Gilbey

Recipes 

How does yeast muliply, and when does it stop multiplying? If I underpitched wouldn't it just continue to multiply until there was no more food (sugar) to eat?

If I am washing yeast and not getting ALL the trub out, how can I get a reasonable measurement of how much yeast I have in my mason jar??

Alan

JoePro

Recipes 

You can ensure you have the proper amount of yeast by making a starter. Using the Mr. Malty calculator, you can estimate yeast population per a given volume.

If you underpitched, it might stress the yeast and cause them to have a long lag phase, which can produce a small amount of off-flavors (really only a concern in competition brewing)

It's not always the BEST idea to re-pitch with washed yeast. Make a starter with washed yeast, grow the guys, and then pitch!

HexKrak

Recipes 

Starters are also going to warn you of any contamination your washed yeasties are carrying.

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Clementine

Recipes 

Didn't your Mom and Dad explain this one

Seriously, from what I have read yeast will multiply based on a few things O2, nutrients and sugar being present to allow the cells to divide (Mitosis). Once all the O2 is gone the yeast then changes from replication to fermentation mode (ie once they have had their fun they make work for us).

Things I know support this concept is when you use a stir plate and you keep putting O2 into the small starter you get lots more yeast.

Gilbey

Recipes 

What are those signs I should look for in my starters made from washed yeast?

I am familiar with Mr. Malty, and I realize he needs to become my friend. How do you measure yeast quantity in a starter? Or in a mason jar?

Now, about this birds and bees thing - I was given a box of condoms and a slap on the back.....did I miss something????

Alan

JoePro

Recipes 

Your taste + smell, primarily. Usually when I decant some wort before pitching, I pour some in a shot glass for sippage. If there isn't anything worrisome or off about the particular yeast profile, I take notes and pitch.

I've had one batch of dead yeast, and I will tell you-- it smells like rotten meat. If you don't have any activity in your starter (i.e. no C02 production, no krausen, no color change), you'll know if it's healthy or not.