Hot Side Aeration

Get advice on making beer from raw ingredients (malt, hops, water and yeast)

Hot Side Aeration

Post by OldThumper » Tue Oct 19, 2010 10:06 pm

Following on from my recent post about my disastrous last few batches of beer (viewtopic.php?f=2&t=36401) can somebody please clarify if Hot Side Aeration really is an issue or not?

I read in JP's How To Brew that you must not splash the hot wort after masing prior to the boil because it may well causes oxidation later on. Has anybody experience of this? The same applies after the boil when cooling.

My wort gets very much splashed after mashing because I run the mash off in to 2 buckets (which are about a 60cm drop from the mash tun) and then I pour the 2 buckets of wort in to my boiler (my boiler is also used for the HLT). IS this likely to cause an issue? I assume lots of other folk do something similar?

If splashing the hot wort is not an issue then the only other cause I can think of is some sort of infection in my fermenter. I was using lots of milton tablets to sanitise for some time but I have just switched to bleach to see if this helps. In the post above I did add that may be DMS is the issue but I am clutching at straws a bit, desperately trying to solve it by considering everything I have read it seems :(

Thanks again all.


Re: Hot Side Aeration

Post by Carpking » Tue Oct 19, 2010 10:13 pm

Hi OT.

I dont think HSA is likely with our british 2 row malts. I too splash hot wort around and dont worry about it at all.


User avatar
Under the Table
Posts: 1120
Joined: Sat Dec 12, 2009 9:55 pm
Location: Cambridge, UK

Re: Hot Side Aeration

Post by Naich » Tue Oct 19, 2010 10:26 pm

The common view on here is that it's just a horror story told whenever brewers sit round the camp fire telling tales of adventure, open taps and boil overs. If it does have an effect it would be very slight as I don't know of anyone on here who has suffered from it in any noticeable way. Your most likely cause is infection and using a better steraliser than Milton tabs will hopefully help. I use Ritchie steraliser which seems pretty good.


Re: Hot Side Aeration

Post by OldThumper » Tue Oct 19, 2010 10:31 pm

Thanks for the reply Carpking - the answer I was hoping for, I think!

Thanks Naich as well! I always thought that poor sanitising would cause an infection or off flavours that would be "vinegary", but I guess other flavours/aromas may be caused as well. This is why I initially dismissed sanitising as a potential issue, and it is not detectable during samples taking during fermentation. Only after at least 1 to 2 weeks onwards is it evident.


Re: Hot Side Aeration

Post by dave.wilton » Wed Oct 20, 2010 8:18 am

I did a lot of reading about Hot Side Aeration for a presentation at London Amateur brewers. I found was that there is very little scientific information available to the homebrewer about this, most of the discussion is still held in the journals. The forums contain a lot of hearsay with nobody actually supporting views.

The main impression I got was that the science behind the issue is sound, so it can have an affect. However, it is a very complex issue with many other factors affecting beer stability as well. The most interesting 'article' I found (which really supports this view) is an interview with "Dr. Charles Bamforth on hot side aeration with Jamil and John Palmer".

The best tip I came across was that aeration is far more of a problem in secondary / bottling so if you are worried start at the end of your brew and work backwards. Most things to put in place are easy and cheap, such as a pipe from mash tun to boiler, so I just do them anyway.

At the bottom are a list of freely available articles on the internet. If anyone would like my complete document PM me

Here are a list of tips from that literature for avoiding in the homebrew environment, however, some are contradictory:

Preventing in the home brew environment:

The grain in the mash should be underlet or infused with hot water from the bottom up. By infusing in this manner, stirring of the grains to insure uniform mixing of the grain and hot water is not necessary. By not stirring the water into the mash, hot oxygen reactions can be reduced. (Millspaw, 1992)

BYO recommends the following technique. Add 3L of water to the mash tun, then carefully add 1kg of malt and gently mix malt into water. Continue this process until all of the malt and water has been added. This process will take longer so be sure to adjust for temperature losses

Palmer (2006) recommends adding water a gallon at a time (to all of the malt) and gently mixing the water in without aerating. He states that HSA is promoted by lipoxygenase at this stage, although as Fix sates the levels required by this reaction are very low.

Millspaw (1992) recommends adding specialty malts only in the mash out. The melanoidins formed at 77°C/170°F are more stable than those formed at the lower temperatures of conventional mashing. By adding these specialty malts only in the mash out, the brewer can make his mash more efficient by optimizing saccarification, maximizing the formation of melanoidins. This will lead to smoother and rounder flavours from the specialty grains, as well as more stable and clearer beers (Millspaw, 1992).

Mash recycling tends to remove a lot of large particulate matter that would otherwise be present in the boil. Millspaw (1992) feels that these techniques are a source of HSA and that the particulates (husks and grits mostly) provide a place for proteins to clump onto during the boil and then settle out more effectively in cooling.

However, Fix emphasises that one of the most important points it achieving reasonable wort clarity in lautering (Fix, 1999).
Transferring to the boiler

In practice if the power is switched on immediately the heating element is covered any uptake of oxygen is immediately driven off by the action of the boil (Alexander, 2009). Personally, I now collect using a tube into a 5 gallon bucket and then siphon from my collection vessel into the boiler.

Post Boil
Older books used to advocate pouring the boiling hot wort from one bucket to another to add oxygen and cool it. Unfortunately, the wort is still hot enough to oxidise and not aerate. Pouring down the side of the bucket to minimise splashing doesn’t help either since this increases the surface area of the wort exposed to the air (Palmer, 2006). Ensure the wort is below 27C before aerating air (Palmer, 2006)

In fresh beers both T-2-N and its precursors are bound up with natural sulphur compounds from yeast metabolism. However, after a lag, which is reduced if thermal or mechanical abuse occurs, the effects of T-2-N become discernible. Millspaw (1992) and Bamforth (2009) also emphasise the importance of storage temperatures. The Arrhenius equation shows that for every 10C rise in temperature a chemical reaction will perform 2-3x faster. For example if you store a beer at 20C a beer may stale in three months. A stored beer at 30C will stale in one month.

Additives could be one solution, however, the effective additives tend to have unacceptable side effects and the neutral ones rarely seem to work (Fix, 1999). The most likely additive to be of any use in the home brew environment is Potassium Metabisulphate (Campden Tablets) added to the mash (Fix, 1999, Spencer, 2006) which binds to carbonyl compounds. These haven’t gained favour in the commercial world because above certain 10ppm levels they must be stated on packaging and we “can let the wine have that dirty labelling” (Bamforth, 2009). It may therefore be an option to us, the bisulphates will bind to the staling aldeydes and masks their presence. However, these bonds are rather short lived in beer, and when they are broken, the staling aldehydes fully reveal their presence (Fix, 1999)

The effects of oxygen pick-up after fermentation are more apparent and severe than the effects of hot-side aeration. If you are thinking about changing your brewing procedure to avoid oxidation, you should begin addressing oxygen pick-up from the end of the process and work your way forward toward mashing (BYO). It is a complex interplay of reactions, including unsaturated fatty acids, melanoidins and iso-alpha-acids. It is therefore too simplistic to focus on just T-2-N as the sole cause of staling in beer (Bamforth, 1999).

Alexander, J (2002). Hot Side Aeration (HSA). Brewers Contact. 9, 2-5. Also published at http://www.craft
BYO. ... -mr-wizard
Bamforth, C. (2009). Hot Side Aeration. The Brewing Network Start at 13 minutes
Fix, G. (1999). Principles of Brewing Science, Second Edition. Brewers Publication (sorry not on the internet)
Garrod, P. (2008). Hot Side Aeration. Brewers Contact. 8, 4-5 Also published at http://www.craft
Spencer, J. (2006) Hot Side Aeration Exeriment 02/11/06. Basic Brewing radio.
Millspaw (1992). Hot Side Aeration and Beer Stability. Zymurgy. 15. Also published at http://oz.craft
Last edited by dave.wilton on Wed Oct 20, 2010 8:55 am, edited 2 times in total.

User avatar
So far gone I'm on the way back again!
Posts: 7701
Joined: Fri Mar 19, 2010 6:22 pm
Location: Derbyshire, UK

Re: Hot Side Aeration

Post by Kev888 » Wed Oct 20, 2010 8:48 am

Excellent stuff - thanks for sharing that!


User avatar
It's definitely Lock In Time
Posts: 6132
Joined: Sun Jun 03, 2007 11:56 am
Location: Mashing In Blackpool, Lancashire, UK

Re: Hot Side Aeration

Post by Aleman » Wed Oct 20, 2010 9:02 am

Nice information Dave, I would be interested in seeing all the stuff you have accumulated although those references will do for a start :D

What they fail to address though, is that the precursors of T2N are more prevalent in 6 row barley than in 2 row, and the levels of these precursors are (or should be) carefully controlled by the maltster . . . when there is a cock up then malt is produced which has the potential to exhibit HSA. However, you then need to consider beer style, in a pale American Standard Beer, made with 6 row and corn or rice, there is absolutely nothing to hide any possible flaw . . .plus there is no dark malt that can provide antioxidants . . . . with extended storage (a couple of months or more) then these beers are likely to exhibit HSA, if any beer is likely to. Remember that a lot of these beers entered into competitions like the NHC have been aged in bottle for some time as they will have already been through earlier qualifying rounds.

Now consider a typical British bitter made with crystal and a little dark malt. The level of t2n precursors is already low, the dark/crystal malts provide a natural antioxidant, and, its not hanging around for moths . . . . . HSA an issue . . . unlikely. I think in the last 30 Years of brewing I have tasted one home brewed beer that exhibited HSA . . . and that was a pale beer that had been made with 6 row malt.

In short HSA is not likely to be an issue in the UK, and will only show itself after extended periods. If you are getting cardboard aromas/flavours then look to other practices before thinking HSA


Re: Hot Side Aeration

Post by dave.wilton » Wed Oct 20, 2010 9:07 am

Aleman, I did pick up on this point, but really struggled to find a credible source where it was discussed. Focus does seem to have shifted towards the maltster, but not to the extent where we as homebrewers can buy low T2N potential malt, we get what we are given! Definitely worth pointing out though and it would help if the literature were more clear when considering countries of origin because it is very important

As for the buffering capacity of dark malts that is discussed in a few of the links I sent, the Milspaw one springs to mind but also FIx if you can get it


Re: Hot Side Aeration

Post by RdeV » Wed Oct 20, 2010 11:00 am

Ever heard any home brewer say, "Y'know, a while ago I had such monster HSA problems, but since I changed X it went away"? No, I've never heard it, not likely to either. At homebrewing scales, its just a fairy tale. Far more likely to see post- ferment oxidation. So just relax is my advice...

My relevant anecdote: Earlier this year I poured a BIABed, near- boiling Munich Helles wort through a big sieve that was placed in a big funnel into a No- Chill cube. Nothing nice about that lot, it has everything against it, but I also entered it into the State competition and it placed 3rd. Oh dear... :oops:

Terrific info though guys, thanks for the share. :D


Re: Hot Side Aeration

Post by dave.wilton » Wed Oct 20, 2010 11:17 am

hot side aeration can be something that isn't immediately obvious, it affects the long term stability of the beer. This is probably why most home brewers don't have an issue!

User avatar
Site Admin
Posts: 10295
Joined: Sun Aug 22, 2004 1:00 pm
Location: Washington, UK

Re: Hot Side Aeration

Post by Jim » Wed Oct 20, 2010 11:51 am

It seems that many British commercial breweries positively invite HSA - it never causes a problem for them, so why should it for us?

My advice is to forget HSA and concentrate on factors that really do affect the quality of your brews.
There is an eagle in me that wants to soar, and there is a hippopotamus in me that wants to wallow in the mud. [Carl Sandburg]

JBK on Facebook
JBK on Twitter


Re: Hot Side Aeration

Post by gnorwebthgimi » Wed Oct 20, 2010 11:57 am

I went through this ghost/gremlin in the beer issue and thought it was HSA because I was splashing my wort around and filtering it a lot. I altered to ensure that I avoided this and there was no difference.

HSA is irrelevant for homebrewers, but I would heed the advice about 6 row barley.


Re: Hot Side Aeration

Post by boingy » Wed Oct 20, 2010 12:30 pm

For me, it's a bit like designing a car and worrying about whether the choice of paint colour will affect the fuel economy. Maybe it does, maybe it doesn't, but if you have reached the point where that is all you have to worry about then the car/beer is probably already pretty good...

You might as well worry about whether the phases of the moon have a tidal effect on fermenting wort (I find that the neap beers are the worst).


Re: Hot Side Aeration

Post by OldThumper » Wed Oct 20, 2010 12:51 pm

Thanks all for the replies :)

There are some useful links there Dave W and I will take a read soon.

I will forget HSA and concentrate on sanitising better.

Is it possible that an infection could not be noticeable until after primary fermentation has finished, say 7 days after the start? If so, then I could easily be suffering with an infection that grows slowly (it starts slowly because the yeast is so active in the first few days?). Do infections always smell bad? My beer has not been bad smelling, just neutral really with no hop aroma or taste and very dry tasting. Can that be a cause of poor sanitation or does it have to be vinegary, like a dodgy pint I often get in the pub?


Re: Hot Side Aeration

Post by dave.wilton » Wed Oct 20, 2010 2:31 pm

There are some useful links there Dave W and I will take a read soon.
As others have said it certainly isn't up there at the top of the priorities! I did all the reading to save others from doing it at LAB. The general consensus there is it is not to worry about it.

Post Reply