Homebrew Beer Tastes Sour? Here’s Why and How to Prevent It

While homebrewing is incredibly fun and rewarding as a hobby, it’s not always sunshine and roses. After a long brew day, weeks in the fermenter, and more weeks in the bottle it can be devastating to discover an off-flavor in your beer. Sooner or later you are bound to make a homebrew beer that tastes sour so I decided to tear this issue apart to find out the reason and how to prevent it!

Homebrew beer that tastes sour is almost always caused by a bacterial infection which produces either lactic or acetic acid as a by-product. Preventing these infections requires proper sanitation before, during, and after the brewing, fermenting, and bottling stages.

For those of you that are trying to diagnose the reason behind a sour beer, read on. Even if you haven’t experienced a sour beer yet during your homebrew adventure though, it’s a good idea to remind yourself what can happen if you aren’t paying attention to what you’re doing on brew day.

Bacterial infection is the most common cause of sour homebrew beer

Without a doubt, the single biggest source of a sour note in your homebrew is a bacterial infection that happened at some point in your brewing process after the boil. It has happened to thousands or millions of homebrewers over the years at one point or another and it just plain sucks.

Infections are super common because there are so many bacteria out in the wild that love to eat sugar just as much as your brewing yeast do!

Once these ‘bugs,’ as they are affectionately called in the brewing community, find their way into the homebrew, they multiply like crazy and compete with your friendly yeast for the food. Since they don’t exactly announce their presence as they jump in, brewers usually won’t realize they have an infection until it’s too late.

The most common bacteria causing infected homebrew beer

Although there could be other culprits, the following types of bacteria are the most likely suspects anytime you have a sourness to your homebrew.


As its name suggests, lactobacillus bacteria produce lactic acid which is the compound that actually produces a sour flavor on your tongue.

There are many different species of the lactobacillus bacteria and they are generally considered to be ‘friendly’ because they hang out in our digestive and urinary systems without causing trouble. As a result, they are extremely common in the wild and it’s even used on purpose in many cases to make certain types of traditional beer, yogurt, and other fermented foods.

You can also find different strains of this bacteria in dietary supplements as well as many medications.


Another lactic acid-producing bacteria, ‘pedio’ is very common in the wild and it is used commercially to ferment many different foods like pickles, sausages, and milk products.

In beer, this bacteria will also produce diacetyl compounds which add a buttery flavor and aroma to beer when present. Basically, think buttered popcorn. Depending on the situation, it can also cause ‘ropes’ of extracellular polysaccharide to form in the beer which looks just as nasty as you think it does!


Unlike the first two bacteria that produce lactic acid from sugar fermentation, acetobacter will produce acetic acid.

Essentially, acetic acid will give your beer more of a vinegary taste than an outright sour flavor. Also unlike the other two bacteria, acetobacter needs oxygen to grow and thrive so if this is your problem you have both a sanitation issue and an oxidation issue because there is normally very little oxygen present in the wort during fermentation.

Brettanomyces or other wild yeasts

If you are picking up sour notes that have a big of fruitiness to them then you might have just picked up a strain of Brettanomyces or some other wild yeast that has been hanging out where you do your homebrewing. Picking up this infection can cause a whole host of different sour, fruity, and downright funky flavors to develop in your homebrew.

When I say funky I mean such endearing things as ‘horse blanket,’ ‘farmhouse,’ and ‘leathery.’

The cool thing is that the brewers that specialize in these beers take their wild yeasts very seriously. I’ve even heard of one operation that ages their beer in oak barrels inside of a barn collecting the dust and cobwebs so they won’t lose their particular wild yeast strains.

Acetaldehyde can sometimes give a sour taste to homebrew

I need to point out here that many new (and veteran!) homebrewers can mistake the sour apple/jolly rancher-like flavor that acetaldehyde adds to a beer for a truly sour note.

Acetaldehyde is present to some degree in all beers because it’s a common by-product of the fermentation process. It’s even an intentional part of the flavor profile for something like a Biere de Garde or American lagers like Budweiser. If you are picking up this flavor while the beer is still in the fermenter then leave it there!

With enough active yeast, this flavor should eventually go away and when people talk about ‘green beer’ this is usually what they are talking about. It’s a beer that hasn’t had enough time to let the yeast do their work of cleaning up off-flavors inside it.

Once the beer is in bottles, this flavor might take a long time to go away or it might not go away at all because there is no longer any active yeast to fix it.

Prevent homebrew beer from tasting sour with proper sanitation

Just like when preventing human bacterial infections, the best way to prevent homebrew from getting infected is to sanitize!

Because the boiling process would kill any wild yeasts or bacteria that were introduced early on in the homebrewing process, sanitation is most important after the boil has been completed and you are cooling the wort, fermenting it, or adding dry hops or other additions in the secondary.

Sanitation also comes into play anytime you are transferring it from one container to another, bottling it, or kegging it.

In all cases, you’ll want to make sure that your equipment is cleaned to remove any visible dirt or grime and then sanitized with a quality sanitizer such as Iodophor or Star-San.

Let’s break down each stage of the homebrew sanitation:

  • Cooling the wort – Once the beer cools below 140 degrees, the game is on. You’ll need to ensure that your wort chiller is clean including any fittings and be careful not to let anything drop into the kettle while you are cooling it.
  • Transferring wort to fermenter – Ensure that the fermenting vessel and lid (if you have one) is clean and sanitized. If you are pouring into it with a funnel, check that. If you are using a rack and tubing, check that.
  • Fermentation – Be sure that you get the airlock in place quickly and add sanitizing solution to it so that nothing can get into the fermenter.
  • Sampling –  If you need to sample, be sure that your tools are sanitized and that you aren’t leaving the fermenter open for too long.
  • Adding dry hops or other additions – This can be tricky because there might not be a way to sanitize secondary additions before you put them in. Typically, hops won’t give you much trouble but you might want to at least boil your hop bag for a few minutes before you use it.
  • Bottling – This is a big one. It can be very difficult to get beer bottles 100% clean, especially if they are used. Carefully clean and soak the bottles in sanitizer before you get ready to transfer and be sure to visually inspect them one at a time. For bottlers, it is recommended that you use a sanitizer that doesn’t have to be rinsed, such as StarSan so that you can just let them drip dry and there won’t be any other opportunity for bacteria to take hold.
  • Kegging – When cleaning kegs, be sure that you have broken them down to all of their individual pieces so that you are able to get every nook and cranny. The dip tube is one of the biggest culprits when it comes to keg sanitation because it is difficult to check inside. Check and double-check it visually and be sure to soak it thoroughly with sanitizer before reassembly.

Consider replacing plastic pieces of brewing equipment

Plastic equipment such as fermenting vessels, tubing, siphons, valves, o-rings, and nuts are great because they are often less expensive than stainless steel pieces.

For beginning brewers and veterans alike, startup costs are a big part of the equation and a tight budget can’t be denied. Even with proper cleaning and sanitation technique, however, plastic equipment can be difficult to get 100% sanitized because it can develop tiny scratches that harbor bacteria.

If you have taken a serious look at your sanitation practices, but you continue to have issues with bacterial infections, then you should consider replacing your plastic brewing equipment if you can, preferably upgrading to glass or stainless steel.

It might be an added cost, but so is wasting time and money on another batch of unintentionally sour beer.

Can you fix a homebrewed beer that tastes sour?

If you came here looking for a way to fix your sour-tasting homebrew, then you are probably going to leave disappointed.

Some off-flavors can be reduced or eliminated with extended time in the fermenter or extra bottle conditioning. This happens because:

  • Active yeast remains in the final product that does some work cleaning up undesirable compounds
  • Sediment and dead yeast continues to fall out of solution and drop to the bottom of the fermenter or bottle
  • Other flavors develop during conditioning that changes or minimizes the off-flavor

Unfortunately, the primary reason for a sour taste in beer is related to lambic or acetic acid. This is a problem because no amount of time or lingering active yeast will reduce these two acids and they will still be just present after the conditioning process. The best way to fix a homebrew beer that tastes sour is to prevent doing it again.

Is sour beer safe to drink?

The short answer is yes.

Assuming that the beer has an off-flavor caused by the standard bacterial infection or wild yeast contamination there probably isn’t anything too dangerous in your beer that you will have to worry about.

After all, the alcohol in the beer coupled with its overall acidity means that no known pathogens can survive in beer.

The biggest thing you’ll have to worry about is the off-flavor itself and whether or not it leaves the beer drinkable. A little sour flavor in an IPA, for instance, might not be such a bad thing overall. That same flavor in a milk chocolate stout, on the other hand, is a whole different story.

The only thing you can do is taste it and make the decision to keep it or dump it.

Some homebrew beer tastes sour on purpose

Before we get started with all of the bad stuff I do want to point out that some types of beer are actually supposed to be sour. If you’ve been a beer enthusiast for a while, you’ve probably tried a few of these before and you’ll understand that they deserve a place in the world of beer.

Some of the most famous examples of this style of beer are the Duchesse de Bourgogne, New Belgium La Folie, New Glarus Raspberry Tart, Rodenbach Fruitage, Cantillon Gueuze 100% lambic, and the Goose Island Gillian.

Typically, these beers are brewed with some combination of wild fermentation, Brettanomyces yeast, and intentional infection with one of the bacteria that we talked about earlier.

Making these beers ends up either being a very complicated process of multiple fermentations and additions or a relatively simple process of open-air or barrel fermentation and aging.

If you haven’t tried any of these, you at least have to give them a taste. I’ll admit that sours aren’t my favorite category of beers, but I’ve appreciated the flavors they bring to the table and at least enjoy them for their novelty compared to the more normal beers on the market.

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