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Cold Conditioning – Fermenter vs Bottle vs Keg

This week Dave from our UK office, tried to settle the age old debate about cold conditioning – should it be done on or off the yeast? And are bottles or kegs the preferred option for your beer? Read about his experiment and findings below.
There seems to be quite a lot of debate about cold conditioning beers and what the best technique is. Some brewers claim that you absolutely have to take the beer off of the yeast cake to avoid getting off flavours from autolysis (the off flavour caused when live yeast cells start to consume the dead yeast cells), whereas other brewers claim that you can leave the beer on the yeast cake as the colder temperature will inhibit any spoilage.
Both techniques have pros and cons, taking the beer off the yeast will give you a clearer beer but you run the risk of introducing oxygen and spoiling your beer. Leaving the beer on the yeast is easier but can potentially cause off flavours such as autolysis.
I decided that it was time to test which technique was best once and for all.
I brewed a very simple pilsner;
OG: 1.054
FG: 1.013
ABV: 5.27%
IBU: 42.66
5kg Pilsner Malt 95.2%
0.25kg Acidulated Malt 4.8%
15g Herkules @ 90 minutes
100g Nelson Sauvin @ 0 minutes
I fermented this out at 10°C for 12 days before moving to a warmer room for a further 2 days. I then split the batch into;
– a Cornelius keg (allowing the beer to settle in one keg before racking it off into a second keg so that it was definitely off of the yeast)
– some bottles
– and the remainder left in the fermenter on top of the original yeast cake.
I then moved all of these to the fridge to condition at 10°C for 4 weeks.
After four weeks we did a tasting of the pilsners. The beers were set out so that every taster tried a bottled beer (cold crashed on the small amount of yeast transferred into the bottle), a keg beer (cold crashed off of the yeast) and a beer straight from the fermenter (left on the original yeast bed to cold crash).
Bottled beer – I was quite interested to see how this turned out because the bottles went straight into the fridge so I wasn’t expecting much carbonation. There wasn’t much need to worry though as the carbonation was fine and the beer tasted good. If I had just tasted the bottles I’d have been happy but because we were able to compare to the kegged version of the beer, this fell a little bit short.
Kegged beer – This was easily the best of the beers that we tried. That crisp, refreshing flavour that you expect from a pilsner with a good hop character. It was extremely clear and fresh and didn’t appear to have suffered any negative impacts from being left in a keg for a month.
Beer from fermenter – This is the perfect beer for proving that autolysis on a homebrew scale definitely can occur. Many brewers online seem to be saying that autolysis only really occurs in large breweries due to the shape of the fermenters used and the pressure the yeast is under in such large vessels. This beer that had been left on the yeast cake for just a month was definitely suffering from autolysis though, with that signature rubber smell and taste. This version of the pilsner was unpleasant to taste, almost undrinkable.

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