Does Bottle Conditioning Raise ABV?

[IrishBrewer420]

I am wondering if bottle conditioning can have a direct affect on the alcohol content of beer. Obviously, we add sugar to trigger a "renewed fermentation", and the CO2 gas which would normally escape through the airlock is sealed in the bottle, thus carbonating the beer. I'm curious that since we've added dissolved sugar and produced gas, does it stand to reason that the beer as gone up a hair in ABV? Even if by only a few decimal points? I know the yeast still has to be active to a certain extent for bottle conditioning to work, so could the beer be slightly stronger upon opening than on bottling day? For the record I'm using dissolved sugar, NOT conditioning tablets. I'd love to hear some thoughts on this, thanks all.

 

[Omahawk]

I believe it does add a small amount of alcohol. Yeast consume sugar and alcohol and CO2 are byproducts.

As a for instance in BeerSmith, i plugged in 5 oz of table sugar into a 5 gallon recipe and got somewhere around a 0.3% increase in ABV. So as long as it carbonated, I believe it also added this small amount of alcohol.

 

[clone63]

It does. It's fermented sugar. About 0.1- 0.2% abv depending on desired co2 vol.

 

[TomVA]

Also discussed here today:

https://www.homebrewtalk.com/showthread.php?t=627162

TomVA

 

[brandonlovesbeer]

Very minimal.

 

[biermann1]

Let some beer go stale and check the gravity.
I did it and against all expectations the measured gravity was dead on
with the FG before bottling.

 

[kh54s10]

Let some beer go stale and check the gravity.
I did it and against all expectations the measured gravity was dead on
with the FG before bottling.

It seems this would be right but not about the ABV. Your FG was X you added a highly fermentable sugar and if fermented out so you read X as close as you can read what would make a .1% to .3% rise in ABV.

4 ounces of sugar in 5 gallons would only be 1.002 OG.

As a test I used Brewers Friend ABV calculator with OG 1.050 and FG 1.010 it gives an ABV of 5.25% I then changed the OG to 1.051 and the ABV went up .13 to 5.38. That with just a .001 change in OG.

 

[bajaedition]

technically yes, measurably no

 

[Yooper]

Let some beer go stale and check the gravity.
I did it and against all expectations the measured gravity was dead on
with the FG before bottling.

No, that would be expected.

The reason is this- the beer is at Fg, which means it's done fermenting all the fermentable sugars.

You add a measured amount of fermentable sugars, and then bottle.

The yeast metabolize that sugar, and so it's gone. Then, the beer is carbonated and the FG is exactly the same as it was when you bottled.

It would be very troubling if it was different, but not if it's the same, as that is the whole idea.

 

[bajaedition]

Here is the problem, the final may be the same however....
You added priming sugar, you raised the gravity, so if you end up with the same final, it is because the sugars added where consumed and converted to CO@ and alcohol. the proof to that is the carbonated beer.

So if the finalis the same, the starting gravity of the beer before bottling was not the original final as sugar was added.

Here is the issue, we add so small an amount of sugar, it is not even worth discussing how much we gain after bottle conditioning

so, Yes the Alcohol goes up, but it is so small it is not really measurable inless you want to use techniques home brewers do nit have.

 

[freisste]

I believe it depends. Sugar tabs are ONLY sugar and are fully fermentable. As such, you add sugar but no volume and your beer gets stronger. NOTE: As Yooper said, you are very likely to read the same FG as you are adding very little sugar and it is fermenting out. For the calculation, you would have to assume the sugar content was added to the OG. So a beer that was originally 1.060 fermented to 1.015 (6% ish), you would assume for example 1.062. This would yield about 6.2%.

If you dissolve sugar in water to add it to your beer prior to bottling, you will have to take into account the volume change. Like the sugar change, it is pretty small and I don't generally take it into account. It is worth a note, however that you could theoretically REDUCE your ABV by adding sugar water to a very high gravity beer. Brewers tend to add several ounces of sugar in a cup or two of water, which is damn near syrup (depending on your definition, it IS syrup). But if you had a really high ABV beer, let's call it a 1.125 OG RIS that you wanted to have low carbonation, you might add sugar water that is actually lower in OG than your wort was prior to fermentation. I'd have to run some numbers to see if that is even realistic.

Just don't worry about it. It's a small change, likely imperceptible to anyone drinking it. And you're not a commercial brewer (I assume).

 

[bajaedition]

If he is asking that question I would bet at high odds he is not a commercial brewer

the chemistry studied by commercial brewers is pretty intense compared to that question.

 

[IrishBrewer420]

Thanks for all the input guys! Even if it is by only a few decimal points a tiny spike in ABV is fine by me. And I am certainly not a commercial brewer, but you never know what the future might hold.

 

[SlitheryDee]

I've heard that the fermentation going on is a "special case" due to the presence of oxygen in the headspace of the bottle. The book I was reading didn't go into any more detail, but after learning a bit more I'm assuming that means that some respiration may take place too. Respiration skews the final alcohol number because it produces co2 and water as byproducts. There can't be very much oxygen in the headspace of a bottle, but respiration also produces much more co2 than fermentation does, so it may account for an inordinate amount of the final carbonation as well.

All that is interesting to think about, but I wonder if it really has any impact. If the oxygen in the headspace is so trivial that no significant respiration occurs, then it's all moot anyway.