[Sca-cooks] Wine was Re: vinegar and sauerbraten

[Louise Smithson]

William this question might be best answered from a brewing standpoint.  

The alcohol content of wine or any brew is determined essentially by two factors.  The amount of fermentable sugar in the brew, and the alcohol tolerance of the yeast used to do the brewing.  
If we start with the sugar content.  Wine is made and has been made exclusively from the juice of grapes (it is only some of the cheap modern wineries that adulterate their content with things like sugar and artificial flavorings).  The sugar content of grapes is determined by the strain of grape and the climate.  Southern wines, which get lots of sunshine and heat have generally more sugar.  As to the strain used, Italian wines are for the most part still made from grape varieties that were known in period, i.e. Sangiovese, Chianti, Montepulciano.  All grape varieties at the time would have been highly regional.  Unless their has been a great deal of breeding to reduce the amount of sugar produced by a grape since the middle ages then we may postulate that the average grape now has just about as much fermentable sugar, as the average grape in period.  (This is not taking into account the things that are done specially to increase the sugar content of the grape such as the noble rot,
 botytris, sun drying (done for a specific Italian wine whose name eludes me), and freezing.  So if we grant that grape juice, from which wine was brewed had the same sugar content now as then our only other variable is the yeast.  

Most modern brewers use a single culture of pure yeast for their brewing.  These strains have been selected for over time, since pasteur and someone finally realized what exactly was responsible for brewing.  There is no way to know what particular strains were being used in period.  Yeast produces alcohol from fermentable sugars.  Yeast will continue to grow until one of two things happens.  They starve to death, i.e. there is no more sugar left.  This is what happens in dry wines, all the sugar is turned to alcohol, the yeast have nothing to eat, they die.  OR They poison themselves, alcohol which is the by product of fermentation is toxic to yeast.  All yeast strains have a tolerance to alcohol.  The highest is that possessed by Champaign yeast, (about 21%) most other wine yeasts possess a lower tolerance, with ale yeasts having a lower tolerance yet.  (Modern brewers have added a third way, death by poison, Sulfites are added to kill the yeast).

There are two possible sources for yeasts in a period winery.  1) The wild yeasts present on the skins of the grapes which enters the wine when the juice is pressed out.  The thing about wild yeasts is that they can be odd. They may have a very low alcohol tolerance, or a moderate one, there is no way to predict this.  2) the brewery itself, if you are continually brewing in the same casks, in the same building the entire place will become colonized with yeasts.  This is why there can be such a difference in the taste of wine brewed from in two places from the same grape.  Each yeast has it's own characteristics both in alcohol tolerance and flavor profile.  (To learn how sugar is turned into alcohol see here http://home.sunlitsurf.com/~mshapiro/sugrconv.html)

So if we start with a juice which contains a standard amount of sugar no matter which yeast we use we can't end up with an alcohol content any higher.  If we have a wine yeast with a low alcohol tolerance, no matter how much sugar you add it still won't make the wine more alcoholic.     Most modern table wines contain somewhere between 11 - 14% alcohol by volume.  Why?  Because that is where the two variables balance out.  The amount of sugar and the tolerance of yeast.  This is a biological and chemical relationship, it has not changed with time.  Thus Medieval wines, which were brewed with grape juice and yeast must have had much the same alcohol range as modern wines. Possibly even less because selection for alcohol tolerant strains had not taken place, and innoculation of the wine with specific selected wine strains was not happening yet.  So your thesis that medieval wines were stronger than modern ones does not stand up to biological truths. Sorry, the habit of watering wines
 was a cultural one.  It is still done today in france and Italy where wine is often watered to serve with lunch and to children.  Because that is simply what is done, not because the wines are strong, but because they wish the flavor and health benefits of wine without the intoxicating effects. 

Helewyse

 


Entirely possible, as well. However, if we consider that Grappa was made by Italian winery
workers out of the 'leftovers' of the vintinig process, and Grappa was still a fairly strong drink
(an assumption based on the strength of modern Grappa, which may be a mistake), it stands to
reason that the fresh wine was quite potent. I am not saying that Grappa is or is not a period
libation, mind you...merely that it has been around for quite some time, and may have been / may
be a barometer by which to guage the strength of wines in Antiquity.

Or I am wrong :)

William de Grandofrt



		
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