I've got 5 different yogurts that I make (viili, Greek, piima, matsoni, fil mjolk), plus a new culture on the way. How does one go about saving/freezing a yogurt culture for later use? I'd like some spare cultures in case something goes wrong with the ones I've got....like I get lazy and don't culture them for a couple weeks and they go bad, or I go on vacation and can't culture them. The cultures came in little packets when I bought them, and they were like a powder. How do they do this?

Deb--Central PA