How Can I Tell If My Beer Is Contaminated?

Question:

I am a new home brewer and getting ready to bottle my first batch. I’ve heard and read the importance of sanitation when it comes making beer which I have tried to adhere to throughout the whole process.

Up until now the beer seems to smell and taste good, but what things might I look for to tell if a batch goes bad (ie. smell, taste, ect…)?

Answer:

Presentation can be in appearance, aroma, flavor or aftertaste and contamination can have several ways of revealing itself.

  • gushing
  • sour smell and/or taste
  • vegetal aroma (rotten)
  • ropiness
  • haziness
  • ring in the neck of the bottle
  • very large amounts of loose sediment (if the beer was properly settled first)
  • over carbonation
  • extreme dryness in mouthfeel
  • excessive diacetyl

These are just a very few. However, it is important to note that many of these (except ropiness and the neck ring) can have very innocent origins, so infection might not be the answer.

For instance, if you were tasting a pale ale, saw that it was hazy and a slight vegetal aroma presented itself, you could consider the beer infected. But you might also have carried through protiens from a low boil, which could also cause some vegetal aroma.

Certain styles like Berlinner weisse, Belgian strong, Flanders Red or Old Brun, have flavors that are entirely appropriate, but would be signs of infection in other styles…