How do I calculate ABV if i add sugar during fermentation?

[CaioOliveira]

I'm convinced now that it is better for yeast if I add sugar when krausen is slowing down. If I understood well, too much substrate in the wort can inhibit the cell's growth and the yeast will go directly to the glucose and it can leave some other fermentable sugars behind. So it would take longer (don't have much problem with that, since i dont believe it would be significantly longer) and if sugar were left behind, it could generate an overcarbonatation during primming. Please correct me if I'm wrong.

But the main question, that makes me not be sure weather I do like this or not, is: How do I calculate ABV if i add sugar during fermentation?

 

[max384]

I'm convinced now that it is better for yeast if I add sugar when krausen is slowing down. If I understood well, too much substrate in the wort can inhibit the cell's growth and the yeast will go directly to the glucose and it can leave some other fermentable sugars behind. So it would take longer (don't have much problem with that, since i dont believe it would be significantly longer) and if sugar were left behind, it could generate an overcarbonatation during primming. Please correct me if I'm wrong.

But the main question, that makes me not be sure weather I do like this or not, is: How do I calculate ABV if i add sugar during fermentation?

I'm not sure about waiting to add sugar until after krausen...

But, to figure out how much the sugar adds to the ABV, you need to input the sugar into whatever software you're using to make your recipe. Using your recipe (without sugar added), take note of the estimated OG according to the software. Then add the sugar into your recipe and take a look at the new OG. Subtract the without-sugar OG from the with-sugar OG. This will give you the additional gravity that adding sugar will add to your recipe. Take this number and add it to your actual measured OG, then use this number when determining your ABV using your OG and FG measurements.

I'll give you a very simple example:

Using Beersmith 2:

10 lb domestic 2-row
estimated OG: 1.052

10 lb domestic 2-row
1 lb table sugar
estimated OG: 1.062

1.062 - 1.052 = 0.010

Let's say that our actual measured OG was 1.049. We would add 0.010 to that.

1.049 + 0.010 = 1.059

So when determining your ABV, you would use 1.059 as your OG in this example.

 

[ArkotRamathorn]

When I do it, adding sugar during primary/high or low krausen, I just throw it into my recipe as a straight up sugar additon as if it was in the boil... There may be a more accurate way to do it, but my personal experience with my beer matches up with the number's data.

So:

OG: 1.050
FG: 1.010

5.25% ABV

You want to bring you beer up to 6.5%, so you add enough sugar to make your beer OG 1.060 (I go with the assumption that, I added it to the boil, batch size hasnt changed, slap the sugar into whatever recipe calculator you use adding it to the original recipe). Add the sugar to the fermenter (I invert it and make a thin syrup so my batch size will increase, but ever so very very slightly).

Check your gravity again in a couple days.

If the gravy reads 1.010 again, you now have a 6.5%(ish) beer. Assuming you mixed the sugar solution in (you probably wont have to, if added just as krausen dies, the whole thing can really ramp up and get churning). You will *probably* end up with higher attenuation than this anyway. I've had beers stall at 1.025, add .5lb or 1lb of invert syrup and check in a couple days, blammo down to 1.013.

I've never noticed over carbonation problems that can be traced to sugar additions during fermentation, if you give it time to finish, I've even added sugar up to 2 weeks after krausen died, and the yeast kick *right* up.

 

[Gavin C]

Why not add the sugar, if it is a component of the recipe, during the last 10-15 minutes of the boil.

Why do you want to add it at any stage during fermentation. Is it relating to a beer with an extremely high gravity or something like that?

Seems like a somewhat pointless and potentially detrimental exercise. In most cases a preplanned starting gravity and final gravity range are used to brew the planned beer.

I'm no help I'm afraid. Just puzzled as to your thought process.

 

[decoleur]

@Gavin_C,

To answer your question, "why not just add all the sugar at the end of the boil?" There are times when you do not want to do that as in high ABV beers that need to step up the fermentables over time to support the health of the yeast and minimize the stress.
Look at the dogfish head 120 recipe for a prime example.
You could do a bigger starter but there is a limit as to how big a starter you want to use.
Right now I am working on a mead that adds maple syrup after the primary fermentation to provide additional flavor characteristics that would be non-existant if I added them with the honey at the start.

HTH,

-decoleur

 

[ArkotRamathorn]

@Gavin_C,

To answer your question, "why not just add all the sugar at the end of the boil?" There are times when you do not want to do that as in high ABV beers that need to step up the fermentables over time to support the health of the yeast and minimize the stress.
Look at the dogfish head 120 recipe for a prime example.
You could do a bigger starter but there is a limit as to how big a starter you want to use.
Right now I am working on a mead that adds maple syrup after the primary fermentation to provide additional flavor characteristics that would be non-existant if I added them with the honey at the start.

HTH,

-decoleur

To add to this.

If I am doing an IPA particularly one thats of a more west-coast tradition. Dry and low to no caramel/crystal malts, even with high attenuation strains of yeast, you'll want to squeeze a tiny bit more out of them to dry it out just a tiny bit more, particularly with a DIPA. Usually when I use this the yeast will blow through the added sugar and keep on trucking into the other more complex sugars still left. Even if they don't go after the more complex sugars, the mouth feel and perceived sweetness will go simply because of the increased alcohol, nothing worse than a really really sticky sweet IPA.

If all that sugar is there at the start of fermentation the yeast will tend to prefer the simple sugars over the maltose sugars, they'll get really pooped out on just the simple sugar, and leave a lot of fermentable maltose behind. Could lead to bottle bombs, or unintentionally sweet beers, decreased hop presence due to higher gravity).

Yes, *perfect pitch rate can alleviate some of the issues with attenuation, up to a point. But you'll eventually run into problems, even with the most perfect yeast management techniques. There are a lot of htings you can do when you run into the situation where you miss your attenuation target by 5-10%, warming it up, or rousing the yeast, adding new/fresh yeast. I can say with a fair amount of certainty (UNLESS you killed the yeast by somehow heating up the beer past 120F while in the fermenter) that the 1 thing you can do that will always help with attenuation is adding a bit of simple sugars like invert syrup**.

First * if you check out the Brulosophy exbeeriment on pitch rate, it does seem in his limited testing that, in some cases perfect pitch rate may not necessarily affect final gravity as much, the yeast is gonna do what the yeast is gonna do.

Double ** I try all other avenues before I go for the sugar, unless its an IPA/DIPA, I'll have already planned a sugar addition right after krausen drops, other beers that arent massive Belgians, I default to warming up or rousing.

 

[ACbrewer]

OP - Max has given a solution to the problem - grab something like beer smith, put in your recipe and have it give you the numbers.

Or you can do the math, which is a bit of a pain, but I suspect everyone who has completed 8th grade has done all of these.

you check the volume of your wort (5 gal) and the OG (1.050) so the total sugar in the initial wort is 250 points. Sugar by the pound has 46 points (or points per pound gallon). Thus adding 1lb of sugar into the wort at any stage would be as if you had 296 (250+46) for the OG, not 250. 296/5gallons = about 59. or 1.059. Since it is 100% fermentable, if the FG is supposed to be 1.012, the FG should still be 1.012. anyhow it will add about 9 points to the OG, but zero to the FG.

there are lists somewhere for the points in a fermentable, normalized to 1lb.

 

[Gavin C]

@Gavin_C,

To answer your question, "why not just add all the sugar at the end of the boil?" ...
HTH,

-decoleur

To add to this.

If I am doing an IPA particularly one thats of a more west-coast tradition. Dry and low to no caramel/crystal malts, ....

Thanks to both of you for this very informative reply. I learned quite a bit right there. I figured it had to due to something relating to a high gravity brew. It makes perfect sense giving the yeast the simple sugars later on; the desert after the starters and main course of maltose has been cleared away. Much appreciated.

 

[CaioOliveira]

Thank guys for your help. I had thought about the weighted average of the gravities but for me its kind of hard to measure exactly how much I have inside the fermentor since it has a not even shape and its not transparent.

Now I'm gonna use the brewing calculator tip that some of you gave. Thank you very much!

 

[Yuri_Rage]

Since specific gravity is a measure of density, you can weigh the fermenter before and after filling it and then calculate volume from there.