What You’ll Need

• Substrate Ingredients:
  • Hardwood fuel pellets (e.g., Traeger hardwood pellets)
  • Soy hull pellets
• Bags:
  • Unicorn XLS-A (10 lb wet capacity)
  • Unicorn 3T (5 lb wet capacity)
• Tools:
  • Calibrated scale (grams and pounds)
  • 2–5 gallon clean mixing bucket
  • Measuring container for hot water
  • Impulse sealer
  • Flow hood (or high-quality laminar flow work area)
• Sterilization Equipment:
  • Presto 23 qt pressure cooker (or All American sterilizer)
  • Bottom Rack (with legs) and top trivet (for saftey) for inside PC

Best Mushroom Species for Master’s Mix

• Oyster mushrooms (Pleurotus spp.) – Rapid colonizers, big yields.
• Lion’s Mane (Hericium erinaceus) – Dense, high-quality clusters.
• Pioppino (Agrocybe aegerita) – Thick stems and full caps.
• Chestnut mushrooms (Pholiota adiposa) – Strong pinset and richer flavor.
• King Oyster (Pleurotus eryngii) – Meaty, market-grade stems.

Why Sterilization is Required

Because soy hulls are rich in proteins, fats, and sugars, Master’s Mix supports both mushroom mycelium and competitive contaminants. Pasteurization cannot eliminate all heat-resistant spores and bacteria, but sterilization at 121 °C (15 PSI) can, making it essential for this recipe.

Exact Weights & Water Volumes

Smart Water Use – Recycling Grain Boil Water

Save the water from boiling grain spawn and use it hot for hydrating your Master’s Mix. This adds nutrients and reduces waste. Plan your workflow so grain boil finishes before substrate prep.

Per-Bag Mixing & Hydration

1) Weigh Dry Ingredients

• For 10 lb XLS-A: 4 lb hardwood pellets + 4 lb soy hull pellets.
• For 5 lb 3T: 2 lb hardwood pellets + 2 lb soy hull pellets.
• Mix thoroughly in a clean bucket.

2) Load Bag

Pour dry mix into the Unicorn bag and settle it flat at the bottom.

3) Add Hot Water

• 10 lb XLS-A: ≈ 3 L hot water.
• 5 lb 3T: ≈ 1.5 L hot water.
• Optional: Use recycled grain water.

4) Let Hydrate

Leave the bag open and undisturbed for 5–10 minutes to allow pellets to fully break down. No need to clip or massage — pellets will hydrate evenly.

Folding & Sterilization Process

• After hydration, fold gussets inward so sides are vertical.
• Do not impulse seal now — bags remain open for sterilization.
• Place a rack/trivet in the bottom of the PC with 3.5 inches of water.
• Load bag upright with space for steam to circulate.
  • 23q Presto can fit one XLS-A or two 3T at a time
• Once safety value closes due to pressure,  place pressure regulator bringing to 15 PSI.
• Sterilize: 2.5 - 3 Hours

Cooling in Front of a Flow Hood (Presto Users)

If using a Presto pressure cooker, place it in front of your flow hood while it cools and depressurizes. This prevents unfiltered air from being drawn inside as negative pressure develops during cooldown. Do not move the PC after cooling — open it in place.

Post-Sterilization Impulse Sealing

1. Once fully depressurized, open the pressure cooker in front of the flow hood.
2. Remove one bag at a time and immediately impulse seal the top, keeping the filter patch clear.
3. Allow sealed bags to fully cool to room temperature if still slightly warm before inoculation.

Inoculation

Work in a sterile environment (flow hood preferred). Open each sealed, cooled bag, add fully colonized grain spawn, reseal, and mix by gently shaking or breaking up the substrate block.

Colonization & Fruiting

• Incubate at 68–75 °F until fully colonized (7–14 days for fast species).
• Cut open or make “X” holes in the bag for fruiting.
• Maintain 85–95% humidity with good fresh air exchange.

Production Planning

With one 40 lb bag each of hardwood and soy hull pellets (80 lb total dry mix), you can produce:

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