Tyndallization Question

[Shamanistic]

Hello my fellow mycologists

I soaked some grain a water/bleach solution and decided off handedly to check the psi I can get from my pressure cooker weight and found that it is only 5 psi which isn't the recommended 15 psi and so I didn't proceed with pressure cooking. It's been soaking for 3 days now and I was thinking that if I tyndallize I might be able to sterilize it but I've also heard of mixed success with it. I am letting the spawn dry out a little and planning on boil/pcing tonight so any advice before then will be very much appreciated!

[Melange]

How did you check the psi of your pressure cooker?

[Bigred]

just pc it for 3 hrs you shall be fine i use a small pc for little batch's it's only 5 psi just let it cool in the pc dont take them out hot

and never soak for more than 24 hrs as you risk bacterial blooms

Edited November 24, 2012 by bigred82

[obtuse]

I had similar concerns about a second hand PC i bought years ago, didnt trust it was reaching right PSI.

So i used tyndallisation with great success. just make sure you boil for at least an hour then let incubate for about 24 in a warm spot, then repeat as necessary, at least another 2 times.

its a lot less energy efficient, and perhaps makes for more opportunities fro contamination, and wont kill everything. but as its kitchen based your not rying to kill etremeophiles, just your usual assortment of annoying characters.

Cheers, Ob.

[Shamanistic]

Cheers for all the advice guys. Melange I weighed the pressure cooker weight and I measured the diameter of the nozzle then you can just calculate it as

weight times 9.8 and then divide by the area of a circle with the same diameter as the nozzle and then times by a conversion factor to get the answer in pounds per square inch. This one is pretty old so maybe you won't be able to do that with newer models, not sure.

[Bigred]

do you think you cold put a presto weight on it

[Sallubrious]

You really want to be careful changing weights unless you know your PC is rated for the extra pressure.

(simplified I wont go into newtons)

Force = pressure *area

So a small change of pressure acting on the entire lid surface area can make a massive difference in the forces applied to the lid.

As an example a 30 cm diameter PC operating at 5 psi

6 inch (radius) squared * 3.141 (π) * 5psi = 565 pounds of force acting on the underside of the lid

Where the same 30cm PC operating at 10 psi

6(inch) squared * π * 10psi = 1130.7 pounds of force acting on the underside of the lid

And the same 30cm PC operating at 15 psi

6 inch squared * π *15 psi = 1696.14 pounds of force.

So it can be very easy to exceed the pressure rating of the PC if you play around with it.

I certainly wouldn't want to be around something like that if anything went wrong, especially if it is full of hot glass, steam and grains ect.

@ Shamanistic, there is some room for error with that calculation method, during operation the steam makes a dynamic seal on the weight and it can have the effect of applying greater resistance than a theoretical calculation would suggest. The only way to know for sure would be to measure the operating pressure with a gauge.

Edit: to fix mixed units of calculation, I sluaghtered that by mixing cm's and inches.

Edited November 25, 2012 by SallyD

[Shamanistic]

Yeah, I would never load the pressure cooker more than it is rated especially because it's about as old as I am. I think it's sketchy enough to even use the damned thing let alone with a huge amount of excess pressure in there.

I think I'll just buy a new pressure cooker in the next few weeks but I want to mycologalise now! (Sweet I made a new word)