The quality marker for hot water extracted Turkey Tail is
beta-glucan.
Turkey Tail contains two types of beta-glucan, which are in part linked to peptides to form
glyco-proteins / proteoglycans a.k.a. PSK / PSP. These are active compounds. To be in line with the clinical research a Turkey Tail extract should preferably be based on a specific deep layer
* cultivated mycelium strain
(COV-1)® of the mushroom. There's
no need for dual extraction because research has never pointed out alcohol-soluble marker compounds.
*"deep layer cultivated" means "cultivated in liquid" as opposed to rice/grains. Sometimes also called 'fermented mycelium'. The advantage is that there is no left-over substrate in the final product, it is pure mycelium, starch-free. This method is only used in Asia.
NOTE: within the EU all Turkey Tail products are considered a novel food and cannot be sold.