E is for Esters
E is for Esters – part 5 of our A to Z guide to craft beer terms.
“Why does this beer taste and smell like fruit?”
Probably the most commonly asked question I hear at craft beer festivals.
In addition to hops, which can lend fruity notes to both the nose and palate, esters are responsible for the light fruit you may detect in certain styles of beer. This may manifest as banana, pear or even anise. It’s a result of a process that occurs during fermentation and is primarily driven by how much acetate transferase (ATT) is present in the yeast.
Without getting too technical, ethanol (the primary alcohol in beer) combines with a molecule called acetyl coenzyme (ACOA) and forms ethyl acetate. This is where you get that pear-like character. In high concentrations, it can lead to a solvent-like character – less than ideal!
The banana flavour present in Hefeweizens is a result of isoamyl alcohol combining to form isoamyl acetate. You’ll also notice a bit in our very own Silvertree Saison. Yeah – science!
The lower the ATT in the yeast, the less esters will be produced. So a yeast with very low ATT might be appropriate for a lager, but when Al or JC are making our English Ale, they use a yeast that is much higher in ATT. This is because English Ales are known for their yeast derived fruitiness, and that’s what we’re aiming for!
Ester production is also controlled by fermentation temperature. The higher the temperature, the faster the yeast grows, which leads to more ATT and higher levels of ester production. That’s one of the reasons temperature control during the fermentation process is so important in achieving consistent results. Can you imagine what First Light would taste like if the fermentation temperatures changed with the seasons?
Luckily, all Devil’s Peak beers are kept in jacketed fermenters. This allows water to be pumped around the outside of the vessel, perfectly regulating the temperature during each step of the process. One of the many reasons your DPBC beer always tastes like DPBC beer.