Beers sweetened with sugar (Karamelbier)

It's been far too long since I posted anything from Schönfeld's "Obergärige Biere und ihre Herstellung". Having been rather distracted by working on the forthcoming book on WW II.

Today we'll be looking at another type of sweetened beer, Karamelbier. One sweetened with sugar rather than artificial sweetener. It's a type of beer which is still produced, I believe, though in tiny quantities.

I'm surprised to discover that the original production method left yeast in the beer. Which seems awfully dangerous in a beer containing lots of highly-fermentable sugar.

"c) Beers sweetened with sugar (Karamelbier)
If sweetener-sweetened beer owes its origin to the war, sugar-sweetened Malzbier (Karamelbier) appeared around 16 years earlier. The original method of production, which is still used, consists, if it is bottled beer, of adding sugar to the beer after fermentation (vat fermentation), then it is filled into bottles and, after sufficient sediment has formed, further fermentation is prevented by pasteurisation.

The formation of sediment can be accelerated by the application of heat, which is often done, and can easily be carried out in such a way that the bottles are either brought into warm rooms or straight into the pasteurisers, which have been appropriately warmed up.
"Obergärige Biere und ihre Herstellung" by Dr. Franz Schönfeld, 2nd edition, Verlag von Paul Parey, Berlin, 1938, page 135 - 136.

I guess pasteurisation would effectively avoid any bottle bombs. Newer methods of making Karamelbier sought to remove yeast from the equation:

"Soon, however, the goal became apparent to fill the sugar-sweetened beer into bottles and containers without yeast. Some proceed in such a way that they transfer the beer into a storage barrel after the sugar has been added and stop the secondary fermentation early when the beer is sufficiently saturated with carbonic acid, and then filter it. Others first filter the lagered beer and transfer it onto tanks into which the sugar solution has previously been poured. Still others add the sugar solution to the shipping barrel before the beer is drawn off.

By means of cold storage and careful filtration, the beer can be made

to contain so little yeast that,

despite its high sugar content, it can still be kept for 8 to 10 days as a draught beer, so that for customers not too distant from the brewery can be supplied without it being pasteurised, without the risk of it becoming "wild" through a vigorous secondary fermentation. Of course, the landlord also has to ensure that it is kept cool. He must not have the barrel lie under the tap for too long. He must be careful to pour the beer quickly. In accordance with sales, he should order the appropriate sizes of barrel and order smaller barrels from the brewery rather than larger ones.

The unpasteurised beer is not suitable for shipping over long distances or for longer storage at the pub. The high sugar content, provides favorable conditions for the growth of yeast, and with increasing growth the attack on the easily-fermentabe sugar increases. It is therefore one of the most important measures to bring the beer to the shipping barrel as bright as possible and thus with as little yeast as possible. But not only this, but also to transfer it with the highest possible carbonic acid content, since the carbonic acid counteracts the yeast's growth; though it is unable to stop it completely."

"Obergärige Biere und ihre Herstellung" by Dr. Franz Schönfeld, 2nd edition, Verlag von Paul Parey, Berlin, 1938, page 136. 

I'm surprised that Karamelbier was sold on draught. Especially given what sounds like an inherent instability. I've never heard of it as anything other than a bottled beer.

Does CO2 really inhibit yeast growth? Never heard of that one before. Wouldn't that bugger bottle conditioning in a beer like Duvel?

"It is therefore necessary, especially with bottled beer, whether it contains yeast or not, to ensure shelf life by pasteurisation. A sufficient level of safety is achieved by a temperature of 70-72º C, which must be maintained for one hour. Rapid cooling is not required. Experience has shown that it is more expedient and more advantageous for the beer to cool slowly, which is why certain devices, e.g. the vapour pasteuriser dispense with water cooling, but rather pull the cart loaded with the bottles out of the chambers shortly after the pasteurization and let the air in the room do the cooling.

The slow cooling has a beneficial influence on Malzbier in that it enhances the roasted, malty, bready taste that is valued in Karamelbier."

"Obergärige Biere und ihre Herstellung" by Dr. Franz Schönfeld, 2nd edition, Verlag von Paul Parey, Berlin, 1938, pages 156- 137.

I wonder why slow cooling enhanced the malt flavours? Is that why UK pasteurised beer tasted so bad? Was it cooled too quickly.