Yeast slant infections

[shoobs]

I made up a batch of about 30 slants about 6 months ago to use for yeast storage. They've been sitting in a box until today, when I decided to use them. I'd guess about 50% of them are infected, with all sorts of different colours and shapes of mould?

What are people's typical hit rates with slants? Is this common? I followed the usual pressure cooking sterilisation methods.

 

[shmang]

Where they stored in the fridge/freezer or in a cupboard?

 

[shoobs]

Where they stored in the fridge/freezer or in a cupboard?

Just the cupboard. I assumed it wouldn't make any difference given they were sterilized and sealed.

 

[Yob]

Their metabolism will be working slower if kept in the fridge resulting in better overall health.

How did you prepare the slants?

 

[shoobs]

Their metabolism will be working slower if kept in the fridge resulting in better overall health.

How did you prepare the slants?

These were pre innoculation. No yeast on them yet. They were prepared using an agar/DME solution syringed into the containers. The whole lot was pressure cooked at 15psi (including lids loosely on the top). Pulled them out of the pressure cooker, laid them on an angle and did up the lids after they'd cooled.

 

[Yob]

If something grew in them mate, they were not sterile.

Spores or some such survived the pressure cooker and other processes.

ed: or they pulled in some wild yeast as they cooled

 

[MaltyHops]

Did you seal them up with parafin tape? (get these from wholesale florist supplies businesses)

If you don't stretch the parafin tape too much when sealing pre-innoc slants, you can reuse the p-tape when you seal it up after innpculating. Definitely put them in the fridge at all times. Seems like a hassle to go to this trouble but if you're to going to the trouble of making slants, precautions are worth taking.

These were pre innoculation. No yeast on them yet. They were prepared using an agar/DME solution syringed into the containers. The whole lot was pressure cooked at 15psi (including lids loosely on the top). Pulled them out of the pressure cooker, laid them on an angle and did up the lids after they'd cooled.

Last time I did a batch, I lined them up in a tupperware container for the cooling/solidifying stage. Being covered up hopefully reduces the amount of mould spores that could land on them as they cool.

Also, did you boil the water and agar/DME as before putting into the tubes?

 

[Yob]

The water used, such is my understanding, shouldnt just be boiled water either, boiled 3 times over 3 days or autoclaved/pressure cookered (which OP says he did)

:icon_cheers:

 

[shoobs]

Putting them in the fridge pre innoculation seems risky. All you're doing is delaying an infection if there is one there.

All good. At least 50% of them are still fine - I was just wondering if others had problems with their slants getting infected pre innoculation...

 

[Yob]

When I mentioned the fridge, it was on the assumption that they had yeast in.

Either way, you know that the practices needs a look, a 50% ratio of loss is a bit high IMO

Cheers

 

[MaltyHops]

Putting them in the fridge pre innoculation seems risky. All you're doing is delaying an infection if there is one there.
...

That's a good point ... and reminds me of a tip I read somewhere (or think I read somewhere) but no longer remember where - to leave blank slants for a few days at room temps for any mould to show up and then store away.

I think a fridge is still the best way to store even blank slants ... and cover in extra layers or container to isolate from other fridge content.