Aeration: Which way is it?

So I'm brewing a Scottish ale tonight and I have had plenty of time to think.

If I were to ask about how to properly aerate wort in a big carboy with plenty of exposure to the air, people wouldn't recommend that I simple shake the carboy - swing that thing around like I'm a Lord of the Rings movie extra - because they would say that is barely effective.

However, if I were to ask about shaking a rather sealed carboy during fermentation to agitate settled yeast, people will openly worry about oxygen getting in! I've read some people don't even so much as touch the fermenters during this phase for fear of oxidation.

Which way is it?

I believe you are confusing oxygen, which is vital for yeast reproduction, often called aeration for an off flavor called oxidation. Oxidation can happen with very little oxygen present.

FWIW I NEVER recommend picking up a carboy full of anything, you are an accident waiting to happen. Get an airstone and O2 tank or a pump and save yourself and the carboy.

It doesn't matter if you venturi, shake, whisk, aerate with a stone and pump you will only ever get 8ppm into solution. Yeast prefer 10ppm at a minimum. 60 seconds of pure o2 with a stone will get you 12ppm.

It's both. There is no contradiction.

Edit. What zamial said.

Yeast need oxygen to do their thing, so before fermentation = oxygen good. After fermentation, exposure to oxygen can lead to oxidation and cardboard-y off flavors, so after fermentation = oxygen bad.

And also what zamial said.

Zamial said:

FWIW I NEVER recommend picking up a carboy full of anything, you are an accident waiting to happen. Get an airstone and O2 tank or a pump and save yourself and the carboy.

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I use plastics ones and I haven't actually lifted them up to aerate them - done more of a vortexy rotation while it sits on the ground. Performing a pseudo hammer-throw with the carboy was just for example. I try to splash it around in the kettle after cooling or during the pour into the fermenter. I'm working on putting together an aquarium pump setup but it's either that or a propane burner setup for now.

My major issue is that imparting air isn't said to be effective when you can shake up an unpitched wort however you want but then the effect of air becomes an issue after fermentation and people worry about the slightest introduction of air at that point.

But if even shaking the thing up isn't going enough to impart air then why is it going to be a problem for something less intense like trying to agitate settled yeast?

Maybe I'm not splitting enough hairs when it comes to taking about oxygen vs. air but oxygen is the only thing I can think of in air that will be reactive.

While I don't think it would be a massive problem, the primary reason is that yeast need oxygen to do their job, as more yeast settle to the bottom they aren't active anymore, even rousing them may not get them active, so if you introduce more oxygen to inactive yeast, you're in trouble.

Arrheinous said:

But if even shaking the thing up isn't going enough to impart air then why is it going to be a problem for something less intense like trying to agitate settled yeast?

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you're missing the point. while shaking it may not provide as much air into solution as the yeast would like, it imparts way more than enough to oxidize a beer. oxygen is used for yeast reproduction, once they stop reproducing any more oxygen exposure leads to oxidation.

It always annoys me when i see posts that say you have to do this or that in order to make good beer. As in the case for using an oxygen tank to aerate the wort, i dont and i'm quite certain that good beer has been made throughout history without the use of an O2 tank and oxygen stone. The truth is you're beer will be fine using agitation method of aeration. Will your fermentation be more vigorous with pure O2? Maybe but doubtful. Ive made lotsa batches using the agitation method and have great results. As for oxidation after fermentation, i transfer my beer manually into a bottling bucket. I am careful not to splash the beer around but im not fanatical about it. Again, ive never had an issue with oxidation either. Relax... Hav a home brew.

Shaking is quite effective in oxygenating the wort. I use O2 but there was a pretty nice article comparing shaking vs using an aquarium pump (pumping ambient air into the solution). They found that the pump didn't do much and the shaking was quite effective, it was capable of infusing a good amount of O2. Using pure O2 is more effective, but shaking is sufficient in most cases.

All I did was stir it fairly good once I took it off the flame, then I poured it through a strainer into the funnel in to my carboy. (the strainer served two purposes, one to get the hop pellets out and two, it added a bit of air to the wort)...

Oxygen early is good as the yeast will metabolize it when forming sterols which allow for permeability of the cell wall by sugar. This is commonly called the "lag phase" or "initial phase". The yeast move on from there to the exponential growth phase, and then the fermentation phase. It's during the fermentation phase that fatty acids are produced. These are what get oxidized to produce the dreaded card board taste.

Therefore, like others have said: Oxygen early is good. Oxygen late is bad.

I have a blog post about this coming up later this month.

You need 1ppm of oxygen per degree Plato of wort. Using air the wort will saturate at 8ppm fairly quickly by agitation. Using pure O2 levels of up to about 50ppm can be achieved.

For a graph of yeast activity see this:
http://woodlandbrew.blogspot.com/2012/12/yeast-cell-growth-observations.html

Question... when you put your beer into the carboy, does it splash alot?? that is usually enough to get a good amount of O2 into the wort. any splashing will get the beer good and oxygenated. too much O2 can have an adverse effect on yeast as they can die with too much O2. the amount of O2 necessary is the same from the atmosphere. this O2 is used to propogate more yeast until they start anaerobic fermentation. The amount of O2 needed at the beginning of fermentation can be reduced by making a large and healthy yeast starter.

https://www.homebrewtalk.com/f13/aging-beer-facts-myths-discussion-84005/

this gives a good discussion about aeration

You could always get a couple of food safe buckets and transfer between them a couple of times before putting into the carboy. Picking up and shaking a full carboy is bad juju. One slip and you can find yourself banned from brewing in the kitchen ever again.

If you use dry yeast, you don't even need to aerate at all. According to Danstar's own website (provider of yeasts like Nottingham), aeration is not even necessary as their yeast accumulates all the nutrients it needs before being dried.

BikeAndBrew said:

If you use dry yeast, you don't even need to aerate at all. According to Danstar's own website (provider of yeasts like Nottingham), aeration is not even necessary as their yeast accumulates all the nutrients it needs before being dried.

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Not all together true as stated in this article referenced from their site.

http://www.danstaryeast.com/articles/aeration-and-starter-versus-wort

Regardless, not providing proper aeration to your wort is poor brewing practice and can be read in the book Yeast by White/Zainesheff

http://www.danstaryeast.com/frequently-asked-questions

I was referencing the above section from their site. I use dry yeast only, have not ever made a starter, & aerate only to the extent that pouring from my brew kettle to the fermenter provides with excellent results. As with most things in brewing, YMMV.

BikeAndBrew said:

http://www.danstaryeast.com/frequently-asked-questions

I was referencing the above section from their site. I use dry yeast only, have not ever made a starter, & aerate only to the extent that pouring from my brew kettle to the fermenter provides with excellent results. As with most things in brewing, YMMV.

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I get that and yes it is not necessary to make a starter with dry yeast but it is preferred to rehydrate it. Starters are recommended for liquid yeast.

As for aeration, it is highly recommended and an important component for yeast health and proper fermentation. I am not trying to argue with your results, only pointing out best practice in the brewing process

GunnyB said:

You could always get a couple of food safe buckets and transfer between them a couple of times before putting into the carboy. Picking up and shaking a full carboy is bad juju. One slip and you can find yourself banned from brewing in the kitchen ever again.

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Even better, what I do is just pour it through a sanitized metal strainer into my buckets.
Do that twice and you'll have a huge bit of foam on top of the wort from the oxygenation.

I usually just keep my transfer tube at the top of the bucket or carboy and let it splash as it's going in. Maybe move the hose back and forth if I'm board.
It's always worked well for me, but I'm going to get an O2 tank and stone because I'm building a much more "contained" system that won't be splashing the wort when I transfer.

If you can splash it around though, you should be fine.

Once your beer has been fermenting vigorously for a day or so, the yeast have consumed almost all of the oxygen in the fermentor. At this point (assuming a sealed fermentor with an airlock), there is no danger of oxidation from any additional stirring/splashing that might happen.

Of course there really is little reason to want to swirl an actively fermenting wort. The yeast do a pretty good job of that by themselves. The only times you might want to swirl are if you are using a yeast that floculates very well, and/or you are brewing a BIG beer. In these cases it might be good to give the yeast a little rousing to keep them active

A lot of good points.

Someday I'm going to just compare all the different methods of aerating and try to test them with some of the equipment in the lab I work at. I could try to measure some level of dissolved oxygen.