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40687RE: [new_distillers] Re: Aeration

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  • Gavin Flett
    Mar 25, 2011
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      So it may be as I had originally suspected, my wash has simply fermented out quicker than expected..

      After reading that I would have say woops. It seems I am again misinformed as to the aerobic and anaerobic phases of the fermentation. In my attempt at making sure the wash had sufficient aeration (plus thinking that yeast growth can occur at least through the 48 hr period) I syphoned it from carboy to carboy twice (one each day) and making sure it had plenty of splash to try and get the oxygen in the mix plus mixing it to get the mash cap down etc, etc..... The yeast I am using is I think W-Yeast and it's a whiskey yeast from my local brew shop and i have experimented with varying temperatures with so far less than pleasing results. I am making my way up to an average temperature of 29C as i had begun in the low 20'sC

      However the oldest batch I have aging right now is about 9 months. I have grown to like drinking 18 and 21 year scotch, so perhaps I have set the bar a bit high, however my goal is still to at least match those. The trouble I am having is, how do I know my product now will turn out delicious in 10, 12, 15 18 years. If anyone can let me know that I will be grategully indebted.

      One more thing, how can I guage how many ppm of oxygen I am getting in my wash?


      To: new_distillers@yahoogroups.com
      From: jamesonbeam1@...
      Date: Fri, 25 Mar 2011 11:44:49 +0000
      Subject: [new_distillers] Re: Aeration

       

      No Gavin,
      Not really kills..  You can not over oxygenate in the first 24 hours.  This is during the yeasts' exponential growth phase which is aerobic and they need all the O2 they can get.  After that, they enter the stationary phase which is an anaerobic phase when the ethanol is produced and no growth happens.
      As Dr. Reines states:

      "In terms of fermentation, aeration is also important but only in the early stages (first 6-24 hours).  Aeration in later stages can oxidize beer constituents and lead to the development of off-flavors.  Since aeration sets the stage for maltose fermentation and alcohol tolerance, it is easy to envision why insufficient aeration could lead to stuck fermentations or incomplete fermentations.  Incomplete fermentations can be manifested as either high finishing gravities or the production of off-flavors especially diacetyl, acetaldehyde, and hydrogen sulfide.  Insufficient aeration is also associated with excessive ester formation.  The profound effect of aeration on yeast is further illustrated in studies where yeast from a poorly aerated beer was repitched into aerated wort and still did not perform well.  Thus insufficient aeration can have a long-lasting effect on yeast. 

       

      In general, it is difficult for homebrewers to achieve sufficient oxygen levels.  The levels of oxygen necessary for optimal fermentation vary depending on the yeast strain.  Ale strains usually need between 8-12 part per million (ppm) while lager strains require slightly higher amounts (10-15 ppm).  At atmospheric pressure the maximum level of dissolved oxygen in wort is approximately 8 ppm and the saturation level decreases further as the gravity of the wort increases.  Thus unless special steps are taken to introduce air or oxygen into the wort, it is difficult for homebrewers to achieve adequate aeration.  Recent studies have shown that oxygenation is by far more efficient than aeration.  Injection of oxygen through a 2 micron diffusing stone can actually supersaturate the wort with 10-12 ppm of dissolved oxygen being reached in 5 gallons of wort by a single 60 second blast of oxygen! "  http://maltosefalcons.com/tech/yeast-propagation-and-maintenance-principles-and-practices

      JB. aka Waldo.


      --- In new_distillers@yahoogroups.com, "gavinflett" <gavin_flett@...> wrote:
      >
      > Does anyone think it's possible to aerate the wash too much to the point where it kills the ferment?
      >


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