10 Common Causes Of Homebrew Off Flavors and How To Fix Them

girl making face after drinking bad beer

Every Home Brewer has high hopes when mixing a batch. Maybe it’s an award-winning flavor. Maybe it’s a new taste that everyone will love, causing you to quit your day job and go pro. Or maybe it’s just a fantastic, crisp beer that will impress the few friends and family whom you choose to share your batch.

But we seasoned home brewers know the truth: sometimes the batches don’t live up to our high expectations. Okay, sometimes they smell and taste terrible. Every chef makes a bad meal every now and then, and home brewing is no exception.

Fortunately, many errors and causes of a bad batch can be corrected. The trick is identifying what is causing the off flavors so they can be fixed.

Most Common Causes Of Off-Flavors In Your Homebrew

As with any cook, there are a number of elements that can cause flavors to be off or a batch to be spoiled. These errors can come from any step of the process. If the equipment is not clean enough, or conversely if there is still disinfectant on some items, then there might be cause for Off Flavors. Temperatures that are too high or too low during the process might be the cause. Improper storage of the ingredients and improper bottling can lead to off flavors. Basically, any number of things can go wrong at any step of the process.

But have no fear: we are here to help. Below we identify common off flavors, their causes, and what you can do to avoid these issues.

Here are the most common off flavors, what causes them, and how it can be fixed.

1) Green Apple or Apple Cider

Cause: Acetaldehyde

This is the most common Off Flavor in home brewing. Acetaldehyde is a natural component of the fermentation process when most of it is converted to ethanol.

Generally, beer can contain low levels of acetaldehyde without affecting the flavor profile. However, the balance can easily shift for several reasons including too much yeast in the fermentation tank, high fermentation temperature, or when fermentation happens too quickly.

2) Butterscotch or Buttered Popcorn

Cause: Diacetyl

During the fermentation process vicuna diketones (VDKs) are produced by yeast. These VDKs are precursors to diacetyl. In a normal fermentation, the yeast will then absorb the VDKs. If the brew is cut short, the VDKs that remain can lead to diacetyl.

Also, these can be caused by bacterial infection by lactobacillus and pediococcus, which can be a result of poor hygiene during the process. Interestingly, winemakers utilize diacetyl when making some Chardonnays.

3) Banana

Cause: Fruity Esters

Unless you are supplying beer to the chimpanzees in the primate house at the zoo, you don’t want your beer to hit you in the face with a bunch of bananas.  If it does, you have too many esters in your batch of beer.

Now banana isn’t necessarily always a bad flavor in beer. In fact, many German Heifeweizen and Belgian wheat beers should have some noticeable banana flavor characteristics in the profile.

Yeast produces esters, and the amount varies by different strains. However, if you pitch the yeast while the wort is too hot, or when the fermentation temperature runs too high,  then more esters may be produced which will cause this noticeable off-flavor.

If this happens, make sure your wort at the optimal temperature before pitching the yeast, or lower your temperature by a few degrees and monitor it regularly throughout your fermentation process.

4) Canned Corn or Cabbage

Cause: Dimethyl sulfide (DMS)

DMS is a common component to many beers, especially light lagers. During the boil, when the compound S-methyl-methionine (SMM) is reduced, DMS is produced.

It appears in lagers because the SMM is reduced early with roasted or toasted malts. DMS is usually removed during the boil via vaporization. However, sometimes if the wort is cooled too slowly the DMS will not evaporate, but dissolve back in the mix. A solution is to not fully cover the brewpot during the boil. Don’t allow the condensed elements to return into the pot from the sides or the lid.

Also, when DMS appears in other types of beer it can be the result of bacterial infections or other poor or insufficiently hygienic brewing processes. If this is case, replace the yeast and make sure your work area is clean.

5) Cardboard

Cause: Oxidation

The key to avoiding oxidation is, naturally, to not introduce oxygen once you complete your primary fermentation. This can be a common problem for many home brewers.

The key is be cautious and careful with your movements. When you transfer beer from the primary to secondary vessel, or from the fermenter to the bottles or a keg, you need to minimize or eliminate splashing. Avoid bulk movement like pouring and dumping. The experts suggest that you “rack quietly.”

Also, oxidation is avoidable when beer ages. There are small amounts of oxygen in all beers in bottles and cans. The longer the beer sits, the more the oxygen present affects the taste.

6) Rotten Vegetables, Propane, or Natural Gas

Cause: Mercaptan

This is the traditional “skunked” beer smell and there are many causes. This can appear if there is too much sulphury odor in the beginning, and also if too much of the yeast goes away during the secondary fermentation process. Dry hopping can also increase the mercaptan presence, but that can be reduced by utilizing copper sulfate in the mix.

Also, of course, exposure to light can cause this to happen. This is why many brewers no longer use clear bottles. Fun fact: mercaptan is one of the prominent chemicals that causes bad breath and flatulence. Another reason to not drink that skunked beer! Second fun fact: mercaptan is the same chemical that skunks release, hence the term “skunked beer.” Don’t let Mercaptan be the captain of your brew!

7) Rotten Eggs, Sewage, Sulfur

Cause: Hydrogen Sulfide

Hydrogen sulfide is a normal yeast byproduct during the fermentation of lagers. Usually, carbon dioxide bubbles will remove hydrogen sulfide from the mix, at least enough to normal undetectable levels.

If the hydrogen sulfide is detectable it could be due to a poor yeast mix. One way to remedy the problem (other than replacing the yeast entirely) is to force carbon dioxide bubbles up from the bottom of the tank.

8) Grass

Cause: Acetaldehyde

No not that kind of grass. If you experience the flavor or aroma of fresh cut grass or chlorophyll, you only have yourself to blame as it’s the direct result of poor storage.

If malt or hops are poorly stored or not dried before being properly stored, then moisture can be picked up. This moisture develops a musty odor which can lead your beer tasting like your front lawn.

9) Medicine, Mouthwash, Band-Aid, Plastic

Cause: Chlorophenol

Yeast produces various phenols, and chlorophenols can be produced from a reaction to bleach and other chlorine-based sanitizers used in the prep area.

The best way to avoid this flavor is to rinse with boiled water after sanitizing. An extra step to be sure, but necessary if these flavors emerge. It also helps to have the best equipment possible, for ease of use and easier cleaning.

10) Vinegar

Cause: Astringent

If the taste of your beer makes you pucker as if you were sucking on a tea bag, then the problem might be astringency. There are a number of factors that could be the cause, such as polyphenols or tannins.

Tannins can be found in the husks of the grains and in fruit skin. Grains that have steeped for too long or been excessively crushed can release tannins. The solution is to not overmill your grains, and to take them out of the water before it boils. During the mash, if the pH exceeds 5.2 – 5.6 you might produce astringent flavors.

Final Say

Creating the perfect flavor profile for your home brew isn’t easy, but perfection isn’t needed. There is a lot of give and take during the process, and sometimes off flavors make themselves known. In fact, the more frequently you brew, the more likely you will have off flavor batches.

However, keep in mind that each batch is different and any slight differentiation doesn’t mean the beer is bad. Your nose (and taste buds) know best. Experimentation and unpredictability is part of the thrill of making your own beer at home.

Happy Brewing!

Alex
Alex

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