Effect Of Aerating Slurry

[Tim F]

Hi all, just wanted to share an observation in case it's interesting to anyone. A few weeks ago, I saved about 500ml of Wyeast 3068 yeast slurry from a brew, and stored it in the fridge. Last weekend I pitched half of this straight into a rye beer. Fermenting at 18C, I saw some airlock activity after 12 hours, and krausen at 24 hours. All seemed ok but after a few days it seemed to stall, and I have had to swirl the fermenter round to wake it up again.

Yesterday I made a wheat beer with the rest of the yeast, but this time I boiled a couple of tbsp of dry malt extract in 500ml water, added the remaining slurry to the flask, and bubbled air through it for 8 hours (using a .4 micron filter + aquarium pump). This time I saw strong airlock activity in 3 hours and had massive krausen within 12 hours. This one was fermenting at ambient temperature so it probably got down to 15 overnight too, but it didn't seem to mind!

I didn't aerate either wort at all - thought it was interesting how much difference it made giving some oxygen to the starter, even for just a few hours. Feeding it before pitching probably helped to wake it up as well. I think I will be doing this again!

 

[bakkerman]

I can second this, I've had good results with waking up a slurry with some 1.040 wort and a good aeration.

 

[pint of lager]

Once yeast flocculate out and form a slurry, the death rate is really fast. I forget the figures but if you are using slurry, you need it fresh, less than a week old. Otherwise, make a starter.

 

[kevnlis]

Just add a bit of olive oil next time

 

[maltedhopalong]

Olive Oil???

 

[bakkerman]

Olive Oil???

Yep! Yeast needs the oxygen to form fatty acids, it uses these in the cell walls.

You can also add the fatty acids through olive oil, it's also doubles as an anti foam agent during aeration.

 

[kevnlis]

I heard it recommended for HBers to only use the end of a wire dipped in olive oil to stir the slurry before pitching. In other words you do not need much at all, in fact I think as little as you can possibly add is best?

 

[etbandit]

Olive Oil???

Here's a paper on it.

View attachment OliveOil.pdf