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Sourmash

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  • Harry
    I ve read almost every distilling-related book there is, and heard many knowledgeable people (JB, Pint etc.) voice their opinions, on the definition of sour
    Message 1 of 1 , Jan 1, 2009
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      I've read almost every distilling-related book there is, and heard many knowledgeable people (JB, Pint etc.) voice their opinions, on the definition of "sour mash" (the object) and "sour mashing" (the process).

      Murtagh & associates  publish a book "The Alcohol Textbook" (expensive) that is considered by the commercial spirits industry to be the Bible.  Now in its 4th edition (5th ed due soon), this is what they say...

       

      Mashing

      Mashing techniques vary considerably, but the

      major difference is whether pressure or

      atmospheric batch cooking is used. Bourbon,

      rye, wheat, Tennessee and corn whisky are

      mashed using batch cookers. Only the `blend'

      or `light' whisky producers use continuous

      cookers. Pressure cooking is usually done at

      124

      oC while atmospheric cooks are done at

      100

      oC. Cooking time varies from 15 minutes to

      1 hr. Conversion time and temperature are very

      consistent among distilleries. Malt is never

      subjected to temperatures greater than 64

      oC; and

      conversion time is usually less than 25 minutes

      to minimize contamination. All distillers use

      backset (centrifuged or screened stillage from

      the base of the still), but the quantity of backset

      will vary based upon the beer gallonage (gallons

      of water per 56 lb distillers bushel of grain) to

      be used. American whiskies have beer

      gallonages in the 30-40 gallon range.

       

       

      YEASTING

      All whisky producers use

      Saccharomyces

      cerevisiae

      , however the yeasting techniques vary

      tremendously between the `modern' and

      `traditional' distillers. The modern distillers have

      elaborate yeast laboratories and will propagate

      a new yeast from an agar slant every week. They

      are very aseptic and accurate, assuring continuity

      of the same flavor. The `traditional' distillers

      use yeast stored in jugs; and though they

      backstock weekly, the potential for gradual yeast

      culture changes and contamination can lead to

      flavor variances. These distillers take extra effort

      and care to ensure that their yeasting does not

      cause ester, aldehyde or fusel oil variances in

      the distillate.

      The most common grains used for yeasting

      are small grains, rye and malted barley. These

      grains are cooked in a separate cooker to about

      63

      oC, and the pH is adjusted to 3.8 with lactic

      acid bacteria grown in the yeast mash. Lactic

      acid production is then stopped by increasing

      the temperature to 100

      oC for 30 minutes to kill

      the bacteria. This aseptic, sterile mash is then

      ready for the yeast from the dona tub grown in

      the laboratory. The yeast

      fermentation temperature is controlled at 27-

      30

      oC; and the yeast propagates until the Balling

      drops to half the original 22

      o Balling reading.

      This yeast mash will have a yeast concentration

      of 400 million cells/ml. Both modern and

      traditional distillers regularly have clean, sterile

      yeasts free of bacterial contamination that may

      cause side fermentations and unusual congeners

      in the distillate. The `lactic souring' and the

      alcohol content of the finished yeast mash (8%),

      along with sterile dona and yeast tank methods

      contribute to the excellent reputation American

      whiskies have for fermentation congener

      consistency. The advantage of using small

      grains are: preservation of enzymes for

      secondary conversion, low steam requirements

      and shorter processing time. Also, because of

      its nutrient value, barley malt is the most

      important constituent of yeast mashes. Corn is

      not used in a yeast mash because it does not

      contain the growth factors required for yeast and

      lactic bacteria growth.

       

       

      FERMENTATION

      Fermentation is the simplest part of the

      production process, but requires more control

      with efficient equipment in order to have stable,

      consistent results. After the two or three cooks

      required are completed, cooled, and transferred

      to the fermentor, the fermentor is `set'. Setting

      the fermentor means filling the fermentor with

      cooked mash, inoculated yeast and backset. The

      yeast mash is pumped in as soon as the first cook

      is added to the fermentor. The addition of

      backset and/or water is done at the end of filling

      to bring the fermentor to the desired final beer

      gallonage. Most distillers use a 30-36 gallon

      mash, and the water:backset ratio determines the

      set pH. Set pH values of 4.8-5.2 are considered

      to be the best starting point.


       

       

      Comments are welcome

      Slainte!
      regards Harry

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