Arcane Lager Brewing: Yeasting the Mash
Pitching Yeast Into the Mash: An Old Idea Revived
It started as a late-night question asked to me at a brewing conference: “Have you ever heard about pitching yeast into the mash?” The idea seemed too strange to be practical, but historical brewing texts, like Kunze’s Technology Brewing and Malting and the VLB textbook The Yeast in the Brewery, suggest it has a real foundation.
Curiosity turned into action when I posted the concept on Instagram. Brewers began experimenting, and to everyone’s surprise, some achieved real results.
What Is Yeast Addition During Mashing?
Adding yeast to the mash involves introducing spent yeast directly into the mash during later stages. It’s not about fermenting the mash but about leveraging yeast as a nutrient source.
Key Parameters for Success
- Dosage: Maximum of 1 kg thick yeast slurry per hectoliter of cast wort.
- Temperature: Mash must stay above 60°C (140°F) to inactivate the yeast.
- Timing: Addition typically happens in the final mashing stages.
Why Add Yeast to the Mash?
Brewers usually discard spent yeast, but adding it to the mash introduces potential benefits:
1. FAN Enhancement
Free Amino Nitrogen (FAN) is critical for yeast health during fermentation. At Escarpment Labs, we measured worts treated with 0.5kg/hL equivalent yeast addition, and found it added ~10 ppm of FAN. This boost can be valuable for adjunct or high gravity brewing or when working with undermodified malts.
2. Improved Nutrient Profile
Yeast autolysis during mashing may release:
- Amino acids from protein breakdown.
- Zinc and other micronutrients are essential for yeast metabolism.
- Cell wall components that could improve fermentation performance.
- Other cell constituents like nucleotides and B-vitamins.
Brewer Feedback
Some early adopters shared their experiences:
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Azlan Graves, Main Street Brewing:
“We use around 10 kg of yeast for a 325 kg mash with a liquor-to-grist ratio of 2.4:1. It’s still part of our process.”
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Kyle Nesbitt:
“We struggled with fermentation lag in our Bru Lite rice lager, using Krispy Kveik. Adding yeast culture to the mash and increasing our Yeast Lightning pitch to 7 g/BBL helped us get consistent batches kegged within seven days.”
These practical results suggest that yeasting the mash might solve specific fermentation challenges.
Considerations for Implementation
While promising, this method requires careful management to avoid process disruptions:
1. Lautering Challenges
Adding too much yeast can lead to stuck mashes or slow runoff. Keeping dosages within the recommended range is critical to avoid issues with filtration.
2. Temperature Management
Mash temperatures must remain above 60°C (140°F) to:
- Prevent premature fermentation.
- Promote controlled autolysis for nutrient release.
Who Should Try Yeasting in the Mash?
Adding yeast to the mash might be especially useful for:
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High-gravity brewing:
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- Enhanced nutrients support strong fermentations in challenging conditions
- Enhanced nutrients support strong fermentations in challenging conditions
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Brewers using undermodified malts:
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- Yeast addition compensates for lower FAN levels
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Resource-efficient operations
- Turn spent yeast into a functional ingredient instead of waste.
- Turn spent yeast into a functional ingredient instead of waste.
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Brewers optimizing yeast nutrition
- Naturally improve fermentation outcomes
Questions for Future Exploration
Further research is needed to fully understand its potential. Key areas for study include:
- The best timing for yeast addition during mashing.
- Effects on different malt varieties and beer styles.
- Long-term impacts on finished beer flavour and stability.
- Selection of specific yeast strains for optimal results.
Rethinking Brewing Waste
Pitching yeast into the mash blurs the line between waste management and process innovation. By recycling spent yeast into the mash, brewers can enhance wort nutrition, improve fermentation, and potentially unlock new efficiencies.
This technique isn’t for every brewery, but it’s a compelling example of how rethinking conventional practices can lead to creative solutions in brewing. And serves as a reminder that the Germans solved a lot of brewing problems eons ago!
