सिंथेटिक ब्लॉक विधि

01The formula, and why it is acidic

DMR's folder formula is sawdust 80 kg, wheat bran 19 kg and calcium carbonate 1 kg per 100 kg of mix. The 2011 manual notes that the institute commonly uses a second formula with sawdust 80 kg, wheat bran 20 kg, cane sugar, calcium carbonate, citric acid and calcium sulphate.

Use broad leaved sawdust. DMR names tuni, mango, safeda or eucalyptus, oak, maple and poplar.

Water is adjusted to 60 to 65 percent and pH to 5.5 to 6.0 using gypsum. Note how different that is from button mushroom compost at pH 7.2 to 7.8. Shiitake wants an acidic substrate.

02Soak, fill and sterilise

Sawdust is soaked first. The folder gives 16 to 18 hours; the 2011 manual says at least two days. Wheat bran soaks for about three hours. Mix all ingredients thoroughly.

Then move fast. DMR says fill the bags at 1.5 to 2 kg immediately after mixing, because fermentation and contamination start otherwise, and the manual keeps the gap between mixing and sterilising under six hours. Use heat resistant polypropylene bags.

Sterilisation is in an autoclave at 22 psi for 1.5 to 2 hours. After cooling, grain spawn goes in at 3 percent on a dry weight basis under aseptic conditions.

03A long incubation with visible stages

Shiitake blocks incubate far longer than oyster bags. The folder gives 60 to 80 days at 22 to 26 C, 500 to 1000 lux and 65 to 70 percent humidity, on a cycle of 4 hours light and 20 hours dark. The manual's table stretches this to 50 to 120 days at 20 to 30 C.

The block passes through visible stages. A thick mycelial coat forms at 6 to 8 weeks. Bumps, which are clumps of mycelium, appear at 9 to 10 weeks. Then the surface browns and the coat hardens. The bag is removed once the block is a third to half browned, with core moisture near 80 percent.

04Induction, fruiting and rest

Induction is a short, deliberate change: 2 to 4 days at 10 to 20 C with 500 to 1000 lux and 85 to 95 percent humidity. DMR's alternative is the cold water shock at 4 to 6 C for 10 to 20 minutes.

Fruiting runs 7 to 14 days. The folder gives 12 to 25 C at 60 to 80 percent humidity and notes that the band is strain dependent; the manual narrows it to 12 to 18 C.

Then rest the blocks 7 to 21 days at 22 to 26 C in darkness. A dry spell after harvest prevents contamination, and a water bath restores the moisture the block lost.