Collection: Mixed Fermentation Beers:

The Evolution of Our Mixed Fermentation Beers at The Kernel Brewery

In 2012, we received our first shipment of used Burgundy wine barrels at The Kernel Brewery in Bermondsey, London. These barrels marked the beginning of what would become our long-term commitment to barrel-aged mixed fermentation beers. That moment sparked a quiet but deliberate transformation in our brewing philosophy—one that embraced the unpredictable beauty of time, wild microbes, and oak.

With these barrels, we started a focused ageing programme, experimenting with how wild yeast, Brettanomyces, and bacteria such as Lactobacillus and Pediococcus could shape the flavour and texture of our beers. Each barrel created its own microclimate, becoming a living vessel for beers that would take months—or even years—to fully express themselves.

As the programme developed, we introduced two large oak vessels known as foeders—5,000-litre ex-Bordeaux wine barrels. These provided the perfect home for longer ageing projects and enabled us to scale up production while maintaining the nuanced character that defines mixed fermentation brewing. The porous oak encourages gentle oxygenation, allowing the beer to develop complex flavours ranging from soft acidity and earthiness to fruit-forward funk.

Over time, this project evolved into a dedicated and diverse range of mixed fermentation beers. Today, we offer a broad spectrum of styles that reflect both tradition and experimentation. These include our iconic Bière de Saisons, foeder-aged beers, bretted pale ales, and Grisettes—each crafted with care and fermented slowly using our house cultures.

Our Core Mixed Fermentation Styles

• Bière de Saison: These beers are dry, delicate, and lightly tart, often with subtle funk and floral complexity. They’re conditioned in oak barrels and made using our house yeast blend, which includes wild strains that evolve over time. Each release is slightly different, a living snapshot of the barrels and microbes at work. We only use fruit that is in season and sourced within the UK, working with independent farmers.

• Foeder-Aged Beers: Fermented and aged in our large oak foeders, these beers develop slowly and take on layered characteristics that can’t be replicated in stainless steel. These are often more rounded in mouthfeel and exhibit depth from long-term contact with wild yeast and wood.

• Bretted Beers: Brewed with Brettanomyces, a wild yeast that contributes tropical fruit, leather, and earthy notes, these beers are both complex and drinkable. Brett beers continue to evolve in the bottle, making them ideal for ageing.

• Grisette: A low-ABV Belgian-style beer traditionally brewed for miners, our version is light, crisp, and often subtly tart. It’s a great entry point into the world of mixed fermentation.

Each of these beers is brewed with intent, aged patiently, and released when we feel they’ve reached peak expression. We don’t rush the process—our approach is to let the beer decide when it's ready.

Enjoy Exclusive Discounts on Larger Orders

We want to make it easy for you to explore this unique side of our brewing. That’s why we offer a 10% discount on all orders of 12 bottles or more. This is a perfect way to sample a variety of our barrel-aged, foeder-fermented, and wild yeast beers at once, whether you're stocking up your cellar or sharing with friends.

We pack and ship with care, and all our beers are 100% vegan-friendly, as part of our commitment to ethical and sustainable brewing.

Need Help? We’re Here for You

If you have any questions about our mixed fermentation range, your order, or delivery, we’re always happy to help.

Please email us at shop@thekernelbrewery.com, or contact us via our Instagram page The Kernel Brewery Instagram and a member of our team will get back to you as soon as possible.