From: dam@dcs.glasgow.ac.uk (David Morning)
Newsgroups: rec.crafts.brewing
Subject: Re: Bud's claims to be "naturally carbonated"
Date: 31 Aug 92 12:05:15 GMT
Organization: Glasgow University Computing Science Dept.

ech@ac.dal.ca writes:

>In article <1992Aug27.144347.8855@novatel.cuc.ab.ca>, hpeyerl@novatel.cuc.ab.ca (Herb Peyerl) writes:
>> David Morning (dam@dcs.glasgow.ac.uk) wrote:
>> : fizz in the bottle. German beers do this but don't ask me how, I just drink
>> : the stuff, maybe it's related to top fermenting vs bottom fermenting (well
>> : that's what the guy in the Heineken factory in Amsterdam told me!!)
>> 
>> That's correct... When you use a top fermenting yeast the sediment actually
>> floats on the top (because the dead yeasties still have on their life-
>> jackets) so when it comes time to bottle, they just skim the sediment off
>> the top and you have clear beer.  Top fermenting yeast is harder to brew
>> with though because since alcohol is less dense than sugar, the alcohol
>> produced by the top fermenting yeast stays on the top of the fermenter 
>> and the yeast doesn't have a chance to get to the sugar's on the bottom.
>> This is why german breweries brew with their fermenters upside down to 
>> alleviate this problem. This is trickier for a homebrewer though. (although
>> I'm sure one of these days Jack will come up with something :-> )
>> 


>Will someone either enlighten me or back me up if I (flamelessly, I hope) 
>exclaim that the above statements make no sense?  First of all Top fermenting
>yeast is usually ale yeast, not for making German lagers, and is the type
>usually used by homebrewers, who will tell you that skimming the top does
>not a clear beer make.  Second, ETOH (ethyl alcohol) is completely miscible
>with water and does not rise to the top.  Third, in an upside-down fermenter 
>the yeast would still float to the top; this has to do with buoyancy and
>gravity, and not where the TOP label sits on the fermenter.  Finally, even
>if top fermenting yeast is removed by skimming, how do you get naturally
>carbonated beer (requiring live yeast in the bottle) without having live
>yeast in the bottle?

Since I started this tale with the Heineken stuff.....

I think Ed's right. It was about 15 years ago I was at Heineken but this
is what I remember of it.

Beer and lager in the UK are top fermented, that is the yeast floats on the
top. (Note for USers: beer includes Ale/fizzy dark stuff, lager is the straw
coloured stuff here)

Heineken (and most Continental Europe beers) are bottom fermented. I can't
remember the detail of how Heineken held the yeast down at the bottom of the
fermenting tank. The reasoning went something like, top fermenting results in
the sediments gradually, through the eefects of gravity drifting further down
into the wort making it difficult to clear (we've all seen the sediment lying
at the BOTTOM of the bottle of some types of beer and wine so it DOES sink
albeit slowly). As a result, heavy filtration is required to remove it 
resulting in virtually all the remaining live yeast being removed. Result?
No natural fizz in the bottle so it requires carbonation.

Bottom fermenting however keeps everything down the bottom of the tank 
including the sediment, hence, when it comes time to remove it, just take the
beer off the top and the sediment is left behind in the tank. Beer is much
clearer and requires little filtration hence live yeasts are left in place
when it gets bottled/canned which results in natural carbonation.

Well,that's how I remember it..time for a Beamish now I think!!!

Dave
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