A pressure cooker is the most important item needed when you want to grow mushrooms at home. It is very important to provide a sterile or pasteurized substrate for the mycelium to colonise.
Without one you will increase the likelihood of contamination growing alongside you’re mycelium and ruining your batch; ultimately wasting your time.
Pressure cookers are the most expensive investment you will have to make when moving into the world of mycology so its important to understand what you are paying for before making an investment.
Often, people will buy a pressure cooker only to outgrow it within 12 months, so in this article I am going to discuss a few different options for people who want to start growing mushrooms from spawn syringes.
Top Choices Of Pressure Cooker For Mushroom Growing:
Presto 01362 6-Quart Stainless Steel Pressure Cooker – This is the cheapest option, it will tightly fit about 6 half pint jars inside. I recommend this option if you are on a very small budget and you are unsure if growing mushrooms is for you. If you enjoy the hobby of mycology you can always upgrade to a larger model if you outgrow this size. A lot of mushroom cultivators will start with a cooker this size using small jars and PF tek substrate.
Zavor EZLock 10 Quart Stove-top Pressure Cooker & Canner – This 10 Quart pressure cooker comes with a number of safety features built-in. This makes it perfect for a newbie mushroom cultivator who may be intimidated by using a pressure cooker. On top of this, 10-Quarts is a very good size as it is not huge yet will hold about 10 half-pint jars which is plenty of spawn for a home-grower.
Presto 01781 23-Quart Pressure Canner and Cooker – This whopping pressure cooker should hold at least 20 half pint jars mean you can create a whole lot of spawn in one go. If space in’t an issue I would recommend this cooker although it is more expensive than the other models. Many mushroom cultivators purchase a 23 Quart Presto as they are reliable and hold loads of substrate. This cooker quite often goes on sale for a cheaper price so make sure to check it out.
Which one would I choose today?
If I was going to buy a pressure cooker today for growing mushrooms at home I would choose the Zavor EZLock 10 Quart Stove-top Pressure Cooker & Canner .
This is based on the following reasons:
- Size – larger but not huge! It can hold a good number of spawn jars at one time (reducing labor, increasing yields), but it is still a reasonable enough size for keeping in your home.
- Built for purpose – clear states this can be used for canning.
- Warranty – 10 years.
- Price – the cost is mid range so if you decide you don’t enjoy growing mushrooms you won’t have overspent.
This option is perfect for a beginner who is just starting the hobby of mushroom growing, this is bigger than the model I started out with but had this been available at the time I definitely would have chosen it. It won’t take up too much space, doesn’t break the bank and has a range of safety features builtin which the older designs lack.
Note: Sometimes the larger brand cooker goes on sale at a very cheap price, so make sure you check out each option first!!!
Do you have recommendations for the UK growers?
This is the size pressure cooker I started out with its cheap and can hold about 8 half pint jars. This is a well built system and are designed to ensure safety as a priority, this can be a huge benefit to people new to the sterilization process.
This is a large GAS HOB ONLY pressure cooker it can fit a fair amount of jars or substrate bags inside of it. Read the note below first before purchasing though.
This is another whopping pressure cooker, comparable to the large presto cookers. However this is a GAS ONLY pressure cooker so no luck if you have an induction hob. This one is also confirmed to reach 15PSI. Read the note below first before purchasing though.
Note: Hawkins pressure cookers are manufactured in India this means some of the sellers on amazon may be sending them from India. This will incur custom charges when the item reaches the UK.
To avoid this find the “other sellers” section on the right hand side of amazon and look for a UK seller.
Sterilization Units for mushroom farm cultivation.
If you are creating a business based around mushroom cultivation then you are probably going to need to maximize your sterilization efforts. This is a proper sterilization unit (known as an autoclave) you would find being used by commercial laboratories. You could fit many spawn bags in this system and it is specifically made for sterilization. It is also possible to get these units as all in one electric systems which is actually really useful albeit pricey.
Do you need a Pressure Cooker for growing mushrooms?
Technically no, for some mushrooms strains such as oysters it is possible to use pasteurized substrates. However, for the majority of strains and substrates it is recommended to sterilize the substrate to give the mycelium a good chance of colonizing to 100% without contamination.
If you want more consistent results and to grow an array of different strains it is always recommended to use a pressure cooker.
What size Pressure Cooker Is needed for Growing mushrooms?
The minimum size pressure cooker needed for mushroom growing is 6 Quart, this will allow you to get 6 half-pint Jars sterilized at one time. Anything below this will greatly reduce your margin for error and increase the chances that you won’t produce any mushrooms from you’re sterilization run.
What to look for in a Pressure Cooker for growing mushrooms?
Size – ensure the product you’re looking at can fit a decent number of mason jars inside. The more spawn jars you can sterilize the more mushrooms you can grow.
Pressure – Ensure your pressure cooker can reach 15PSI, this is level of pressure required to bring the temperature inside the pot to sterilize the substrate. In Europe it is harder to find a pressure cooker will reach the full 15PSI but it is not hard to find a product which can push pressure to 14+PSI (just leave your jars to sterilize longer if so).
Hob Type – Ensure the pressure cooker will function with the type of hob you have. There are plenty of options which can be used on all hob types however its always best to check as some can not.
Things to bear in mind.
- Ensure the pressure cooker does not run out of water while functioning.
- Never block the vent on your pressure cooker.
- Regularly clean and maintain your pressure cooker.
- Do not remove your sterilized jars until the pressure cooker has cooled.
Why is a Pressure Cooker important in mushroom cultivation?
In short, pressure cookers sterilize the substrate destroying harmful contaminants which could compete with your Mycelium.
Pressure cookers are important when growing mushrooms as they sterilize the different substrates which the Mycelium is going to eat. Contaminant such as mold spores, bacteria and other fungi spores are everywhere and the substrates we use during mycology are the perfect nutritional meal for them. When the correct moisture and nutritional conditions are met (after we soak the substrates) the spores and bacteria germinate and multiply, taking over your substrate.
By heating our substrates to a high temperature in the pressure cooker we are destroying the spores and bacteria which may have been present on the substrate. This will give the mycelium you introduced into the substrate a head start to establish itself before reintroducing the substrate to the contaminated open air again.
How to use a Pressure Cooker for mushroom cultivation?
In this section, I am going to do a brief outline of how you would use a pressure cooker to sterilize jars, spawn, substrate bags or other growing utencils.
1. Examine Pressure cooker
As discussed in most pressure cooker user manuals it is usually a good idea to inspect your pressure cooker every time before use. Failing parts could be dangerous.
These are the things I like to check before beginning:
Cleanliness – Is the pressure cooker free from residue and build up, particularly around the inside of the lids.
Clear safety valve – Is the safety valve clear and working correctly? When the items I am sterilizing are inside the pressure cooker does it block the safety valve?
Rubber sealing ring – Is this clean and free from residue? Is there any damage to the ring which may cause leaks? Is underneath the ring clean?
Opening/Closing mechanism – Is this working as intended and free of obstructions (such as your jars).
2. Fill Pressure Cooker with Water
Whatever pressure cooker you purchase in the end should have a minimum and maximum fill suggestion displayed on the inside of the cooker. When you are first using your pressure cooker I would suggest filling it up to at least the minimum line as suggested in the manual.
If you are wondering how much water to use in a pressure cooker while sterilizing PF tek then just fill the pressure cooker with water until the minimum line (around 2 pints). This is a safe measure until you fully understand how to maintain pressure in the cooker during the process.
Once you become more confident with the pressure cooker you can work with smaller volumes of water in the pressure cooker as you learn how to maintain pressure without drying the cooker out.
3. Insert Items
In Short: Place items into a pressure cooker, ensure the lids are covered with foil. The items should be raised from the bottom and not touching the perimeter.
It’s time to place all the items you wish to sterilize into the pressure cooker.
Normally I use the vegetable rack which comes with the pressure cooker and place that on the bottom of the pressure cooker.
If you don’t have one of these you can line the bottom of the cooker with the rings from the mason jars. The main purpose is to raise the items from the bottom of the cooker to avoid them from contact burning.
As mentioned earlier ensure that the safety valve is not being blocked by any of the items and it is still possible to open and close the pressure cooker with the items inside.
Ensure that your items are not touching the perimeters of the pressure cooker some people like to put a damp cloth around the outside of the items to ensure a barrier remains.
4. Seal the pressure cooker
Perform one last check of the Pressure Cooker lid, mechanism, and the contents inside.
Wipe down the outside and bottom of the cooker to ensure no water or food has splashed onto the bottom (I always make a mess).
Finally, close the pressure cooker and apply the correct setting.
5. Heat the Cooker until hissing.
Now, this section is pretty dependent on the type of Pressure Cooker you have but the general consensus is to put the cooker on full heat until the pressure builds up and it begins to hiss.
Once the pressure is maintained (hissing for 10 minutes) turn the cooker down too low to maintain the pressure (for me this is not the bottom dial but the 3rd tick).
This will maintain the pressure while preventing all the steam from escaping and drying out the cooker, resulting in lost pressure.
Leave to sterilize for the time in which it is required for your tek. Once finished turn off the heat and leave to cool overnight.
NOTE: LEAVE THE COOKER TO COOL OVERNIGHT DO NOT OPEN IT UNTIL THE CONTENTS HAVE COOLED THIS CAN RESULT IN ISSUE WITH YOUR SUBSTRATE.
6. Clean after each use.
Once you have finished with your pressure cooker clean it to ensure it is ready for the next use. This will also reduce the cleaning and checking needed for the next time you use it.
It is always a good idea to maintain the most prized possession in your mushroom cultivation arsenal, so look after your pressure cooker and always refer to the manual FIRST!
What materials can be used inside a pressure cooker?
I am in no way a pressure cooker safety expert when it comes to items that can be used inside of a pressure cooker. It is always best to refer to the manual for this sort of information before taking advice on the internet.
I can tell you a few items which I regularly use inside my Pressure Cooker without issues:
- Glass Jars/Beakers – I use these all the time while making grain Jars.
- Mushroom Cultivation bags – Designed for pressure cooking.
- Plastic containers that display the 5PP symbol as shown here.
- Turkey Bags – I use this for sterilizing/pasteurizing bulk substrates as I can reuse them.
- Tinfoil and elastic bands – These always go over the top of the Jars I’m using.
- Syringes – These can be sterilized when wrapped in tin foil however there are easier methods out there for this.
- Poly Fill/Micropore Tape/EZ felt (with RTV silicone) – These generally make up the contamination barrier on my lids.
How long to Pressure Cook Grain spawn?
15-PSI for at least 90 Minutes.
When working with grain spawn you want to leave the quart grain jars to sterilize for at 15-PSI for at least 90 minutes, this should be a sufficient enough time to eradicate contaminants and spores.
If you are using a lower PSI like 10-12 PSI the sterilize for 2.5 hours (although 15 Psi is always recommended).
How long to Pressure Cook Agar
15-PSI for at least 20 Minutes.
Agar will heat and sterilize in about 20 minutes, this is due to agar being made up mostly of liquid. Once complete it can be removed and then allowed too cool before use.
How long to Pressure Cook PF-Tek
15-PSI for atleast 60 minutes. 10 – 12PSI for 2 hours.
PF-tek is a pretty easy substrate for beginners. It can be sterilized in a shorter period of time to grain jars. Alongside this you can even use a lower PSI for a longer period of time with PF-Tek.