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Thread: Hot Side Aeration

  1. #1
    Join Date
    Nov 2004
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    Henley-on-Thames, England
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    Hot Side Aeration

    Hi Guys,

    I've been brewing on a new plant that has some hot side aeration (HSA)
    issues in the process...specifically, splashing in the underback/grant and
    the kettle.

    What should I be looking for in my packaged product (keg now, bottles
    shortly) as a result of this HSA? Currently the kegs are kept cold and
    consumed within 3-5 weeks and I'm not picking up any flaws from it. Mash is
    single infusion at 65C.

    Am I right to be worrying about it? Or, is this a case of HSA really not being
    a problem?

    I think I'll just fix the problems and stop worrying...but any advice and experience appreciated.

    Cheers,
    Jeff Rosenmeier (Rosie)
    Chairman of the Beer
    Lovibonds Brewery Ltd
    Henley-on-Thames, Englandshire
    W: www.lovibonds.com
    F: LovibondsBrewery
    T: @Lovibonds

  2. #2
    Join Date
    Oct 2002
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    Chesterfield, UK
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    1,709
    Where are you aerating ? It sounds like you are aerating in the kettle. You can only realistically aerate just prior to the wort cooler, so the oxygen does not stay in contact with the wort to appreciably oxidide the wort, but is immediately cooled so the oxygen stays in solution If you are trying to oxygenate / aerate in kettle, then virtually all will immediately flash off. You will have virtually none remaining in solution when the yeast hits the wort.

    Hot side aeration with ales is not normally too much of a problem, especialy if using air rather than pure oxygen. It is the lager brewers who voice concerns over colour pickup in particular, and because so many are low flavour products - some oxidation can be picked up - but often not in final package if the beer gets oxidised due to poor O2 control or overpasteurisation

    Cheers
    dick

  3. #3
    Join Date
    Nov 2004
    Location
    Henley-on-Thames, England
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    Thanks for the reply Dick!

    Sorry, to be clear, we're not aerating in the kettle and the underback on purpose...it's just the design of the system. I was just wondering if it was worth worrying about or not as you often hear of people fearing hot side aeration.

    We aerate again on the way to the fermenter (cold side) with regular old air, and have decent results...

    Cheers,
    Jeff Rosenmeier (Rosie)
    Chairman of the Beer
    Lovibonds Brewery Ltd
    Henley-on-Thames, Englandshire
    W: www.lovibonds.com
    F: LovibondsBrewery
    T: @Lovibonds

  4. #4
    Join Date
    Jan 2003
    Location
    Palau
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    HSA issues

    There are those who don't think HSA is much of a problem (outside of color increase). They argue that the wort is too hot to dissolve oxygen and that any oxygen that does dissolve will be flashed off just as quickly. Hot aqueous solutions tend not to dissolve gases as well as cool liquids, it's true. I believe that HSA is a problem based not on dissolved oxygen, but on the much quicker reaction rates at high temperatures. Any oxygen entering the wort would likely react very quickly to promote staling reactions before it flashes off. Hot aqueous solutions tend to be more reactive than cold ones. Much more so. And the reaction doesn't need oxygen to dissolve--it can still occur as a surface phenomenon. Splashing increases the surface area. These staling reactions include trans-2-nonenal, which tastes like wet paper/cardboard and often takes time to develop. I've found that they can limit shelf life substantially. That being said, if you store the beer cold, and serve it all before 5 weeks, then maybe your concern hasn't had time to manifest itself. Why bother, right? Let sleeping dogs lie. But then again, for the minimal effort it would take to decrease the HSA problems you've outlined, you could gain some minimal increase in quality. Up to you! Cheers!

  5. #5
    Join Date
    Mar 2006
    Location
    Germany
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    184
    Whether or not your beer is fresh, there can be evidence of hot side aeration in the flavor, especially in lighter beers. A harshness in the aftertaste is not uncommon, instead of pleasant bitterness from the hops. Then there's the aforementioned cardboard, etc. later, as well. Even those fruitier, darker beers will benefit from lack of hot side aeration.

    As Gitchegumee and many others have pointed out time and again on this forum: there is a big difference between oxidation and oxygen going into solution.

    The heat during mashing, sparging, boiling and in the whirlpool provides the energy of activation for many reactions including oxidation. These are chemical reactions, which change the molecules from good to bad things for your finished beer (for the most part, although melanoidins are made, as well). When the wort is cool the energy of activation is low and therefore not as much oxidation occurs, although some still does. This is one reason that aerating is better than oxygenating.

    When oxygen goes into solution in the beer, like salt does in water, it is still itself, i.e. no chemical change has taken place - this is merely a physical occurrence. The solubility of oxygen goes up as the temperature drops.

    These are the two main reasons to get the wort down to a low temperature during cooling.

  6. #6
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    Oct 2002
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    Chesterfield, UK
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    Actually I think you'll find that you kill the yeast if you leave it hot. But seriously.... I wouldn't worry too much about hot aeration if you are brewing darker ales, and really you probably won't really notice much with lighter ales or lager styles. I would be more concerned about the ability to sterile filter the air / oxygen consistently. Hot side aeration has a distinct advantage there, and unless you spnd a fortune with Pall / DomnickHunter et al, then you are probably better off going for hot side aeration

    Cheers
    dick

  7. #7
    Join Date
    Oct 2013
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    Ireland
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    Chemical reactions and hot side aeration

    It's interesting to note that 100 years ago, brewers actually valued hot side aeration as an important part of the process. Prominent brewing scientists like Jean de Clercq talk about it. It's supposed to
    * darken the wort
    * reduce bitterness
    * help the beer clear
    The wort would oxidise at high temperatures during the first few minutes of its residence time in the coolships. Here's a passage from Moritz and Morris's textbook on brewing from Victorian times
    Oxygen taken up by hot wort plays a different part. It is not mechanically dissolved, but is chemically fixed, entering (as Pasteur shows) into some form of combination with the hop resins. It is this form of aeration that plays so important a part in the natural clarification of beer, or in its ready clarification by isinglass finings. When resins are modified by chemically fixed oxygen, they conglomerate into particles of greater density: these sink easily to the bottom of the storing vessel, forming a compact sediment, and leaving the supernatant beer bright. When, however, for some reason or other, the aeration of the hot wort is incomplete, the resinous substances, instead of conglomerating and acquiring the density necessary for their rapid deposition, remain suspended in the finished beer in a very fine state, and in that condition they are equally unready to deposit naturally or to yield to the action of finings. (E. Moritz and G. Morris, A Textbook of the Science of brewing, 1891, p. 272)
    A lot probably depends on the style of beer and the ingredients you use and the rest of the process. I don't know if it would be suitable for beers of today, but I reckon that brewers 100+ years ago probably knew how to make good beer.

  8. #8
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    But don't forget that oxidation when using a coolship would undoubtedly be greater than nowadays if using a plate heat exchanger as the residence time at above say 70 C is measured in seconds rather than minutes or probably more like hours. So I would expect darkening and flavour changes to be far less of a problem now.

    I've used hot aeration with ale, mild and stout worts without a problem, but admit to not having used it with lager colour worts.
    dick

  9. #9
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    Oct 2013
    Location
    Ireland
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    HSA harsh bitterness or reduced bitterness?

    I find it interesting that HSA aeration is said to lead to a harsh aftertaste by some but also reduced bitterness by others.

    I think we have to take everyone's observations at face value, which suggests that there's another factor at play.

    Reading around a bit, when authorities like de Clercq attribute benefits to HSA, they are talking about oxidation reactions that happen after the boil, whereas authorities like Kunze and Narziß who attribute negative consequences to HSA are talking about oxidation during malting, milling, mashing and lautering (oxidation of malt derived lipids in particular).

    So the take home is:
    HSA in mash --> BAD
    HSA in hop-back/whirlpool/coolship --> GOOD

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