This week I’ll cover the symptoms and causes for a solvent-like off-flavor in your home brewed beer. While not common, even a slight solvent-like flavor can ruin an entire batch of beer.
Solvent Off-Flavors in Beer
Solvent off flavors include hot, paint-thinner, nail-polish remover, turpentine, wood-finish or other harsh flavors and aroma. The intensity can very from a slight hot finish to the beer to a very strong turpentine flavor. Fortunately it is fairly rare in home brewing.
The main cause of solvent off-flavors is a compound called Ethyl Acetate which is also widely used in glues, nail polish remover and other household solvents.
Ethyl acetate is actually an ester produced by the “esterfication” of alcohol during fermentation. It is a very common by-product of fermentation, and it comes from an enzyme called Acetate Transferase (AAT). The enzyme AAT is yeast specific, but is common for many ale yeasts, particularly for English ale yeasts which are high in esters.
In small quantities, ethyl acetate produces a pear-like, fruity or rose flavor and aroma that we associate with esters in many beer styles. However if the production of ethyl acetate is not controlled properly you can get an excess produced, leading to solvent flavor and aroma.
So basically solvent off flavors are caused by out of control ester production. Ester production is increased at higher fermentation temperatures so often we will find solvent off flavors when a beer is fermented too hot.
To mitigate solvent-like off flavors you need to choose a yeast that has your desired level of ester production and also control the fermentation temperature to make sure it does not rise too high. Keep in mind that often the temperature in the center of your fermenter is higher than the surface, so it is best to monitor fermentation temperatures using a thermowell or similar device so you know what the actual fermentation temperature is.
That’s a quick summary of the main cause of solvent-like off flavors as well as how to control it. Thanks for joining me on the BeerSmith Home Brewing Blog. Be sure to sign up for my newsletter or my podcast (also on itunes…and youtube…and streaming radio station) for more great tips on homebrewing.
