Quantification Of Esters Produced With Kveik Under Varying Fermentation Conditions Using HS-SPME/GC-MS

Kveik is a strain of ale yeast, Saccharomyces cerevisiae, isolated from Scandinavian farmhouse breweries, that is new to the U.S. market and can ferment at high temperatures without the overproduction of volatile aromatic esters. This has the potential to greatly decrease production times, thereby increasing throughput in the brewery. Little research has been done to quantify the effects that varying fermentation conditions, such as temperature and starting gravity (density of the solution due primarily to dissolved malt sugars prior to fermentation), has on the production of esters when using Kveik for fermentation. For typical ale yeast, fermentation temperatures range from 18-20 C and anything above will produce undesirable esters. In excess, these compounds are responsible for undesirable flavors and aromas. Using head space solid phase microextraction gas chromatography with mass spectrometry (HS-SPME/GC-MS), ester production from four Kveik strains fermenting worts at 1.040, 1.060, and 1.080 original gravities at 25 C and 37 C was quantified. An increase in fermentation temperature was shown to decrease ester production for all yeast while changing the starting gravity had no predictable effect. The results from this study can be used by brewers to predict the results of altering fermentation temperature more accurately when using Kveik yeast.