How to avoid contaminating your beer

Are there any health or safety risks involved in drinking homemade beer?

Are you asking yourself this question? If so, you’re not alone. It’s a question I get all the time when I tell people I’m a home brewer. We’ve all heard about the dangers of distilling alcoholic products at home…you know…the moonshine that can make you go blind. It’s enough to make any rational human being think twice about making their own alcoholic beverage.  But, dear reader, I have great news for you! If you’re making beer at home, you don’t need to stress about it. Why? Because…

There are no known toxic microorganisms that can survive in beer.
In fact, it is  impossible to produce poisonous methyl alcohol – the stuff that can make you go blind, when brewing beer. Now, that’s not to say beer can’t get contaminated.  It can happen. But “contaminated beer” is just another way of saying bad beer. And bad beer is just that: bad-tasting beer. You’re not going to get botulism or any other scary-sounding foodborne health concern if your drink bad beer.  The worse that will happen is that your taste buds will be deeply offended that you put them through such torture. Bad beer won’t kill you, but it may make you sad.
Just as its easy to make amazing beer at home, if you don’t pay attention, you could easily make contaminated beer.  At pretty much every step of the brewing process, you could contaminate your beer. That’s why cleanliness and sanitization are so critical to a successful brew.

Signs your beer is contaminated

So, how do you know if your beer has gone bad? Here are the classic signs you should dump your beer down the drain instead of your esophagus:
    1. Foaming bottles. You’ll know it when you see it. You’re all set to show-off your latest home brew to your friends, pop off the lid, and like an angry volcano, the bottle starts foaming out beer vigourously. Don’t bother trying to recover any of the beer. Dump the rest of the bottle down the sink. Of course, ignore what I’ve said here if you deliberately highly carbonated your beer, or have poured yourself an aged sour beer. But I’m assuming at this stage you’re brewing “clean” beers and kept your priming sugars in check at bottling time.
    1. Horrendous smell. Again, you’ll know it when you smell it. If you can’t stand the smell of your beer, that’s Mother Nature’s way of making sure you only drink quality craft beer. Your body’s a temple, after all.
    1. Mold floating on top. If this happens, it’s likely to happen in the fermenter. Your beer has been infected by something. Cut your losses and dump it.
    1. Beer tastes worse with time. One of the great delights of home brewing, is that bottle-conditioning helps the beer improve in favour over time. But if you’re finding that the flavour is depreciating with time, you’ll want to drink your batch up more quickly or toss the beer out. Stale beer has a taste that’s often described as wet cardboard or sherry-like. This is a classic sign that your beer got oxidized (exposed to a bit too much oxygen).  This could have happened when you bottled your beer, especially if you splashed your wort around. Remember, when you’re transferring beer, you want a quiet siphon. If the beer has skunky smell, it got exposed to too much light. Remember, keep your beer in a dark place, away from direct light. It’s at the greatest risk of being light struck when its in the glass carboy, or if you’re using clear or green bottles. If your beer smells more like molasses, it could be on its way to becoming malt vinegar. I suppose that’s not a complete loss…perhaps it’s an excuse to make fish and chips?
    1. Slimy strands in the beer. I have yet to come across this one, but this type of contamination has been documents as a Lacto infection.  If your beer has a milky layer at the top, you’ve got a bacterial infection. In either case, toss out the beer. Now, I remember in my early days thinking I had contaminate beer because I noticed what looked like residue on the side of the bottle neck in the airspace between the beer and the cap. But it was actually dew, which is completely normal. Just trust your taste buds. If it tastes off, it’s probably off.
  1. Any one of these off-flavours. I have written a detailed post with all the possible off-flavours you could get in your beer. As you’ll see, almost every single one of these can be avoided with good sanitization and being mindful not to add too much oxygen to your wort.

 How to avoid contaminating your beer

Bad beer sucks. It’s never fun, having waited 4-6 weeks for the moment you can enjoy the fruits of your labour, only to discover your beer is contaminated. Just keep these tips in mind the next time you’re brewing, and you should be in good shape.
    1. Clean your equipment well. I’ve developed the habit of cleaning my equipment almost immediately after I use it. That’s usually the easiest time to clean the gear. Trying to scrub off caked yeast or syrup later can make for an annoying brew session. This includes my bottles. As soon as I pour out my beer, before I take that first sip, I rinse out the bottle and check to make sure there is no sediment left in the bottom. Doing this eliminates the need to scrub them on bottling day. I don’t bother using dirty or moldy bottles anymore. They’re too much of a pain to clean. If you are going to do it though, make sure to use a bottle brush to scrub away at the residue. Also, I discovered this the hard way once: dishwashers will make your bottles look clean on the outside, but they can’t properly scrub the inside.
    1. Pay attention to sanitization. Of course, your wort and priming sugars don’t require special treatment, as they will be boiled. Otherwise, you need to sanitize everything that comes in contact with your beer, from the moment you take it off the boil. Your job will be so much easier if you use Star-San as your go-to sanitizer. Immerse all of the equipment in the sanitizer solution for at least 2 minutes, and you’ll be set. Don’t forget to sanitize the inside of your hoses, ranking cans etc. I also always keep a spray bottle with sanitizer solution. It’s a tip I picked up recently and it’s made a world of a difference. It helps you sanitize easily and quickly throughout the brewing process.
    1. Do not aerate hot wort.  This is another one I learned the hard way. I always read that hot wort was safe from contamination, since it was just coming off the boil. I also knew that I had to cool it quickly, because that “in-between” temperature range is when the wort was at its highest risk of contamination. When you’re beer is above 140°F (60°C), wild yeasts and bacteria can’t contaminate your beer.  And that’s true.  But what I only learned years later is that hot wort is very susceptible to oxidation, especially as it cools. So avoid splashing hot wort around. Your goal is to keep the wort still as you cool it quickly below 80°F (26°C). If you cool the wort too slowly, di-methyl sulfide will continue producing before it has a chance to boil off, which will eventually cause unwanted flavours in the finished beer.
    1. Try to start active fermentation as soon as possible. Pitch the wort with active yeast as soon as possible. You want your wort to take to the yeast before it has time to take to other microorganisms. Ideally, you want to see fermentation activity within 6-8 hours after you pitched the yeast.
    1. Make sure the pitching yeast is not contaminated.  If you’re using dry yeast, don’t forget to sanitize the scissors before you cut open the packet.
    1. Store fermenting beer in dark areas. Light can destroy your beer, especially in a glass carboy. No one wants skunky beer.
  1. Store bottled beer in cool and dark areas. We know that light’s a natural enemy, but so is heat, which can break down flavor compounds and promote unwanted fermentation (increased CO2 pressure) and potentially exploding bottles.

Keep these seven things in mind, and you should have few contaminated batches. And if it happens, take solace in the fact that you’re not alone. It happens to all of us. You can only learn from your mistakes. Hopefully, you can learn more from mine. And trust me, I learned a lot (pretty much everything above) the hard way.

Last Updated




18 responses to “Are there any health or safety risks involved in drinking homemade beer?”

  1. Dan

    great info! thanks.

  2. James

    Brilliant advice… thanks mate. SenSible, well-written and valuable to a beginner like me.

    1. Thanks so much James!

  3. Branden

    I accidentally used yeast that was opened, but folded IN the eggs shelf of MY fridge for a few weeks. When I opened the ferementor it smelled like potent, not so clean alcohol. It had no other of smells or anything wrong with it. After being open for just a few minutes, that smell went away. My question is it safe? I will taste it and judge it anyway, but just wondering if it’s a no go.

  4. Preyan

    Awesome review. You put my mind at ease. First homemade brew for me. I paid more attention to my Beer than I ever did to my new born Baby

    1. Amazing! How did brew day go?

  5. Derek

    So I’ve brewed for the 1st time, it’s been 10 days and I had to take a small sample to test, it tastes like beer and is a little sweet yet so few more days, my question is is it normal for it to look milky at this time.

    1. Hey Derek, what beer style are you brewing? Do you have a picture? SOunds like suspended yeast to me, but shy of seeing a photo, tough to troubleshoot.

  6. RiCh

    I’m monitoring a batch at the moment, i Used a used stockiNg to dry hop. I boiled the stOcking first but it seems to have imparted a pretty rank chemical flavour into the beer. I’ve removed the stocking and Im now tossing up whether to ditch tHe whole batch or go through the pain of bottling to see if tHe flavour goes away.

  7. Susan

    Made my own homemade pineapple beer and it’s been a week now…
    The texture is slimy………..not sure why it turned slimy.

    1. Hi Susan,

      I wonder if you’re dealing with pectin issues?

  8. Tomar

    Great article sir…..

  9. Earl Logan

    my local brew shop assures me i wont get stale beer when BOTTLING if i splash the beer into the BOTTLE,because of the £1-50 piece of tubing they sold me in the kit to bottle with,

  10. […] is unavoidable in contaminated beer. It’s like bacteria or wild yeast found their way into a bottle. Sediment in beer is […]

  11. […] sour or vinegary flavor due to acetic acid, or a buttery flavor due to diacetyl. It is possible for contaminated beer to have a sour or off-putting flavor. A bad beer’s flavor can be identified by a variety of […]

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.