What is the extraction ratio ? 1:1 ? 8:1 ?

Using ratio's as a quality marker stems from herbal practice: a dried herb (± 10:1) is more potent than the fresh one in general - this is applicable even to kitchen herbs! Many Chinese producers are actually in the herbal business and added mushrooms as an extra source of income in the past decade. They are also using the same processing and quality indicators for mushrooms, but this is completely wrong because mushrooms are not -structurally speaking- cellulose based (like herbs) but have a chitinous structure. Chitin needs specific processing -involving heat or enzymes/fermentation- to release the bioactives - see elsewhere in these FAQ.

Using a ratio-indicator with mushrooms is potentially deceiving, because it only indicates a decrease in volume / weight (which one is never specified, somehow), and in itself reveals nothing about chemical compostion or bio-availability - the consumer still has no clue if the product is in fact therapeutically useful.

A ratio claim is also impossible to verify, how can you prove that, let's say a 30:1 claim, is incorrect ?

Mushrooms contain a lot of water, up to 90% (e.g. Agaricus blazei fruiting bodies). Drying and pulverizing them will already decrease the volume and the weight significantly; completely dry ABM powder is already meeting the 10:1 ratio; 90% water has been removed, 10% dry matter is left. But no extraction of bio-actives took place and the bio-availability is still low.

The bottom line: a ratio-indicator in itself means nothing. This statement should be backed up by a detailed breakdown of bio-actives on the supplement facts label to have any meaning.

The only thing that is worth looking for for a consumer is the information on the supplement label (it is prohibited by law to lie or use deceiving phrasing on this label): the exact percentages of bio-actives such as beta-glucans should be there.
If not, avoid it - the therapeutic potency might be questionable. Testing for beta-glucan is easy and cheap - so why not do it unless the outcome is not what you want ?

As an example, have a look at the image below. The most powerful extract is the dual extract (hot water/ethanol) on the right. It has twice the volume of the hot water-only extract. So volume-wise the hot water extract might be 14:1 and the dual extract only 7:1, but to draw the conclusion the 14:1 extract is the most potent one would be wrong.
 A basic hot water extract (freeze dried) and a full spectrum dual extract (spray dried). The dual extract's particle size is much smaller but the total volume is larger. Smaller particles means better absorption and solubility, which improves bio-availability and therefore therapeutic effect.