The alcohol burn (alcoholic)

Some alcohols taste warm and there are others which taste like jet fuel.  The jet fuel beers taste overly alcoholic and burn as they travel down your throat.  Other unwanted alcohol flavors include strong unwanted banana flavors, chemical flavors like acetone, or overly spicy flavors.  These flavors are often called the jet fuel flavors.

The off flavors are caused by propanol, butanol, isobutanol, isoamyl (the strong banana flavor) as well as several other undesired alcohols.  These alcohols are known as fusel alcohols.  This family of alcohols has more than two carbon atoms in the molecule, and often gives beers the taste of really poor tequila.  Fusel alcohols also have an oily feel to them.  One way to spot fusel alcohols is an oily layer on top of the wort during or after fermentation.

Really high levels of these fusel alcohols, as in poor quality moonshine, can cause illness, nausea, or even a coma.  In homebrew, fusel alcohols are not in high enough quantity to pose a concern other than bad taste.  For some styles fusel alcohols are not only acceptable, they are expected.  Stronger beers such as barley wines are a good example where some fusel alcohol is desired.  These flavors however should never taste like solvent.

The jet fuel flavors are usually caused by fermenting your beer at a temperature too warm for your yeast (over 80 F).  In fact, this is the most common cause for fusel alcohols.  When your yeast produces alcohol in warmer temperatures, they produce more fusel alcohols.    The easiest way to avoid this problem is to pitch your yeast at the proper temperatures.

Other factors which can contribute to higher amounts of fusel alcohols are elevated levels of amino acids in the wort, anaerobic conditions (low oxygenated wort), continuous agitation of the wort, excessive yeast growth, or wort with an already high ethanol concentration.  Fusel alcohols can also form if your beer sits on the trub too long.

These causes of fusel alcohol have the same underlying problem – stressed yeast.  To avoid the alcohol burn, you need to keep your yeast happy as possible in the best wort environment as possible.

• Fusel alcohols are alcohols with more than 2 carbon atoms
• Jet fuel beer is usually caused by too warm temperatures or stressed yeast from low oxygenated wort
• Make sure you ferment the beer within the correct temperature range
• Move your beer off of the trub as soon as fermentation completes

Creamed Corn/Cooked Vegetables (DMS)

If your beer has an unwanted cooked corn flavor or worse yet, it tastes like oysters, you might have a DMS problem.  DMS (dimethyl sulfides) occur in beer either naturally or from a bacterial infection.
The naturally occurring DMS comes from S-methyl methionine (SMM), a product of malt germination.  SMM levels in the malt are reduced when it is roasted and never forms as DMS later in your wort.  This makes DMS less of an issue in beers that use roasted malts.

DMS is more of a concern in lighter beers, especially lagers, because the lighter grains do not have the SMM removed from roasting.  The levels of SMM in your malt are directly related to the levels of DMS in your wort.  DMS “breaks” off from SMM during the boil of your wort.

A cooked corn flavor is usually a sign of a DMS problem

As your wort boils, DMS is produced and boiled off.  It evaporates and is removed from your beer.  That’s good.  If you boil your wort with the lid on, the DMS will condense and fall back into the kettle.  That’s bad.  If you want to avoid DMS, step one is to boil your wort with the lid OFF the brew kettle.

Step two is to boil your wort for at least an hour.  The longer your boil is over 158 F, the more DMS is removed from your wort.  Slow cooling of your wort will also allow DMS to form, so you want to cool your wort as quickly as possible.

DMS can also form from bacterial infections.  An infection can convert Dimethyl sulfoxide (DMSO) into DMS by removing the oxygen.  To avoid bacterial DSM, make sure you are practicing good sanitation techniques.

• Bacterial infections will cause a cooked vegetable flavor
• Boil your wort for at least an hour with the lid off
• Lighter beers, such as Pilsners, are more susceptible to DMS problems

Related Articles

• Why does my beer taste bad?
• Why does my beer taste bad? (Part 2)
• 6 questions to ask yourself before pitching your yeast

© 2009 – 2010, fermentarium. All rights reserved.

Please see the fair use guidelines for republication. If you would like to submit articles to fermentarium.com, please review our Guest Post Guidelines.

Don't forget to "like" fermentarium on facebook

Related Posts

1. 8 clever uses for bad beer
2. Why does my beer taste bad? (Part 2)
3. Why does my beer taste bad?

Buttered Popcorn or Butterscotch (diacetyl)

Diacetyl is a natural by-product of fermentation.  Diacetyl in very low amounts (50 parts per billion) will impart smoothness to the beer.  A bit more diacetyl in your beer will taste a bit like butter or butterscotch.  Artificial butter is made with diacetyl, but ironically butterscotch itself usually has no diacetyl.  Slightly more diacetyl and eventually your beer will be undrinkable.

If you’ve ever noticed a slippery butterscotch flavor in Chardonnay wines, it’s because they have a bit of diacetyl inside.  Unfortunately recent trends have been to allow too much.  These are the wines many refer to as “butter bombs”.  Many ales have butterscotch notes which are quite nice.

Popcorn is great at the movies, but really tastes nasty in your beer

When the butterscotch becomes too much, the beer starts to taste like buttered popcorn.  Diacetyl is produced during the fermentation process, but usually is reabsorbed by the yeast.  If the yeast is interrupted, goes into dormancy too soon, or the fermentation stalls the yeast will not have a chance to reabsorb the diacetyl.

You can also get diacetyl from bacterial infections.  If you have other “symptoms” such as sour flavors, strange looking bacteria in the wort, etc… then you need to revisit your sanitation procedures.

Your beer can get diacetyl flavors if you pitch too little yeast or old yeast.  The reason is there might not be enough yeast at the end of the fermentation to reabsorb the diacetyl.  If the yeast dies or flocculates before absorbing all the diacetyl, the remaining diacetyl will impart flavor to your beer.  Sometimes this is a desired effect, other times not so much.

Diacetyl problems unrelated to bacteria can be corrected before bottling/kegging with a diacetyl rest.  A diacetyl rest is warming up your lager at the end of the fermentation so the yeast can wake up and absorb the diacetyl.  If you are making a lager, move the carboy to a warmer location and let the yeast finish their work for a few days.  Since ales are usually at a warm temperature, leave the ale alone for a few days more until the flavor goes away.

• Perform a diacetyl rest at the end of your fermentation – for lagers increase the temperature
• Pitch proper amounts of yeast – old yeast or too little yeast can cause these off-flavors
• Don’t rack too soon – if you rack before the fermentation is complete, the yeast cannot absorb the diacetyl

Band-aid flavor (phenols)

The band-aid flavor is usually caused by a reaction of phenols with chlorine.  Chlorophenols are created when phenols react with chlorine from bleach or other chlorine-based cleaners.  These molecules can affect the taste in single parts per billion – tiny amounts can ruin the flavor of your beer.

If your beer has the dreaded band-aid flavor, you are introducing chlorine into your beer at some point in your process.  The chlorine can come from you city’s tap water or possibly your cleaning solution.  If you are using a chlorine-based cleaner, make sure you rinse your equipment thoroughly with boiled water.  A better solution is to never use chlorine to clean your equipment.

Some wild yeast can produce this flavor, but it is more likely the problem is coming from chlorine.  If you are practicing good sanitation techniques, the first step to correct this problem is to eliminate every possible source of chlorine.  Make sure your sanitizers are not using chlorine and use filtered water.

• Chlorine-based sanitizers mixed with phenols produced by fermentation
• Some yeast strains, such a Bavarian, will produce some clove-like phenol flavors which are desired
• Too much chlorine in your city water can give this flavor
• Don’t use chlorine, instead opt for a no-rinse sanitizer like StarSan

© 2009 – 2010, fermentarium. All rights reserved.

Please see the fair use guidelines for republication. If you would like to submit articles to fermentarium.com, please review our Guest Post Guidelines.

Don't forget to "like" fermentarium on facebook

Related Posts

1. Why does my beer taste bad? (Part 3)
2. Why does my beer taste bad?
3. Saving a wine kit from accidental sorbate

There are several ways your beer can go wrong.  When you have a bad beer you can cry in it, or you can learn from it.  In the next few articles, we’ll look at what bad flavors your beer can get and what causes the particular off-flavor.

My beer tastes like green apples (acetaldehyde)

Green apples are great, but pretty crappy in beers.  If your beer has the flavor or aroma of green apples, this flavor is usually caused by acetaldehyde.  Acetaldehyde, sometimes called ethanal, is formed by the yeast before the Glucose is converted to alcohol.

Glucose -> pyruvic acid -> acetaldehyde -> ethanol

Since acetaldehyde is an intermediate step, usually “green” beers have this off-flavor.

The green apple flavor means the fermentation process halted before completion.  This could be caused by pitching into wort with too little oxygen, not pitching the correct amount of yeast, or just racking your beer too early.  If you haven’t already racked and kegged/bottled the beer, the solution is to warm up the fermenter a bit so the yeast can “finish the job”.

Some literature and several books state adding too much cane or corn sugar will give beers a cidery flavor.  It’s more likely the wort was nitrogen-deficient, oxygen deficient, or missing something else the yeast needed to complete the fermentaion.  Many Belgian beers use sugar to lighten the body of the beer.  I haven’t come across too many unintentionally cidery Belgian beers.

The reason many cite sugar as the culprit is table sugar is sucrose, a sugar which yeast cannot easily ferment.  Sucrose (table sugar) however breaks into fructose and glucose, both easily fermented by yeast.  Heat and acid (your wort) will easily break the bond of this disaccharide.

• Green apple beers are usually “green beers”
• Acetaldehyde is the compound usually associated with hangovers
• Sugar isn’t usually the cause of cidery beer
• Pitch proper amounts of yeast at a cooler fermentation temperature to avoid “green apples”
• Time can fix this problem

Is your beer tea-bagged? (astringent)

If your beer makes your mouth pucker up faster than a very strong Earl Grey tea, your beer may be too astringent.  This means there is too much tannin in the beer and anyone drinking it will get the instant “bitter beer face”.

One source of tannins comes from sparging your grains in wort where the pH is too alkaline (greater than 6) or your sparging water temperature is too high.  When the wort pH is over 6, tannins and silicates are extracted from the malt husks.  Tannins are also extracted if your sparge water temperature is too high (over 170 F).

You can get this off flavor in an extract brew as well if you steep your specialty grains too long or at a high temperature.
Another source of this bitterness can come from a bacterial infection.  Acetobacter is a genus of bacteria who can convert ethanol (your beer’s alcohol) into acetic acid.  This astringency will taste more like vinegar.

• The tea bag flavor usually comes from too many tannins
• Don’t mash your grains too hot
• Some bacterial infections can some vinegary astringency flavors
• Modify your brewing techniques to avoid this in the future

© 2008 – 2010, fermentarium. All rights reserved.

Please see the fair use guidelines for republication. If you would like to submit articles to fermentarium.com, please review our Guest Post Guidelines.

Don't forget to "like" fermentarium on facebook

Related Posts

1. What does sugar do to your beer?
2. How to make a Chimay White Clone
3. Why does my beer taste bad? (Part 2)