cocoa powder's affect on final gravity

I made a stout and added 4oz cocoa powder with 15 minutes left in the boil. I measured OG at 1.064, and after 3 weeks its down to 1.030. It seems like its done, but the FG is a lot higher than I expected. Beersmith estimated the FG to be 1.015, but I didn't add the cocoa into beersmith. I did hit the estimated OG. I did an iodine test and had full conversion with a 90min mash. Used Winsor yeast.

So my question is how does the cocoa affect the final gravity? Does 1.030 seem out of whack?

Here's the 5 gallon grain bill:

10# Munich
1.5# Flaked Oats
1# Chocolate Malt
.5# Roasted Barley
.25# C120
+ 4oz Cocoa powder @15

Sounds like a stalled fermentation. I couldn't imagine cocoa adding 15 points to your FG. Did your temps stay consistent throughout?

Cocoa powder shouldn't add anything to your gravity since it doesn't contain any sugars. What was your mash temp?

Mash temp was 152. Temps were pretty consistent in the mid to upper 60s.

So should I pitch more yeast? I have a pack of nottingham in the fridge I could use. I have already racked it into a corny keg, but I could easily put it back in the fermenter.

I think getting it down below 1.020 would be worth it. How does it taste to you? Since it is in a corny you could just let it ride if you like how it tastes. Personally once I like how it tastes I stop messing with it and start drinking it

Well, it tastes like a half fermented chocolate stout. Very sweet. Very chocolatey. But, I was expecting the sweetness from the Munich base. I'm going to rack it back into a carboy and pitch more yeast. Thanks for the input.

apshaffer said:

Well, it tastes like a half fermented chocolate stout. Very sweet. Very chocolatey. But, I was expecting the sweetness from the Munich base. I'm going to rack it back into a carboy and pitch more yeast. Thanks for the input.

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Best of luck. Hopefully you will let us know the outcome.

JLem said:

Cocoa powder shouldn't add anything to your gravity since it doesn't contain any sugars. What was your mash temp?

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Is that really true? SG isn't measuring sugars, it's measuring density. Seems to me if cocoa powder is dissolved into water it would raise the gravity. In this specific example (4 oz of cocoa powder), I can't imagine it'd be much, but it would affect it wouldn't it?

biestie said:

Is that really true? SG isn't measuring sugars, it's measuring density. Seems to me if cocoa powder is dissolved into water it would raise the gravity. In this specific example (4 oz of cocoa powder), I can't imagine it'd be much, but it would affect it wouldn't it?

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Cocoa powder doesn't dissolve in water - it is basically just in suspension. I suppose there may be some compounds in it that dissolve, but I don't think you would detect any appreciable gravity change.

JLem said:

Cocoa powder doesn't dissolve in water - it is basically just in suspension. I suppose there may be some compounds in it that dissolve, but I don't think you would detect any appreciable gravity change.

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Gravity is a measure of the density of the liquid in comparison to water (1.00). Density is a measure of mass divided by volume.

If you have cocoa powder mixed in, chances are your volume may have changed a tiny bit, but not much. Mass, on the other hand, may have changed a decent amount. I'm not gonna do any research into it, but I wouldn't just discount it. However, it could be that both mass and volume increase in correct proportions for it not to matter. Food for thought....

nickmv said:

Gravity is a measure of the density of the liquid in comparison to water (1.00). Density is a measure of mass divided by volume.

If you have cocoa powder mixed in, chances are your volume may have changed a tiny bit, but not much. Mass, on the other hand, may have changed a decent amount. I'm not gonna do any research into it, but I wouldn't just discount it. However, it could be that both mass and volume increase in correct proportions for it not to matter. Food for thought....

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The hydrometer measures the density of the liquid. If something is dissolved in it (like sugar) the mass will increase but there will be little volume increase, so the density will be higher (more mass per volume). However, if something is suspended in the liquid and not dissolved (like cocoa powder) neither the mass nor the volume of the liquid changes, so density is unaffected. As an extreme example...the density of water does not change when you add a handful of sand to it.

I pitched a pack of US-05 (what I had) two weeks ago. I just racked to my keg and the gravity measured 1.024. It a little higher than I expected, but it is what it is.

This thread made me dumber.

1. Just assume cocoa was sugar... Plug into beersmith or calc by hand and it would add what, 1-2 points? So not being sugar, cocoa will add less than that.

2. A FG of 1.024 sounds like lousy attenuation. Calculate it and see what safe ale says its supposed to be. 75% would put you at 1.016. I Fear your beer will be rather sweet.

JLem said:

As an extreme example...the density of water does not change when you add a handful of sand to it.

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And (for the purposes of this thread) cocoa powder = sand. It falls out of suspension pretty quickly in my experience.

dwarven_stout said:

And (for the purposes of this thread) cocoa powder = sand. It falls out of suspension pretty quickly in my experience.

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precisely

Are you using a refractometer to measure the FG by chance?

Agreed. If so, a refractometer can't be used to measure gravity of fermented beer.


I pitched a 1.5L starter in mine, and after 7 days, it was at 1.011, so pretty much done (target is 1.010). Measured with hydrometer, and the cocoa powder didnt cause any measurement issues. Most of it is on the bottom of the carboy anyways.

That being said, I tasted the beer (this recipe) when I took a reading, and it was sweet and kinda boozy, and nowhere near ready. Definitely needs a good month and a half rest. I'm expecting it'll be awesome when I serve at Thanksgiving.

I use a hydrometer, and I agree it's lousy attenuation. The question is why the lousy attenuation. I thought maybe it had something to do with the cocoa powder, but apparently not. At least not to the degree I experienced.

In my 5 years of brewing all grain, I have never had an attenuation issue. If anything, my beers finish drier than beersmith predicts. Not sure why it happened this time. Ambient temps were fairly constant (60's), mash temp was 152ish. I used 2 pack of yeast pitched a few weeks apart, and it spent 5+ weeks in the fermenter. It should be finished. It went from 1.064 to 1.024. I agree it should have finished about 10 points lower, but it didn't. I'm not pitching any more yeast. It in the keg now, and I'm moving on.