Pressure Cookers

Every mushroom cultivator values the pressure cooker's unmatched ability to sterilize. Acting as a fortress against contaminants, it's the cornerstone for a fruitful harvest.

Why Use a Pressure Cooker?

The disappointment of seeing contaminants overtake a carefully prepared substrate can be discouraging. These unwelcome guests – from bacteria to fungi – can sabotage the growth of your mushrooms, leading to lost time, resources, and heartache. More than just nuisances, these contaminants can outcompete and conquer your mycelium, making cultivation a fruitless endeavor.

Enter the pressure cooker. By generating a combination of high heat and pressure, it eradicates even the most resilient of endospores, ensuring that your growth medium is a clean slate. With a pressure cooker, the odds are tipped in your favor, and successful cultivation becomes a norm rather than an exception.

Which Pressure Cookers to Buy

Not all pressure cookers are crafted equally, especially when the stakes are as high as ensuring perfect sterilization. When on the hunt for the ideal pressure cooker, several critical criteria should guide your decision:

  • PSI Gauge: It's not just about pressure but knowing the exact pressure. A PSI gauge is non-negotiable, ensuring you always have a precise reading of the internal pressure.
  • Maintain 15 PSI: A magic number in sterilization. Only entertain pressure cookers that can consistently reach and sustain 15 PSI – the threshold needed to vanquish bacteria and rival fungi.
  • Capacity: Size does matter. Aim for a cooker that can accommodate multiple jars or bags, preferably with a capacity exceeding 20 quarts. This ensures scalability in your cultivation endeavors.
  • Durability: Sterilization is a recurrent process, and you need a cooker that stands the test of time. Investing in quality now can save future heartaches and costs.

Pressure Cooker Suggestions

Presto 23-quart Pressure Cooker Review

Meet the Presto 23-quart pressure cooker, a trusted companion for many in the mushroom cultivation journey. Whether you're sterilizing agar, liquid cultures, spawn or substrate, this cooker doesn't disappoint. Newcomers will appreciate its user-friendliness, consistent performance, and pocket-friendly price. Capable of accommodating seven to ten 1-quart jars, it ensures sizable batches with every use. While assembly is minimal, care is paramount. Proper drying post-use and proactive maintenance can prolong the Presto's lifespan.

After countless uses, my Presto remains reliable, cementing its position as a top choice for beginners in mushroom cultivation.

Pros: Ample capacity, user-friendly design, cost-effective, dependable performance, minimal maintenance.

Cons: Longevity is tied to care; some components may need eventual replacement.

All American Pressure Cooker

When discussing top-tier pressure cookers, the All American brand inevitably enters the conversation. Though I lack firsthand experience with this titan, its stellar reputation precedes it. Most feedback revolves around its robust build and performance, with the primary deterrent being its premium price tag.

Pros: Sturdy build, generous capacity, designed for longevity, unparalleled performance.

Cons: Pricier than most models, might feel a tad heavy or bulky for some users.

Pressure Cooker Components

This section provides a detailed overview of the Presto 23-quart pressure cooker. Keep in mind, similar components are also found in other pressure cooker brands.

Pressure Cooker Pot


This roomy 23-quart pot allows for the simultaneous processing of multiple cultivation materials.

Inspect the inside closely, and you'll notice measurement marks. The one nearest to the bottom marks 3 quarts. To spot them, find the handle with an arrow; it points directly to these marks.

Over time, discoloration inside the pot is typical. To remove stains, cook a mixture of water and cream of tartar at 15 PSI.

Pressure Cooker Lid / Cover

Lid / Cover

The lid houses the vital elements of the cooker. To secure it, align the arrow on the handle with the one on the lid, then twist the lid to seal it.

Ensure the cover remains undamaged, especially the rim. A deformed lid can interfere with sealing, jeopardizing the maintenance of the desired pressure.

Pressure Cooker Gauge

Pressure Gauge

This gauge displays the pressure in PSI (pounds per square inch) and is one of the few components requiring assembly. Before using the cooker, confirm that the needle is at '0' and the gauge is undamaged. Protect the gauge from submersion in water and potential physical damage.

For accuracy checks, you can visit specific centers or contact Presto's consumer service. If found faulty, replace the gauge prior to using your cooker.

Replace Pressure Gauge
Pressure Cooker Sealing Ring

Sealing Ring Gasket

This black rubber ring, found inside the lid, ensures pressure retention.

Always check the sealing ring gasket for any signs of damage before use. To maintain its condition, dry it well after each use. General wear may necessitate its replacement every 2 to 3 years.

Replace Sealing Ring
Pressure Cooker Air Vent - Locking Mechanism

Air Vent/Locking Mechanism

This silver component, stamped with "TOP", locks the lid in place as pressure rises. Water and steam release during pressure buildup is normal and occurs through this vent.

Over time, the gasket on this mechanism may need replacing, especially if it shows signs of wear like cracks or nicks.

Replace Air Vent/Locking Mechanism
Pressure Cooker Overpressure Plug

Overpressure Plug

Located behind the pressure gauge, this black plug acts as a safety feature, ejecting if pressure levels become hazardous. As pressure rises, it's normal for the plug to seem protruded.

Replace the plug if you observe any signs of deterioration.

Replace Overpressure Plug
Pressure Cooker Vent pipe

Vent Pipe

This component allows steam and pressure to escape. An external weight regulates this pressure. It's crucial to ensure the vent remains unblocked. When held against light, the vent should be transparent. Avoid using toothpicks for cleaning; they can leave residue. Opt for a pipe cleaner or a similarly resilient tool.

Pressure Cooker Weight

Weight / Pressure Regulator

When the cooker reaches the desired temperature, position the weight over the vent pipe to manage and stabilize the pressure.

You might notice the steam release can be quite audible. To diminish this, consider adding 17 grams to the weight; three quarters are a perfect fit.

A word of caution: Always ensure you've removed the weight prior to opening the lid. It might seem obvious, but it's an easy step to overlook, resulting in the weight tumbling to the ground.

Safety First: Pressure Cooker Guidelines

Operating a pressure cooker is not inherently dangerous, but like all tools, using it without due care can lead to accidents. When you’re dealing with pressurized steam, it's important to follow safety guidelines to ensure you and your surroundings remain safe.

Basic Safety Precautions

  • Read the Manual: Always read the user's manual before operating any pressure cooker. While most cookers operate similarly, there might be brand-specific procedures or safety measures to be aware of.
  • Seal Properly: Always ensure that the lid is correctly sealed and locked before starting. Never force it open. If you have difficulty opening the lid after cooking, it usually means there's still pressure inside.
  • Monitor Regularly: Don’t leave your pressure cooker unattended. Keep an eye on the PSI and make sure it stays steady. If the pressure goes beyond the recommended level, reduce the heat.
  • Clear Vent: Ensure the vent is clear and not obstructed. Before every use, check the vent for any blockage.
  • Check Seals and Gaskets: Before using, always check the rubber seals and gaskets for any signs of wear, tear, or cracks. If found, replace them before using the cooker.
  • Release Pressure: Always allow the pressure to release fully before opening the lid. There are usually two methods to release pressure: natural release (letting the cooker cool down on its own) and quick release (using the vent). Consult your manual to know which method is recommended for your specific cooker.
  • Fill Correctly: Never overfill the pressure cooker. Leave at least a third of its capacity empty to allow steam to build.
  • Hot Surfaces: Remember that the cooker, especially the metal parts, can get very hot. Use oven mitts or a thick cloth when handling.

Worst-Case Scenarios

The worst-case scenarios with pressure cookers often involve the device exploding due to excessive pressure. While modern pressure cookers have multiple safety features to prevent this, older models or malfunctioning devices can be at risk. An explosion can cause hot materials and steam to scatter everywhere, leading to severe burns and damage to property. Always ensure your cooker is in good working condition and do not use it if you suspect any malfunction or damage.

Common Mistakes to Avoid

  • Overfilling: As mentioned, always ensure there's enough room inside the cooker for steam to form.
  • Using Damaged Parts: If the sealing ring, pressure valve, or any other part looks damaged or worn out, replace it before using the cooker.
  • Force Opening: Never try to force the cooker open. If it doesn’t open easily, it's a sign there’s still pressure inside.
  • Ignoring the PSI Gauge: For those with a PSI gauge, it's not there for decoration. Monitor it and adjust the heat to keep it within the recommended range.
  • Skipping Cleaning: After each use, clean the cooker thoroughly, especially the vent and the sealing ring, to ensure there's no residue or particles that might interfere with its operation next time.

How to Use a Pressure Cooker

1) Inspect Your Pressure Cooker

Before operating your pressure cooker, ensure that all parts are in working order.

  • Sealing Ring: Ensure there are no tears or damages.
  • Vent pipe: Ensure nothing is clogging the vent.
  • Air Vent/Locking Mechanism: It should not stick and must slide with ease.
  • Overpressure Plug: It should fit securely to the lid and show no signs of damage.
  • Pressure Gauge: It should read zero with no evident signs of damage.

2) Add Water

Begin by pouring in the required 3 quarts of water, reaching the first notch of the pot. Though distilled water is the best choice for your cooker's longevity, using warm tap water is also an option. To tackle potential hard water stains, remember to add a few tablespoons of white vinegar.

Start by placing empty 4oz jars or jar lid rings at the base of the pot to prevent jars from floating and potentially breaking. Set the cooking rack over these. By doing so, you ensure your items stay submerged, optimizing the sterilized surface area. When using jars, tilt them to release any trapped air bubbles beneath.

Pressure Cooker Notches

3) Prepare and Add items

For pressure cooker preparation, cover any lids with filter ports using foil. Fold bags to deter steam from infiltrating the filter patch, preventing unnecessary moisture from entering your cultivation medium.

Strategically arrange your materials inside the pressure cooker. Incorporate empty jars if needed to stabilize contents and prevent breakages.

Pressure Cooker Packed

4) Seal the Lid and Start Heating

Align the arrow on the lid with the handle's arrow, ensuring the lid sits snugly on the pot.

Set your pressure cooker on a stove with high heat. Refrain from adding the weight initially. Once steam consistently emerges from the vent pipe without sputtering, place the weight on it. Typically, reaching this stage takes about 10 minutes.

Pressure Cooker Seal Lid

5) Bring Up to Temp and Monitor Pressure

As pressure builds within the cooker, monitor it diligently. Once the desired PSI is achieved, adjust the heat and set your timer.

Fine-tune the heat until a consistent desired PSI is maintained. Periodically check the gauge to ensure consistent pressure.

Pressure Cooker Gauge and Weight

6) Finish Cooking

After the predetermined duration, switch off the heat and let the pressure subside. DO NOT OPEN the pressure cooker until the gauge reads '0'.

Maintaining and Cleaning Your Pressure Cooker

Proper care extends the lifespan of your pressure cooker and ensures efficient performance:

  • Routine checks: Periodically examine the gasket, valves, and seals for wear and tear.
  • Cleaning: After every use, clean the cooker thoroughly to prevent residue build-up and maintain its performance. If you seek to preserve its gleaming finish, scrub on some Bar Keepers Friend, it does wonders.
  • Storage: Store your pressure cooker correctly, ideally with the lid inverted, to allow parts to air out and prevent odors.

Common Issues and Troubleshooting:

Undercooked or Overcooked Substrate

  • Deviating from the recommended pressure or temperature.
  • Using inaccurate timing methods.
  • Mechanical issues with the pressure cooker leading to inconsistent heating.
  • Always monitor and ensure the pressure cooker attains the proper PSI (typically 15 PSI for mushroom cultivation) before timing.
  • Utilize trustworthy timers, such as smartphone alarms or dedicated kitchen timers.
  • Inspect your pressure cooker periodically for wear and damage, replacing parts as necessary.

Contamination Even After Pressure Cooking

  • Inadequate sealing of jars or bags prior to cooking.
  • Pressure cooker not attaining the required temperature or pressure.
  • Post-cooking contamination during handling or inoculation.
  • Delaying inoculation of sterilized substrates.
  • Ensure that jars or bags are sealed without any damage.
  • Confirm the cooker reaches the necessary PSI.
  • Work in sanitized environments, like a still air box, especially after pressure cooking and during inoculation.
  • Inoculate the substrate immediately after cooling to minimize contamination risks.

Water in the Jars/Bags

  • Adding excessive water to the pressure cooker.
  • Improper sealing leading to water entry.
  • Overly wet substrate pre-pressure cooking.
  • Adhere to manufacturer's recommended water levels, ensuring water doesn't reach the topmost jars or bags.
  • Check the sealing mechanisms for integrity.
  • Monitor substrate moisture, ensuring it's damp but not drenched.

Inconsistent Sterilization Across Batches

  • Stuffing the pressure cooker with too many items.
  • Varied jar/bag sizes or materials in one batch.
  • Uneven heat distribution.
  • Load the cooker ensuring there's enough space between items for even cooking.
  • For uniform cooking, maintain consistency in jar or bag size and materials.
  • For stovetop cookers, ascertain even flame distribution. For electric models, ensure uniform functioning of the heating element.

Pressure Cooker Not Sealing Properly

  • Gasket wear and tear.
  • Debris causing sealing interference.
  • Vent or pressure regulator blockage or malfunction.
  • Examine and replace the gasket periodically.
  • Ensure the cooker's rim and lid are free from obstructions.
  • Inspect and clean the vent or pressure regulator. Replace parts if signs of damage or wear are apparent.

Common Questions

Can a pressure cooker explode?

Modern pressure cookers are equipped with safety features like an overpressure plug that activates if PSI reaches hazardous levels. Releasing steam when the plug ejects might cause burns. However, by operating the cooker at safe PSI levels, such incidents can be avoided.

Should a pressure cooker hiss?

Yes. Hissing from a pressure cooker is standard. As the weight or pressure regulator releases steam to maintain a specific PSI, a hissing sound is produced.

Do you need a pressure cooker to sterilize cultivation material?

While some unconventional methods may sterilize without a pressure cooker, they pose a high risk of contamination. Thus, they aren't recommended.

Can you use an Instapot for sterilization?

The suitability of an Instapot for sterilization depends on its capabilities. Most Instapots can't consistently reach and maintain the required 15-PSI, making them unsuitable for this purpose.

Will plastics melt in the pressure cooker?

Many plastics are susceptible to melting under the conditions inside a pressure cooker. However, specific plastics like mushroom bags and some harder plastics can withstand these temperatures. Typically, if plastic is oven-safe, it should withstand pressure cooking.

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