What is ‘mixed ferm’ beer?

I’m rather annoyed with myself. In a recent newsletter I lazily referred to saisons as being ‘mixed ferm’.

That was wrong. They are not. Or, at least, they don’t have to be. It’s not a characteristic of the style. I guess some saisons might also be mixed ferm, but you can be a perfectly good saison without it. You can even be the best: Saison Dupont.

But what is ‘mixed ferm’ anyway? Well, that shouldn’t take take too long to clear up, so here’s a quick explainer.

The ‘ferm’ part is just short for fermentation. The ‘mixed’ part means that a beer was fermented with a mixture of yeasts and microbes, as opposed to just a single strain. (Which is how the vast majority of beers are made.) This can also be called mixed-culture fermentation, which again just means ‘made with lotsa bugs’.

The microbes in question are mainly Saccharomyces (brewer’s yeast), Brettanomyces (wild yeast), Lactobacillus (lactic acid bacteria), and Pediococcus (lactic acid bacteria). There are a few other unconventional microbes that sometimes get called on in brewing.

And that’s about the long and the short of it. But if you feel like you want to read more, here’s a list to get you going.

• What Exactly Is Mixed-Culture Fermentation? by Diana Hubbell in October.
• milkthefunk.com wiki on mixed fermentation
• Blog post on mixed fermentation by Yonder (and really, these guys should know!)
• Brewers’ Perspectives: Mad for Mixed Fermentation by Emily Hutto on Craft Beer and Brewing

One final note, saison yeast is a particular strain of Saccharomyces. You can read more in this excellent post, A Guide to Saisons and Saison Yeasts, on the Maltose Falcons website.