S-05 Attenuation

[doublehaul]

I recently brewed a 1.084 OG beer. It didn't have any straight sugar or anything, mostly 2 row and munich with a little bit of crystal malts. I hydrated and pitched 2 packs S-05 and had pretty wild fermentation for 1 week+. It was in a fermentation chamber at 66-68F and more recently I've had it at more like 68-70F. I'm at about 2 1/2 weeks right now; just added my second round of dry hops. It seems to be done at 1.020, so about 76% attenuation. Is this about what to expect with S-05?

 

[peterj]

Yeah that sounds about right. I usually get around 77% attenuation from US-05. It's a fairly high attenuator.

 

[BigFloyd]

76% would be pretty normal for that strain (same as WLP001). What temp did you mash at?

 

[doublehaul]

Shot for 153F, but had a mixup at the brew store and got a bigger than expected grain bill (was going to be a 1.060 beer!), so it was a really thick mash so temperature wasn't really consistent throughout the mash.

 

[doublehaul]

as a side question - everyone says WLP001 and wyeast 1056 are the same strain as S-05, should I expect the same attenuation with those 2 then?

 

[BigFloyd]

as a side question - everyone says WLP001 and wyeast 1056 are the same strain as S-05, should I expect the same attenuation with those 2 then?

Yes.

 

[rkbarnes82]

I've been mashing my DIPAs around 148 lately and have seen attenuation between 80-82. But I also had some dextrose in the recipe.

 

[doublehaul]

I've been mashing my DIPAs around 148 lately and have seen attenuation between 80-82. But I also had some dextrose in the recipe.

I wonder if you can calculate how much dextrose will boost your attenuation

 

[peterj]

I wonder if you can calculate how much dextrose will boost your attenuation

Since it should ferment out completely, I usually just look at what the predicted FG would be without the dextrose in there and use that as the FG. Then you could calculate the attenuation using that FG and the OG with the dextrose.

 

[doublehaul]

Since it should ferment out completely, I usually just look at what the predicted FG would be without the dextrose in there and use that as the FG. Then you could calculate the attenuation using that FG and the OG with the dextrose.

Hmmm I am not sure I understand

 

[peterj]

Hmmm I am not sure I understand

Yeah I guess that was a little confusing. For example let's say you have a beer that contains 1 lb of dextrose with an OG of 1.080. Let's say your average attenuation is 75% with US-05. Without the dextrose your OG is 1.071 so if you calculate your FG from that using 75% attenuation it would be 71-(71*0.75) which is about 1.018. This should also be your FG with the 1 lb of dextrose in the beer because the 9 gravity points the dextrose adds should ferment out completely. So your attenuation would be ((80-18)/80)*100 = 77.5%.

Does that make sense, or is it just more confusing?

 

[feinbera]

I don't think that's accurate... alcohol has an SG lower than 1.000, so, all that 100%-fermentable dextrose fermenting out should actually leave your gravity a bit lower than it would've been if you hadn't added it. Think about wines and meads, with their extremely fermentable sugars and beastly yeasts; they ferment to sub-1.000 gravities if you don't halt fermentation.

I couldn't tell you how much lower your FG is due to alcohol from fermented dextrose, or how much dextrose you'd need to even make a measurable difference, but (it's entirely possible that) you can't just pretend it's not there.

 

[peterj]

I don't think that's accurate... alcohol has an SG lower than 1.000, so, all that 100%-fermentable dextrose fermenting out should actually leave your gravity a bit lower than it would've been if you hadn't added it. Think about wines and meads, with their extremely fermentable sugars and beastly yeasts; they ferment to sub-1.000 gravities if you don't halt fermentation.

I couldn't tell you how much lower your FG is due to alcohol from fermented dextrose, or how much dextrose you'd need to even make a measurable difference, but (it's entirely possible that) you can't just pretend it's not there.

It is true that ethanol has an SG of 0.787 I think. But your average attenuation calculation already includes the effects of the lower SG of ethanol. I think the slightly higher amount of alcohol produced by dextrose compared to wort is negligible in the FG. It might lower it by a point, but I doubt you would even see a measurable difference. And I'm not saying the way I do it is exact. It's just good for a rough estimate, which is as good as you're going to get when trying to predict FGs anyway.

 

[crushingblackdoom]

Oh, brewing.... Now, do I over think this stuff, or is this when I should Underthink it? Hmmmm....

 

[doublehaul]

Yeah I guess that was a little confusing. For example let's say you have a beer that contains 1 lb of dextrose with an OG of 1.080. Let's say your average attenuation is 75% with US-05. Without the dextrose your OG is 1.071 so if you calculate your FG from that using 75% attenuation it would be 71-(71*0.75) which is about 1.018. This should also be your FG with the 1 lb of dextrose in the beer because the 9 gravity points the dextrose adds should ferment out completely. So your attenuation would be ((80-18)/80)*100 = 77.5%.

Does that make sense, or is it just more confusing?

Makes sense, thanks for the explanation!