Sponsored
Eduardo Liza-Diaz, MSc
Fermentis
Marcq-en-Baroeul, FRANCE
Jeffrey Walsh, Jr.
QA Lab
Sapporo-Stone Brewing
Escondido, California, United States
PART 1 "Hazy IPAs Demystified: Yeast's Role in Aroma and Stability & Evaluating an Experimental Yeast-Derived Nutrient for Performance in High Gravity Brewing"
Abstract: The Hazy IPA beer style has infamous popularity among brewers since its origination for more than a decade worldwide. Hop-forward aromas and pronounced haziness are defining characteristics of this beer style. The aromatic complexity of this beer style is influenced by yeast-driven biotransformation including polyfunctional thiol release (e.g., 3SH, 4S4M2Pone) and continued biotransformation (3SHA) from non-volatile hop precursors (cysteinylated and glutathionylated forms). A critical visual aspect of this beer style is a dramatic and persistent haze that must remain stable to over time. In the typical Hazy IPA beer matrix, haze is primarily attributed to interactions between specific proteins, carbohydrates, and polyphenols derived from various ingredients, such as oats and hops. Additionally, yeast plays a critical role in haze formation, yet a gap in knowledge remains.
This study investigated the impact of yeast on thiol release and haze stability through two consecutive phases, an initial lab-scale screening (30L brew/2L fermentations) and pilot scale applications (20hL/1hL fermentations). Preliminary evaluations were conducted on several yeast strains and blends for their ability to release polyfunctional thiols, maintain haze stability, and contribute to detailed sensory attributes. Lab-scale evidence demonstrated two strains, SafAle™ K-97 and SafAle™ S-04, with dominant performance in both thiol release and haze stability. Further building upon these results, the scope of yeast strains was expanded to include additional commercially available Hazy IPA yeast products in the pilot scale. This phase largely focused on brewing practicality by utilizing nephelometric monitoring of haze evolution in beers stored at 4°C and 20°C over a six-month period.
These findings highlight effective yeast strains for optimizing haze stability and thiol bioavailability in Hazy IPAs. The consistency between lab-scale and pilot-scale results reinforces their reliability for commercial brewing applications, providing brewers with valuable tools to enhance both sensory attributes and long-term haze stability. Moreover, this study contributes to closing the knowledge gap in brewing yeast science by advancing the understanding of yeast-driven biotransformation and its role in haze formation, offering insights for both researchers and brewers seeking to refine haze-positive beer production.
PART 2: "Yeast Propagation and Fermentation Nutrient: Case Study into Biomass, Fermentation Profiling, and VDK"
Abstract: As high-gravity (HG) and very high-gravity (VHG) brewing techniques become increasingly prevalent in modern brewing operations, challenges such as slower fermentation kinetics, incomplete attenuation, and increased off-flavor production have emerged. These effects are largely attributed to stress placed on yeast under HG/VHG conditions, including osmotic stress, ethanol toxicity, and nutrient limitations.
To explore strategies for overcoming these limitations, a pilot-scale fermentation trial was conducted using an experimental yeast-derived (YD) nutrient supplement, designated EXP024, provided by Fermentis. The trial was executed on the Stone Brewing pilot system with two conditions: a control fermentation (no nutrient) and a treatment fermentation (+EXP024).
Preliminary results demonstrated that the EXP024-treated batch exhibited enhanced yeast biomass generation and faster fermentation kinetics compared to the control. Notably, the +EXP024 condition showed accelerated diacetyl (VDK) drop , with earlier reduction below sensory threshold. These improvements suggest the supplement may help reduce tank residency times and improve overall fermentation efficiency.
This work highlights the potential utility of targeted yeast derivative supplementation as a tool to optimize performance in high gravity brewing environments and supports further investigation into its broader application.
Speaker: Eduardo Liza-Diaz, MSc – Fermentis