Oxidation In Wort ...

[simpletotoro]

hi ...if you couldn't be buggered reading this or replying to it fair enough...
but here goes anyway..i've been reading (or trying to anyway ...is long) about the no chill method ...particularly about the botulism bit...anyway i read this post in there and am now full on confused..

QUOTE(Darren @ Feb 15 2007, 05:02 PM)
Hot wort will not absorb oxygen.Boiling wort will absorb none!! I see many of you are also squeezing your cubes to exclude ALL the head space to minimise the chance of oxidation.

why i'm confused is because i always thought you have to oxygenate your wort before you pitched your yeast and that oxidation only occured after anerobic respiration had finished...but from that quote of darrens it seems to me that you can get oxidation at anytime ...and only oxygenate your wort when it is time to pitch your yeast is this correct?
i put this in this thread and not the no chill thread because i figure this might be a real basic question that every one else already know the answer to but me
cheers simpletotoro

 

[Trent]

Simpletotoro
Oxidation is cause by a chemical reaction where oxygen molecules bond to beer molecules in hot wort (hot side aeration) or post fermentation, where the yeast wont gobble it up anymore.
Yeast needs oxygen to reproduce aerabically, before it produces alcohol anaerobically, so you aerate your oxygen prior to pitching hte yeast. As far as squeezing all the headspace from your cube to prevent oxidation, I couldnt tell you if that works (or how), but in general, the less headspace you have, the more hot wort is sanitising the sides of the cube, and the less chance you have of getting an infection take hold when the wort is at a cool enough temp for yeast to start munching hte sugars.
HTH, i have had a few!
T.

 

[simpletotoro]

Simpletotoro
Oxidation is cause by a chemical reaction where oxygen molecules bond to beer molecules in hot wort (hot side aeration) or post fermentation, where the yeast wont gobble it up anymore.
Yeast needs oxygen to reproduce aerabically, before it produces alcohol anaerobically, so you aerate your oxygen prior to pitching hte yeast. As far as squeezing all the headspace from your cube to prevent oxidation, I couldnt tell you if that works (or how), but in general, the less headspace you have, the more hot wort is sanitising the sides of the cube, and the less chance you have of getting an infection take hold when the wort is at a cool enough temp for yeast to start munching hte sugars.
HTH, i have had a few!
T.

thanks for that did a search and found this link
http://oz.craftbrewer.org/Library/Methods/...r/HSAmash.shtml
which explained this "hot side aeration" thing..never heard of it ....
i'll be more careful in the future now...this is a quote from it "

Oxygen Although it is very important to limit the exposure of the hot wort to oxygen, it is equally important that enough oxygen be present in the post-boil wort to insure a proper fermentation. Oxygen should be dissolved in the cooled wort prior to pitching the yeast. Brewing yeast require oxygen and other trace gases for their reproductive phase, this is essential for a normal fermentation. When the oxygen is introduced to the wort at low temperatures (21C/70F and lower) the problematic reactions which can damage the beer do not occur.

thanks again simpletotoro