On June 18th, we explored fermentation – in various forms!

We started with a very brief overview of yeast and fermentation. Then we talked about closed vs. open fermentation and how the fermentation vessel can impact beer’s flavour. Finally, we ended with a discussion on fermenting with wild yeast and bacteria, including mixed and spontaneous fermentation. 

If you’d like to listen back, you’ll find the recommended reading and a recording of the session below.

Session recording:

Recommended reading:

Fermentation basics: Yeast

John Palmer’s How to Brew is a homebrew bible, but it also helps make the technical side of brewing make a lot of sense – homebrewer or not! The below links are to a few short sections from Chapter 6 on yeast to give us a bit of a primer for the rest of our chat.




Bonus reading: If you’d like to learn more about what’s actually happening during fermentation, John covers this in Chapter 8. We won’t go into this level of detail during the session though – as our focus is more on what happens when you change the fermentation vessel and/or introduce different microorganisms for fermentation.


Open vs. closed fermentation

At Anchor Brewery in San Francisco, their iconic Steam Beer (the classic example of a California Common) is produced using open fermentation. These articles compare closed fermentation to open fermentation – not only the process changes, but their flavour impact.



Bonus video: Open fermentation in action of Sierra Nevada’s Big Foot Barleywine.


Mixed fermentation: 

These two articles give a bit of a primer on what mixed fermentation is. These beers aren’t clean, traditional styles like ale or lager; they’re brewed with a mix of microorganisms (from traditional brewer’s yeast, to wild yeast and bacteria), BUT, these microorganisms are intentionally added into the brew (they don’t settle in spontaneously… as that’s what makes spontaneous fermentation unique. Which you’ll learn more about next!) 



I mentioned this final piece, from John Laffler at Off Colour Brewing in Chicago, during our Saison & Brett beer week. His main takeaway is that most mixed ferm beers are being lumped into a catch all category of ‘sour’, but some of these ‘wild’ beers aren’t actually sour… and not all ‘sour’ beers are wild.  (Yes, this can be a bit tricky to tease apart, but we’ll hopefully make it clear during Thursday’s session!)


Spontaneous fermentation: A video!

I wanted to make sure I wasn’t only giving us reading this week and I stumbled upon this lovely video on YouTube featuring brewers of spontaneously fermented beers. It’s 35 mins long, but even if you’re only able to watch the first 18 mins (part I), that’d be great, as it covers what spontaneous fermentation is in a really visual way. (Then if you’ve got time, keep watching. It’s like a love letter to lambic.)