[Sca-cooks] Leven: yeast or sourdough?

Terry Decker t.d.decker at att.net
Sun Oct 10 19:54:59 PDT 2010


Berme is Middle English for barm, so your assumption is essentially correct. 
It is not beer residue, but the active fermentation from the top of the ale 
pot.  S. cerevisiae, brewers or bakers yeast, is a top fermenter while most 
beer yeasts are bottom fermenters.

In general, beer drinking regions use ale barm for leavening while other 
areas tend to sourdough.  The earliest reference (that I have located) to 
using ale barm is found in Pliny.  Imperial Rome is an exception in that 
after the Gallic Wars the practice of using ale barm for leavening move from 
Gaul into Rome and other parts of Italy.  Other than that, most 
Mediterranean countries leaven with sourdough.  At some point, which I have 
not yet determined, France required all bakers to leaven with sourdough, the 
law being changed at some point in the 20tgh Century.  I would have to dig 
for the references, but I think Toussaint-Samat gives a basic Francocentric 
interpretation of the expansion of baking and Michael Grant gives other 
details in his works.  There is a smattering of French baking law in 
Boulanger (IIRC).  Most of the information on the subject is in snippets 
scattered among works on other subjects.

Sourdough is the product of an environmental created symbiosis between a 
yeast (often on of the Candida) and some variety of lactobacillus.  The 
actual combinations are very localized and vary widely in rise and sour 
taste.

Bear

> Recipes frequently don't say--and if they do refer to yeast, especially in 
> a translation, the word might actually mean sourdough. I gather that 
> sourdough, technically, is not yeast but a different organism with similar 
> effects, but even assuming that's right, there is no reason to expect 
> people in period to know.
>
> Our working assumption is that "berme" means yeast from beer residue and 
> that otherwise the leven is beer yeast in beer drinking areas, sourdough 
> in areas that don't drink beer, including the Islamic world. But I don't 
> think we have any really solid evidence on the subject--does anyone else?
> -- 
> David/Cariadoc




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