How much to pitch

Toy4Rick · Aug 27, 2011

Hey gang,

I have some WLP300 that has eaten it's way through 3 batches so far. The second batch was pitched entirely into the 3 batch. The third batch was washed and has been in the fridge for 6 weeks yesterday.

As you can see, the pint mason jar had about 1" slurry on the bottom so when making my starter last night, I poured out most of the water on top until I had equal slurry and water, shook that up and added it to the starter (2Qts). This morning it is fermenting pretty well in a 1 gal jug.

My question is this, there is about 1/2" of trub on the bottom of the starter jug with the beer layer in the middle and a very small krausen layer on top, should I shake and pitch the whole thing or try and decant the beer off the trub?

Hopleaf11 · Aug 27, 2011

If you're harvesting yeast and then rinsing (or some people use the term washing interchangeably) then you shouldn't have to make a starter. We homebrewers do starters to increase the volume of yeast slurry. You've already got that. The only added benefit of making a starter once you already have the appropriate yeast pitching rate (which can be calculated at mrmalty.com) is that you'll be pitching the yeast at high krausen. Very active yeast gets to work faster.

There's a good podcast episode of Brew Strong on the Brewing Network that covers yeast washing and repitching. Check it out.

Toy4Rick · Aug 27, 2011

I made a started for 2 reasons basically on the advice of my LHBS. 1) 7 weeks in the fridge, 2) Too many dead cells would give off flavors. They advised me to not pitch all the yeast in the starter due to dead cell count and allow the good yeast to multiply enough to get me going.

So this is where it gets confusing for me. Mr. Malty shows I need 14 oz of yeast at this time, 1.049OG, 5.005 total volume, production date of 7/11/11 and I left the concentration and the non yeast at default values.

In my Qt (OP I said Pt, my bad) mason jar, I had about 5oz of yeast, meaning I would need to nearly tripped that to get my total volume?

My last batch of Centennial Blond they said tasted a bit diacetyl from stressed/under pitched yeast or fermenting at to high a temp.

Not sure I want to risk my next batch or not

Thanks in advance
Toy4Rick

Hopleaf11 · Aug 27, 2011

Yeah I noticed the timing after I replied. Probably a good idea to make a starter for yeast that's been in the fridge for six to seven weeks.

Ok so you're making a starter and you need 14 oz. You can just step up the starter until you have your total pitch. The process is the same as making your initial starter except you decant off the beer before adding the yeast to new wort. Repeat until you have 14 oz.

Clementine · Aug 27, 2011

I get slightly different numbers when I put your values into Mr Malty however that said, you still need more than 5oz. The thing is Mr Malty is calculating the amount of gunk at the bottom of the jar you need to pitch. This includes non yeast, dead yeast and yeast hence why the amount of slurry you have to pitch changes with when it was last used. So if you have a starter that has now pure yeast + some more hot break as well as the rest of the junk from the initial cake then it all is probably a bit much to get Mr Malty to figure it out for you.

Another way to look at this is take Mr Malty and change the figures of wort size to match the amount of slurry you have. This will give you an approximation of how many billion viable yeast cells you have in your original sample. When I changed wort size to 2.5 gallons it tells me you have 86BYC.

From your original calcs you need around 170BYC so we need to double your yeast. You could think of your 5oz of yeast as a white labs tube they have around 100BYC (when fresh) to at 86 BYC it is just like a tube that is about a month old. So depending on how you make your starters you will need anything from a 2.5qt starter to a 1qt starter on a stir plate and you can use the liquid yeast tab on Mr Malty to figure that out.

On how much to pitch of the starter, I would be tempted to crash cool, decant and pitch all the yeast and trub looking stuff. If you try to separate yeast from trub you are going to lose a significant amount of your yeast and will risk under pitching. Don't forget to crash cool WLP300 is a really poor flocculator and you don't want to miss out on yeast that you can get by just sitting it in the fridge for a while longer.

Hope this helps and it did not get to confusing

Clem