Why is My Homebrew Beer Leaving a Sour Taste?

Sour homebrew leaving a bad taste in your mouth? We explain the causes and give you the tips needed to prevent this unwanted hombrewing side effect



8/27/202310 min read

a glass of beer on a table
a glass of beer on a table

Unravel the essence behind the sour taste in your beer as we dive deep into the brewing process, common off flavours, and the intriguing world of sour beers.

This is an essential read for brewers who aim to perfect their brew or explore the craft of brewing sour beers.

With insights into the brewing process and tips to avoid unwanted sourness, this article is a brewer’s companion to mastering the art of brewing.

Why Does My Beer Taste Sour?

Quick Answer: When a homebrewer notices their beer tastes sour, it's often due to bacterial infections like lactobacillus or acetobacter, wild yeast strains, high fermentation temperatures, oxidation, or mashing issues, all stemming from inadequate sanitation or process missteps.

The journey of understanding the sour taste begins with recognising the common off flavours in your brew. A sour flavour in your beer can be a result of various factors during the brewing process.

The most common cause is bacterial infection or wild yeast infection that occurs due to improper sanitation. The culprits often include lactobacillus and pediococcus, which produce lactic acid, souring your beer.

Understanding the brewing process is crucial to pinpoint where the sourness can originate. From the moment you mash the malt, to the time you bottle the beer, any exposure to unwanted bacteria or wild yeast can result in a sour taste. It’s a battle against unwanted microbes that every brewer must face.

The Brewing Process: Where It All Begins

The brewing process is a delicate journey from wort to beer. It starts with mashing where the malt is mixed with hot water to extract sugars. This is followed by boiling with hops, and then cooling the wort down for fermentation. The fermentation process is where the yeast does its magic, converting sugar into alcohol.

However, if unwanted bacteria or wild yeast find their way into your brew during any of these stages, they can ferment the sugars in undesirable ways, leading to a sour taste.

Acetic acid and lactic acid are common products of such unwanted fermentation, contributing to the sour flavour in your beer.

What Causes the Sour Taste?

The primary cause of the sour taste is the production of acids by unwanted microbes. Lactic acid produced by lactobacillus and acetic acid produced by acetobacter are the usual suspects.

Another cause can be acetaldehyde, a compound naturally produced by yeast but usually converted to ethanol alcohol. However, if the fermentation process is interrupted or goes wrong, acetaldehyde can remain in the beer, giving it a sour apple taste.

It’s a fine balance that brewers need to maintain to ensure the desired flavours develop in their brew. While some sourness can be desirable, especially in styles like Belgian Lambics or Berliner Weisses, unintentional souring can ruin a batch of beer.

Is All Sourness Bad? Embracing Sour Beers

Not all sourness is bad. In fact, sour beers are a whole category of craft beer that many brewers and beer lovers adore.

Brewing a sour beer intentionally involves controlling the souring process to achieve a delightful tangy flavour. It’s an art and science that brewers have perfected over centuries.

Sour beers can be complex, flavorful, and incredibly refreshing. They are brewed using a controlled mix of yeast and bacteria to achieve the desired level of sourness and flavour profile.

So, if you are intrigued by the sour flavour in your beer, exploring the world of sour beers could be an exciting venture.

Common Culprits: Acetaldehyde and Diacetyl

Delving deeper into common off flavours, acetaldehyde and diacetyl stand out. As mentioned earlier, acetaldehyde gives a green apple tartness, whereas diacetyl imparts a buttered popcorn flavour. Both can be undesirable in high concentrations and are usually signs of fermentation issues.

Understanding the chemistry behind these off flavours and how to control them is crucial for a brewer. It’s all about ensuring a healthy fermentation process, right yeast strains, and good sanitation practices to keep these off flavours at bay.

Identifying and Controlling Bacterial Infections

Bacterial infections are a common cause of sourness in beer. Bacteria such as lactobacillus and pediococcus, along with wild yeast strains, can introduce unwanted acids into your brew, leading to a sour taste.

Good sanitation is your first line of defence against bacterial infections. Ensuring that all your brewing equipment, especially the fermenter, hoses, and bottles are well-sanitised can significantly reduce the risk of infection.

It’s about creating an environment where your chosen yeast can thrive without competition from unwanted microbes.

Souring Techniques for Crafting Sour Beers

For those who wish to venture into the world of sour beers, understanding souring techniques is essential. Kettle souring and wild fermentation are popular methods used by brewers.

Kettle souring involves adding lactobacillus to the wort in a controlled environment before boiling to kill the bacteria, leaving behind the delightful sourness.

Wild fermentation, on the other hand, is about letting nature do the work. It involves exposing the brew to natural yeast and bacteria, often by leaving the fermenter open to the air. It’s a riskier and longer

process but can result in unique and complex flavour profiles.

A Tale of Two Brews: Sourness in Lager vs Ale

When comparing lagers and ales, the brewing process and the yeast involved significantly influence the potential for sourness and other off-flavours. Let's delve into how sourness manifests in these two distinct types of beers.

The Yeast Factor

The primary difference between lagers and ales lies in the yeast. Ales use a top-fermenting yeast called Saccharomyces cerevisiae, while lagers employ a bottom-fermenting yeast known as Saccharomyces pastorianus. The fermentation process, temperature, and the yeast's behaviour play a pivotal role in the taste of your beer.

Ales, being fermented at warmer temperatures, are often more susceptible to bacterial infections or wild yeast infections, which can cause sourness. On the other hand, the cold fermentation process of lagers is less inviting to these unwanted guests, making it a bit easier to avoid unintentional sourness.

Brewing Process Nuances

The brewing process for ales and lagers has its unique set of steps and conditions. A key to avoiding unwanted sourness is good sanitation. Ensuring every piece of equipment from the fermenter to the hose is well-sterilised can significantly reduce the risk of bacterial infection, one of the most common causes of sourness.

Moreover, the way you aerate the wort, manage the fermentation process, and even how you bottle the beer can influence the final taste. Oxidation, for instance, can lead to offness that might be mistaken for sourness. It's important to limit oxygen exposure to avoid this common off taste.

How to Fix a Sour Batch of Beer?

So, you’ve brewed a batch of beer and it’s gone sour unintentionally. Don’t despair! While it might not be what you planned, sometimes, a slightly sour beer can still be enjoyable.

However, if it’s a recurring problem, revisiting your sterilisation practices and fermentation control is essential.

Understanding the cause of sourness, whether it’s bacterial infection, wild yeast, or fermentation issues, and addressing them in future brews will help you avoid unwanted sourness. It’s all about learning and adapting in your brewing journey.

The Hose: Your Unexpected Enemy

The humble hose, a crucial tool in transferring wort and beer, can be a source of bacterial contamination if not properly cleaned and sanitised. Even a small amount of residue or a tiny crack can harbour unwanted bacteria, leading to a sour taste in your beer.

It’s a reminder that every aspect of the brewing process, no matter how small, plays a significant role in the final flavour of your beer. Ensuring that your hoses and other equipment are well-sanitised and in good condition is crucial.

Fermentation Control: The Key to Desired Flavours

Fermentation control is where the magic happens. It’s where you, as a brewer, have the most influence over the flavour of your beer.

Ensuring a stable fermentation temperature, choosing the right yeast strain, and allowing enough time for the fermentation process to complete are crucial steps to avoid unwanted sourness.

Moreover, understanding the fermentation process, recognising when things go awry, and knowing how to fix them is part of the learning curve in brewing. With experience, you’ll be able to manage the fermentation process to produce the flavours you desire in your beer.

Exploring Other Off Flavours in Beer

While sourness can be an intriguing or undesired taste in beer depending on the context, it's not the only off flavour a brewer might encounter. Knowing and identifying other common off flavours can significantly enhance your brewing skills and the quality of your beer.

Here are some of the other off flavours and their common causes:

  • Buttered Popcorn (Diacetyl)

    • As mentioned earlier, diacetyl can impart a buttered popcorn or butterscotch flavour to your beer. It's a compound that yeast produces naturally, but usually reabsorbs. If you're tasting diacetyl, it might indicate a rushed fermentation or a yeast health issue.

  • Green Apple (Acetaldehyde):

    • Acetaldehyde, also mentioned before, can give your beer a green apple or freshly cut pumpkin flavour. It’s a natural intermediate compound in the production of alcohol, but a sign of incomplete fermentation if present in noticeable amounts.

  • Skunky (Lightstruck):

    • Exposure to light, especially sunlight or fluorescent lights, can react with the hops compounds in beer, creating a skunky off-flavour. Brown bottles provide some protection, but clear or green bottles offer little defence against light exposure.

  • Metallic:

    • A metallic taste can arise from the exposure of beer to metal throughout the brewing process. Ensure that all your metal equipment is brewery-grade and well-maintained to avoid this off-flavour.

  • Cardboard (Oxidation):

    • Oxidation can result in a stale, cardboard-like flavour. It usually occurs when beer is exposed to oxygen post-fermentation. Be cautious during bottling and ensure your caps form a good seal to prevent oxygen exposure.

  • Corn or Cereal (DMS):

    • Dimethyl sulphides (DMS) can give your beer a cooked corn or cereal flavour. It's typically produced during malting and can be evaporated during a vigorous boil. Ensure a good boil and promptly cool your wort to avoid DMS.

  • Band-Aid (Phenolic):

    • Phenolic off-flavours can taste like medicine, Band-Aid, or smoky. They usually stem from bacterial contamination, chlorine in the brewing water, or the use of heavily phenolic yeast strains.

  • Alcoholic (Higher Alcohols):

    • A harsh alcoholic or solvent-like taste can be due to the presence of higher alcohols produced during fermentation, often from high fermentation temperatures or under-pitched yeast.

  • Catty (Mercaptans):

    • Mercaptans can give a catty or sulphur-like off-flavour. They are usually the result of yeast stress or bacterial contamination.

  • Sulphur:

    Yeast naturally produces some sulphur compounds during fermentation, but these should dissipate with time. A strong sulphur aroma can indicate a problem with the yeast or fermentation conditions.

Sour Homebrew Beer: Wrapped Up

The journey through the diverse tastes in brewing, from the tang of a sour beer to the unexpected offness, is a testament to the endless learning and adventure this hobby entails.

Every brew, whether it hits the right notes or ventures off the flavour path, is a step forward in the ever-evolving craft of brewing.

So, as you unravel the mysteries of sourness and tackle the challenges of off-flavours, remember, every sip, every brew, and every discovery is a chapter in your unique brewing story.

Here’s to many more brewing adventures and the continuous pursuit of the perfect pint. If you want more homebrewing tips, information or more, head over to the Brewpedia blog now!


Q: Why does my beer taste sour?

A: Sourness in your homebrew can be caused by a few different factors. One common cause is a bacterial or yeast infection, such as from Brettanomyces. Another possible cause is a high level of acetic acid, which can give a vinegar-like taste to your beer. It's important to pinpoint the specific cause of the sourness in order to find the best solution.

Q: How can I fix my sour beer?

A: The easiest way to avoid sourness in your beer is to practice good sanitation throughout the brewing process. Make sure to thoroughly sterilise all equipment and fermenters to prevent bacterial or yeast infections. Additionally, be careful when handling and transferring your beer to avoid introducing any unwanted flavours. If your beer has already turned sour, there may be nothing that can be done to save it.

Q: What can cause a beer to turn sour?

A: A beer can turn sour due to various factors. It could be a contamination during the brewing process, such as introducing wild yeast or bacteria. Improper sanitation or not following proper fermenting practices can also contribute to a sour beer. High temperatures during fermentation or extended low fermentation times can enhance the growth of unwanted microorganisms that produce sourness.

Q: How can I prevent my beer from turning sour?

A: To prevent your beer from turning sour, it is essential to maintain a clean and sterilised brewing environment. Make sure all equipment is properly cleaned before use. Follow a strict fermentation schedule and monitor the temperature closely to prevent the growth of unwanted microorganisms. It is also important to properly store your beer in a cool and dark place to avoid any flavour changes.

Q: What are some common off-flavours in homebrew?

A: Besides sour flavours, there are several other common off-flavours that can occur in homebrew. Some examples include estery or fruitiness, which can be caused by yeast fermentation at high temperatures. Cidery flavours, reminiscent of apples, can result from improper fermentation or excessive exposure to oxygen. Rotten or vegetable-like tastes may indicate bacterial contamination or malt quality issues.

Q: Can the flavour in my beer change after it's been bottled?

A: Yes, the flavour in your beer can continue to develop and change even after it has been bottled. This is especially true if the beer undergoes a process called "conditioning" or "maturation" in the bottle. During this time, the yeast can continue to ferment and produce new flavours. It's important to note that not all changes in taste are desirable, and the beer should be monitored closely to ensure it doesn't develop any.

Q: I'm new to brewing, what's the most important thing to remember to avoid off-flavours?

A: The most important thing to remember as a beginner brewer is to practice good sanitation. Properly clean and sterilise all equipment, fermenters, and bottles to prevent any unwanted microorganisms from infecting your beer. Pay close attention to temperature control and fermentation times to avoid the growth of off-flavour-causing yeasts or bacteria. Following a recipe closely and using quality ingredients can also help to prevent undesired effects.

Q: Is there anything that can be done to salvage a beer that tastes off?

A: If your beer tastes off and has developed an unpleasant flavour, there may be limited options for salvaging it. It's best to taste a sample of the beer and assess the severity of the off-flavour. In some cases, blending the beer with another batch or adding agents may help mask or balance the off-taste. However, it's important to note that not all beers can be saved, and it may be necessary to accept the loss and learn from the experience.

Q: How important is it to use liquid yeast for avoiding off-flavours?

A: Using liquid yeast can help in avoiding this as it provides a greater range of yeast strains to choose from. Different yeast strains can produce different tastes and aromas in your beer, so selecting the right yeast for your desired style can enhance the overall quality and flavour. However, it's important to note that the fermentation process, temperature control, and sanitation practices play a significant role in avoiding off-tastes regardless of the yeast type used.

Q: What can be done to avoid infections in my homebrew?

A: To avoid infections in your homebrew, it's crucial to maintain a clean and sterilised brewing environment. Start by thoroughly cleaning and sanitising all equipment, including fermenters, airlocks, and brewing utensils. Use a sanitiser that is suitable for brewing and follow the manufacturer's instructions. Take care when transferring your beer and avoid exposing it to the air unnecessarily. Proper storage conditions, such as keeping the beer cool and dark, can also help prevent infections.