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Master Brewers Program

Session: Posters: Yeast & Microbiology I

P-39 - Evaluation of Potential for Kettle Souring and the Formation of ‘mousey’ off Flavor

Wednesday, August 13, 2025
4:30pm - 5:15pm PDT
Location: Sinatra Ballroom Foyer
Abstract: Brewers strive for every batch of beer to be within analytical and sensory parameters. Most brewers have experienced beers developing off flavors even when the analytical and sensory data is within expectations during processing. Tetrathydropyridine (THP) or what is sometimes described as the ’mousey’ off-flavor or for some people, a Cheerio’s flavor, can unpredictably develop in sour beer fermentations and possibly in kettle sour beers. This study explored laboratory-scale kettle sour beer production using two different bacteria inoculations preboiling, followed by fermentation with an ale yeast. These treatments were compared to a standard brew with no bacterial inoculation preboil with the ale yeast fermentation. The wort was a mix of barley (90%) and wheat (10%) malts, mashed at 65oC for 60 minutes producing a 12oPlato wort. A 20 IBU was targeted with Cascade hops. Post-fermentation beer was stored at 20oC. There was no THP detected using sensory within a two month period post fermentation. The next phase of this research with explore dosing with specific amino acids (lysine and proline) known to be precursors for THP development. In addition, specific minerals such as Mg2+ is also implicated in THP development will be assessed in a factorial experiment.