Sunday, 3 January 2010

Fullers yeast starter

Suppliers of liquid yeast tend to package it up in quantities that will only just ferment 5 gallons of yeast; so long as you aerate loads after pitching. You could obviously buy more of it but that can get expensive and, depending on how old the yeast is, you may end up just pitching a load of yeast with a high percentage of dead cells anyway as this stuff doesn't keep indefinitely.

The best way to be sure that you are pitching enough healthy yeast is to make a starter. I use a stir plate to encourage aerobic fementation as that's the time where the yeast reproduce making lots of fresh, healthy, new cells.

Here's a picture of my yeast starter for tomorrow's (actually today's) brew. It's about 4.5l of wort made with DME to an OG of 1.040 with a load of slurry from an earlier, unused starter added about 4 hours ago.

You can see my refractometer standing upright at the back of my stirplate. It's a great piece of kit that every brewer should have.

The cold weather came in handy tonight as I was able to bring the temperature of the wort from boiling to pitching temperature within minutes just by dunking it in a bucket of water that was sitting by the back door. After I broke the ice on it it was a perfect wort chiller!

As the source of the slurry had been sitting in the kitchen for a couple of weeks I did a quick check on the health of the cells prior to pitching. The photo to the right shows that the yeast cells are healthy. There's a little debris around but no nasties that I can see.

I'll do a viability check on the starter (using methylene blue as an indicator) prior to pitching into my wort. It it's infected (which I doubt, looking at the activity in the flask right now) I'll pitch a fresh tube of WLP002 and aerate like mad.

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