Off Flavors in Brewing: Expert Strategies & Remedies to Keep Them at Bay

All beers are an amalgamation of numerous different flavors, each brewed and formulated in different ways. Beer is pretty similar to music, as one man’ gold can be another man’ garbage.

You may find a particular beer to absolutely delicious, and your buddies may find it absolutely atrocious.

Beer Off Flavors

Each of us has different flavor preferences and different sensitivities to different flavors. With that said, there are a set of characters which are a big NO for all.

Some of these “Off flavors” are inherent in almost all beers though in controlled and desirable proportions.

To identify these off-flavors, you need both experience and time. With this list, we try to concise all the learnings you will ever need to recognize, control, and eliminate these off-flavors.

Some of the most common off-flavors and ways to avoid them are…

1. Diacetyl (2,3-butanedione)

Tastes like: Buttery, Milky, Buttermilk, Oily, Lower levels taste like butterscotch.

Importance: Usually used in some levels in English Bitters, Dry Stouts, Scotch Ales.

Effect of Aging: The milky taste intensifies over time as heat accelerates its breakdown process.

Caused By: Caused by short boiling at lower temperatures or mutated yeast. This usually happens during the fermentation process. The existence of some kind of Bacteria can also give rise to this.

Control Methods:

  • Boil the brew at high temperatures for appropriate amounts of time.
  • Oxygenate your fermentation well.
  • Increase the temperatures, as your fermentation process nears its end.
  • Wait for some time, before taking your beer off yeast.

2. Mercaptan (ethanethiol)

Tastes Like: Drain-like, sulphury, or rotting garbage. This compound is also used to make natural gas odorous. And no one wants to taste natural gas while enjoying their beer.

Effect of Aging: This contamination also increases with time, thus increasing the properties of smelling like rotting garbage.

Caused By: Mercaptan is often a by-product of yeast-autolysis.

Control Methods:

  • Always ensure proper sanitation and cleanliness
  • Ensure to Siphon beer off yeast in the first four weeks of the fermentation process

3. Lightstruck (3-methyl-2-butene-1-thiol)

Tastes Like: Sulfury, Skunky, sunstruck. It can be mistaken as Mercapton but is less offensive than Mercaptan.

Effect of Aging: The results get subdued over time. However, if kept in darkness, there are chances of

Caused By: Lightstruck is usually caused due to a chemical reaction between artificial light and daylight.

Control Methods: While buying commercial beer, always opt for brown bottles. Always ensure not to keep the bottles in darkness.

  • Use fewer hops
  • If your beer is stout on hops, avoid drinking out in direct sunlight
  • Keep your bottle of beer outside the sunlight, to stop starting the reaction. Remember, once it starts, there is no going back.
  • You may want to keep the freshly brewed beers in kegs or brown bottles, as it only allows for around 5-30% of the light to get through.
  • Using fewer hops might be a good idea too.

4. Hydrogen Sulphide (H2S)

Tastes Like: Sewer, Rotten eggs

Importance: Very minute quantities give freshness to beer, which can change to an off-flavor very soon.

Effect of Aging: Its effects can increase during the maturation period.

Caused By: Yeast strains are known to provide a small amount of hydrogen Sulfide during fermentation. Other causes include bacterial infections and autolysis.

Control Methods:

  • The fermentation process releases CO2, this CO2 scrubs the hydrogen sulfide, therefore give enough time t your beer.
  • Larger yeasts will result in more formation of H2S
  • Choose a yeast strain carefully
  • Ensure you oxygenate the wort well

How To Practice it?

The addition of Sodium Metabisulfite can reduce the formation of h2s due to yeast strains. One can go for sodium metabisulfite tablets. Dissolve one Campden to an ounce of beer to see visible changes

5. Caprylic (octanoic or caprylic acid)

Tastes Like: Goat cheese, milk-like

Importance: Caprylic is an essential ingredient in many matured lagers

You will find it as a popular ingredient in long matured lagers and lambics.

Caused By: These amino acids are a result of the yeast metabolism process during the fermentation. The production of this compound increases as pH increases

6. Butyric (butyric acid)

Tastes Like: Baby vomit, rancid, cheese, rotten milk

Importance: Always considered as an off-flavor in beer.

Caused By: Generally caused by bacterial infections in sugar syrups, during sour mashes, when packaged.

Control Methods:

  • Proper sanitation is must get rid of this smell
  • Do not put your mashes at a temperature of below 90F

Here’s a short summary of the less common reasons for off flavors:

Off FlavorDescriptionCauseHow to Fix
AcetaldehydeA green apple aroma, or freshly cut pumpkin.Yeast breaking down sugar too quickly or not given enough time to fully ferment.Allow beer to ferment longer.
AlcoholicA hot, vinous flavor.Too much sugar during fermentation.Use less sugar or ferment at a lower temperature.
AstringentA puckering sensation similar to eating a grape skin.Over-crushed grains or boiling grains.Avoid over-crushing grains and never boil them.
ChlorophenolA medicinal, band-aid like flavor.Chlorine in brewing water.Use filtered water or treat with campden tablets.
DiacetylA butter or butterscotch flavor.Yeast not given enough time to re-absorb during fermentation.Allow beer to ferment longer or raise fermentation temperature.
DMS (Dimethyl Sulfide)A cooked corn or cabbage flavor.Malt not boiled long enough or cooled quickly enough.Boil wort longer and cool quickly.
Estery/FruityA flavor of apples, pears, citrus, etc.Fermenting at too high of a temperature.Ferment at a lower temperature.
GrassyA freshly cut grass flavor.Old, improperly stored ingredients.Use fresh ingredients and store them properly.
LightstruckA skunky aroma.Beer exposed to light.Store beer in a dark place.
MetallicA flavor of pennies or blood.Metal in brewing equipment or water.Use stainless steel equipment and adjust water.
MustyA flavor of mold or mildew.Contaminated ingredients or equipment.Clean and sanitize equipment and use fresh ingredients.
OxidizedA flavor of cardboard or sherry.Oxygen exposure post fermentation.Minimize oxygen exposure.
PhenolicA flavor of cloves, smoke, or plastic.Wild yeast or bacteria.Sanitize equipment and avoid wild yeast.
SolventA flavor of paint thinner or nail polish remover.Fermenting at too high of a temperature or using bad yeast.Ferment at a lower temperature and use good yeast.
Sour/AcidicA sour taste.Bacterial contamination.Sanitize equipment and ingredients.
SulfurA rotten egg aroma.Yeast breaking down amino acids.Use a different yeast strain or allow beer to age.
VegetalA flavor of green beans or bell peppers.Old ingredients or DMS.Use fresh ingredients and boil wort longer.
YeastyA bready or doughy flavor.Yeast in suspension.Allow beer to ferment longer or cold crash.

How To Control These Off Flavors?

As mentioned, some of these off-flavors causing elements are already inherent in beers, therefore cause, and control of these off-flavors is very much co-related.

The primary step is to identify the very cause of the off-flavor in question.

Flavors, especially those which result in contamination, are a big NO. These are caused by a lack of sanitation and inferior brewing methods.

Off flavors that are not caused by contamination are results of discrepancies in the brewing process. These include uncontrolled temperatures during the fermentation process, poor technique, choosing a wrong yeast and weak boils.

As mentioned, it is essential to identify the source to eradicate these flavors. Therefore, we suggest some of the most commonly found characteristics, their origin, and how to avoid them.

Frequently Asked Questions

What are “Off Flavors” in beer?

Off flavors in beer refer to undesirable tastes or aromas that deviate from the intended flavor profile of a particular brew. These flavors can arise from various factors, including the brewing process, ingredients, storage conditions, and more. Recognizing and controlling these off flavors is crucial for producing high-quality beer.

How can Diacetyl be controlled in beer?

Diacetyl, which gives a buttery or butterscotch flavor, can be controlled by boiling the brew at high temperatures for appropriate durations, ensuring proper oxygenation during fermentation, increasing temperatures as fermentation nears its end, and allowing the beer to sit on the yeast for some time before removal.

Why is Lightstruck flavor considered undesirable?

The Lightstruck flavor, which can taste sulfury or skunky, is caused by a chemical reaction between artificial light and daylight. This off flavor can be avoided by storing beer in brown bottles, keeping them out of direct sunlight, and using fewer hops in the brewing process.

What causes the Hydrogen Sulphide (H2S) flavor in beer?

Hydrogen Sulphide (H2S) imparts a sewer or rotten egg taste to the beer. It can be produced by yeast strains during fermentation, bacterial infections, and autolysis. To control this off flavor, it’s essential to give the beer enough time during fermentation, choose the right yeast strain, and ensure proper oxygenation of the wort.

How can one practice controlling the off flavors in beer?

To control off flavors, it’s crucial first to identify their cause. Many off flavors result from contamination due to poor sanitation or inferior brewing methods.

Others arise from discrepancies in the brewing process, such as uncontrolled fermentation temperatures, incorrect yeast selection, and weak boils.

Proper sanitation, adherence to brewing guidelines, and understanding the characteristics of various off flavors can help in their prevention and control.


As discussed earlier, the taste is something that can be very subjective, and what may be a lip-smacking beer for someone may be heard flushed down the toilet. With that said, these off-flavors, which more or less are undesirable by all, must be avoided at all costs.

As we can observe, these off-flavors are caused by two primary reasons. The first one lacks proper sanitation, a reason you need to take care of all sanitation and cleanliness standards while going through the process.

The second primary reason is the lack of implementation of the brewing process. A lot of brewers often find themselves turning on the heat a little late, not giving the beer enough stand time, and small factors like these can spoil an entire batch of beer. Being thorough in your brewing process is important.

You’ll need to know the above terms and more should you be interested in pursing becoming a professional beer judge. The good news is that this skill is not hard to learn with a bit of the right practice.

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