Luminous7 said:

(Natalensis spore swab plate)






Mold, or Myc?

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Both

For sure that´s mold, will soon turn green from the centre.
Most likely aspergillus or penicillium.

       

Smellyhobbit said:

I would

Let me clarify. I would if I needed the harvest. Currently I’ve got enough on hand that I can toss less than ideal fruits, but let’s say this is your only box and you need some fruits asap. Then yes I’d trim and save them.

They’re not going to go bad, though. Some mushrooms have dimples.

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Smellyhobbit said:

Rockin and congrats. But yeah those dimples just happen. They’re not really a concern.

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LadysKnight said:

Tell Stipe to enjoy his break, we have the Reverend.

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Quote:

One cubic foot of water will become 1646 cubic feet of steam when evaporated at zero psi gauge pressure and a temperature of 212°F. One cubic foot of steam weighs 0.03732 pounds, and one pound of steam occupies 26.796 cubic feet at zero psi gauge pressure and a temperature of 212°F.

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Quote:

According to Dalton's law of partial pressures, the total pressure by a mixture of gases is equal to the sum of the partial pressures of each of the constituent gases. The partial pressure is defined as the pressure each gas would exert if it alone occupied the volume of the mixture at the same temperature.

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Translation:

Trapped/mixed gasses (cold encapsulated gas) mixed with steam (steam is a gas) will result in a lower temperature than would be achieved if steam alone occupied the space.

As mentioned above, the steam takes up 1600 times more volume than the boiling water below, which forces the trapped gasses up and out of the vent tube. Once a sufficient amount of time has elapsed steam will have penetrated the filters/holes in bags, jars, and the voids within the media. Once sputtering has stopped and the steam flows uninterrupted from the valve, the unit has been purged. 10-15 minutes is sufficient for a 23q Presto, I prefer 15.

An easy way to test this is by using an autoclave thermometer. Expose the thermometer to your planned minimum purge cycle to record temperature. If the pressure guage reads 15psi but the thermometer failed to achieve 121°C, you need to increase time to purge. This is why longer purge cycles are preferable.

Thankfully this has already been verified by both Bod and myself.

Pressure allows water to exceed 100°C, the resulting steam is saturated with latent heat which is the mechanism by which all microorganisms have their DNA denatured, including pesky thermophilic bacterial endospores.

The pressurized steam makes contact with load surfaces, penetrating voids to condense and make contact with microorganisms. While purging is necessary to penetrate voids in the media and to achieve sterilization temps, clean/rinsed grains are required to take full advantage of these mechanisms. An overburden of filth not only increases bioburden but prevents contact with the grains surface where CFUs (colony forming units) reside.
If steam didn't penetrate the load, it wouldn't transfer latent heat to the surfuce upon which it condenses to denature the DNA of microorganisms. (Where voids are present)

There are loads that are not permeated by steam for obvious reasons as they don't have voids, sawdust blocks would be a great example of this, and the interior of PF cakes.

Failure to to penetrate the load will result in cold spots insulated by trapped gas and media (where voids are present) which would result in CFU survival, resulting in contamination. This is why longer exposure times are preferable.

The above penetration is evidenced by the way spawn bags seal on cool-down. The steam enters the voids in the bag taking up more than 1k times the volume of water, then condenses back into water on cool-down, shrinking the bag around the grains as steam returns to it's original state collapsing the voids between the individual grains. This is the  mechanism responsible for sealing spawn bags. If this wasn't the case you wouldn't have vacuum sealed bags.

If you fail to allow your pc/autoclave to sufficiently cool before removing bags you'll have a weak seal.

Although steam has greater volume than liquid water, it's not all that "wet". Despite the penetration capabilities of steam it will not throw off moisture content of spawn or substrate including PF. Snow behaves in much the same way, it may occupy a greater volume of space than liquid water, but once melted it actually contains very little water relative to it's volume.

It's thanks to steams ability to occupy space,  penetrate voids, and to condense on load surfaces, that we can can be assured that high latent heat is effectively/efficiently transferred to load surfaces. It's for these reasons we have any assurance (statistical probability) of sterility.

A note on sterility assurance:

For sterilization, it is required  to achieve a sterility assurance level (SAL) of 10^-6. One log 6 reduction to reduce bioburden to 1 CFU, and an additional log 6 reduction to achieve a SAL of 10^-6which is a 1 in 1,000,000 chance of a single non-sterile unit survival.



A total 12 log reduction is required for pharmaceutical practices. A 6 log SAL where 12 log reduction is required, the sterilization time should be a min of 121°C for 30 mins. I've verified the 23q Presto @ 60 mins with self contained biological indicator ampoules, but less is not more.

I hope the above explanation helps with the confusion surrounding steam sterilization. It's important to keep in mind both the properties of steam and the nature of voids. There's no mechanism preventing steam from entering open vessels, or occupying the voids within, unless of course there aren't any voids to occupy.

Furthermore: The above properties of steam or not only responsible for the vacuum that produces a seal in spawn bags but is also why AAs with valves (ie 1941x) produce a vacuum on cooldown, while Prestos do not.

This is autoclave theory in a nutshell.

Skropi said:

Luminous7 said:

Mold, or Myc?

(Natalensis spore swab plate)

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I am willing to bet that it is mold. Let's wait for the more experienced folks though. Oh, may I ask, how long from streaking to germination?

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Stipe-n Cap said:

LadysKnight said:

Tell Stipe to enjoy his break, we have the Reverend.

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Furthermore: The above properties of steam or not only responsible for the vacuum that produces a seal in spawn bags but is also why AAs with valves (ie 1941x) produce a vacuum on cooldown, while Prestos do not.

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