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Yeasts - Species and Strains

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  • Harry
    With a very few exceptions (notably Kluyveromyces, a milk yeast) almost all of the yeasts employed in the alcoholic beverage industry belong to the species
    Message 1 of 1 , Nov 1, 2007

      With a very few exceptions (notably Kluyveromyces, a milk yeast) almost all of the yeasts employed in the alcoholic beverage industry belong to the  species Saccharomyces Cerevisiae:

      Scientific classification
      Kingdom:Fungi
      Phylum:Ascomycota
      Subphylum:Saccharomycotina
      Class:Saccharomycetes
      Order:Saccharomycetales
      Family:Saccharomycetaceae
      Genus:Saccharomyces
      Species:S. cerevisiae

      "Saccharomyces" derives from Greek  and means "sugar mold". "Cerevisiae" comes from Latin, and means "of beer". Other names for the organism are:

      • Brewer's yeast (the apostrophe may be missing or after the s), though other species are also used in brewing
      • Ale yeast
      • Top-fermenting yeast
      • Baker's yeast (the apostrophe may be omitted or placed after the s)
      • Budding yeast

      This species is also the main source of nutritional yeast and yeast extract.

       

      Strains:

      Many strains  and variants of strains of S. cerevisiae have been isolated, or bred, or engineered for use in alcholic beverage production.  Broadly speaking, they fall into one of two categories, either for grain-based or fruit-based liquors.

      Grain Suitable Strains:

      These include all of the beer-type yeasts.  They are selected for their notable addition of flavours to the beer.  For details on some of the yeasts available, go here...
      http://www.byo.com/referenceguide/yeaststrains/

      Fruit Suitable Strains:

      As the title suggests, these are most suitable when using various fruits as substrate to produce wines.  Details of most types can be found here...
      http://www.honeycreek.us/yeast.htm

       

      Distiller's Strains:

      Distilling is a unique situation where the beverage has gone through a heating, boiling & separation process to remove a large percentage of water and byproducts from the end product.
      Brewers and Winemakers quickly find that much of the carefully crafted flavours of the beverages they are used to dealing with, are also stripped away from a distilled product.  Hence in distilling, the emphasis in yeast selection is one of reliability and higher alcohol yield, rather than specific flavour traits.

      Having said that however, excellent unique results are possible from selecting strains with known characteristics as some of these traits do escape the rigors of distilling, but nowhere near to the extent they are found in a beer or wine.  There's no reason why a particular known strain used in brewing or winemaking should not be employed in distilling, if the substrate or sugar source is one that the strain is accustomed to fermenting.  The only proviso is that if the yeast strain in question leaves a lot of sugar behind (some beer strains), this will cause problems further along in the distilling process - foaming, burnt taste, poor yield.

      There have been a few dedicated distillers strains developed, notably by Lallemand (Lalvin)  (Danstil series ) and Whitelabs.

      If you study some of the strains mentioned above, you will quickly see that there are duplications - Lalvin's ec-1118 is also produced by Gervin, Red Star and Whitelabs.  It is in fact the strain S. cerevisiae BAYANUS.

       

       

      New Strains:

      New strains are constantly being developed for specific purposes.  A notable recent player is the fission yeast Schizo-saccharomyces pombe, reported to be a very fast acting, high-heat and high -ethanol tolerant strain.  I found this information in an online paper here...
      Canadian Journal of Microbiology 

      <extract>
      Twenty-seven Schizosaccharomyces pombe isolates from seven cachaça distilleries were tested for maximum temperature of growth and fermentation, osmotolerance, ethanol resistance, invertase production, and trehalose accumulation. Two isolates were selected for studies of trehalose accumulation under heat shock and ethanol stress. The S. pombe isolates were also characterized by RAPD-PCR. The isolates were able to grow and ferment at 41°C, resisted concentrations of 10% ethanol, and grew on 50% glucose medium. Four isolates yielded invertase activity of more than 100 µmol of reducing sugar·mg–1·min–1. The S. pombe isolates were able to accumulate trehalose during stationary phase. Two isolates, strains UFMG-A533 and UFMG-A1000, submitted to a 15 min heat shock, were able to accumulate high trehalose levels. Strain UFMG-A533 had a marked reduction in viability during heat shock, but strain UFMG-A1000 preserved a viability rate of almost 20% after 15 min at 48°C. No clear correlation was observed between trehalose accumulation and cell survival during ethanol stress. Strain UFMG-A1000 had higher trehalose accumulation levels than strain UFMG-A533 under conditions of combined heat treatment and ethanol stress. Molecular analysis showed that some strains are maintained during the whole cachaça production period.
      </extract>

      I have no way of proving it, but I suspect that this strain, or a mix of this strain and Bayanus, is being tested in some of the more recent so-called Turbo Yeast mixtures.  I'm willing to stand corrected if a manufacturer will step up to the plate with evidence to the contrary.

       

      Slainte!
      regards Harry

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