How to Sterilize Using an Instant Pot

Affordable Sterilization for the Home Cultivator

Sterilization is the invisible foundation of successful mushroom cultivation. Without it, even clean techniques and pure cultures can fall to contamination. For home growers, the Instant Pot offers an affordable and surprisingly effective way to achieve consistent, reliable sterilization — no lab autoclave required.

🍄 Why Use an Instant Pot?

The Instant Pot is a countertop pressure cooker that, when used correctly, creates a pressurized steam environment reaching ~239°F (115°C) — hot enough to sterilize most small-scale mushroom cultivation materials like:

• Grain jars

• Agar media

• Liquid culture (LC) broth

• Syringes and small tools

It’s not quite a 15 PSI autoclave, but it’s perfect for beginner to intermediate home cultivators with limited space and budget.

🔧What You'll Need

• Instant Pot (6-quart or larger; fits up to 6 standard mason jars)

• 1–2 cups of water (for steam)

• Mason jars (with proper lids, explained below)

• Heatproof vessels (for LC or agar)

• Recommended: trivet

• Isopropyl alcohol and a flame source (for sterile work)

🧪 Setting Up for Sterilization

1. Choose and Modify Your Lids

You have two main options for lid setups:

🛠️ Option 1: Modified Lids (Recommended)

Use plastic mason jar lids for durability and reusability - they won’t rust and hold up well to repeated sterilization.

Make your own: punch two holes, cover one with micropore tape (for gas exchange), and seal the other with RTV silicone for injection access.

Or buy parts: You can purchase filter patches and injection ports to create professional-looking lids.

🛠️ Option 2: Unmodified Lids (Beginner-friendly)

Place the lid upside down and loosen a quarter turn to prevent pressure buildup.

This will stop the jar from sealing during sterilization and allow for venting.

2. Load Your Jars

• Grain jars: Fill ~⅔ full with hydrated grain.

• Liquid culture or agar: Use heatproof containers (like canning jars or polycarbonate bottles).

• Place jars in the Instant Pot on a trivet or rack above the water line.

• Trivet use is highly recommended: While the Instant Pot heats evenly, direct contact with the metal base can cause glass microfractures, not always immediately, but they can lead to cracked jars over time.

⏲️ Pressure Settings and Time

Use the "Pressure Cook" or “Manual” setting on High Pressure.

🔁Rough Sterilization Chart for different PSI settings.

Because Instant Pots typically max out around 12.5 PSI, they don’t reach the same sterilization temperature as a lab autoclave (15 PSI = 250°F). To compensate, you’ll need to increase your sterilization time by ~1.5×.

🧠 Why it matters: Contaminants like bacterial endospores require sustained exposure to higher temperatures. At 11 PSI, you’re hitting around 239°F — not quite 250°F, but enough with longer sterilization times.

🔓 Post-Sterilization: Let It Depressurize Naturally

🛑 Never quick-release pressure after sterilization.

Let the Instant Pot release pressure naturally (20–45 minutes).

Quick-release can cause:

• Boil-over of media

• Cracked jars

• Incomplete sterilization

🚫When the Instant Pot Isn’t Enough

✅ Ideal For:

• Up to 6 mason jars of grain

• Agar, broth, and LC prep

• Syringes, tools, and small batches

• New or small-scale growers

❌ Not Ideal For:

• Large or dense substrate bags

• High-volume production

• High-risk medicinal species with longer sterilization needs

• Consider upgrading to a pressure canner (15 PSI) or lab autoclave for bigger projects or commercial work.

🌱 The Final Word

The Instant Pot makes reliable sterilization accessible for nearly every home cultivator. When used properly — with attention to lid setup, jar loading, and extended cycle times — it produces clean, contamination-free substrates ready for inoculation.

Whether you're prepping grain jars for lion's mane, pouring agar plates, or sterilizing tools, this simple kitchen appliance bridges the gap between casual hobbyist and serious cultivator.