FERMOALE Weiss is the latest active dried yeast in the AEB Brewing portfolio, ideal for producing the well-balanced ester and phenol profile of German wheat beer styles. Originating from Freising, Bavaria, this Saccharomyces cerevisiae strain produces the characteristic balance of esters and phenols found in styles like Hefeweizen/Weisse, Kristal Weizen, Dunkel Weizen, and Weizenbock. Below we explore the best practices and fermentation properties of FERMOALE Weiss to help brewers achieve the desired flavour profile and consistency.
Effect of Temperature on Fermentation character
The balance between banana esters and clove/phenolic notes depends on fermentation conditions:
More Banana Esters: Higher fermentation temperature (22-24°C), lower pitching rate, reduced wort aeration, and higher original gravity.
More Clove & Spice Phenolics: Lower fermentation temperature (16-18°C), higher pitching rate, increased wort aeration, and moderate original gravity.
Temperature gradient
Why Does Temperature Affect Aroma Compounds Production?
Yeast metabolic rate is highly dependent on temperature. At higher temperatures (22-24°C), yeast metabolism accelerates, leading to increased production of fuel alcohols and acetate, key precursors to ester formation. The enzyme alcohol acetyltransferase (AATase) becomes more active, facilitating the conversion of acetyl-CoA into esters like isoamyl acetate, which contributes to banana and pear-like aromas.
Conversely, at lower temperatures (16-18°C), yeast metabolism slows down, leading to reduced ester production and favouring phenolic development. Phenolic acid decarboxylase (PAD) remains active, efficiently converting ferulic acid (present in wheat malt) into 4-vinyl guaiacol (4VG), which gives wheat beers their characteristic clove-like aroma. The lower metabolic rate at cooler temperatures further suppresses ester formation, allowing the phenolic notes to dominate, resulting in a more pronounced spice character in the final beer.
Temperature Effect on Cell Membrane Fluidity & Nutrient Uptake
Yeast cell membranes become more fluid at higher fermentation temperatures, which allows for faster transport of nutrients and metabolites. This increased fluidity enhances ester production, contributing to the fruity aroma profile of the beer. However, when fermentation temperatures rise too high—typically above the yeast strain’s optimal range—it can result in an overproduction of fuel alcohols. These higher alcohols are by-products of intensified yeast metabolism under stress conditions and can impart solvent-like or harsh flavours to the final beer.
Pitching rates: what does lower and higher do?
Lower Pitching Rate
Lower pitch rates mean fewer yeast cells are available to carry out fermentation, which increases the workload on each individual cell. This causes a higher metabolic demand, leading to increased production of secondary metabolites like esters (banana and fruity notes) as a by-product of the yeast’s heightened activity. However, going below 50 g/hL can lead to sluggish fermentation, inconsistent attenuation, and the potential production of unwanted by-products due to yeast overexertion.
To avoid these issues, brewers should adhere closely to the minimum recommended rate of 50 g/hL. This ensures an adequate yeast population to carry out efficient fermentation while still promoting ester formation. It is essential to calculate pitching rates accurately based on wort gravity and volume, monitor yeast viability and vitality prior to pitching, and maintain proper wort oxygenation (typically targeting 8-10 ppm dissolved oxygen for ales like wheat beers). Additionally, the use of yeast nutrients when necessary will help support healthy fermentation performance and prevent excessive yeast stress. Click here to look at our whole range of nutrients
Higher Pitching Rate
A higher pitching rate (up to 80 g/hL) promotes clean, steady fermentation with lower ester levels and a more pronounced phenolic (clove/spice) character. High pitching rates are especially useful in high gravity or adjunct-heavy worts where yeast vitality is critical.
Wort Oxygenation Levels & Effects
Lower oxygenation levels, typically in the range of 4 to 6 ppm dissolved oxygen (DO), encourage the production of higher concentrations of fruity banana esters, particularly isoamyl acetate. Brewers aiming for a beer with prominent banana notes and a rich ester character should also pair this lower aeration with higher fermentation temperatures (closer to 24°C), lower pitching rates, and a higher original gravity wort. However, caution is necessary when applying low oxygenation, as insufficient oxygen can stress the yeast, potentially leading to sluggish fermentation, increased diacetyl or acetaldehyde production, and reduced yeast viability for re-pitching. Additionally, the higher fermentation temperatures used alongside low aeration must be carefully controlled to avoid generating excessive fuel alcohols or overpowering esters.
Conversely, higher levels of wort aeration, around 8 to 10 ppm DO promote a cleaner fermentation with enhanced expression of phenolic compounds such as clove, pepper, and nutmeg. This approach, combined with lower fermentation temperatures (closer to 16°C) and higher pitching rates, results in a well-balanced beer where the phenolic notes take center stage. Nevertheless, high oxygenation also comes with considerations. Excessive oxygen can suppress ester production, risking a beer that lacks the desired fruity complexity. Over-oxygenation before yeast pitching may lead to oxidation of wort components, potentially impacting long-term flavour stability.
By carefully managing oxygenation levels within these ranges, brewers can fine-tune the flavour balance of their wheat beers while minimizing risks associated with yeast health, fermentation performance, and beer stability.
Malt Selection for German Wheat Beer Styles
Mashing Schedule: Ferulic Acid Rest
Having a Ferulic Acid Rest at 44-46°C can greatly enhance mash performance and flavour development. This can promote the release of ferulic acid, which yeast later converts to 4-vinyl guaiacol, contributing to clove-like phenolic notes.
Water Profile
Chloride to Sulphate Ratio: A chloride-heavy water profile enhances the soft, full-bodied mouthfeel of wheat beers. Avoid excessive sulphates, which can make the beer too dry.
Avoid Chlorine & Chloramine: These compounds can react with phenols to produce chlorophenols, leading to unwanted medicinal off-flavours.
pH Control: Aim for a mash pH of 5.2-5.4 to optimize enzymatic activity and enhance malt smoothness.
pH Drift in Wheat Beer Fermentation
Wheat beers can experience a significant pH drop during fermentation due to their high protein and phosphate content. Wheat malt has a lower buffering capacity compared to barley malt, allowing the yeast to acidify the wort more effectively. As fermentation progresses, yeast produces organic acids such as lactic, succinic, and acetic acids, which naturally lower the pH.
Typically, wheat beers start with a wort pH of 5.2-5.4 and finish around 4.1-4.4. Hefeweizens tend to have a final pH of 4.2-4.4, while Dunkel Weizen and Weizenbock may finish slightly higher at 4.3-4.5 due to their maltier profiles. Monitoring pH throughout fermentation is essential to prevent excessive acidity, which can result in an overly tart or sharp flavour profile.
Avoiding Off-Flavours
Excessive Clove (Phenolics): If overpowering, try slightly increasing wort aeration or fermenting at as lightly higher temperature.
Lack of Banana (Esters): If missing, increase fermentation temperature and lower wort aeration
Sulphur (H2S) issues
FERMOALE Weiss has low sulphur production, but excess stress on yeast or poor fermentation conditions can cause unwanted sulphur-like aromas.
How to Avoid Oxidation
Wheat beer styles are especially prone to oxidation, which can cause reduced phenolic content and muted esters during prolonged storage. Consider the use of Antioxin to control and protect against oxidation.
Click here to read our full evaluation of Antioxin SBT in lowering aging compounds, helping to prevent stale or aged flavours and extending beer shelf life by improving oxidative stability and lowering specific oxidative compounds.
References
Bamforth, C. W. (2009). Beer: Tap into the art and science of brewing (3rd ed.). Oxford University Press.
Briggs, D. E., Boulton, C. A., Brookes, P. A., & Stevens, R. (2004). Brewing: Science and practice. Woodhead Publishing.
Casey, G. P., & Ingledew, W. M. (1986). Ethanol tolerance in yeasts. Critical Reviews in Microbiology, 13(3), 219–280. https://doi.org/10.3109/10408418609108744
Gibson, B. R., Lawrence, S. J., Leclaire, J. P. R., Powell, C. D., & Smart, K. A. (2007). Yeast responses to stresses associated with industrial brewery handling. FEMS Microbiology Reviews, 31(5), 535–569. https://doi.org/10.1111/j.1574-6976.2007.00076.x
Lodolo, E. J., Kock, J. L. F., Axcell, B. C., & Brooks, M. (2008). The yeast Saccharomyces cerevisiae – The main character in beer brewing. FEMS Yeast Research, 8(7), 1018–1036. https://doi.org/10.1111/j.1567-1364.2008.00433.x
Meilgaard, M. C. (1975). Flavor chemistry of beer: Part II. Flavor and threshold of 239 aroma volatiles. Journal of the American Society of Brewing Chemists, 33(4), 167–182. https://doi.org/10.1094/ASBCJ-33-0167
Narziss, L. (2005). Sulfur dioxide in beer production. Journal of the Institute of Brewing, 111(3), 169–177. https://doi.org/10.1002/j.2050-0416.2005.tb00701.x
Siebert, K. J. (1999). Effects of protein–polyphenol interactions on beverage haze, stabilization, and analysis. Journal of Agricultural and Food Chemistry, 47(2), 353–362. https://doi.org/10.1021/jf980703o
Stewart, G. G. (2017). Brewing and distilling yeasts. Yeast, 34(6), 227–237. https://doi.org/10.1002/yea.3236
Verstrepen, K. J., & Derdelinckx, G. (2003). Flavor formation by Saccharomyces cerevisiae: The role of carbon–sulfur lyases in the generation of volatile sulfur compounds. Applied Microbiology and Biotechnology, 63(2), 136–144. https://doi.org/10.1007/s00253-003-1420-1
© 2025 neumaker. All rights reserved. This article may be shared/forwarded for personal or educational purposes, provided it remains unaltered and includes proper attribution. Reproduction, distribution, or use in any other form—including but not limited to commercial purposes, republishing, or adaptation—without explicit written permission is strictly prohibited.
Ana Victoria Vasquez de la Peña
ana@neumaker.com.au
21 March 2025