Last time, we looked at some of the most common off-flavors that might creep into your homebrew (or beer you’ve just bought at the local for that matter).

In today’s post, we continue our journey through foul flavors. Sounds lovely, doesn’t it?


Off-Flavor #4: Acetaldehyde

This off-flavor will remind you of green apple, apple puree, or freshly cut Granny Smith apples. This is another substance that is present in all beer: yeast produces it during fermentation.
But in high concentrations, it is always considered a flaw.
Remember, we’re making beer here, so apple flavors are generally not ideal!
 How to stop it
Acetaldehyde can be formed by bacteria, so check your sanitizing processes. Especially in the cold-side of you brewery, i.e. the chiller, fermenters, transfer hoses and tubes, etc.
Occasionally, this green-apple monster can be created by aeration during bottling. So make sure you fill your bottles (or kegs) from the bottom up, and fill slowly! To be super-sure, purge your bottles and kegs with some CO2 before filling them.

Off-Flavor #5: Oxidized

Good for packaging, sucks as a flavor
Oxygen is important in the brewing process. Yeast needs the stuff, just like us, to remain healthy. But good old O2 comes with it’s own shadowy side. When introduced during mashing or bottling, it can ruin beer.
Damn you oxygen and all your noble gas buddies!
You’ll know your beer’s been oxidized if it tastes one-dimensional and smells like wet paper, cardboard, or that old library scent. Sometimes, it can even taste like white pepper, but not in a good way.

How to stop it

Oxygen can creep into beer when you don’t bottle correctly, so ensure that you bottle nice and slowly. Purge your bottles or kegs with CO2. Make sure that your racking equipment doesn’t have tears or holes that can let air in during transfer. Don’t whisk sugar into your bottling bucket, stir it very, very gently or not at all.
Also, you may not be getting a good seal on your keg or crown caps, so check those as well along with your capper.
Exposure to light can also lead to problems, so make sure you’re using brown bottles and not storing your beer in UV light. Generally, poor storage of beer can often lead to oxidization problems.

Off-Flavor #6: Ethyl Hexanoate


Ethyl Hexanoate is another natural product of fermentation, and can, in certain concentrations, be acceptable in a host of different styles of beer.
It’s flavors and aromas are fruity, dried apple, slight aniseed, slight perfume, or somewhat floral.
In high concentrations, it can make you beer taste more like a cheap apple cider than beer. The horror!

How to stop it

Esters like Ethyl Hexanoate are tied up in the fermentation of beer. Yeast health, pitching rates, fermentation temperatures, and available oxygen are all important when you want to eliminate this off-flavor.
Make sure you yeast has a healthy environment to grow in. Aerate your wort before pitching yeast and if you’re brewing high gravity beers, add some yeast nutrients in the boil to help those little buggers out.
A common cause is overly high fermentation temperatures. Because homebrewers often struggle with temperature control, especially in the warmer months of the year, this can be a real pain. Try to maintain a steady fermentation temperature of between 16 and 18 degrees C for ale yeasts and see if that does the trick.
That’s it for off-flavors for now! We’ll no doubt be looking into them again some time soon, but for now, leave comments if you detect any other nasty surprises in your homebrew and I’ll happily assist! 


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