Characterization of genotype and beer fermentation properties of Norwegian Farmhouse Ale Yeasts

Abstract

Eight different Norwegian Farmhouse Ale Yeasts from Voss, Stranda, Lærdal, Hornindal and Olden were donated to IBT for analysis. The yeast were phenotypically characterized and two beer styles were produced under laboratory conditions, a pale ale and a traditional Honndalsøl. The sensory properties were assessed on an untrained panel as a Duo-trio test and the composition of volatile compounds produced during fermentation and after bottling at different fermentation temperatures was determined using dynamic Head space GC-MS. A genetic analysis of the yeasts internally transcribed spacer 1 and 2 region was performed to assess their species and genetic relationship between the strains. The Kveik strains were compared to reference yeast. All Kveik except one was classified as the genus Saccharomyces, two were classified as S. boulardii, two were classified as S. cerevisiae, one was classified as S. bayanus / S. pastorianus, two were unclassified specie of the Saccharomyces genus. Phenotypical characterization showed a variation of maximum growth rate with over 20 \% of selected Kveik strains. Flocculation varies between fully flocculating and non-flocculating. As fermentation temperature increase, the concentration of esters and alcohols increase except longer chained esters. During the fermentation, the concentration of alcohols decrease, esters decrease over time as well except ethyl acetate, ethyl octanoate and ethyl decanoate. A sensory panel could distinguish between 3 of the 5 tested yeast strains.