Attenuation & Sugar primer

[CreekBrewery]

I did a search and found some info about attenuation and sugar additions but not the detail I was hoping for. What I would like to know (I hope I'm not the only one perplexed about this) is how to properly design beers around and manage expectations when using sugar additions in beer. Is there a way to "know" or at least have an educated guess on attenuation.

Is there some kind of equation like this (very rough I know)...
(wort * standard attenuation) + (sugar * 100% attenuation) = ABV

I know alpha and beta rests for the wort effect fementability but I'm just looking at the sugar side in this question.

 

[david_42]

Yeah, you just forgot the multiplier.

( (wort * standard attenuation) + (sugar * 100% attenuation) ) *1.3 = ABV

 

[CreekBrewery]

Dude, are you f'ing with me
Is it really that easy? Where the hell is that from?

 

[Anubis]

Here?

 

[kanzimonson]

Yeah I think this is a concept that is so freakin simple and yet people are dying to overcomplicate it. The best way I describe it is:

-Say you have a house recipe with an OG of 1.050 and an FG of 1.010.
-If you add a reasonable amount of sugar in addition to the existing recipe, you would increase the OG, but the FG would still finish about 1.010.
-If you sub out some of the original recipe's malt with sugar, making sure to have an OG of 1.050, your FG will be lower than 1.010.

The oft repeated phrase "sugar drys out a beer" is only really referring to when you substitute sugar for malt. Just adding sugar on top of an existing recipe will only add extra alcohol. While this will change the flavor, it won't really make it less sweet.

 

[CreekBrewery]

Thanks kanzimonson, that explanation helps my understanding of what is going on and especially what "sugar drys out a beer" really means.

What is the best method for calculating FG when subbing sugar for malt as your example gave? Anubis, your link contained some good info but does it apply here? I'm still learning so some of it may have been over my head

Thanks for the good info!

 

[kanzimonson]

What will your FG be? Well, as with all things that deal with yeast, the answer is "it depends."

There are so many factors that determine the attenuation of a certain beer that I don't think you could ever truly predict. Sure, we can make an educated guess and come pretty close... sometimes you'll even guess the right number, but I think this is just hind sight bias.

The best you can do is to use david42's formula. First, do some research on the yeast strain you're using. I use 1968 in most of my ales, and its attenuation range is 63-70% (I think). So pick the mid point of 67% (I've come to know the yeast and my system so that I usually achieve 69%).

So you want to brew a strong brown ale with this yeast, but you want it to have a drier finish. You decide on an OG of 1.070, and you decide that 10% of your fermentables will come from treacle (let's just assume treacle is 100% fermentable). WITHOUT the treacle, your OG would be 1.063. If you multiply 1.063 by 67%, you get an estimated FG of 1.021. But as I mentioned in my post above, adding sugar to this beer will increase the OG without changing the FG. So your apparent attenuation will be 69%.

I think this method is good enough for predicting your FG within say 3 points, but I wouldn't be surprised to be proven wrong. More importantly, you have a better understanding of what's going on in your beer. For example, I use 1968 because I love its malty profile and I usually like the residual sweetness it can leave, but in the case of bigger beers such as the one above, I will frequently add 5-10% sugar just for a little extra dryness.

Last thing I wanted to mention that just reinforces the "it depends" argument: I have a spreadsheet where I keep track of all my batches' attenuation numbers by yeast strain. I enter the percentage specialty grains, percentage sugar, mash temps, and then the OG, FG, and attenuation are all charted. I haven't been doing it too long, but already I see very little trending. The only things I've really learned are common sense anyway: darker malts and higher mash temps generally lead to lower attenuation, but even that is not a hard and fast rule.

 

[CreekBrewery]

Good stuff. The way I was thinking about this was from a "all things being equal" perspective. I know that's not very real world in this case but though it may be a good starting point for understanding sugar.

If I'm following this correctly, now that I've reread your posts a few times, it is best to design your beer first without the sugar. Using a middle of the road attenuation number from specs' or one from your personal experience you get to the FG you'd like to see. Finally you add in the sugar you need to get to your desired OG or ABV. Very general but that's what I'm understanding.

You were right that it is pretty straight forward. I figured there was some calculus involved or maybe some derivatives

 

[Calder]

I've come to know the yeast and my system so that I usually achieve 69%.

That's really low!

 

[kanzimonson]

That's really low!

Not for 1968. I hate 1056 for so many reasons... terrible flocculation, ultra-dry finish, and low ester production.

To really get down to it, it's rare that I design my beers with an exact FG in mind. It's all about the OG to me. Most of my beers are in the 1.055-1.065 range... this is a product of lots of experimentation, getting to know my yeast, and seeing what kind of profile I like. Ultimately most of my beers end up 5.3-5.7%ABV, but I don't really care.

All these predictions are great, but there's really no comparison to the value you can get from experimenting. Make the same beer over and over, making little changes to it. Different hops, different mash temps, sub in some sugar, sub in some smoked malt, whatever. You'll learn so much about your ingredients and methods that will intuitively spill over into your other beers. Eventually you'll narrow down the profiles that you like. I feel like I've gotten to a point where every beer I'm making is the best I've ever made, and each one is better than the last. It's a good feeling.