Mold Cultures In Spray Bottle - Life Expectancy & How To Make Sterile Water

[iain]

Quick question: how long will mold cultures (geo & p. candidum) last reconstituted in water, stored in a spray bottle in the refrigerator? I have some that have been in there for a couple of weeks now and would rather use them than mix up a new batch. Thoughts?

[linuxboy]

Pure spores? In sterile water? 5-20 years.

Normal water/impure spores (spores with media or substrate)? maybe 6-12 months?

Anything else depends on how you did it. Do you mean they're mixed together?

[iain]

I have a spray bottle with distilled water, a pinch of salt, a pinch of sugar, and a small amount of Choozit Geo 13 and P. Candidum. I sprayed some cheeses a few weeks ago and put the remainder in the refrigerator. I just wasn't sure if it would still be effective, or if I should mix up a new batch using new freeze-dried cultures.

[linuxboy]

You're fine. After it becomes turbid, you have about 2 weeks before you need to rebatch that mix. if you did it in sterile water, it would last years.

[arkc]

Where do you get sterile water?

[linuxboy]

I make mine. For a quick solution, take RO or distilled water, and boil it, or if possible, boil in pressure canner. Cool and use. Or filter through a bacteriological filter. Or autoclave.

[arkc]

Thank you.

arkc

[susanky]

Some spores can survive boiling, right?  So using distilled water solves this problem?  My water supply is a cistern.  I usually boil water before using to dilute rennet etc, but always wonder if something might survive.
Susan

[linuxboy]

Some spores can survive boiling, right?

Many can, yes. That's why one autoclaves, 121C for 15-20 mins.

So using distilled water solves this problem?

mmm, if one has a good process, most of the time, yes.

I usually boil water before using to dilute rennet etc, but always wonder if something might survive.

Yes, but honestly, there's more risk of contamination from the environment/during handling than spores surviving. It's typically a non-issue in practical use.

[susanky]

Good to know. Though I DO have access to an autoclave. Maybe I'll sterilize a half-gallon or so...
Susan