Controlling Esters in Wit and Weizen Yeasts

Brewers making Witbiers and Weizens often ask how to fine-tune yeast expression to either bring out more banana or more citrus character. These beer styles are also defined by a spicy clove note, which should be balanced with the fruity esters for an authentic profile. Understanding and adjusting fermentation conditions can help you guide the flavour profile you want from your Wit or Weizen yeast.

Accentuating Citrus

The citrus expression from Weizen and Wit yeasts is primarily driven by biotransformation, specifically the conversion of geraniol into beta-citronellol during fermentation. To maximize citrus character, start by using geraniol-rich hops such as Citra or Centennial. Suppressing banana esters is also important when targeting a cleaner citrus profile.

Recommended process for enhancing citrus:

Ferulic acid rest: Hold the mash at 43–45°C for 10–20 minutes to boost 4-vinyl guaiacol (4-VG) production, setting the stage for clove and citrus character.
Main mash: Rest at 63–65°C to favour beta-amylase activity. This produces a maltose-rich, lower-glucose wort. Beta-amylase works more slowly, so a longer mash of at least 60–75 minutes is recommended.
Fermentation temperature: Pitch and ferment at 17–18°C. Cooler fermentation limits the formation of isoamyl acetate (banana ester) and supports a more restrained fruity profile.
Nutrient addition: Use Yeast Lightning nutrient to maintain yeast health. A complete nutrient profile can help suppress excessive acetate ester production and keep fermentation clean.
Yeast selection: Choose a yeast with naturally low banana production. Escarpment Labs Fruity Wit is a good option here, offering a more orange and citrus-forward profile without prominent banana.

Accentuating Banana

If your goal is to create a more banana-forward beer, you will want to promote acetate ester production, specifically isoamyl acetate.

Recommended process for enhancing banana:

Wort composition: Create a wort richer in glucose. This can be achieved by mashing at a warmer temperature (67–69°C) to favour alpha-amylase activity, which releases more glucose alongside dextrins. Alternatively, you can add small amounts of simple sugar (such as dextrose) to the kettle or fermenter to boost available glucose.
Yeast selection: Choose a yeast strain known for strong acetate ester production. Escarpment Labs Weizen I is a classic option for prominent banana character.

Accentuating Clove

To boost the spicy clove character in your Wit or Weizen:

Ferulic acid rest: Incorporate a mash rest at 43–45°C for 10–20 minutes. This step promotes the release of ferulic acid from malt, which yeast will convert into 4-VG, the primary molecule responsible for clove aroma and flavour.

General Tips for Boosting Esters

If you are looking to boost ester levels in your Wit or Weizen beers, here are a few proven techniques:

Increase fermentation temperature: Warmer fermentation (within the safe range for the strain) generally encourages more ester formation.
Pitch slightly less yeast: Underpitching (by about 10–20%) can push yeast metabolism toward higher ester production.
Minimize oxygen after pitching: Limiting oxygenation after pitching stresses yeast slightly, encouraging more esters (note: proper oxygenation at pitch is still critical).
Use a wort with higher glucose content: More simple sugars generally support higher ester production.
Select ester-prone yeast strains: Some strains are naturally higher ester producers than others.
Manage pH carefully: A starting wort pH around 5.2–5.4 supports healthy yeast activity and consistent ester profiles.
Use moderate to low nutrient additions: In some cases, a slight limitation of FAN (free amino nitrogen) can boost ester production, but this must be carefully balanced to avoid stuck fermentations.

Summary

Small adjustments to your mash schedule, fermentation temperature, yeast nutrient management, and strain choice can have a big impact on the final flavour balance between citrus, banana, and clove in your Wit or Weizen beers. Target the right conditions for the profile you want and consider bench-scale or pilot-scale experiments to find the best combination for your brewery.

For more detailed tips on yeast-driven flavour development, check out our Yeast Flavour Biotransformation Guide.