Detecting and Dealing With “Off” Flavors in Your Homebrew

In your quest to develop as a home brewer, you will run in to a number of false starts when it comes to constructing recipes and churning out batches. Most often, these false starts won’t become obvious until you’ve gathered friends around to taste that first bottle you want to crack open. So while everyone is making faces about your beer, start taking notes. An “off” flavor, or a flavor that is not expected in the beer you intended to brew, is common, and happens to even the most veteran of brewers. While this batch may be bad, you can start to figure out where it went wrong right away.

An “Off” Flavor is Not Always Bad…

What is an “off” flavor for one style of beer might be a sought-after flavor in another style of beer. It all depends what you are trying to make. For instance, while a phenolic taste – which comes across as medicinal and with a slightly plastic smell – would be considered an “off” flavor in a lager, it is actually desirable in small amounts in some Belgian style and in German wheat beers. Particularly if you are using a pre-measured kit, you might end up with some flavors you weren’t expecting, because of someone else’s idea of what the style should be.

… Unless It’s One of These

That being said, there are certain flavors that are not welcome in any style of beer. Oxidation, which tastes like stale, wet cardboard, is one such flavor. Neither is severe astringency, which is a puckering or drying of the mouth. This differs from bitterness or sourness, both of which are desirable in some styles.

Common “Off” Flavors and Their Prime Causes

Here is a list of the most common “off” flavors, what they taste like, and their most likely causes. This can give you an idea of where to start looking for the solution to the problem.

  • Acetaldehyde (Cidery, green apple-like taste) – Caused by prematurely ending fermentation or increased oxygen contact after fermentation.
  • Astringency (Drying and puckering of the mouth) – Lots of causes, including poor sanitation, high pH levels in the water, overhopping, excessively high sparge temperature, or even crushing the grains too much.
  • Cardboard (Tastes like papery, wet cardboard) – Usually caused by over-aging a beer, particularly a hop-forward beer, but also from aeration of hot wort.
  • Diacetyl (Buttery, butterscotchy flavors accompanied by slick mouthfeel) – Caused mainly by premature racking or low fermentation temperatures, but also can stem from bacteria.
  • Dimethyl Sulfide (Tastes like cooked corn) – A myriad of causes, including poor sanitation, a shortened boil, yeast issues, using low-temperature sparge water, or the overuse of adjuncts in the recipe.
  • Grassy (Musty, fresh-cut grass) – Most often caused by mold or bacteria developing in the grains, extract or even hops prior to brewing. Can be avoided through simple quality control of ingredients.
  • Metallic (Iron taste in the back of the throat or front of the mouth) – Almost always caused by poor-quality metal utensils made from materials other than stainless steel – iron and aluminum tools will both impart this quality. In some cases, can be caused by old, improperly-stored grains.
  • Phenolic (Clove-like, medicinal, vaguely plastic) – Poor sanitation, over-sparging, or using the wrong yeast. Certain yeasts will produce phenols naturally, make sure you are not using one of those yeasts.
  • Sherry-like (Papery, stale, with wine traits) – A result of aging and oxidation.
  • Soapy (Oil, with hints of dish detergent) – Caused by leaving brew in the primary fermenter for too long. This leads to the fatty acids in the trub breaking down, and causing this flavor.
  • Solvent (Tastes like paint thinner or a more extreme case of harsh alcohol) – Stems from a combination of high fermentation temperature plus oxidation, but also from using plastic that is not food-grade plastic.

Diagnosing “Off” Flavors

This is one reason you need to take copious notes and keep track of your equipment and ingredients. You can get input from friends, family even other area home brewers to figure out the “off” taste you need to deal with. Many hobby brewers will be happy to help you identify the proper tasting note – just make sure to tell them the beer is “off” in the first place, no one likes being surprised by bad beer.

Using their tasting notes, your notes, and the list of common causes, you can likely diagnose the problem and figure out a solution for the next batch. Then, it’s just a matter of getting your hands dirty again and putting out a new, improved batch of beer.