Hey, everyone. This one matters.
I've seen breweries pitch the same culture 15+ generations without tracking it—then wonder why fermentation is inconsistent. Yeast drifts with every generation. Here's how to track it and when to repitch.
Yeast cultures drift with each generation. Strain characteristics, viability, and fermentation performance change over time. Breweries that repitch without tracking generation count risk inconsistent beer and, in extreme cases, contamination or off-flavor development. Generation tracking supports both quality and cost control. Strain characteristics, viability, and fermentation performance change over time. Breweries that repitch yeast without tracking generation count risk inconsistent beer and, in extreme cases, contamination or off-flavor development. Generation tracking is a discipline that supports both quality and cost control.
Why Generation Matters
Each time yeast is harvested and repitched, it undergoes another cycle of growth, fermentation, and stress. With each generation:
- Viability may decline. Older cultures may have lower cell counts and slower starts.
- Phenotype may drift. Flocculation, ester production, and attenuation can shift.
- Contamination risk increases. The longer a culture is in use, the more opportunities for wild yeast or bacteria to enter.
Most breweries establish a maximum generation count for each strain—often 5 to 10 generations for ales, fewer for lagers. Beyond that, they repitch from a fresh culture or a banked vial. Without generation tracking, you do not know when you have reached that limit.
What Generation Tracking Requires
For each batch, you need to know:
- Strain: Which yeast strain was used.
- Source: Where the yeast came from—a fresh pitch, a propagation, or a repitch from a previous batch.
- Generation: The generation count at pitch. If the yeast came from Batch 501, and Batch 501 was pitched with Generation 3 yeast, then Batch 502 is Generation 4.
The tracking can be simple: a spreadsheet or a field in your batch log. The critical part is consistency. Every batch that receives yeast must record the source and the generation. If that is not done at pitch, the information is lost.
Propagation Events
When you propagate yeast—from a vial to a starter, or from a starter to a propagator—that is a propagation event. The generation count may or may not increase, depending on how you define it. Some breweries count only fermentation generations; others count propagation steps. The important thing is to have a clear definition and apply it consistently.
Planning Repitches
Generation tracking supports production planning. If your IPA strain is at Generation 8 and your maximum is 10, you have two batches left before you need a fresh culture. That affects scheduling: you may need to order a vial, plan a propagation, or prioritize certain batches to use the current culture before it ages out.
Cost Implications
Yeast is a significant cost. Liquid cultures and specialty strains cost more than dry yeast. Propagation requires time, labor, and materials. Repitching extends the life of that investment. Generation tracking helps you maximize repitches without exceeding quality limits—squeezing more batches per culture while maintaining consistency.
Integration with Batch Records
Generation data belongs in the batch record. When you log a knockout, you should record the yeast strain and generation. That creates an auditable history: Batch 502 used Generation 4 yeast from Batch 501; Batch 501 used Generation 3 yeast from Batch 498; and so on. If a quality issue arises, you can trace it back through the yeast lineage.
Yeast propagation and generation tracking are operational details that compound over time. The breweries that treat yeast as the biological asset it is—with clear tracking and defined limits—will have an edge in consistency and cost.
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How BrewLedger Supports Batch and Yeast Tracking
BrewLedger tracks batches from knockout through packaging. Batch records can include yeast strain and generation, linking each batch to its yeast source. If you are building or improving your yeast tracking process, BrewLedger provides the structured batch foundation. See how it works when you are ready.