Why does my beer taste bad?

Brewing beer — By on July 30, 2008 at 8:34 pm

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.

green apples

Green apples are great for cider. Beer? Not so much.

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

I am a avid homebrewer and winemaker. I’ve been making my own beer and wine for many years. I started making beer when I was in college (mostly because the drinking age in the United States is 21). My first few beers were horrible. The beers are much better now, and I often supply my neighborhood with free beer!

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