Pre-Sterilised Grain Spawn Bags — Skip the Autoclave, Go Straight to Inoculation
No pressure cooker. No autoclave cycle. No sterilising anything yourself. Our Pre-Sterilised Grain Spawn Bags arrive ready to inject — sterilised in a commercial autoclave, sealed with a self-healing injection port and a breathable 0.2 micron filter patch, with an isopropyl alcohol swab included in every bag so you can sanitise the port and get straight to inoculating. Choose from Millet, Organic Wheat, Organic Rye, or Organic Popcorn — the widest grain range of any pre-sterilised bag on the Australian market — in 500g, 1KG, or 2KG finish weight.
Choose Your Grain
Millet Best Value
Small, even-sized grain with a high surface-area-to-volume ratio. More inoculation points per kilo means faster, more even colonisation and better spawn-to-substrate coverage than larger grains.
Organic Wheat Classic Choice
Certified organic wheat berries — the grain most commercial AU growers build their spawn program around. Reliable hydration, consistent mycelial run, forgiving for less experienced growers.
Organic Rye Grower Favourite
Certified organic rye berries with a tougher hull. Slower to break down than millet or wheat, so spawn holds its structure and stays usable for longer once fully colonised — the mycologist's long-standing standard.
Organic Popcorn Exclusive
Certified organic popcorn kernels — a larger, denser grain not offered by other Australian sterilised grain bag suppliers. Slower colonising but nutrient-dense, popular for species that reward a richer grain substrate (Shiitake, Reishi, King Oyster).
What You'll Notice
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✓ No sterilising equipment needed — every bag arrives ready to inject
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✓ Faster start — inoculate within minutes instead of a full day of soak, simmer, and sterilise
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✓ Self-healing silicone injection port — inject with a liquid culture or spore syringe, no flow hood required
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✓ Isopropyl alcohol swab included with every bag — sanitise the port and go, nothing extra to buy first
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✓ 0.2 micron filter patch for clean gas exchange without contamination risk
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✓ Consistent grain-to-water ratio every batch — no guesswork on hydration
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✓ Four grain options in one listing — mix and match for different species without reordering
The Science
Sterilisation removes competing organisms so your inoculated culture has the entire grain to itself — this is what separates a sterilised substrate from a pasteurised one, and why grain spawn colonises so much faster and cleaner than bulk substrate. Each bag is autoclaved at 121°C / 15 PSI for a hold time matched to its finish weight (2KG bags run longer than 500g, since heat needs to fully penetrate a larger grain mass to reach sterilising temperature at the core). We add 3% by weight of calcium sulphate (gypsum) and calcium carbonate (chalk) to every bag — gypsum stops the grain clumping into a solid mass as it colonises, and chalk buffers pH toward the slightly alkaline range most gourmet species prefer, discouraging bacterial and mould competitors.
How To Use
| Finish Weight |
Inoculation Volume |
Method |
|
500g SM
|
~5mL liquid culture/spore syringe or 50g spawn
|
Wipe the injection port with the included alcohol swab, inject through the port, gently distribute liquid across grain, incubate |
|
1KG MD
|
~10mL liquid culture/spore syringe or 100g spawn |
Same method — one full syringe typically covers one 1KG bag |
|
2KG LG
|
~10–20mL liquid culture or 200g spawn |
Same method — avoid over-injecting in one spot; larger grain mass benefits from wider liquid distribution |
Incubate at 22–24°C out of direct sunlight. Colonisation typically takes 10–21 days depending on species and culture vigour — faster-growing species (Oyster varieties) sit at the shorter end, slower species (Reishi, Shiitake) take longer. Once fully white, break up the grain inside the sealed bag before mixing into bulk substrate, or use directly for a grain-to-grain expansion.
Storage & Safety
Store unopened bags at room temperature, out of direct sunlight, and use within 30 days of receipt for best results. Once injected, keep at 22–24°C during colonisation. Do not consume raw or sterilised grain — this product is intended for mushroom cultivation only. Keep away from children and pets prior to and during colonisation. If a bag arrives damaged, torn, or with a compromised filter patch or injection port, photograph it and contact us before inoculating — sterility cannot be guaranteed once the seal is broken.
Specifications
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Contents: Sterilised grain (Millet, Organic Wheat, Organic Rye, or Organic Popcorn) with 3% calcium sulphate (gypsum) and calcium carbonate (chalk) by weight
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Bag type: Heat-resistant polypropylene grow bag, self-healing silicone injection port, 0.2 micron breathable filter patch
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Included: 1x isopropyl alcohol swab per bag for sanitising the injection port before inoculation
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Finish weight options: 500g, 1KG, 2KG
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Sterilisation: Autoclaved at 121°C / 15 PSI, hold time scaled to bag size
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Origin: Australian Grown
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Certification: Wheat, Rye, and Popcorn sourced Certified Organic; Millet is conventionally grown
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Inoculation: Ready to inject on arrival — no sterilising equipment required
Hand-Prepared on Tamborine Mountain
Kai Kai Farm is a family-run, certified organic farm in Queensland's Scenic Rim, founded by Quintin and Amy. Every bag in this range is sterilised through the same autoclave process we run our own farm's grain spawn through — we're not outsourcing this to a third party, we're using it ourselves. When you buy from us, you're supporting a small local business focused on accessible, science-backed mushroom cultivation.
