One of the biggest concerns with any homebrewer – but particularly new brewers – is contamination. Is your beer, mead, or wine contaminated? While contamination is quite rare if you’re rigorous with sanitization, it can happen. The bacteria, Lactobacillus, is a common contaminant in homebrew – but how do you tell if it’s there? And what do you do when you find it?
If your beer, mead or wine has a sour or tangy flavor, similar to yogurt or sour fruit, it may be contaminated with Lactobacillus. You may see a white pellicle on top of the brew, though this is not a perfect indicator. If your brew is infected with Lactobacillus, as long as there is no mold, it is still safe to drink.
In fact, Lactobacillus is a pretty standard microbe used in many food and beverage applications, and is something we as humans have been using pretty much forever. Brewers even sometimes purchase cultivated strains of Lactobacillus and intentionally pitch them alongside their chosen yeast!
So if you find a sourness in your brew or a white pellicle on top, do not necessarily be afraid of it. It is worth at least tasting the beverage before you dump the entire batch.
But how can you be sure that it’s Lactobacillus and not something else? And what should you do with the batch once you’ve figured that out? What about your brewing equipment, and future batches?
What Is Lactobacillus?
First, let’s discuss specifically what Lactobacillus is, so we can better know what to look for and what we’re working with.
In technical terms, Lactobacillus is a genus of bacteria, specifically Gram-positive lactic-acid-producing bacteria. It functions similarly to yeast, although not exactly the same – consuming sugar to produce primarily lactic acid rather than primarily alcohol.
Compared to other, similar, possible contaminants like Pediococcus, Lactobacillus reproduces quickly and works much faster to produce this lactic acid. It works in a much cleaner way than other similar bacteria, and does not typically leave behind as much diacetyl and other funkier off-flavors. This produces a much cleaner sourness, and is why Lactobacillus is the most common choice for souring brews, as well as other food-related applications like making yogurt.
To me, this sounds a lot like comparing clean-fermenting lager yeasts to ale yeasts that typically throw off more estery flavors!
Lactobacillus is one of the most common beer, mead and wine contaminants – along with Brettanomyces and Pediococcus. Often if you have a contamination (meaning you did not intentionally pitch one of these microorganisms into your brew) then you probably have a combination of these three, possibly some Acetobacter as well.
(Note that all of these contaminants listed are safe!)
Lactobacillus prefers a pH of 4.0 to 5.0, meaning it likes to work in brews that are more acidic than your standard 5.2 to 5.6 in beer wort, although the yeast will bring the pH of the wort down during fermentation, and Lactobacillus itself makes a brew quite acidic from its own processes. Musts for mead and wine are typically acidic to begin with, between 3.0 and 3.9 – on the lower end of this spectrum, Lactobacillus has a harder time.
It also has a preference for higher temperatures, and can work in fermentations up to 115° or 120° F!
Despite what you might read in forums and such, some strains of Lactobacillus can actually produce alcohol! There are even reports of some homebrewers making sour beer entirely from Lactobacillus – with no yeast involved in any way! This isn’t common, however. Even the Lactobacillus strains that can produce alcohol have low attenuation characteristics, and produce much more lactic acid than alcohol.
Usually, alcohol production is left to the yeast – either the strain you pitched or the wild yeast that got in alongside the bacteria.
How Do You Determine If There is Lactobacillus in Your Beer, Mead, or Wine?
The characteristic sign of Lactobacillus in a beer, mead, or wine is the clean-tasting sourness of lactic acid, similar to yogurt or sour fruit. Funkier flavors indicate other contaminants. It may also produce a pellicle, though this is not specific to Lactobacillus.
Sometimes, the first thing you see to indicate an infection occurred is a pellicle across the top. This pellicle will be white, and often look like a solid sheet, although it can also have bubble-like formations or ripples throughout (see the image provided).
Newer brewers commonly see normal signs of fermentation and confuse them for a pellicle. Things like vigorous foaming or little blobs of sludge floating on top of the brew are normal yeast activity and not an issue at all!
Additionally, if you see mold, I suggest you dump the batch. Mold can be very hazardous. It should be obvious what is mold compared to a pellicle – it’s often furry and looks the same as mold that you would find on your food!
For more information on dealing with mold (including how to determine if the formations on your brew actually are mold) check out this other article in the series!
Formation of a pellicle mean that your infection is safe – but it doesn’t specifically mean it’s Lactobacillus. In fact, pellicle formation isn’t very well studied and science doesn’t exactly know a lot about what it is or why it forms. Furthermore, while we think that Lactobacillus and Pediococcus can form pellicles, it may be more likely that they’re only a result of Brettanomyces fermentation – and usually, when contamination happens, the bacteria comes in along with wild yeast.
So it’s a lot easier to determine if you have a Lactobacillus infection by going on taste. The characteristic sign of lacto is the lactic acid – and as said a few times already, Lactobacillus works quickly and produces a much cleaner sourness than other similar contaminants.
The flavor of Lactobacillus is best described as sour, tart, or tangy – like yogurt or sour fruits. If you’re getting more of a vinegary acidic taste, it might be Acetobacter – another microbe that is safe (and often used in food and beverage products).
Most likely, though, if you did not intentionally pitch Lactobacillus in a controlled way – it is the result of contamination and infection – then you probably have a combination of any or all of the microbes listed. This means that you can have any combination of flavors from them!
You Have a Lactobacillus Infection in Your Beer, Mead or Wine: What Now?
If you are like many brewers, finding out that your beer, mead or wine is contaminated may be your worst nightmare! However, it is important to realize that there are safe infections – those that, while not intentional, will not hurt you – and unsafe infections. Lactobacillus (as well as wild yeast and some other bacteria) in your brew is very safe.
If you determine that you have a Lactobacillus infection in your beer, mead or wine, it may not be the end for your batch or your equipment. It is perfectly safe, and it may be worth tasting the brew before deciding to keep it or dump it. Some equipment may be compromised but can be used for future sour or wild brews.
When you notice that your brew is infected, your first inclination might be to dump it – and if that’s what you decide to do, then don’t feel bad about it! It’s often better to err on the safe side and avoid something that might be hazardous.
However, if you are able to determine that the infection is not a result of something hazardous (basically as long as it’s not mold or botulism) then it might just be worth keeping after all.
If all signs point to Lactobacillus being the contaminant (or at least one of them) then you might be pleasantly surprised. Brewers commonly purchase strains of Lactobacillus just as they would brewer’s yeast, and pitch them alongside their chosen yeast to create a sour flavor profile. It’s actually desired in certain kinds of beer, mead and wine – particularly sours.
However, if you have Lactobacillus in your batch and it’s definitely an infection – not intentional – then you likely have other contaminants as well. Pediococcus in particular can produce some off-flavors and a thick, ropy texture that many find off-putting, and Brettanomyces makes a brew very funky in ways often described as horse blanket or leather.
All of these combined could turn out to be wonderful – or absolutely terrible. But it’s worth tasting just to be sure!
If you find that you like it, then you may end up with a batch of beer, mead or wine that, while completely unintentional, is quite tasty.
Alternatively, if you don’t like it, there’s nothing wrong with dumping it. At least you know now that it wasn’t worth saving.
Brettanomyces can sometimes clean up these off-putting flavors and the ropy texture of Pediococcus, but it takes a very long time and isn’t consistent. If you want, you could give it time and see if it ages well – but that’s completely up to you.
Now, what about the equipment?
Anything made from stainless steel or glass can be cleaned up nicely to remove all contaminants. As long as you clean these things thoroughly and sanitize them well, you should have no issues.
However, anything made from plastic, vinyl, or something similar can harbor bugs like Lactobacillus and you may never get them out. The bacteria likes to get into any scratches or it can penetrate the material, and any future batches you use this equipment for will show the same signs of contamination.
If you tasted the batch and it wasn’t bad, you might actually want to keep this equipment. Go ahead and buy replacements for your “normal” brews, but you can use the “contaminated” equipment for some fun sour or wild experiments!
Just be sure to keep it away from the rest of your equipment – or else it’ll all get contaminated.
If you don’t like the flavor – or otherwise don’t feel comfortable with it – then it’s fine to toss it out.
Will a Lactobacillus Infection in Your Beer, Mead or Wine Kill You?
If you’ve read the article to this point, you should already know the answer to this. But let’s get to the main questions every brewer who discovers this issue is asking: is Lactobacillus hazardous? Will it make me sick? Will it killI me?
No, a Lactobacillus infection in your beer, mead or wine will not kill you or make you sick. Lactobacillus is not hazardous to your health, and in fact is used in many food and beverage products you likely already consume. If your brew is infected with Lactobacillus, you can drink it safely.
Lactobacillus is ubiquitous and normally harmless. In humans and animals, it is found in the intestinal tract and performs many beneficial functions, including immunomodulation, suppression of enteric pathogens, and maintenance of intestinal flora.
It’s what produces the probiotics everyone is looking for in things like yogurt!
This doesn’t mean that you can go around telling people that your sour brew is actually healthy – but it’s no more harmful than a “normal” alcoholic beverage.
