good airation = lower FG.....

[croc4]

For a while now I have had my beers finish a little higher than expected, (in the 1.020, from ~1.05x range).
I had tried going over my process and materials etc to figure out why this was happening. Well this weekend I believe that I have nailed it. I brewed up a batch in normal fashion and then pitched it on the yeast cake of a previous batch, expecting a huge fermentation, it never came.
It just fermented as normal albeit in much shorter time.

So that leads me to believe that I am under aerating the wort!.
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[chris1kanobi]

That may be true. How to you airate now? Did the beer finish lower? Have you checked your hydrometer's calibration?
If you are all-graining, perhaps you are not getting a good conversion and creating a less fermentable wort? Are you making yeast starters?

http://www.knology.net/~sprevost/beerwine/

[croc4]

The beer(s) in question finished at 1.018-1.020 which based on the yeast and the OG was a little too high.

I have tried varying several factors to see where the issue is, and none of the changes made any real difference in the FG.

My normal Aeration technique was to run the wort into my primary by way of a siphon sprayer attached to the end of my siphon tubing. Then giving the carboy a good shaking after it was full. I thought this was sufficient, but it may not have been.


So I have eliminated all other factors (I believe) and the only thing left was the aeration issue.

If this is not the issue then I'm at a loss as to why my FG are high.


As a side note, The last batch I did was in Secondary for 2 weeks, it went in at 1.020 and came out at 1.020. ;-(
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[chris1kanobi]

It does sound like something right from the get go. Does the beer taste sweet? The gravity will not drop very much in the secondary. Pitch a big, healthy, active starter and airate well. Are you using extract? Have you changed brands recently? I use a bottle of pure oxygen and a plastic aquarium airation stone. The oxygen bottle will last for a very long time. I have had mine for over a year and it is still going strong. Good luck :)

[croc4]

The beer does not taste too sweet, so it does not come out too bad, but I know it could be better.

I have tried a few different types and brands during this experiment to narrow down the issue, they made no difference.


Yep I'm an extract brewer, I have not taked to leap to AG yet.


The final nail / clue was when I pitched on top on a previuos yeast cake, you don't get a starter much larger than that ;-), and the fermentation was "normal", I had expected a huge fermentation.

I ordered a aeration system from NB to cure this aspect of my process, so hopefully things will be on track shortly

Thanks,
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[tj beerman]

i want to use an O2 stone do you use it after you pitch your yeast

[chris1kanobi]

Before you pitch the yeast. Oxygen can damage yeast cells called "scrubbing" so you want to airate the wort before you pitch the yeast to give them an oxygen rich environment to be fruitful and multiply. :D

[toneyc]

An oxygen setup may be better from a sanitation standpoint, but to me its just one more complication. I've used the whisk method for my last several batches and it works great!! Lag time is down to 3 hours or less.

:)
Toney.

[GunNut76]

I agree with toneyc. You can get 2-3 good SS whisks for the price of a barebones O2 system and my lag times are down to about 3 hours...4 hours if I don't rehydrate the yeast.

croc4- You could always just beano it down! :D

[danno]

Originally posted by chris1kanobi
Before you pitch the yeast. Oxygen can damage yeast cells called "scrubbing" so you want to airate the wort before you pitch the yeast to give them an oxygen rich environment to be fruitful and multiply. :D

so you're saying that the oxygen bubbling out of your stone is crashing into yeast cells and damaging them? not sure I buy this, since after your ferment gets going, it's swirling around like crazy... Chris, you have a cite for this?


Originally posted by GunNut76
I agree with toneyc. You can get 2-3 good SS whisks for the price of a barebones O2 system and my lag times are down to about 3 hours...4 hours if I don't rehydrate the yeast.

however, it's really tough to whisk inside a carboy....

[croc4]

I have actually tried pilsner enzyme, and that does bring down the FG a few points,
but this seemed like cheating a bit. I wanted to make sure that I had eliminated any other issues that I had in my process, and aeration seemed to be the last one.

My results from the last batch were much different, but there was a slight problem, my LHBS changed DME suppliers so that kind of negates any chance of comparing results with and without the aeration system ;=(.

But in any case, after using the air pump, the lag time was reduced and the ferment was much stronger and lasted longer.
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[chris1kanobi]

Humans consume oxygen at their own rate just like yeast. Adding the yeast and then forcing oxgen into the wort would be similar to trying to breathe with an air hose set at 40 psi. Of course the air could be added gently to avoid this. The other debatable reasoning is that the oxygen molecules can damage the yeast cell wall. The oxygen is better utilised when it has saturated into the wort. This subject is still debateable and not much research has been done on it, because adding oxygen to wort at any time is still better than none at all. And if you are going to do it why not make it less chaotic and friendly to the yeast? A good experiment would be to make and split a starter batch. Then oxygenate one and pitch afterwards. In the other pitch the yeast and then airate and see which has faster signs of fermentation and more total yeast cells after fermentation. :D These links do not address the airation subject directly, but do explane cell walls, membranes and oxygen issues. Any one have more information?

http://hbd.org/hbd/archive/3099.html#3099-5 "Yeast growth"

http://consumer.lallemand.com/danstar-lalvin/fortnightyeast.html#oxygen

The Lallemand FAQ article also points out that the best time to add oxygen to wort is 12-24 hours after fermentation has started. It does not mention damage caused by adding oxygen after fermentation has started. It does mention that adding too much oxygen can produce a thicker cell wall, and make it more diffacult for the cells to bud.