barrelboy wrote:Hi all, I also harvest yeast cake and pitch into other brews however I'm not up on this "test tube" process. Warra could you please explain or if too complex refer us to an appropriate site,thread. Would be appreciated.
Cheers BB
It's quite a simple process.
I start with a new Wyeast smakpak, or a White Labs tube.
As they are new, I pitch them straight into a 4 litre starter. (2/3rds LDME, 1/3 Dextrose, to a SG of about 1.040)
I make sure I aerate the starter with an airstone and an aquarium pump on a regular basis for the first 8 or so hours (I don't have a stirplate as yet). That gives the yeast sufficient oxygen to grow.
Once it's fermented out, I chill the starter, which will drop most of the yeast out of suspension.
I pour off the starter beer, and add a little boiled and cooled water, just enough to get all the yeast into suspension.
I fill 3 or 4 test tubes with the suspended yeast, seal them and keep them in the fridge.
The balance of the yeast gets pitched into my beer.
Then, I plan successive brews so I can use a cup or so of the yeast cake to pitch into the next batch. The yeast is harvested at bottling time. I brew again within 1 or 2 days, and pitch the harvested yeast.
So, the ecominics work out quite well.
The initial cost of a new liquid yeast, say $10, although I have had them for $5 from my usual supplier when they are a few months post production date.
Initial starter ingredients, about $4.
Total for the initial build up about $14, but this gives me about 4 brews if I repitch the slurry, say $3.50 per batch.
Subsequent starter build up from test tube, about $3 each. If I use the slurry, it's even cheaper.
The process is much the same building up a test tube, but I start with a ½ litre, then bump it up with another 2½ or 3 litre the next day to give me a total of 3 to 3½ litres.
Now, that's for ale style yeasts.
For lager yeasts you need to build up a larger starter, about 5 to 6 litres, and I tend to not use them more than once or twice. However, as you really need to use 2 packs of dry yeast to properly cold pitch a lager, it still works out well in comparison.