Sometimes the beer doesn’t reach our expectations and underdelivers with unwanted flavors. This can happen due to homebrewer’s inconsistency and lack of discipline or knowledge but can also happen due to bad luck, bad recipes, or ingredients.
It’s also not unusual that we as homebrewers make mistakes throughout our journey both at the beginning when we are learning and later when we experiment with new stuff to upgrade our brewing game.
I have had off-flavors in many of my beers before I learned what causes them, so let’s see what are the common off-flavors in homebrews and if is there a way to fix the mess.
Sweet off-flavor
Causes
Sweet beer is among the most common off-flavors in brewing that beginners experience. Sweetness is caused by unfermented sugars which means the fermentation has not been completed. Homebrew shouldn’t be sweet unless it’s intentional in some styles such as milk stout, ciders, and sweet meads as otherwise, it means the final gravity is not achieved due to poor fermentation.
Sweet beer doesn’t only taste bad, but it can be dangerous if you bottle it as the remaining sugars may continue to ferment inside a bottle and eventually cause bottle bombs.
Another problem of sweet beer is the lack of alcohol and character as the sugar hasn’t been fully absorbed by the yeast.
How to fix/avoid
To fix a sweet beer all you have to do is to let it ferment for longer assuming the yeast you pitched is still alive and healthy. After you let the beer ferment for longer, the problem will be fixed and you can continue with bottling and conditioning. If you are unsure when the fermentation is complete you can read more about it in my dedicated article or use a hydrometer and take readings of final gravity if you know the original gravity (more explained in the mentioned article).
Fruity, ester off-flavor (banana and tropical fruits are common)
Causes
Fruity flavors are caused by the high amount of esters which contribute to a variety of fruity flavors such as banana or mango flavors. Esters are a normal product of successful fermentation, but the warmer you ferment the more esters will grow. Esters are also associated with the type of yeast used, so some yeast will produce more esters at higher temperatures while some yeast will produce less.
How to fix/avoid
If you don’t want obvious ester, fruity notes in your beer you can use yeast type which is not known for noticeable ester production or you can ferment at the lower scale of what the yeast supports. For instance, I often rely on Safe Ale S-05 and S-04 yeasts and both will produce esters that will noticeably increase the fruity character of beer if fermented above 68°F (20°C). Yet, when I ferment between 60.8°F (16°C) and 64.4°F (18°C), the beer doesn’t taste fruity at all and the yeast rather produces a dryer, neutral flavor effect.
If your beer already ended up with a high amount of esters, it may not be bad as it’s not considered a classic off-flavor but rather as a preference. If you don’t like it it will be hard to remove esters from the already fermented beer but you can mix it with another low-ester batch or mask it with other ingredients such as herbs, spices, or hops.
Vinegary, acidy, apple cider off-flavor
Causes
The vinegary flavor is associated with infection and this is a prime example of poor sanitation. This vinegary flavor is undesirable in beers and most other brews with the exception of making kombucha or homemade vinegar. The cause for the vinegary flavor is poor sanitation of equipment, but it could also be a cleaning mistake where nasties were left alone untouched.
How to fix/avoid
It’s impossible to save an infected brew as once it turns vinegary it’s only going to get worse.
If you experience this off-flavor you should update your sanitation game and figure out what mistake you were making. The infection can happen everywhere after the wort has cooled, so it may be a problem with fermenter sanitation, later dry additions, airlock issues, dirty siphons, spigots, bottles, or priming solution. I recommend that you check my guide to sanitation and cleaning as there I mention how to properly sanitize brewing equipment.
The astringent, bitter off-flavor
Causes
The astringent flavor is defined as a tingling, drying effect in the mouth and technically it’s not a flavor but rather a sensation. This off-flavor (although technically not a taste but a sensation) is common in wines but is rarely accepted in most other brews and is almost never accepted in beers. Well, some beer styles are more forgiving of this off-flavor, and depending on people who enjoy it may be lesser or bigger of a deal.
Astringent (some people may describe it as bitter out of misinterpretation) is caused by tannins which get released into a beer during meshing. Tannins are a protective substance found in plants, bark, and fruits whose function is to deter animals and insects from biting them. In beer brewing, tannins are found in husks of the grain and too much of it can cause this unpleasant sensation which is on the other hand, very pleasant in wine as it comes from grapes that are full of tannins.
How to fix/avoid
Although tannins are found in the husk, they won’t get realized into the wort unless the temperature is higher than 170°F (76.6°C) during meshing or the PH values of the wort are over 5.8. Another misconception is that squeezing a brewing bag will release tannins, but it won’t unless the temperature and PH are wrong. Keep squeezing the bag and check out my dedicated article to see why it’s a good practice.
If the tannins are already present in beer to an unbearable level, you can increase carbonation volume or back sweeten it with lactose. However, sweetening a beer will only work in styles like stouts, or IPAs and rarely in others, so Co2 increase or combination with nitrogen may be a better option.
Metallic, bloody off-flavor
Causes
Iron-like flavor also similar to blood or coins is usually a consequence of using low-quality metal equipment like brewing kettles and kegs. It’s not suggested to brew in aluminum or other metal kettles which are not stainless steel as they can leak unwanted chemicals. Besides this, a large amount of iron present in water can also be an issue as even improper storing of grains.
How to fix/avoid
To never experience this issue use fresh ingredients, don’t use questionable water quality, and always brew with stainless steel! It’s worth having a good stainless steel kettle as it won’t ever cause off-flavor or toxic issues, will last a long time, and will properly distribute heat. This off-flavor will remain and it will be difficult to get rid of it.
Cardboard, stale, decaying vegetable off-flavor
Causes
For cardboard, the stale, decaying vegetable flavor is sometimes accompanied by a wet base room smell, oxidation is always the cause.
Oxidation is among the worst nightmares for every brewer as it’s difficult to completely negate oxygen with homebrewing equipment and methods, so sometimes a single mistake can introduce extra oxygen which will ruin the batch.
How to fix/avoid
To reduce the chance of oxidation you should be careful not to introduce oxygen during or after primary fermentation is complete. Oxygen is good prior to fermentation kicks in as yeast needs oxygen as a nutrient to start working which is also the reason why it’s recommended to aerate the wort after pitching.
However, the biggest error that introduces oxygen is either during racking from one container to another or bottling. Splashing is the number one reason for oxidation at mentioned stages, so be careful not to splash by gently transferring brew with a siphon or a bottling wand from a bottling bucket into bottles. If you use a keg instead of bottles, it’s important to purge the keg with C02 to remove the oxygen trapped inside.
Another tip for reducing the odds of oxidation in the bottles is to have a good standard for leaving headspace inside a bottle.
By the way, also ensure the airlock works at all times and that there are no leaks in the container!
If the beer is oxidized, there won’t be a single method that will help it and it will only get worse as time passes.
Skunky, burnt rubber off-flavor
Causes
For skunky, burnt rubber associated off-flavors and smells the wrongdoer is the hops which got lights truck. Skunked beer is not a nice experience but believe it or not it’s not unusual to find skunked beer in some bars and stores, so not everyone instantly associates this as an obvious issue. After all, some people are used to bad beer and can hardly tell it apart from good beer if all they drink is bad beer their whole life.
How to fix/avoid
Keep your beer away from sunlight or artificial lights like LED lights at all times. Even 20 seconds of direct exposure to these lights is enough to strike the hops.
You can use brown bottles or kegs to overcome this issue as the light won’t have an easy time penetrating through them. During fermentation, you can use plastic or stainless steel fermenters as they block lots of light and if it’s a glass fermenter always cover it with a layer of some cloth. It’s also recommended to keep the fermenter in the shade where no light can reach it (a halogenic bulb is fine, but still cover glass fermenters as they offer literally 0 protection).
Once skunked beer, always skunked beer, so don’t let it happen.
Soapy, detergent-like off-flavor
Causes
This soapy, detergent-like flavor can happen if the recipe contains lots of ingredients with fatty acids. When given enough time these fatty acids will compose these off-flavors but it will only happen if you condition for a long time in a fermenter with lots of sediment at the bottom.
How to fix/avoid
By filtering sediment out, you greatly reduce the odds of this off-flavor as most of these fatty acids will be mixed with yeast and protein particles from which the sediment is formed. Simply, apply any method to drop the sediment and clear the beer prior to long conditioning times, kegging, or bottling. A secondary fermenter is a nice way to go around this problem.
Filtering and conditioning may help reduce this after-taste.
Acetone, paint thinner off-flavor
Causes
These off-flavors are always associated with alcohol, higher fermentation temperatures, or both. Most heavy beer styles like imperial stouts and barley wines will have a distinctive alcoholic flavor which in the early phase can seem like acetone or paint thinner off-flavor. The reason behind this is natural, a high amount of alcohol is always going to be more obvious in a beer than a low amount unless masked with other ingredients.
High fermentation temperatures are also associated with alcoholic off-flavors as yeast produces harsher alcohols such as butanol, propanol, isobutanol, and phenolics, so sometimes these off-flavors can be experienced in low and mid-ABV brews.
How to fix/avoid
While it’s normal that high-ABV beers taste alcoholic, the harsh alcoholic flavor should mellow during conditioning. A high-ABV beer with a strong alcoholic flavor may mellow after 6 months or more, but eventually, it will always mellow in the end. Secondly, it’s important to pay attention to other beer ingredients and the ratio between alcohol and hops to create an optimal ratio (read about IBU).
In case the high fermentation temperatures are the reason, letting the beer condition for longer will also fix this problem, and next time you can simply ferment at a lower temperature scale.
Sulfur, rotten egg off-flavor
Causes
The sulfur flavor and smell are truly disgusting as no one is keen on rotten eggs yet this is completely normal in the process of fermentation of many lagers and wheat beers. This is caused by many lager yeasts as while the yeast absorbs sugars and creates CO2 and alcohol it also does other things and some of them are the creation of hydrogen sulfide responsible for sulfur, rotten egg smell, and taste. This rarely happens with ale yeasts, so those who are not experienced with lager yeasts may be negatively surprised, but there’s nothing to worry about.
How to fix/avoid
The harsh sulfur smells are the strongest during fermentation but as the fermentation finalizes most of this smell and flavor will be already gone. However, it may not completely go away depending on the yeast type, so further conditioning will be necessary. I recommend using a secondary fermenter for as long as the flavor is present as you want to allow the fumes to escape through an airlock. After all, lagers are traditionally stored and conditioned under lower temperatures longer than average ales for a good reason.
I have also dedicated an article to this problem, so check it out if you are worried about sulfur.
Bready, yeasty off-flavor
Causes
If your brew tastes bready it can be due to a problem with the yeast. After all, yeast is similar to bread taste. The causes of this off-flavor can be simply the fact that the brew contains lots of sediment as it’s full of yeast particles that give off this bready, yeasty taste.
The second possibility is that yeast autolysis occurred which means the yeast has eaten itself and pushed unwanted chemicals into the brew. However, if this is the case it would mean that you probably left the brew sitting on a thick layer of sediment in the primary fermenter for a long time. Yeast autolysis is also associated with a sulfur flavor, so if the brew tastes both bready and a bit sulfur-like it’s probably yeast autolysis that caused the off-flavor.
How to fix/avoid
If sediment that makes the beer muddy and hazy is the case, you must only filter the sediment out of the brew and the off-flavor will be gone.
Tip: A little bit of sediment usually enters bottles as it’s difficult to fully filter it out in homebrewing, so be careful not to pour the last inch of the brew from the bottom of a bottle.
If yeast autolysis is the case, the bad aftertaste may mellow over time but unfortunately, it may permanently affect the batch. So, next time don’t let the beer stay on a thick layer of sediment in the primary but rather immediately bottle or transfer to a secondary fermenter.