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Thread: Aldahydes

  1. #1
    Join Date
    Apr 2003
    Location
    Rutherglen 3685 Vic Australia
    Posts
    29

    Aldahydes

    What does any know about aldahydes?
    My beer after being stored filtered seems to have a papery flavour, but its not oxidation or old ingreidents, the beer is carbonated & under pressure. I looked up the flavour profile it has & found that aldahydes produce this flavour.
    Does anyone know anything?
    I know they can be produced in fermentation & can occure in to warmer conditioning temps, but what about filtered beer?
    How would it effect the shelf life of the final product especially if it is pasturised?
    MIKE S

  2. #2
    Join Date
    Apr 2004
    Location
    Hastings, MI, USA
    Posts
    263
    Well from what I can see, Aldehydes aren't really responsible for 'papery' characteristics in a beer: Aldehydes, sorry about the crappy MIDI, the controls are at the bottom of the page.
    As far as I know, 'papery' tastes/aromas are from oxidation of wort --- although you state that it's not oxidation, I can't specifically nail the blame for that flavor on Aldehydes.

    --Rob
    Last edited by RobZamites; 05-17-2004 at 03:52 AM.

  3. #3
    Join Date
    Oct 2002
    Location
    Tadcaster, Yorkshire, UK
    Posts
    1,099
    Aldehydes are a result of oxidation, not just of the wort, but tends to be due to excess oxygen in presence of low levels of yeast (possibly due to oxygenation late in the fermentation when there is insufficient yeast activity to mop up the oxygen rapidly and completely), or due to bacterial contamination (some yeasts tend also to produce aldehydes) The description is often described as being that of bruised apples, or sometimes "grassy" - i.e new cut grass.

    Papery or cardboardy flavours tend to be produced when filtered beer is oxidised. This is exacerbated by pasteurisation, though I guess this will not apply in your case.

    The mere fact that the beer has been carbonated does not ensure the beer is free of oxygen, particularly after packaging.

    Basically, after the end of fermentation, the potential for oxygen pickup needs to be minimised, flushing lines and tanks with CO2 nitrogen / water as appropriate. Don't forget that if you carbonate beer with bought in CO2 it must be food grade AND oxygen free.

    Pasteurisation will not eliminate off flavours, often making them worse, or permitting rapid chemical reactions to give other off flavours.

    Hope this helps

    Dick
    dick

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