6 Tips on How to Brew Sour Beers from the Mad Fermentationist

Sour beer has risen to “holy grail” status for many craft beer drinkers, and not surprisingly more and more homebrewers are exploring how to brew high-quality funky beers at home.

We asked Michael Tonsmeire, author of American Sour Beers, for a few pointers on brewing beer with a wild side! Tonsmeire, who runs the popular blog The Mad Fermentationist, also gave a seminar on The Influence of Mashing on Sour Beers during during the 2014 National Homebrewers Conference, and the audio/visual presentations are available for download.

Here’s what Tonsmeire had to share:

1. Pitch plenty of brewer’s yeast.

Unless you are attempting a 100% Brettanomyces or spontaneous fermentation, pitch as much brewer’s yeast as you would for the same wort/strain if you were brewing a clean beer. This will ensure a healthy primary fermentation, improve consistency, and reduce the chance of off-flavors.

2. Use a variety of microbes.

A packaged yeast/bacteria blend provides a solid base of lactic acid bacteria (i.e., Lactobacillus and Pediococcus) and Brettanomyces, but most benefit from added biodiversity. The easiest option is dregs from two or three bottles of your favorite unpasteurized sour beers (the fresher and lower alcohol the better).

3. Minimize oxygen contact during aging.

When oxygen from the atmosphere is allowed to contact the wort it is used by Brettanomyces and Acetobacter to convert alcohol into acetic acid (the primary acid in vinegar) and ethyl acetate (smells like nail polish remover). Keep the airlock filled, select a tight-fitting bung, avoid buckets, and don’t pull samples more than once a month.

4. Brew more than one batch.

Sour beers can take months or even years of fermentation before they are ready to drink. Starting a new batch every few months creates a pipeline, allowing you to look forward to mature beers while you work on young batches. Having multiple batches aging simultaneously also opens up blending, where the artistry and creativity of sour beer brewers truly shine.

5. Don’t bottle until the gravity is stable.

Wait until gravity samples are identical month-over-month. The fermentation of only .003 is enough for full carbonation without the addition of priming sugar, so even bottling at a relatively low gravity there is a risk that explosive over-carbonation will eventually develop. With a stable gravity, you can prime using a standard priming sugar calculator. A couple grams of wine yeast rehydrated can speed up carbonation, but usually isn’t required.

6. Hand down your old gear.

Sour beers are intentionally fermented with the most common beer spoilage microbes. While fastidious homebrewers can successfully share post-boil gear between clean and sour beers, a safer option is to maintain two separate sets of gear (e.g., fermentors, racking cane, bottling bucket, bottling wand, tubing). Rather than buying a new set for the sour beers, hand down your clean gear after it becomes too worn or scratched to use otherwise.

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