How do I keep mushroom spawn free of contamination in production?

Contamination control is the whole game in spawn production. The key steps are, prepare and sterilise the grain medium fully in an autoclave at proper pressure and time so nothing survives, let it cool in a clean space, inoculate only under a laminar flow hood or in a very clean sealed chamber with sterile technique, flame your tools, work fast and cleanly, and use pure fresh mother culture from a reliable lab. Keep the inoculation room and incubation room scrupulously clean, control the incubation temperature, and inspect bottles regularly, discarding any that show green, black or other mould or any sour smell at once so they do not contaminate the rest. Control humidity and pests in the rooms too. Personal hygiene, clean clothing and limiting who enters the lab also matter. Master these basics through hands on training at DMR Solan or an SAU before you sell, because your customers crops depend on your spawn being pure.