Dry-Hop Creep Potential of Various Saccharomyces Yeast Species and Strains

Abstract

Previous research has shown that hops contain enzymes able to hydrolyze unfermentable dextrins into fermentable sugars when added during the dry-hopping process. In the presence of live yeast, these additional fermentable sugars can lead to an over-attenuation of the beer; a phenomenon known as “hop creep”. This study attempts to analyze the effect of different Saccharomyces yeast species and strains on hop creep, with the intent to find an ability to mitigate the effects of dry-hop creep by using a specific yeast. Thirty different yeast species and strains were chosen from commercial and academic collections and propagated for pilot fermentations. Brews were performed at the Anheuser-Busch Research Brewery (1.8 hL, 10 °P, 20 IBU) at UC Davis and split to 40 L cylindroconical fermenters, with one fermenter in each yeast pair receiving 10 g/L Centennial hop pellets towards the end of fermentation. Standard analytical measurements were performed over the course of fermentation, with real degrees of fermentation (RDF) and extract measured on an Anton Paar alcolyzer. In order to preemptively determine the amount of hop creep to be experienced with each unknown fermentation, bench-top fermentations with 20 g/L dry-hops were performed concurrently and compared to the pilot scale fermentations. RDF was significantly higher (p < 0.01) on dry-hopped than non-dry-hopped fermentations beginning two days post dry-hopping to the end of fermentation, with the exceptions of SafAle™ BE-134, a S. cerevisiae var. diastaticus, and UCDFST 11-510, a S. mikatae. No apparent correlation between flocculation and increased RDF was shown in dry-hopped treatments. pH was significantly different between the dry-hopped and non-hopped fermentations (p < 0.05 one day post dry-hop, p < 0.01 for all subsequent days); this may have impacted on additional attenuation. No yeasts in this study indicated their use for mitigation of dry-hop creep, but this is a first look at beer fermentation for some of the chosen yeasts. The results also present a new perspective on how hop creep varies in fermentation.

Brewing Efficacy of Non-Conventional <em>Saccharomyces </em>Non-<em>Cerevisiae </em>Yeasts

“…Research Pilot Brewery at the University of California, Davis. Brewing parameters, as well as the malt, hops, water chemistry, mashing regime, pH, boiling parameters, and knockout temperatures followed the same method as outlined in previous research [65]. The experimental beer recipe was similar to an American Pale Ale or Session IPA, with a target original gravity of 10 ºP, to yield a 4.2% (v/v) alcohol beer under standard ale fermentation conditions.…”

“…Figure 2.Yeast propagation schematic following previous methods[65]. Yeasts were propagated to a final approximate total of 40.0 x 10 10 cells in each bottle with a total of 390 mL of propagation wort, equivalent to the…”

“…All transfers of yeast and wort were done in a laminar flow hood or positive pressure room. Yeast colonies were transferred from PDA plate or package of active dry yeast via sterile inoculation loop to propagation wort and propagated stepwise over the course of 11 days following the methods outlined in previous research[65] and Figure2. All propagations were performed at room temperature on a platform orbital shaker (Innova™ 2000, New Brunswick Scientific; Edison, NJ, USA) set to 150 rpm.…”

Brewing Efficacy of Non-Conventional Saccharomyces Non-cerevisiae Yeasts

“…A total of eight all-malt pilot-scale brews were performed on the 1.8 hL Anheuser-Busch Research Pilot Brewery at the University of California, Davis. Brewing parameters, as well as the malt, hops, water chemistry, mashing regime, pH, boiling parameters, and knockout temperatures followed the same method as outlined in previous research [65]. The experimental beer recipe was similar to an American Pale Ale or Session IPA, with a target original gravity of 10 • P and 20 IBU from Centennial (8.3% AA, Hopsteiner, New York, NY, USA) in the kettle, to yield a 4.2% (v/v) alcohol beer under standard ale fermentation conditions.…”

“…All transfers of yeast and wort were performed in a laminar flow hood or positive pressure room. Yeast colonies were transferred from PDA plate or package of active dry yeast via sterile inoculation loop to propagation wort and propagated stepwise over the course of 11 days following the methods outlined in previous research [65] as well as Figure 2. All growth took placeat room temperature on a platform orbital shaker (Innova™ 2000, New Brunswick Scientific; Edison, NJ, USA) set to Beverages 2021, 7, 68 5 of 15 150 rpm.…”