Biotransformation might sound like a buzzword from a sci-fi novel, but in the world of homebrewing, it’s a powerful tool for crafting flavour-packed IPAs. In a recent webinar hosted by Lallemand Brewing, technical experts Eric Abbott and Scott Sharp-Heward broke down the science and shared practical tips that every brewer - from hobbyist to pro - can use to elevate their hop game.
What Is Biotransformation?
At its core, biotransformation is the chemical modification of hop compounds by yeast during fermentation. This process can unlock new flavours, intensify aromas, and even smooth out bitterness. Think of it as a flavour amplifier that works behind the scenes.
Why It Matters for IPAs
Modern IPAs, especially hazy, juicy, and New England styles, rely heavily on hop-derived aromas like tropical fruit, citrus, and stone fruit. Biotransformation helps convert hop precursors into these desirable compounds, making your beer more expressive and complex.
Key Compounds to Know
- Terpene Alcohols (e.g., linalool, geraniol): Floral, citrusy, and fruity.
- Thiols (e.g., 3SH, 4MMP): Tropical, passionfruit, grapefruit - potent even in tiny amounts.
- Esters Add stone fruit and pear-like notes.
Practical Tips for Homebrewers
1. Hop Selection Matters
Choose hop varieties high in bound precursors (e.g., Nelson Sauvin, Simcoe) for early additions and those high in free aroma compounds (e.g., Citra, Mosaic) for dry hopping.
2. Timing Is Everything
Add hops during the whirlpool or early fermentation (within the first 24–36 hours) to maximise yeast interaction and biotransformation.
3. Yeast Strain Selection
Some strains are better at freeing bound compounds. Lallemand’s New England, Nottingham, and Voss strains showed strong biotransformation potential.
4. Use Enzymes Wisely
Products like Aromazyme can help release terpene alcohols, especially when used with bound-rich hops.
5. Cold Maturation
Let your beer rest at 4°C for 3–5 days post-fermentation to allow yeast to release more thiols.
6. Gentle Handling
Thiols are volatile—avoid rough transfers and consider closed-loop transfers to retain those precious aromas, and avoid oxygen pickup which can quickly cause a beer to go stale and strip it of it's desirable aromas.
7. Low Alcohol? No Problem
Even session IPAs can benefit from biotransformation. Just be mindful of hop rates and yeast health.
8. Hop Burn Solutions
If high dry hop rates lead to harshness, consider using yeast-derived products like Lallemand’s ISY Enhance to round out the mouthfeel.
Our Experience with Biotransformation
We've always relied on large whirlpool hop additions to provide the foundation for biotransformation to occur in our hop forward beers. We typically save all of our dry hop additions until after final gravity has been reached then wait at least a few days in order to give the yeast a chance to cleanup any diacetyl and any other other undesirable compounds that may still be there from fermentation.
We also typically employ a soft crash to reduce the temperature of the beer before adding our dry hops in order to minimise the risk of hop burn and hop creep from occurring.
We recently tried splitting up our dry hop addition and added the first part a few days into fermentation, and the rest after final gravity and cleanup has completed as outlined above. The results were very good with loads of dry hop aroma and flavour so this is something we're going to look at implementing more in future batches.
The other benefit of dry hopping during active fermentation is the yeast activity can actually help rouse the hops and move them around the fermenter which helps improve utilisation and hop oil extraction - a double whammy when combined with the benefits of biotransformation as well.
Dry hopping after a soft crash sees the hops generally sink to the bottom of the fermenter which could lead to reduced extraction unless they are roused within the fermenter somehow.
Final Thoughts
Biotransformation isn’t just for commercial breweries. With the right ingredients, timing, and process tweaks, homebrewers can harness this natural phenomenon to craft IPAs that burst with character. Whether you’re chasing juicy tropical notes or refining your hop expression, biotransformation is a tool worth mastering.
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