In the last post we discussed diacetyl, a buttery flavor that is one of the most common off flavors in beer. Next up is another common off flavor, acetaldehyde. If you’ve ever had a beer that smelled or tasted like apples, you’ve enjoyed acetaldehyde. It can’t hurt you at the levels you’ll find in beer, it just tastes bad. Actually, acetaldehyde is in all beer, but typically at undetectable levels. It’s unacceptable in most styles, a rare exception can be a French Biere de Garde.
Acetaldehyde is an off flavor that most people can smell as easy as they taste it. Not all off flavors have such a robust aroma. Cover your glass with your hand and swirl it to release CO2, then remove your hand and take a whiff. How ‘bout them apples? Take a taste, letting the beer flow around your mouth before you swallow. It reminds some of the fake apple in the green Jolly Ranchers.
Like Diacetyl, acetaldehyde is a byproduct of fermentation. It’s a naturally occurring substance that is cleaned up as the yeast go about their business. But when the yeast are rushed, they don’t finish the job and you get “green” beer. Green beer is not dyed St. Paddy’s Day Bud Light, it’s immature beer that was bottled before fermentation was complete. It’s rarely a problem you’ll find from established breweries. You’ll more likely experience acetaldehyde in new start-up breweries, and especially in home brew. Acetaldehyde is quite common in beer from impatient novice home brewers.
Here’s to flawless beer! Cheers.