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Thread: Dissolved Oxygen levels in barrels after aging

  1. #1
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    Dissolved Oxygen levels in barrels after aging

    Does anyone have dissolved oxygen values for beers aged in barrels? I am looking to develop a chart showing starting DO values in beer going into barrels, the level after 3 or so months, and values after 1+ years in a barrel. Let me know if you have values you could supply me with

    Cheers,
    James

  2. #2
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    Hi James,

    The problem with this methodology is that oxygen reacts as it enters the barrel; it's not like it waits around as free oxygen for you to measure. For the same reason, measuring packaged DO/headspace O2 later than immediately after packaging is fairly useless.

    The best I can come up with off the top of my head would be to measure compounds that indicate oxidative damage, e.g. trans-2-nonenal, but those types of compounds can be moving targets as well.

    Joe

  3. #3
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    Very good point.

  4. #4
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    There are a great number of factors that can influence the DO2 level over time - initial level, presence of yeast, etc. Generally oxidation is quite rapid, changing over hours rather than days, months. There is a method for measuring oxidation using dichlorophenol indophenol but from my recall that can be quite variable and results also depend on the level of oxidation pre-packaging.

  5. #5
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    I tried to use that method in a large (2 million hl / pa) brewery when I first came into the business, back in '76 (scary!!) to try and check the calibration of the then new fangled electrochemical oxygen sensors. This was a really good way to waste hours of time. So I really don't recommend it. Fortunately I got enough vaguely sensible results to confirm the EC sensor was "reasonably" accurate, and certainly a damned sight more repeatable than colour methods. Also, colour determination only worked reasonably well on lagers and very pale beers - useless on stouts and dark milds, brown ales etc.
    dick

  6. #6
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    Dick - are you thinking of the indigo-carmine method? DCI is used as a redox indicator, so doesn't give a measure of oxygen level itself, but rather the reduced-oxidised state of the sample.

    The DCI method was to add a small quantity (as I recall 0.55ml...strange amount) to a 10ml aliquot of beer then shake it manually alongside a 'blank' of the same beer. The DCI changes from blue to colourless at a rate that is dependent on the amount of oxidation present, so the test sample colour returns to match the 'blank'. The time taken had to be 20sec +/- 2sec. Outside this, the analysis was repeated with either more or less DCI until the target time was reached. The quantity of DCI used, multiplied by a factor, gave a quantitative measure of the redox state of the beer, ie. whether it has previously been oxidised significantly.

    I spent every Friday afternoon doing these as part of my then employer's UK production contract with a large Australian brewer.

    However, returning to the original question...assuming the barrel is purged of air prior to filling, I would expect the oxygen level to drop in a similar profile to bottled/canned beers, ie. quickly immediately after filling such that, at 6+ months after fill, the levels were well into single-digit ppb tending towards zero.

  7. #7
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    Hi Tim

    I think you are right - Indigo Carmine method, or what passed for a method. I had to produce standard tints for a range of oxygen levels, and then try ang get pure beer samples (i.e. no additional oxygen from the bottle) and inject liquid (presumably IC as you say). However getting samples of beer with no additional oxygen from the water in the sample bottle, or not picking up any oxygen when the sample was injected, proved nigh on impossible. If memory serves me well, it was a digox, for what that is worth.

    Cheers
    dick

  8. #8
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    Quote Originally Posted by dick murton View Post
    ...and then try ang get pure beer samples (i.e. no additional oxygen from the bottle) and inject liquid (presumably IC as you say).
    We used sample bottles with septa, 2 hypodermic needles and a lot of *!?#*#*! language, as I recall!

    DO2 meter could have been either Digox or IL540...the latter used a pre-mounted membrane (I still have one on my desk as a reminder...)

  9. #9
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    septa, 2 hypodermic needles and a lot of *!?#*#*! language

    My experience exactly!
    dick

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