Thursday, February 27, 2014

Common Off-Flavors In Homebrew - Part 1: How Often Do Infections Occur?

I'm starting to think that brewers have gotten almost too good at emphasizing the importance of sanitation. It's the first thing beaten into the head of new brewers, not just because it is important, but because it's kind of easy (these days.) The hardest thing about properly sanitizing is convincing people that the foam from Star San is really actually okay, for real. We stress sanitization so successfully that, among the homebrewers I know and talk to, a genuine infection is quite rare — maybe a "once in a few years" kind of thing. Other off-flavors, meanwhile, are much more likely to arise, and yet less likely to be dealt with.

As I launch into this here mini series about the most Common Off-Flavors in Homebrew (which may end up being an ongoing thing, if I think of more in the future), I wanted to start with the beer-ruiner all new homebrewers scrub in fear of: infections.

We're taught that nebulous and uncertain wild yeast lurk everywhere, waiting to smother a beer in a gnarly pellicle and spike it with sour flavors. And this true, essentially. There are wild yeast everywhere, and they can drastically affect how a beer turns out if you aren't careful (or just have some bad luck). But I've got to wonder: are such infections really that common? Or are they more of a necessary boogeyman to warn new brewers of, to instill the importance of sanitizing carefully and treating your beer with respect?

Are there, ultimately, a number of over-looked off-flavors that are far more likely to warp a batch than some rogue wild yeast? I think yes.

An argument could be made that a real infection is easy to catch, and dump, before anyone else is going to try it. In other words, homebrewers are so careful about infections, and so paranoid of incurring one, that the average friend and homebrew-drinker is much less likely to be subjected to an infected batch. This could be part of it: an infection is perhaps the only off-flavor that might create a visible, physical sign of its presence. You can see a pellicle form, but you can't see chlorophenols.

To offer some purely anecdotal and therefore scientifically-useless evidence that infections aren't that common, I am fermenting just about everything in my house right now with lactobacillus, and I am not any more concerned about cross-contamination than at any other time. I've been fermenting beers with Brettanomyces and souring microbes almost my whole brewing career, and have encountered only two batches of homebrew that were almost definitely infected. One of them was a beer of my own, a hoppy pale ale that was destined for a party. I suspect that I didn't properly sanitize the mesh bag that I used to dry-hop, because there looked to be the start of a pellicle when I went to package it. Nonetheless, the beer still tasted perfectly fine, and was mostly consumed at the party. The only specific flaw I could pick out in it was an increased level of Acetaldehyde, probably from the early stages of wild yeast activity. No one else noticed anything else amiss with the beer.

The second batch of beer I've encountered which was probably infected was an IPA that my friend brewed. According to him, he forgot to pitch yeast to the beer after brewing and did not realize this until two days later. When he went to check in on the beer, it was fermenting on its own anyway. In the end, the beer was uneven but kind of interesting: it tasted not unlike a crudely-assembled Brett IPA. We called it "Magic Jesus Juice" due to its seemingly miraculous spontaneous conception, but I still wonder if he might have drunkenly pitched some kind of yeast and just forgotten he'd done so.

What about you — what are your experiences with infection in homebrew? Do you think infections are a common cause of bad batches, or an unpredictable, infrequent strike of bad luck?

Stay tuned for Part 2 and beyond!


  1. Great write up. I think people are far too quick to call out infection when they experience a flavor that they don't like. There are lots of off flavors that you can have in a beer and not all of them are from some sort of infection.

    As for me I've only had two confirmed infections, one was a dark Belgian pumpkin beer that I'm pretty sure was infected with lacto some how since it basically turned into a black Berliner oddly enough. The second confirmed infection was a Saison that I discovered the air lock removed and traces of gray and white cat hair on the stopper. Other then that I might have had an Brett infection in a dry hopped Hefewizen once that I had to use my Brett racking cane for but I was going to drink it quickly so I didn't care. I constantly ferment tings with Brett and will often use the same carboys and have not really experienced any negative affects. As long as you do a good job of cleaning up afterwards you'll be fine.

  2. Excellent points and advice, Have recently helped a friend with infection spread outward from an infected washed yeast starter as he pulled/ bleached all his equipt. he felt might have touched., Glad it's uncommon, as you say. Other off flavors def. more common, need more careful monitoring than we give, even large breweries a la Crooked Stave and diacetyl in some recent batches.

  3. In my experience, the plastics that are used to produce most racking canes are awful at best. They're not rated for high-heat and will breakdown quickly, causing cracks that not only introduce oxidation but also pesky critters that live in those cracks. Having been trained sanitation once from How to Brew and again in a brewery setting, high-heat water mixed with PBW is enough to clean anything. I think most infections are incurred during the transfer process. & my only infection has been traced to the racking cane. So beware! :)

  4. I've had more than a few infected batches from using washed yeast to the point that the wild yeast that inevitably find their way into our beers took hold.


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