Off flavors can really ruin your beer. And make you question how things could have gone so wrong. You tell yourself you did everything right. But somewhere along the line, your beer took a turn for the worse. Sometimes it can be due to stress yeast, or due to improper techniques. And sometimes it just kind of happens without you doing anything wrong.
The key to mastering off-flavors is being able to identify them and what typically causes them. That way you can backtrack and look at your notes to see if you can pinpoint the area that needs to be fixed for the next brew. And if you are still having trouble with off-flavors in your beer check our Common Mistakes made by Homebrewers.
Oxidation is most commonly identified as a wet cardboard dull flavor. As hoppy beer brewers know it also greatly impacts the hop characteristics in the beer. Not only does it dull the hop aroma and flavor. It can turn the beer sickly sweet like hard candy. It can also impact the color of your beer making it more noticeable in hazy beers.
Oxidation can happen anytime once fermentation has begun. Oxygen helps support yeast growth at the beginning of fermentation. But after it’s in full swing any additional oxygen exposure can really ruin your brew. That means avoiding splashing, roughly transferring, or opening your fermenter needlessly. When packing purge your keg with CO2 before transferring it. For bottlers, you’re going to do the second fermentation in the bottle. So when you add priming sugar the fermentation kicks back up and the yeast will consume any oxygen left in the bottle.
Unfortunately, once your beer is oxidized there’s no going back. Depending on how badly you oxidize your beer will reflect on how quickly you see changes in your beer. There’s really no way to fully prevent oxidation.
Sulfur is a unique off flavor because for some beer a little sulfur is actually accepted. When it’s too much it can make it hard to drink. Sulfur is commonly identified by a strong aroma that reminds of rotten eggs. For the most part, it only impacts the aroma of the beer.
Sulfur can come about in a few ways but most simply it comes from stress yeast. When the yeasts are working hard to convert the sugars into alcohol they can get overwhelmed. If they don’t have enough nutrients or there’s not enough of them to do all the work. To combat this its always smart to pitch a good amount of healthy yeast by making a starter.
Thankfully sulfur is one of those off-flavors that can actually be cured. Not always but in some less extreme cases. All you need to do is to give it some time. Leave the beer in the fermenter for a few extra days or weeks until the sulfur smell dies down.
When acetaldehyde is present in large amounts you notice it can be described as a strong green apple flavor. This off-flavor can be increased for a number of reasons such as stress yeast, bad sanitation practices, and oxidation during fermentation.
Most notably this can come about when you package or consume beer when it’s too young. This can happen with a lot of flavors. But if you keg up or bottle your beer while still at the tail end of fermentation it can lock in those off-flavors. Just let the beer rest in the fermenter until you don’t notice it anymore.
Diacetyl is naturally created during fermentation and can be reabsorbed by the yeast. It can be identified as buttered popcorn and even give an oily slick mouthfeel. Near the end of fermentation, you can do what’s called a diacetyl rest. This is where you raise the temperature of your fermenter 3 to 4 degrees for a few days to speed up the yeast. Diacetyl can also occur when there’s a bacterial infection. Lactobacillus is one bacteria known to promote it.
5. Dimethyl Sulfide (DMS)
DMS is said to be perceived as cooked cabbage or even a tomato paste. To understand where DMS comes from we first need to look at S-methyl methionine or SMM which is a precursor to DMS. SMM is produced during the germination of grains and then its converted to DMs during the boil.
Its most notably found in pilsner malts and some adjuncts. The best way to remove DMS is to have a vigorous boil. The experts say at least 60 minutes. Malting has come a long way over the last few decades. So we think you don’t have to worry about this one too much.
When you take a step back and look at all those off-flavors. A lot of time it comes down to the basic brewing skills. Practice good sanitation, pitch a lot of healthy strong yeast, control fermentation temperature, avoid oxidation and give it some time. These key steps will help you be on your way to better-tasting beer.