zxcvbob wrote:

> I'm baking whole wheat bread today. It just started its second rise.
>
> I'm out of bulk yeast and used a packet that I found in the fridge. It
> was a couple of years old, but it is rising very well.
>
> If I save a ping-pong ball sized piece of the dough, will that have
> enough yeast in it to leaven a batch of pizza dough tonight?

Sure it will - with a little help. You'll want to feed it so the yeast
grows. I'd mix it with an equal volume of warm water (110F), some
sugar or malt, a handful of flour and a small pinch of salt. A dash of
oil wouldn't hurt.

If using the entire thing, factor the liquid volume in your
calculations for the pizza dough. Subtract it from how much you'd use
normally and just add the difference when making the final dough.
Should work fine.

Or treat it like a sponge and just use some of it in the normal
sponge-leavened fashion.

Pastorio