Monday, 23 March 2015


After almost three years brewing clean and sour beers side by side, I recently had my first unwanted LAB infection.  Worse than that, since I top-cropped and repitched yeast between several batches in quick succession, at least three different beers were affected.  More embarrassingly still, I sent at least one to a local competition before I realized it was turning sour!

It started when I noticed an ordinary bitter I was bottling was a little tart.  At first I thought I must have added too much lactic acid in the mash, since there was only a slight sourness.  The beer was still young, and highly hopped, so I thought a lactobacillus infection was unlikely, and the time-frame was too short for pediococcus.  But as the beer conditioned, the sourness became more pronounced, and I noticed the same sharpness developing in two more beers.  There were no other obvious off-flavours beyond this tartness: no diacetyl, no phenols, no gross enterobacter-related aromas.  I guess the source might be a particularly aggressive strain of lactobacillus?  Who knows.

Interestingly, not all the beers brewed with repitches of this yeast are showing signs of infection.  I just bottled the last one---a pale ale---after giving it a few extra weeks in secondary to show signs of infection.  It still tasted perfectly fine.

I'll admit that when I first realized what was going on, I thought about giving up on brewing clean beers entirely.  At least 75% of what I brew these days undergoes mixed fermentations, and it would make life a lot easier if I could embrace them entirely.  But I love bitter beer too much, and there isn't enough of the kind I like cheaply available nearby for me to give up on making my own.  So, until I live within stumbling distance of a pub selling good cask-conditioned bitters, and can afford to buy fresh Taras Boulba and XX Bitter by the case, I'll still want to brew clean beers at home.

I have my own theories about where the infection originated (hint: if you're top-cropping, make sure you label the yeast in your fridge, even if its all the same strain and you're certain you know where each jar came from!).  But I didn't want to mess around with isolating potential sources, so I decided to replace all of my plastics: clean fermenter, tubing, bottling bucket, auto-siphon, etc.  It will take me a while to finish doing this, but I was planning on brewing tart saisons for the next month or so anyway, so I'm not in any rush.

So, there you have it.  I was pretty demoralized by this for a while---its been a month since I brewed anything, which is a long time for me---but its really not that big of a deal.  I'm confident that with some new plastics and extra vigilance I can continue to brew clean and funky beers side by side.  In fact, I'm going to brew a clean batch tomorrow, making temporary use of a new six gallon carboy before I turn it into another sour solera.

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