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Does anyone have any good ideas on a reliable way to activate basic grocery store yeast?

I realize this is a total beginner's question. I've built a small yeast ranch at home with my kid, and we're trying to learn how to innoculate agar'd petri dishes with home grown samples we're trying to make from basic grocery store yeast. Eventually, want to do more advanced experiments, but for now...we're just looking for some growth.

So far, our best attempts at using grocery store yeast packets have yielded no results (i.e. no visible growth). My best attempts to find a good recipe have lead nowhere. I see lots of good advice on how to follow sterile procedure on making agar'd dishes and how to innoculate from an existing slant; but we thought it'd be easy to just start with grocery store yeast instead of buying a slant.

FYI -- there's obviously some kind of growth happening on the petri dishes. When we break from sterile procedure and invite contamination; then it's clear something (not yeast) is happily growing on the plates.

My mistakes that could've lead to zero growth on the petri dishes include: (A) Perhaps adding the dehydrated yeast to water that's way too hot? (B) Perhaps I did not add enough wort or sugar for the yeast to feed on? (C) Maybe i should've let the dissolved yeast ferment for a while before innoculation?

Would very much appreciate any help from someone more experienced on this.

best wishes...

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  • $\begingroup$ You might actually get better advice at Seasoned Advice. Make sure you search their site first. $\endgroup$ – MattDMo Feb 2 at 20:35
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Yeast grows very well in liquid. The initial innoculum from the store will visible grow (“prove”) in warm water with a little sugar.

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