Questions about sterilization in pressure cooker

[groovymf]

Hi all,

Did my first homebrew(experiment) yesterday and all went well. However, still some questions about sterilization.

I am using a simple 4L pressure cooker from amazon with max 13psi. I've seen some scientific literature and people on mushroom forums say that 15psi is not needed per se, but a lower psi will be sufficient for sterilization. It just needs to run for a longer amount of time.

"The sterilization is preferably done at temperatures ranging from 100-140°C for 3-30 mins at varying pressures. Preferred combinations of temperature- time-pressure including the following:

121°C for 20 mins at 103 kPa (15 psi)
132°C for 3 mins at 186 kPa (27 psi)
115°C for 30 mins at 69 kPa (10 psi)

But other combinations can be used if desired. Generally, the higher the temperature and pressure, the shorter the time required for adequate sterilization."

However, this recommendation was not for laboratory glassware but for glucocorticosteroids. I can not find any other literature on it.

Still based on this, I think 30 to 40 minutes should be suffucient for 13psi and also based on all the other information I've seen.

Anyone else using a simple pressure cooker as an autoclave? How long do you run it?

Does anyone use an airfryer to dry afterwards?

(For drying, since I don't have an oven, I do put everything in the airfryer, still slightly covered with aluminium foil.)

 

[groovymf]

Using this filter system btw.

 

[SunnyInAZ]

Is there a reason you don’t just take your brew to 100deg C and call it a day? I clean with 100% IPA and take my brew to 100deg C for 2-5min and never had any issues…all bacteria dies at 100C even just getting to 75deg C is sufficient…

 

[groovymf]

Is there a reason you don’t just take your brew to 100deg C and call it a day? I clean with 100% IPA and take my brew to 100deg C for 2-5min and never had any issues…all bacteria dies at 100C even just getting to 75deg C is sufficient…

I've considered this option when I was researching, but came to the conclusion that the 'right way' to do sterilization was by using a autoclave(or pressure cooker). Not to say that other methods wouldn't work, I just thought that this was the best way.

And I have purchased the pressure cooker now, so I would like to use it.

I have read that some organisms can survive high temperatures(also in the oven with dry heat), so boiling would not be enough, but the steam of the autoclave will kill everything.

Also compound degradation might be an issue. Not sure though.

With steam, every organism should be gone for sure and no need to go above 60 degree celcius when brewing.

 

[ThinkTrenbolone]

View attachment 261532
Using this filter system btw.

how has this been for you? good setup?

 

[micro2000]

You will be fine with 13psi for 25-30 minutes. Sterilization is a function of not only temp and pressure but microbial concentration. The general rule for sterilization validation is the ability of a cycle to kill 1,000,000 cells of a very heat resistant bacteria. Unless you're brewing in a gas station bathroom, most mixes will never have this level of bacteria and they will usually not be very heat resistant. Everything will likely be killed within the first 5-10 minutes easily.

 

[bonacris]

You will be fine with 13psi for 25-30 minutes. Sterilization is a function of not only temp and pressure but microbial concentration. The general rule for sterilization validation is the ability of a cycle to kill 1,000,000 cells of a very heat resistant bacteria. Unless you're brewing in a gas station bathroom, most mixes will never have this level of bacteria and they will usually not be very heat resistant. Everything will likely be killed within the first 5-10 minutes easily.

Bacteria might die but you won't kill endotoxin at this temp.

 

[ALIGIZER]

Bacteria might die but you won't kill endotoxin at this temp.

What can you do for neutralize the endotoxin ?
I have seen many post about endotoxin, and the probable danger of long term exposure

 

[bighunanballs]

360f for 3 hours will denature endotoxins. It will also more than likely mess up your brew. I've never tried it personally to see what happens after this heat for that long

 

[ALIGIZER]

Ok so at this point for limit the amount of endotoxin, we have to maintain as possible perfect sterilization and cleaning protocol

 

[egruberman]

Why would you use a pressure cooker and not dry heat sterilization for glassware?

 

[bighunanballs]

Why would you use a pressure cooker and not dry heat sterilization for glassware?

Not everything touching the process stream is glassware, but yes you can most certainly dry heat sterilize glassware and stainless steel. You won't be able to do that with your viton/butyl seals or gl45 septum caps and vacuum bottle top adapter/etc so you'll still need a pressure cooker for lower heat sterilization.

 

[egruberman]

You won't be able to do that with your viton/butyl seals or gl45 septum caps and vacuum bottle top adapter/etc so you'll still need a pressure cooker for lower heat sterilization.

No argument here. I have an autoclave on hand and went to use it for glassware. After doing some reading on protocols came to the conclusion that dry heat was probably better.

 

[bighunanballs]

No argument here. I have an autoclave on hand and went to use it for glassware. After doing some reading on protocols came to the conclusion that dry heat was probably better.

It prob is since you can denature endotoxins at high heat. But I wouldn't use my food oven to do it in

 

[egruberman]

It prob is since you can denature endotoxins at high heat. But I wouldn't use my food oven to do it in

Is my tempering oven sufficient?

 

[bighunanballs]

Is my tempering oven sufficient?

I mean you could but is it spotless clean? No metal particulates, slag dust or other metallurgical contaminates? I prefer buying equipment that is only used for lab work. If you're careful and clean your tempering oven should be fine

 

[ALIGIZER]

Pls guys can you give me some tips or rate my setup sterilization.
I clean all stuff that I want to sterilize with bleach and then I rinse with demineralized water. I then put all the bottles and rubber stopper returned on the tray. I sterilize 15 minutes at 136C. After that I put in the oven at 100 degrees still on the tray (which is more in the shape of a seal). I wait as long as it takes for everything to be dry.
For fill each vial I use bottle top dispenser ( sterilized) so I return vial 1 by 1 and caps it immediately. Never had an issue but want to improve it and minimize all impurities and endotoxins.

 

[qadsan]

No argument here. I have an autoclave on hand and went to use it for glassware. After doing some reading on protocols came to the conclusion that dry heat was probably better.

I use a Wayne S500 dry heat sterilizer for my glassware. You can pick them up refurbished for half the cost of new, or at an even better deal as used on eBay.

 

[groovymf]

how has this been for you? good setup?

Works very well. Be careful with the tube connection part, it is relatively weak. Recommend to use a proper hand vacuum pump and not one of these plastic ones. I use a simple brake bleeding pump.

You will be fine with 13psi for 25-30 minutes. Sterilization is a function of not only temp and pressure but microbial concentration. The general rule for sterilization validation is the ability of a cycle to kill 1,000,000 cells of a very heat resistant bacteria. Unless you're brewing in a gas station bathroom, most mixes will never have this level of bacteria and they will usually not be very heat resistant. Everything will likely be killed within the first 5-10 minutes easily.

I've ditched the cheap pressure cooker and got a large one with a pressure gauge and weighted pressure relief valve. Just doing 15psi for 15min now. I was not sure if that cheap pressure cooker even got to 13 psi in the first place.

For drying, instead of the airfryer I mentioned, I now use a large/deep pan with a heightened plateau at the bottom. I put the lid on with a slight gap to release moisture. With a kitchen oven or airfryer it will move a lot of new air inside which is not good.

I think this is good enough without actual laboratory equipment like a lab oven and autoclave.

 

[groovymf]

Forgot to mention: be aware to only use distilled water inside of the pressure cooker, otherwise expect mineral buildup on the glassware. For the same reason, before placing the materials in the pressure cooker, after cleaning, make sure to give a final rinse with distilled water.

When drying, watch out for plastic which can melt, it's best to place it higher up on top of any bottles and beakers and for a short amount of time. Same for any filter membranes. I have lost a couple of bottle caps and one filtration adapter this way. (only the blue part around the glass membrane can take a lot of heat)