Bottle fermentation over - time for cooling

After 48 hours at 6°C

The beer has now been bottle fermenting (what you'd call Nachgärung in german) for a week at about 22°C (in my office). In case you missed the previous post, the idea of the bottle fermentation is that the beer builds up CO2 in a closed environment. The CO2 can't escape (it's in a bottle), so the beer gets fizzy. And how do you create the CO2? Well, when yeast is fed with sugar it breaks the sugar down into alcohol and CO2 (in about equal parts). So when the main fermentation (in the keg) is over, you basically have flat beer (as the CO2 escapes). When bottling each bottle gets a little sugar and the remaining yeast (in suspension) in the beer takes care of the rest. The aim is that you can decide beforehand how fizzy the beer should be (Weizenbier is typically fizzier than, say Kellerbier) and going on the temperature you can figure out how much sugar you need per litre of beer. More experienced brewers don't use sugar at all - they tap off Jungbier before it is finished fermenting (i.e. there is still sugar in it which can be coverted to alcohol and CO2) and keep it separately, in the fridge. In german it is called the Speise. Before bottling, the Jungbier is piped onto the Speise and mixed in. This is actually how it is supposed to be done. The method with sugar is a bit of a workaround (incidentally, the new Reinheitsgebot actually allows this for top fermenting beers). There is also a method called Grünschlauchen, which means bottling before the beer is finished fermenting in the keg. Grünschlauchen means you really have to keep an eye on the rest sugar though - and you run the risk of either flat beer or (worse) bottle bombs (where there is too much sugar left in the Jungbier).

My beer is now in the fridge since yesterday, at about 6°C. One bottle was in since the day before, for testing. I tried some of it last night (the glass in the picture is 100ml - perfect for testing). It still has a bit of a wild taste and definitely needs a couple of weeks in the cold. I was also quite surprised to see how much CO2 it had developed. I'm not sure that a Klosterbier should be fizzy - it seems like a beer that should be drunk out of a Steinkrug and shouldn't have that much gas. It was good to see that between yesterday and today the foam got a bit more stable. It's too soon yet to decide if the foam didn't work out (I'd need to check the log of the mashing to see why).

Other than that, there is now nothing to do except wait. From the 500ml bottle I kept as a sampler, I'll try 100ml every night. Next weekend, the beer should have settled down somewhat, though I expect it will be at least two weeks before it will be properly 'drinkable'.