I bought a 6 liter pressure cooker from Ikea a couple of weeks ago.

So I'm eager to use it on some big fresh pedro but also a little afraid of it (I shouldn't have looked those youtube movies of blown up pressure cooker situations...).

I saw Dg warning in several threads of letting the foam boil off first otherwise there is a risk of blocking the valves with possible result of blowing up the pressure cooker. Is this really a significant risk? How do you make sure the foaming starts again as you close the lid?

Would blending the cactus first have a big advantage over little diced cubes extraction wise?

Any tips about precautions to take and preparation times with the pressure cooker are welcome.

6 liter PC is what i use for cacti extraction, very efficient !

my way :
- 1 kilo of fresh fully hydrated cactus cut in dice(1/2 cm3) (whole cactus minus waxy skin and spines) + 2,5l of water + a dash of vinegar
- boil it with the cover on but not sealed (no pressure) and i check regularly if foam is building. In my short experience with fresh material, foam is not much a problem, so after a while, as foam don't raise, close the lid and PC for 30min.
- filtration, be sure to squeeze to get the most of liquid
-repeat 2x30min, no need to check the foam, you can close the lid from the begining.

And remember, if the pressure release valve stop making noise it means this gona happen :

Holy cow! That's kind of funny and not funny at the same time.

Was that your kitchen in the picture, Dans? It must have been a hell of a bang...

By the name of the holy frog, no.

And to be honest, the first problem with cactus in a PC would be to repaint your kitchen by spraying foam through the valve. But the picture says "be carefull folks !".

Thanks DansMaTete especially for the nice image. It's really comforting .
I think I just have to try it. Keep your eyes on the newspaper for an exploded PC story and the following trial against the largest DIY furniture store.

Just blend it super fine with a turbo blender and boil it for a few hours...

A good PC nowadays has not just 1 pressure regulating valve, but also a breaking disk that rips open before the pot goes boom. I would believe this safety redundancy became a standard.
Of course you don't want the redundant to pop in action, that broken disk is definitely open and needs replacement at least.

The only time I ever had problems with foaming was when using dried pedro powder. Cubes of fresh material have never done that IME. If you keep half an eye on the pressure gauge you'll be fine.

I've found it unnecessarily time consuming to de-spine and peel skin. Chop it up spines and all and toss in the PC with some water and have at it.

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As an experienced PC user (altho not for cactus, yet...) when cooking foamy foods (e.g. pulses) it's generally recommended to add a splash - about a teaspoon - of oil, to the cooking water, to minimise foam creation. But might this trace of oil magically hoover up some freebase mescaline...? IDK, but I doubt it

Another possibility might be to acidify with phosphoric acid, as this is used in various industrial applications to control/reduce foaming...

In theory, done properly, a PC should produce less foam than regular cooking, as it's exposure to atmospheric oxygen that helps stabilize foams, and cause overflow situations. With a PC, almost all air is expelled during the heating up phase, being driven out by the water vapour which takes its place.

If you watch your PC carefully, and remember that when it's up to pressure you should reduce the heat almost to minimum, in order to safely maintain it at the desired pressure level, your ears and eyes should let you know if anything is going awry pretty quickly.

Finally, I have successfully extracted tough roots by grinding and placing them inside a mason jar, with acidified water, closing the jar, and standing that in water inside the PC, before sealing it. Obviously you need a jar that can fit inside your sealed PC. Search for 'home canning pressure cooker' for more info. There's a bit more thermal inertia in this set up, meaning it takes about twice as long to heat up (and cool down). Don't be in a rush to depressurize and open up, unless you want to spray your kitchen with hot liquid and glass fragments... Just go for a walk, while you leave it to cool to room temp...

Thanks for all the info.



According to the manual it has 3 safety mechanisms. Still there are quite some modern day PC disasters on youtube



Maybe I should blend one or two big cuttings and boil and also boil one or two in sliced cubicles and than see which method yields the most. I assume you mean regular boils and no PC boils.



I will do so, the spines on my supposed to be pedros are neglectable. I will remove only the cores.



I'm not reallly in a rush. It seems that the general consensus is that PC ing the cactus breaks down cells pretty fast and is very efficient. Maybe you're right about taking the safe route, especially because it keeps me occupied. Maybe I'm simply not ready yet for next step boiling



Thanks for the tip, could work out nice for the foaming prevention. But the basification of the tea could possibly result in saponification with the NaOH reacting with the oil. But still useful when the tea is to be consumed.



That's kind of a challenge. I have a ceramic cookplate and although according to the PC manual it is supported, reducing heat has kind of a latency. As a result you have to act a little ahead I guess.

Mine (Tefal) has a third pressure protection as well, in the form of main the silicon seal ring that will bulge outwards by the pressure and making a leak hole open for the pressure to escape.

Number 1 is the normal pressure regulating valve (2 settings), this one could be clogged by food stuff.
Number 3 is the breaking disk, normally un-clogable by food.
Number 4 is the silicon ring that can bulge outwards making room for the hole above, fairly non clog-able too I suppose.

(number 2 and 5 are manual safety mechanisms that make opening impossible when there is pressure inside)

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After using a PC i won't go back long boil. It saves time and energy : no need to freeze&thaw or blending, no over consumption of gas or electricity (made from coal or nuclear most of the time), no need to check if it doesn't run out of water (happened once cause i was doing something else and forgot) and, please, don't over estimate the danger (or don't use car, there there is a big danger). It's not rocket science, just don't be stupid and reckless, don't over fill the PC, check how it reacts at the first boil before to lock the lid and listen to the valve (pchhhhhhhhhhh ).

I understand people who wants to boil for hours, i did it before to get a PC, it works very well but it also have some down side. IMHO, i think it's stupid to not use a PC if you already have it, it's a good tool.

Finally, I have successfully extracted tough roots by grinding and placing them inside a mason jar, with acidified water, closing the jar, and standing that in water inside the PC, before sealing it.
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Wow..I never thought the cacti roots had any alcaloid in them worth the work!

I always disposed of the cacti root material...

So NOT cactus roots!

Other roots, woody ones, so please don't go off the well-trodden paths on my account

I love the PC. I cooked chips, after the third boil I put the cactus in a blender, dropped the mush in a nutmilk bag and boiled it again thrice until the ball of mush lost its bitterness. The nutmilk bag made it easy to squeeze the tea out. Made the final filtering a breeze.