Maskell, D. L., Heriot-Watt University, Edinburgh, UNITED KINGDOM
Poster
Ales and other beer styles that at one time may have been considered niche in many markets are enjoying huge growth in their popularity around the world. This is in no short measure due to the explosion of the craft brewing scene, where small brewers have had the flexibility to respond quickly to increasingly sophisticated consumer demands. Or, alternatively used these products to carve a niche in what is an increasingly competitive market. High-gravity brewing is a relatively simple technique that is well established in the production of many lager beers that is increasingly of interest to the craft brewer producing other styles of beers. The work presented here examined the impact of low (10°P), medium (15°P), and high (20°P) gravity worts on several strains of ale (Saccharomyces cerevisiae) yeast using lager yeast (S. pastorianus) as a control. Yeast viability and fermentation performance was monitored, and HS-GC-FID was used to detect changes in yeast metabolic by-product production. This work was undertaken to begin to fill the gap that surrounds the use of ale yeast in high-gravity fermentations, the clear majority of the published material being focused on lager yeast. Greater understanding of how ale yeasts perform under high-gravity conditions will allow users of these strains to consider the impact high-gravity brewing may have on their final product, while at the same time allowing an increase in production volume. The results of these preliminary studies found that, as was expected, the higher the starting gravity the greater the fermentation time. The utilization of available free amino nitrogen also increased with gravity (between 5 and 15%). Examination of flavor compounds in diluted beer found that the production of esters and higher alcohols was strain specific. Most strains demonstrated an increase in the production of ethyl acetate, isobutyl acetate, whereas the concentration of total higher alcohols generally decreased with the increase in gravity. These results mean that the response of the strains investigated to worts with higher gravities are strain specific, and if utilizing high-gravity brewing techniques, as with lager yeast, trials will be needed to ensure that the final diluted sales gravity beer matches the profile of the original product. A great deal of further work is needed in this area; some small examples being needed to determine the impact on yeast physiology for these strains, the consequences of serial repitching and to investigate the influence of colored and specialty malts and grains in the production of these beers.
Dawn Maskell is the director of the International Centre for Brewing and Distilling at Heriot-Watt University in Scotland (U.K.). Dawn has a Ph.D. degree from Oxford Brookes University, where she researched brewing yeast aging and stress tolerance under the tutelage of Prof. Katherine Smart. Prior to this Dawn gained an honors degree in brewing and distilling from Heriot-Watt University. Before joining the ICBD in 2015 she worked on the valorization of brewery and distillery co-products and is a co-founder of a spin-out company, Horizon Proteins, which utilizes protein from the co-products generated by the Scotch malt whisky industry. Dawn is a member of the American Society of Brewing Chemists and the Institute of Brewing and Distilling, with a Diploma in Brewing, and is an accredited chartered scientist. Dawn is also on the Board of Examiners for the Institute of Brewing and Distilling and the programme committee for the Worldwide Distilled Spirits Conference 2017.
View Presentation
