Aeration and Oxidation differences...

[deranged_hermit]

What is the difference between Aeration and Oxidation. I know that you are supposed to avoid oxidation, and that aeration is a procedure during the beginning stages of brewing. but both seem to be the same to me. exposing the wort to oxygen, just at different times, am i correct? what are some aeration procedures you all use and recommend for a beginner brewer?

thanks in advance

 

[BlightyBrewer]

You are correct.

Aeration is the act of introducing as much oxygen into the beer just prior to pitching the yeast. The yeast need oxygen to multiply before starting the feast on the maltose in your beer and converting it to alcohol and CO2.

Oxidation is the contamination of the beer during and after fermentation, leading to off flavours.

Aeration techniques range from shaking the fermentor, pouring the wort between two vessels repeatedly, stirring vigorously, using an aquarium pump, filter, and airstone, or using an airstone with a clean, bottle O2 supply.

 

[Kaiser]

Aeration/Oxygenation refers to dissolving O2 in the wort.Oxydation refers to the binding of oxygen in a chemical reaction and it requires a prior aeration/oxygenation. It only poses a problem to stability and flavor if it happens at higher temperatures (mash, boil, pre-chilling) or in the presence of alcohol (during and after fermentation). There is only one window in time, when you want to (need to) aerate/oxygenate: the cooled wort. In this case the oxygen will be taken-up by the yeast (which is also a form of oxyadation) before it can react with the alcohol that will be produced later.

Kai

 

[BlightyBrewer]

The oxidation at high temps that Kai refers to is know as Hot Side Aeration (HSA).

 

[Kaiser]

It is interesting to note that HSA has the same effects as getting oxygen into your fermented wort (now it is beer). At higher temperatures the oxygen can attach itself to compunds that remain in the wort. But since this is a rather loose connection, the oxygen is released after time and will react with the fermantation products leading to the same staleness as aeration would do.

But don't worry about HSA unless there is lots of spashing of hot wort in your system.

Kai

 

[MightyTaco]

Has anyone ever had the siphon not start out real stong where it took 20-30 seconds for the beer to completely fill the transfer tubing causing some splashing/swirling actually inside the tube? This happened to me while tansfering from the primary to the botteling bucket in my last batch. Is this creating too much airation at this point?

 

[Kaiser]

This happened to me while tansfering from the primary to the botteling bucket in my last batch. Is this creating too much airation at this point?

I know what you are talking about and this used to worry me to. But there is only a little amount of air in therse bubbles (we are not talking about leaks in the hose-tube connection where you pull in air) and only 20% of that air is O2. This is way to little to cause an effect. And the good thing is, that you have some live yeast around that will pick up any O2 available to them.

Kai

 

[Baron von BeeGee]

Has anyone ever had the siphon not start out real stong where it took 20-30 seconds for the beer to completely fill the transfer tubing causing some splashing/swirling actually inside the tube?

Nearly everytime I start a siphon. What I do is pinch the tube gently where it's not full of wort/beer and that seems to force the air bubble out and get the full siphon going much faster than letting nature take its course.

 

[Denny's Evil Concoctions]

As for cold side oxidation.
You want O2 in your Cooled wort for the first 24 hours. That is when the yeast is in it's aerobic reproductive phase. After that it goes anerobic and the O2 is no help to the yeast. The CO2 the yeast produces scrubs the remaining O2 out of the fermenting wort.

Be especially carefull when transfering to the secondary, since most of the fermentation is complete and CO2 production is minimal, and will not scrub any new O2 out of the batch.

If you find that you have splashed to much or are excessively paranoid, you can add a 1/2 teaspoon of Ascorbic Acid to a 5 gal batch to reduce oxidation.