioning time or krausening does not work, in your next homebrew ensure the appropriate amount of viable yeast is pitched, the wort is adequately oxygenated and the fermenting wort is left on the yeast longer.
Also, avoid aeration after fermentation has started. Condition at slightly higher temperatures, especially with lagers and when bottling, minimize O2.
Alcoholic
Tastes/Smells Like:
Overpowering alcohol flavour, bitter, acetone, paint thinner, spicy, sharp, undesirable “hot” sensation in the throat
Possible Causes:
Fusel alcohols such as propanol, butanol, isobutanol, and isoamyl alcohol as well as phenolic alcohols such as tyrosol are usually responsible for unpleasant alcohol flavours. Limited amounts of these alcohols can be desirable in high alcohol beers such as barley wines or strong ales and are much more noticeable in lighter style beers.
Fusel alcohols can be produced by excessive amounts of yeast, or when the yeast sits too long on the trub. This is one reason to move the beer off of the hot and cold break when the beer is going to be spending a lot of time in the fermenter.
How to Avoid:
Avoid fermenting at temperatures exceeding 26ºC. If the beer is going to be sitting in the fermenter for longer than a couple of weeks, it is a good idea to remove as much sediment from the wort as possible before transferring it to the fermenter. A secondary fermenter can also be used to help reduce the amount of contact time the beer has with the trub.
Astringent
Tastes/Smells Like:
Tart, vinegary, tannin, drying, puckering sensation, may feel powdery or metallic in the mouth, like sucking on a grape skin or a tea bag.
Astringency is usually identified as a harsh bitterness sensation to the palate, which can be accompanied by some grainy, husk-like flavour. This off-flavour can be misinterpreted as hop bitterness, though with some practice it becomes easier to discern the difference between the two.
Possible Causes:
Astringency can be caused by many different factors. Polyphenols or tannins are the number one cause of such flavours. Tannins are found in the skins or husks of the grain as well as in the skin of a fruit. Steeping grain for too long or grain that has been excessively milled or crushed can release tannins. When mashing, if the pH exceeds 5.2 – 5.6, astringent flavours can be produced. Oversparging the mash or using water that is too hot are common causes for exceeding the mash pH range. Over-hopping can also lend a hand in creating astringent qualities.
How to Avoid:
Avoid grain that has been “over-milled”. Grain should be cracked open but not crushed or shredded. When sparging, pay close attention to the temperature and the amount of the water used. When steeping grains, be sure to take them out before the water gets to a boil. Fruits should never be boiled in the wort, and are better of added during fermentation. Make sure that the amount and varieties of hops used are the correct types for the style of beer.
Chlorophenol
Tastes/Smells Like:
Plastic, Vinyl, Iodine
Possible Causes:
Using chlorinated tap water to brew or rinse equipment is the most common cause for plastic-like or medicinal flavours. Medicinal flavours can also be the result of using cleanser or sanitizer that is chlorine or iodine based. Some wild yeast will contribute to a similar medicinal taste.
How to Avoid:
Don’t use chlorinated water to brew or to rinse equipment that will come into contact with the beer. If chlorinated water must be used, use a water filter that removes chlorine or boil the water for 15 minutes and then cool to room temperature to force out any chlorine that may be present. Always use the recommended amount and concentrations of sanitizers. Most sanitizers will not cause any off flavours when used properly.
And the most important key to avoid any off flavour is to ensure proper sterilisation and cleaning methods are in place before, after and during brewing.
Cidery
Tastes/Smells Like:
Apple Cider, Wine, Acetaldehyde (apples)
Possible Causes:
Cidery flavors can have several causes but are often the result using too much corn or cane sugar is the most common cause for wine or cidery flavours. Generally, 0.5kg of sugar per 19L batch is considered the limit before cidery flavours start developing. Acetaldehyde can also give off a green apple, cider-like quality.
How to Avoid:
Try cutting down on the amount of corn or cane sugar being used. Using an alternate source of fermentable sugar can help to reduce cidery or winey flavours. Dried or Liquid malt extract will not give off any cider flavours. Honey is another good substitution as it is almost fully fermentable but it will leave a slight to strong honey aroma and taste depending on how much is used. If the cause is the yeast rather than cane or corn sugar, lagering may help cidery flavours to dissipate over time.
Diacetyl
Tastes/Smells Like:
Butter, Rancid Butter, Butterscotch, Buttermilk, Oily, Slickness in the mouth and tongue and smell of an unpopped bag of butter flavour microwave popcorn. Lower levels can appear almost Caramel-like. Easier to detect in light lagers, any added complexity in a beer such as darker more robust flavours will make detection more difficult.
Possible Causes:
Diacetyl is naturally produced by all yeast during early fermentation, but is usually reabsorbed by the yeast cells. Non-reabsorption or overproduction is caused by feeble or short boiling, low temperatures during fermentation, mutated yeast, or racking too soon. It can also be formed by bacteria contamination. It is generally regarded as a flaw when detected in lagers. Some brewers and drinkers alike desire small amounts in ales.
How to Avoid:
Taking the following steps will help yeast to properly reabsorb diacetyl in wort: Always boil vigorously for the appropriate amount of time. Yeast that is highly flocculant may fall out of suspension before it gets a chance to absorb the diacetyl, using medium flocculation yeast should give the yeast a good chance to absorb diacetyl. Always use high quality yeast and avoid weak or possibly mutated strands that may be incapable of handling diacetyl properly. Allow yeast to begin initial growth with the use of a yeast starter. Supply sufficient oxygen for yeast growth, but avoid over oxygenating especially after pitching yeast. You should also allow enough time for yeast to fully ferment at appropriate temperatures. You can up the temperature slightly as you near fermentation to help yeast reabsorb diacetyl.
Dimethyl Sulfide (DMS)
Tastes/Smells Like:
Cooked vegetables, especially creamed corn, cabbage, tomato, tomato sauce and shellfish/oyster-like flavours. When caused by a bacterial infection, DMS has a more rancid character, closer to cooked cabbage than corn. It is usually the result of poor sanitation. Repitching the yeast from an infected batch of beer will perpetuate the problem.
Possible Causes:
DMS comes from a sulfur-based organic compound (S-methyl methionine, or SMM) produced when grain germinates during the malting process. Six-row lager malts and Pilsner malts have the highest levels of this compound. As do some adjunct grains such as corn. Like diacetyl in ales, DMS is common in many light lagers and is considered to be part of the character. DMS is produced in the wort during the boil by the reduction of SMM.
When malt is roasted or toasted, the SMM is reduced beforehand and does not manifest as DMS in the wort, which explains why it is more prevalent in pale lagers. In other styles, DMS is a common off-flavour and can be caused by poor brewing practices or bacterial infections. DMS is continuously produced in the wort while it is hot and is usually removed by vaporization during the boil. If the wort is cooled slowly these compounds will not be removed from the wort and will dissolve back in. It can also come from wild yeast or bacterial contamination during fermentation.
How to Avoid:
Higher moisture content in malt increases the SMM, so make sure you store your malt in a dry, cool place. When boiling the wort, DMS is driven off through evaporation. It is very important to always maintain a strong rolling boil for at least one hour. Some brewers boil for 90 minutes to ensure that as much DMS is driven off as possible. Avoid letting condensation drip back into the wort and never cover your kettle completely during the boil. Long cooling times can also lead to excess amounts of DMS. Cool your wort to pitching temperature as quickly as possible with a wort chiller or ice bath. Finally, a strong fermentation with lots of Co2 production helps to clean up DMS since the bubbles carry DMS away, so pitching high quality yeast is a must.
And the most important key to avoiding any off flavour is to ensure proper sterilization and cleaning methods are in place before, after and during brewing.
Estery/Fruity
Tastes/Smells Like:
Fruit, especially banana, to a lesser extent, pear, strawberry, raspberry, grapefruit and nail polish like at higher levels.
Possible Causes:
Esters are a naturally occurring byproduct of fermentation. Certain ales are supposed to have these fruity flavours, such as Belgian ales and Hefeweizens which are expected to have banana flavour components. There are certain types of yeast that produce more esters than others. Strong fruity flavours or fruity flavours that are inappropriate for the style of beer are sometimes a result of under pitching or high fermentation temperatures. As a general rule, the higher the fermentation temperature, the more esters the yeast will produce. In addition to high fermentation temperatures, low oxygen levels can also help increase the production of esters.
How to Avoid:
Always pitch enough yeast for the gravity of your beer and oxygenate well. Keep fermentation temperatures under 24ºC when possible. Fermenting over 24ºC has been shown to drastically increase esters. Fermenting between 15º – 18ºC will reduce ester production considerably, however, be prepared for a slower fermentation. Always use the correct yeast for the style of beer being brewed. Yeast strains made for Belgian or German wheat beers are made to produce fruity characteristics, so if you are trying to avoid beers that taste like bananas, avoid using these strains. If you do brew a beer with a high level of Isoamyl Acetate, try ageing it to decrease the ester.
Grassy
Tastes/Smells Like:
Freshly cut grass, musty and flavours reminiscent of chlorophyll
Possible Causes:
Musty, grassy aromas and flavours are usually the result of grains or extract that have developed mould or bacteria prior to being used. Aldehydes can occasionally form on old malt, which can lead to a grassy flavour. Hops, if not processed correctly prior to packaging/storing, can also develop similar off flavours.
How to Avoid:
Always store grains or extract in a cool, dry, dark place. Check ingredients for discolouration, off smells or tastes, prior to brewing. Milling grain just prior to brewing will help to keep it fresh. Pre-milled grain should be used in 2-4 weeks from the time it is milled. Always use high quality hops. If using homegrown hops, make sure to properly cure them before long-term storage. As a general rule, if ingredients look, smell and/or taste good, they should be fine to use.
Husky/Grainy
Tastes/Smells Like:
Raw grain, fresh wheat, dry, harsh, green, nutty flavours comparable to astringency from tannins and/or oxidization. These flavours are more evident in all-grain beers due to poor grain crushing or sparging practices.
Possible Causes:
Most often caused by the isobutyraldehyde in malt, but other aldehydes can supply the grainy character. Over milled grain can cause husky, grainy off flavours. Highly toasted malts can also contribute to husky, grainy qualities. Over sparging and at too hot of temperatures can also lead to the tasting fault.
How to Avoid:
Following the same precautions to avoid astringency should help with any grainy or husky flavours. Avoid grain that has been shredded or crushed. When using homemade toasted grains, allow them to age for 1-2 weeks after milling to allow harsh aromas and flavours to dissipate. Don’t mash for more than 2 hours and keep sparge water to below 75ºC. Cold conditioning a husky or grainy tasting beer will usually help the off flavours to fall out of suspension.
Medicinal
Tastes/Smells Like:
Cough syrup, mouthwash, Band-Aid™, smoke, bitter, herbal, drying and clove-like (spicy)
Possible Causes:
A variety of different phenols are almost always the cause for medicinal flavours in beer. Phenols can cause solvent, astringent, plastic and medicinal flavours. Medicinal-tasting phenols are usually brought out during mashing and/or sparging and are caused by incorrect pH levels, water amounts and temperatures. Using chlorine or iodine-based sanitizers improperly can bring out Chlorophenols. Yeast also produces phenols, and a clove-like characteristic is deliberate in some ale, especially Hefeweizen and other wheat beers.
How to Avoid:
Follow proper mashing and sparging techniques. Filter water where possible and keep sparge water below 75ºC. You should always follow the specific directions for different sanitizers. Taking the same precautions to avoid Chlorophenols and astringency should help to wipe out the chances of medicinal flavours. Always use the proper yeast for the style of beer being brewed.
Metallic
Tastes/Smells Like:
Metal, mainly iron, rusty or coppery. Also described as tasting like pennies or blood, Felt on the front of the mouth and back of the throat
Possible Causes:
Wort being boiled in unprocessed metals, mainly iron, but also aluminium, and steel (excluding stainless) is usually the source of metallic flavours. Metallic flavours can also be extracted from metal brewing equipment, bottle caps and/or kegs. Using water that has high levels of iron will impart iron flavours. Improperly stored grains can also cause metallic off flavours.
How to Avoid:
Use stainless steel pots and brewing equipment (fittings, spoons, etc.) when possible or substitute with food grade plastic or glass. Avoid using iron for anything that will be coming in contact with beer/wort. If using a ceramic coated steel pot, always check for cracks or scratches before using. Stainless steel will not give off any metallic flavours. Aluminium pots will generally only cause metallic flavours when using alkaline water with a pH over 9. If using an aluminium pot, you can “bake” the pot in an oven at 120ºC for 6 hours to increase the protective oxides. Always use fresh, properly stored grain. Avoid using water with iron in it, such as unfiltered well water.
And the most important key to avoiding any off flavour is to ensure proper sterilization and cleaning methods are in place before, after and during brewing.
Mouldy
Tastes/Smells Like:
Mould, mildew, musty, damp, earthy, old cellar, mushroom or beet like. Moulds are quickly recognized by their smell and taste. Black bread moulds and mildew can grow in both wort and beer.
Possible Causes:
This one is usually caused by mould or fungus contamination of raw materials or brewing equipment improperly sanitized and stored. Mould can grow in beer and wort and is almost always the result of storing fermenting beer in a damp, dank area. Using extract or grain that has developed mould can impart mouldy, mildewy flavours as well.
If the infection is caught early enough, it can often be removed by skimming or cleaning of the surface before it significantly contaminates the batch. Chances are though that the spores have contaminated the batch and it could crop up again.
How to Avoid:
Always store your fermenter in a dry, dark place. Avoid storing your fermenter in damp, dank or humid surroundings. Check all ingredients for off smells, flavours and/or discolouration prior to brewing with them. Discard any mouldy grain. If mould is found in malt extract, it is recommended that it be thrown out. A mouldy extract can still be used if the mould is scraped off but be prepared for off flavours in the final product.
And the most important key to avoid any off flavour is to ensure proper sterilization and cleaning methods are in place before, after and during brewing.
Oxidation
Tastes/Smells Like:
Stale or old, wet cardboard, sherry, papery, pineapple, decaying vegetables, increased bitterness, harshness. At low levels can have a inky, musty quality.
Oxidation is probably the most common problem with beer including commercial beers. Beer that has been oxidized can instil aromas and flavours reminiscent of cardboard, wet paper or just a general “stale” characteristic. While oxidation can sometimes take the form of sweet and sherry-like qualities, adding depth to some styles like barley wine or old ale, it is rarely a desired trait in beer.
Possible Causes:
Oxidation occurs when oxygen negatively reacts with the molecules in the wort or beer. An excessive level of oxygen being introduced to the beer, especially while the wort is still warm or after fermentation is complete, can create cardboard or sherry-like flavours. The more oxygen a beer is in contact with the faster and more severe the oxidation. Cooler storage temperatures slow the process.
Too much headspace in bottles can lead to oxidation as well. On the other hand, aeration of wort before pitching yeast is necessary for yeast and good fermentation.
How to Avoid:
The key to preventing oxidized beer is avoiding the introduction of oxygen after fermentation. Oxidation is almost always a result of unnecessary splashing of fermented beer. When transferring beer from one vessel to the next, prevent splashing by transferring beer with tubing rather than pouring straight in. Keep the end of the transfer tubing beneath the liquid line and avoid getting air pockets in the transfer tubing. Also, keep exposure of wort to outside air at a minimum. Hot side aeration refers to wort becoming oxidized while it is hot. Warm liquid is more inclined to absorb oxygen and therefore, it is recommended that when the wort is over 26ºC, splashing be avoided. During and directly after the boil splashing is not much of a concern, as oxygen can’t really dissolve into a liquid that hot. Cool wort as quickly as possible and do not aerate wort until it is under 26ºC. Do not aerate beer after fermentation starts. When bottling, only leave about 1-2cm of headspace. If kegging, purge kegging equipment with CO2 before using.
Skunky
Tastes/Smells Like:
Aroma of skunk, musty, sulfury or can be similar to burned rubber or cat musk.
Skunky and rubbery flavours or aromas in homebrew can be signs of “light-struck” homebrew and should be avoided. Beer becomes light-struck when the isohumulone bittering compounds in hops come into contact and react with specific wavelengths of light. Brown glass bottles effectively screen out these wavelengths, but green bottles do not. Skunky aroma can also be caused by using Cluster hops for late boil additions.
Possible Causes:
Lightstruck is caused by a chemical reaction between daylight or artificial light, riboflavin in the beer, and hop alpha acids. When hops are exposed to UV rays from sunlight or fluorescent lights, the alpha acids breakdown and react with the hydrogen sulphide that the yeast makes. This reaction creates mercaptan. Mercaptan is the same chemical skunks secrete when they spray which is why the smell of “light struck” beer is so similar to that of a skunk.
Some commercial breweries (such as Heineken and Corona) use chemically modified hop alpha acids which do not react with riboflavin, allowing them to continue to use their signature green or clear bottles.
How to Avoid:
When fermenting beer in a clear container, always keep it out of any direct sunlight or fluorescent lamps. A simple paper bag or towel wrapped around the fermenter will help to keep light out. All clear containers will let UV light in, however, brown bottles will filter a majority of UV rays and help to keep your beer “skunkless” for longer. Avoid green or clear bottles as these let almost all UV light in. Light-colored beers and beers with a lot of hops (Pilsners or IPAs) are more prone to becoming skunky. Dark beers and beers that utilize isomerized hop extracts are less susceptible to becoming light struck.
When drinking a beer keep your bottle or glass out of direct sunlight especially if it’s heavy on the hops. It takes a very short time to start the reaction and once started there’s no way to stop it. Keep homebrew away from light, once packaged in bottles.
Soapy
Tastes/Smells Like:
Soap, detergent, oily, fatty.
Possible Causes:
Keeping beer in the primary fermenter for a long time after fermentation is complete can cause soapy flavours. After a while, the fatty acids in the trub start to break down and soap is essentially created. Soap is, by definition, the salt of a fatty acid; so you are literally tasting soap.
How to Avoid:
Transfer beer into a secondary if you plan on aging it in the fermenter for a long period of time. Very light beers and lagers are more susceptible to absorbing and exhibiting off flavours than ales and darker beers.
Solvent-Like
Tastes/Smells Like:
Paint thinner, nail polish remover (acetone), harsh, sharp, in extreme cases can cause a burning sensation of tongue and throat, comparable to harsh alcohol or ester flavours.
Also described as “hot” or high in fusel alcohol qualities, solvent-y brew is often characterized by an unpleasant heat from alcohol, and in some cases a burning sensation on the palate. It can be perceived in flavour, aroma and mouth feel.
Possible Causes:
These flavours often result from a combination of high fermentation temperatures and oxidation. They can also be leached from cheap plastic brewing equipment or if PVC tubing is used to transfer wort. The solvents in some plastics like PVC can be leached by high temperatures.
How to Avoid:
Avoid fermenting at temperatures higher than the suggested range for the yeast being used. Avoid oxidation of beer. Never use plastic or vinyl equipment that is not marked as food grade. Some food grade plastics leach toxins after reaching a certain temperature. If plastic parts will be exposed to hot liquids or high temperatures, check the temperature rating with the supplier or manufacturer.
To address solvent-y beers, first try simply setting the flawed beer aside and giving it time. Sometimes beers need longer ageing periods to round out flavours and aromas.
Sulphur/Hydrogen Sulphide
Tastes/Smells Like:
Sulphur, burning match, rotten egg, raw sewage. May remind you of the smell close to hot springs, or a geothermal vent.
Possible Causes:
Hydrogen sulphide, which is the chemical responsible for giving sulphur its unpleasant smell, is naturally produced by all yeast during fermentation. Many lager yeasts can create overwhelming sulphur-like aromas. Ale strains generally make such small amounts that the odour is unnoticeable.
Other possible causes are a bacterial infection and yeast autolysis.
How to Avoid:
Give your beer enough time. During fermentation, the production of hydrogen sulphide is inevitable. Co2 will carry most of the hydrogen sulphide away. Conditioning or lagering after primary fermentation is complete should make any leftover sulphur smells or tastes fade over time. Select your yeast strain with care. Ensure you cast enough healthy yeast and oxygenate the wort well. Consider using a yeast nutrient to up the zinc content in the wort.
And the most important key to avoiding any off flavour is to ensure proper sterilization and cleaning methods are in place before, after and during brewing.
Sulphur/Hydrogen Sulphide
Tastes/Smells Like:
Sulphur, burning match, rotten egg, raw sewage. May remind you of the smell close to hot springs, or a geothermal vent.
Possible Causes:
Hydrogen sulphide, which is the chemical responsible for giving sulphur its unpleasant smell, is naturally produced by all yeast during fermentation. Many lager yeasts can create overwhelming sulphur-like aromas. Ale strains generally make such small amounts that the odour is unnoticeable.
Other possible causes are a bacterial infection and yeast autolysis.
How to Avoid:
Give your beer enough time. During fermentation, the production of hydrogen sulphide is inevitable. Co2 will carry most of the hydrogen sulphide away. Conditioning or lagering after primary fermentation is complete should make any leftover sulphur smells or tastes fade over time. Select your yeast strain with care. Ensure you cast enough healthy yeast and oxygenate the wort well. Consider using a yeast nutrient to up the zinc content in the wort.
And the most important key to avoiding any off flavour is to ensure proper sterilization and cleaning methods are in place before, after and during brewing.
Sour/Acidic
Tastes/Smells Like:
Tart, Sour Milk, Acidic, Citrusy, Vinegary, acrid, felt on the sides of the tongue towards back of the mouth. At higher levels may give a peppery, almost burning mouthfeel.
Possible Causes:
Any perceived sourness is due to added acids in the form of raw materials (i.e. fruit), fermentation, and/or bacterial contamination or inoculation. Extremely sour or vinegary flavours are almost always the result of a bacterial or wild yeast infection. Lambic style beers are beers that have been purposely exposed to specific types of wild yeast and bacteria to create the unmistakable cidery and sour flavours they are known for.
How to Avoid:
Bacteria and wild yeast are in the air, all around us, all of the time. These bacteria and yeast only fall downward – they will not crawl up and in. Make sure to thoroughly sanitize everything and anything that will be coming into contact with beer post boil. Don’t mash for longer than two hours and if sour mashing, avoid oxygenating and keep above 54ºC. Cover your kettle when cooling your wort. Wort or beer that is under 82ºC is prime breeding ground for bacteria and wild yeast.
Dirt cannot be sanitized so clean equipment prior to sanitizing if it is visibly dirty. If using a plastic fermenter check it for any scratches, as these are a great place for bacteria to hide. Only open the fermenter when necessary. Use high quality yeast and/or make a yeast starter. The faster the yeast starts to ferment, the more likely they will overpower or push out any wild yeast and bacteria. Proper sanitation is one of the most important things when it comes to making great homebrew!
Sweet
Tastes/Smells Like:
Overly sweet or sugary, cloyingly sweet, sickly sweet, oversweet, syrupy, jammy, candy
Possible Causes:
Some degree of sweetness is desired in most beers, but a beer that tastes like unfermented wort is most likely the result of the yeast quitting prematurely. Stuck fermentation is when the yeast ferments for several days and then suddenly stops. The result is a gravity that is much higher than the correct final gravity for the wort.
Using a yeast that doesn’t have a high tolerance for alcohol in a high gravity beer can leave too much residual sweetness. A sudden drop in temperature can cause yeast to go dormant and stop fermenting. Also, beer that is lacking the right amount of hop bitterness can cause an unbalanced sweetness. Unbalanced sweetness is often described as “cloyingly sweet”. Using too much fruit flavouring or other adjuncts can cause a sickly-sweet beer as well.
How to Avoid:
Always use high quality yeast and make sure you are pitching the correct amount for the gravity of the wort or make a yeast starter. Use the proper strain of yeast for the style of beer being made. Highly flocculant yeast can sometimes fall out of suspension before fermentation is over, however pitching enough yeast will usually prevent this. If you are aiming for a dry, less sweet beer, use yeast with a high attenuation percentage. If making a beer with very high alcohol content, it is very important to use yeast nutrients. Monitor fermentation temperatures and avoid fermenting lower than the suggested temperature range. It is possible to revive dormant yeast by gently swirling the fermenter and gradually raising the temperature. Otherwise, pitching more yeast is another option. When formulating recipes, keep in mind that you can highlight a sweet or bitter taste, but the balance of flavours is what makes a beer enjoyable. If using fruit extracts or flavouring, start with a little and add more to taste.
Yeasty
Tastes Like:
Yeast, bready, can be harsh or slightly sulphur-like
Possible Causes:
The cause of this flavour is pretty easy to understand. If the yeast is unhealthy and begins autolyzing (essentially eating itself) it will release compounds that can only be described as yeasty. Also if the beer is green, too young, and the yeast has not had time to settle out, it will have a yeasty taste. Watch your pouring method too, keep the yeast layer on the bottom of the bottle.
How to Avoid:
If a beer such as a lager is going to be kept in a fermenter for a long period of time, using a secondary vessel is recommended. Always leave a majority of the trub in the primary fermenter when racking to a secondary fermenter, bottling bucket or keg. Some yeast sediment is unavoidable when carbonating in the bottle. If yeast sediment is present leave the last inch or so of beer in the bottle when pouring.
Hopefully now after reading this you can avoid the 21 common off flavours in brewing!
Advocating Beer Variety 