What are the methods for identifying the quality of edible mushroom spawn?
1 Appearance identification
For users without special equipment, the quality of spawn can be judged by the senses, which is the so-called appearance identification. High-quality spawn should have five characteristics: pure, true, strong, moist and fragrant.
Pure means the spawn has high purity, no contamination by foreign microorganisms, no patches, no inhibition lines, and no "spawn regression" or "spawn breakage" phenomenon. True means the hyphae are normal and have the authentic morphological characteristics of the parent. For example, the hyphae are pure white, glossy, grow evenly and neatly, connect into blocks, and are elastic. Strong means the hyphae are thick and robust, with vigorous growth, many and dense branches, and quickly recover and colonise the substrate. Moist means the spawn has moderate water content, the substrate is moist, fits tightly against the bottle (or bag) wall, and shows no shrinkage, looseness or accumulated liquid.
2 Heat resistance test
Culture the subcultured mother spawn at a suitable temperature for one week, take it out and culture it at 35 degrees Celsius, then after 24 hours put it back at the optimum temperature and observe the recovery of the hyphae. Those that recover and germinate quickly, with few hyphae collapsing and yellowing, are better.
3 Contamination check and growth vigour determination. Fill an Erlenmeyer flask with liquid medium (for example, PDA medium without agar), sterilise it, then inoculate the crushed spawn to be tested, culture at about 25 degrees Celsius for about one week and observe. If bubbles and a mycoderm appear and there is a sour, spoilage smell, it indicates that the spawn is mixed with foreign microorganisms; if the above phenomena do not occur, the spawn is pure and free of contamination. Then observe the spawn floating on the liquid surface: if it grows quickly in all directions, and the hyphae are robust, powerful and vigorous, with neat edges that keep thickening, it indicates that the strain has strong growth vigour; if the hyphae grow slowly, are sparse, and the hyphal layer is thin, it indicates weak growth vigour and it is not suitable for production.
4 Cultivation trial identification
Put the substrate in a wooden box. If 1-2 days after sowing, needle-like hyphae can be seen on the substrate and grow regularly in all directions, and after 3-4 days they spread into the new substrate while the hyphae on the original spawn continue to develop in all directions without wilting, then this is fresh, robust spawn that is easy to establish.
5 Fruiting test
On well-developed hyphae, cover with 3.3 cm thick large soil particles and 1.6 cm thick small soil particles, adjust the moisture well, and observe their growth into the soil particles. If at an air temperature of 18-20 degrees Celsius, after 15-20 days, small young mushroom primordia can be seen forming within the hyphal covering layer, then this is normal fruiting; if after the first batch of fruiting bodies is harvested, the second batch of fruiting bodies appears after only a very short interval, then it is a high-yield spawn.