hist-brewing: ale yeast (was:lemonade)

ulfin at portup.com ulfin at portup.com
Sat Jun 2 20:14:51 PDT 2001

Angus says:
>And you've never/seldom had a batch go up to and above 7%? Perhaps you
>need more oxygen in your batches then.

Er, that may be too much oxygen, not too little.  Oxygen promotes aerobic
fermentation which produces more yeast and some alcohol, rather than
just alcohol. Anaerobic fermentation is a more sugar-efficient method of
alcohol production, but it requires a high pitching rate (of freshly active
yeast) to skip the propogation stage.

I'm with Angus on the sweetness issue.  The sweetness in beers is
more commonly due to *unfermentable* sugars (the chewy saccharide
chunks and dextrins between maltotriose and soluble starches), rather
than *unfermented* sugars left over after the alcohol poisons the
yeast.  The latter is a more common method of providing residual
sweetness in wines and meads.

Unlike honey, barley wort contains a very complex array of sugars.
For beer sweetness, one merely selects a yeast with poor attenuation
so that only the simplest sugars are fermented out completely (oh, and
mashes high for complexity).  But in meadmaking, where the must is
almost entirely monosaccharides (glucose with a touch of fructose),
attenuation is irrelevant; one selects a yeast with a low alcohol
tolerance.  (Of course, in either case, the more honey or malt sugars
you put into it, the more you have left at the end.)

Dan Butler-Ehle

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