Harvested yeast amount and starters

[Buford]

I have 5 tubes of yeast harvested from a previous batch, but the amount in each tube seems pretty small (about 1/4 to 1/3 of the amount in a new White Labs tube). If I make a starter with these tubes, should I use more than one, or is this amount enough to propagate in a 1 L starter? I've never reused harvested yeast before.

 

[Iordz]

There is enough yeast to propagate 5gal, if you wanted to. I culture yeast on slants and build up my starters from, literally, 100 yeast cells. So you would probably want to start with a small amount of wort, maybe 100ml sterile wort. Once you see activity, around 12-24 hours, you transfer to 400ml of sterile wort. From here you can step up to 1L. The key is having sterile wort (pressure cooker), and not stepping the volume up by more than 4x the original volume, you can go from 10ml to 40ml, but 10ml to 80ml would be pushing it. It's best to transfer the yeast when it is active, this ensures a healthy, energetic yeast starter. You might want to perform any transfers over a flame source to ensure no foreign bacteria infects the starter.

 

[TheJadedDog]

Just make a small starter and step it up over a few days to increase cell count.

 

[Buford]

Is a small initial starter as important if I'm using a stir plate (since that produces much higher yeast growth than an intermittently shaken starter)?

 

[Iordz]

Yes, yeast growth depends on many factors and one is the volume of wort. Too much or too little wort will affect the propagation of the yeast. Most brewers will double the volume of the starter, essentially stepping up time two. The limit is around four times the volume, going over is not very efficient. What the stir plate does is add oxygen, which is another important aspect of yeast growth. The plate will allow you to propagate even more, healthy, yeast.

 

[TheJadedDog]

Yeah, I'd still start with a smaller volume of wort and step it up over time even with the stir-plate. Ultimately you'll get more cells due to the stir-plate, but you don't want to stress the yeast initially.

 

[Buford]

Do you think it would be sufficient to start with a 200 mL starter and step up to 1 L after a couple days on the stirplate?

 

[TheJadedDog]

I'd follow Iordz advice further back in the thread and start with 100mL, then step up to 400mL, then step to 1L.

 

[DAAB]

A initial 1-200ml starter will result in a greater number of new cells in the 1L starter and is the way i'd go.