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General Category => Yeast and Fermentation => Topic started by: gmac on October 01, 2011, 03:31:43 AM

Title: Building up an old WLP vial
Post by: gmac on October 01, 2011, 03:31:43 AM
I have a vial of WLP lager yeast I bought back in the spring but I never used because it got too warm.  I'm going to assume that there are at least a few live yeast still in the vial since it was stored in the fridge since I got it.  The BBF date is Aug 6.
Should I try to step this up in a smaller starter first or is it still close enough to pitch into a larger starter (3L)?  It is the WLP833 German Bock strain.
Title: Re: Building up an old WLP vial
Post by: chezteth on October 01, 2011, 11:41:22 AM
I would suggest starting with a smaller starter such as 200mL.  Last time I used some old yeast I started with a 200mL starter then built it up from there into a larger starter.  It worked very well.
Title: Re: Building up an old WLP vial
Post by: tygo on October 01, 2011, 02:38:55 PM
I would suggest starting with a smaller starter such as 200mL.  Last time I used some old yeast I started with a 200mL starter then built it up from there into a larger starter.  It worked very well.

+1 I do this with any yeast where the viability is questionable.  Works great.
Title: Re: Building up an old WLP vial
Post by: gmac on October 01, 2011, 02:42:05 PM
How long in the 200 ml starter?  My normal starter routine is not great because I'm away for work a lot.  I usually do 2L of 1.040 wort, pitch the yeast saturday and swirl often Saturday and Sunday.  Then it just sits on its own until the following Friday when I chill it for pitching Saturday or Sunday the week following.
When stepping up should I follow the same process? (yes, buying a stir plate would be a wise investment...)
Title: Re: Building up an old WLP vial
Post by: tygo on October 01, 2011, 02:43:49 PM
The initial step will take less time usually.  Depends on how many cells you're starting with.  After a couple days you can just pitch it into the next sized starter.  No need to chill and decant that small of a volume. 

Your normal procedure will probably work just fine it'll just take longer obviously.
Title: Re: Building up an old WLP vial
Post by: gmac on October 01, 2011, 05:36:01 PM
So, help me understand the biology behind this.  What is the factor that makes stepping up from 200 ml to 2 or 3L better than just pitching into 3L directly?  I'm going to do the small step, not arguing but I am looking to better understand the benefit and difference.
Title: Re: Building up an old WLP vial
Post by: tygo on October 02, 2011, 01:17:25 AM
It has to do with the pitching rate, the number of cells pitched into the given volume of wort.  Lower pitching rates will result in less cell growth.  So you can pitch the smack pack into the 3L and you'll get more yeast growth than in the 0.5L but at a lower yield (less percentage growth in cell count).  Which may not give you the total amount of cells you're trying to achieve.

By starting with a smaller starter you're generating some amount of growth, so that when you pitch to the larger starter step you're inoculating that with a higher pitching rate to maximize the number of cells you're growing. 
Title: Re: Building up an old WLP vial
Post by: 1vertical on October 02, 2011, 02:48:27 AM
Very timely topic. I am gonna have to grow up a tube of mexican lager that is pretty old and frail.
thanks  ;)