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Yeast attenuation and bottle refermentation

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  • Yeast attenuation and bottle refermentation

    So, we're using a yeast for primary fermentation rated at around 70% apparent attenuation. If I do a forced ferment test, I'm assuming that in the actual fermentor I'll be getting down to about 70% gravity between the original gravity and the fast ferment test gravity.
    Now if we are going to bottle referment, how worried should I be about that remaining 30% of sugars, which I am assuming are fermentable?
    I'll be adding some more of the same yeast but fresh for the bottle fermentation. When I'm calculating my priming sugar for around 3.5 volumes of CO2, should I just ignore that 30%? My gut tells me that those are more complex fermentable sugars and that the simple priming sugars will pretty much be the only sugars eaten if I'm using the same type of yeast and they didn't eat the 30% before. But then again, fermentable sugars are ... fermentable. But yeast can be tricky little critters to figure out.
    I just want to avoid gushing problems, and given this is a pretty carobnated beer, I have a bit less room for error than something less carbonated.
    Br. Francis
    Birra Nursia
    Norcia, Italy

  • #2
    Yeast attenuation and bottle refermentation

    I think yeast manufacturers put attenuation ratings on their yeast for comparison purposes between strains, because they are rarely accurate in real life. Just make sure the beer has finished fermenting before you dose in the priming sugar and as long as you are using the same yeast from the primary fermentation you should be in good shape for bottle conditioning.
    Troy Robinson
    Quirk Brewing
    Walla Walla