Bottles too full?

[dmm_au]

Hi,

I'm on my second batch. The first coopers larger went really well. The second, coopers stout seems a bit flat.

I think it's because I filled the bottles a lot more on the second batch. The last bottle which wasn't as full seems to have worked better.

As a test, I've opened and closed 6 bottles as a test. I figure the yeast needs oxygen to process sugar and because the bottles are very ful there isn't enough oxygen to work with.

Is this a good theory?

Perhaps it will work anyway, but take longer??

[lethaldog]

If your using a little bottler which i would assume you would be then there is no concern, i always fill to the top then once you pull the bottler out there is plenty of head space left, some brews just take longer to carb up

[OldBugman]

stouts for me always seem to take longer to carbonate.

[Chris]

Basically, your theory is wrong. Yeast don't need oxygen at this stage, as the process is anaerobic.

As lethal said, if you are using a little bottler, you can't really overfill your bottles.

As Buggerman said, stouts tend to take longer to carbonate.

(Sorry about that Bugman)

[OldEvan]

As mentioned above, fermentation of the sugar by the yeast is anaerobic (doesn't require oxygen).

In fact, from what I remember in chemistry:

C6H12O6 > 2C2H5OH + 2CO2


Basically, that says that fermentation turns Glucose (sugar) into Ethanol (alcohol) and Carbon Dioxide. As oxygen is not present in the equation it is not required.


The yeast may stop when it:
- Runs Out of Sugar to convert
- Is killed by high alcohol levels or temperature


So, after a long and probably unnecessary Chemistry lesson we can conclude that lack of oxygen in the bottles won't affect the yeast fermenting your priming sugar. Could have just said that to start with hey?

[rwh]

With oxygen

(glucose) + 6(oxygen) ==> 6(CO2) + 6(water) (aerobic respiration)

or without:

(glucose) ==> 2(CO2) + 2(ethanol) (anaerobic respiration)

There are some losses due to other processes (such as growth); these equations don't describe 100% of the yeasts' metabolism. Note also that in the presence of oxygen more CO2 is produced.