My home-brewed ales are consistently attenuating well beyond Wyeast published ranges and I wondered if dry-hopping could be the explanation. Here’s a concrete case study (my most current pale ale) to illustrate my point:
Wyeast publishes the max attenuation for 1056 at 77%, which with my OG of 1.062 would produced an FG of 1.016 and an ABV of 6.0% (per Beersmith). Instead, my FG is 1.011, my apparent attenuation iis 81.4% and my ABV is 6.7%. This is nuts! The attenuation I’m getting seems more in line with Belgian strains fermenting at higher temperatures than APAs fermenting in the 60’s. I deliberately optimize attenuation by: (1) generous yeast starter pitching rates, (2) thorough wort oxygenation, and (3) fermentation temperature control in an upward-only direction (all preached by JZ) - but the numbers I’m getting just seem too high. This is why I’m suggesting dry-hopping could be factor.
Following the addition of pellet hops to the fermenter I clearly see a dramatic increase in CO2 blow off (4 oz of pellets, in this case). Most literature attributes this to dissolved CO2 outgassing as a result of the sudden introduction of nucleation sites to the wort - with the implication that this is therefore not proof of additional fermentation in and of itself. I’m unconvinced. While pellet hops do indeed provide nucleation sites and therefore spur outgassing (duh), I don’t see how the increased movement and agitation of CO2 through the wort would not inhibit the yeast’s proclivity to flocculate. Much like a stir-plate prevents yeast from dropping out of suspension, the increased activity and motion of gases inside the fermenter would likely slow yeast from dropping out of suspension. We also know that there is a strong correlation between flocculent yeast strains and attenuation percentages. So if outgassing inhibits flocculation, why would it not consequently maximize attenuation?
For purposes of this discussion, I ask that we assume accurate equipment readings (I used both hydrometer & refractometer) and the absence of bacterial or wild yeast contamination as factors influencing our conclusions.
- Malt Bill = 92% American 2-Row, 8% Crystal 60L
- Mashing = Single-step at 156 F (Herms recirc for 1 hr @ ~ 1.75 quarts/pound)
- Yeast = Wyeast 1056, stir-plate starter to ~ 375 Billion cells
- Fermentation = Oxygenated with stone in the fermenter and yeast pitched @ 62F. Allowed wort to rise over 3 days to 68 F; final week at 70 F while simultaneously dry-hopping, 2-week total time in fermenter before crash-chilling
- Brew house = PID-controlled Herms using standard Sanke keggles
- Fermenter = Standard sanke keg modified with Darrin’s tri-clamp fermenter kit (Brewershardware). Temperature controlled with Ranco controller - never more than 1 F wort variance from set point - as measured by sensor in thermowell
Wyeast publishes the max attenuation for 1056 at 77%, which with my OG of 1.062 would produced an FG of 1.016 and an ABV of 6.0% (per Beersmith). Instead, my FG is 1.011, my apparent attenuation iis 81.4% and my ABV is 6.7%. This is nuts! The attenuation I’m getting seems more in line with Belgian strains fermenting at higher temperatures than APAs fermenting in the 60’s. I deliberately optimize attenuation by: (1) generous yeast starter pitching rates, (2) thorough wort oxygenation, and (3) fermentation temperature control in an upward-only direction (all preached by JZ) - but the numbers I’m getting just seem too high. This is why I’m suggesting dry-hopping could be factor.
Following the addition of pellet hops to the fermenter I clearly see a dramatic increase in CO2 blow off (4 oz of pellets, in this case). Most literature attributes this to dissolved CO2 outgassing as a result of the sudden introduction of nucleation sites to the wort - with the implication that this is therefore not proof of additional fermentation in and of itself. I’m unconvinced. While pellet hops do indeed provide nucleation sites and therefore spur outgassing (duh), I don’t see how the increased movement and agitation of CO2 through the wort would not inhibit the yeast’s proclivity to flocculate. Much like a stir-plate prevents yeast from dropping out of suspension, the increased activity and motion of gases inside the fermenter would likely slow yeast from dropping out of suspension. We also know that there is a strong correlation between flocculent yeast strains and attenuation percentages. So if outgassing inhibits flocculation, why would it not consequently maximize attenuation?
For purposes of this discussion, I ask that we assume accurate equipment readings (I used both hydrometer & refractometer) and the absence of bacterial or wild yeast contamination as factors influencing our conclusions.
