Beta glucan standardization can generally only be done with extracted products-- you keep extracting and concentrating until you reach the desired concentration with hot-extraction processes followed by spray-drying or the use of solvents to precipitate the beta glucans out of solution. Often with "standardized" beta glucan mushroom products, the standardization of beta glucan content is achieved by spiking the mushrooms with cheaper- and easier-to-produce yeast-derived beta glucans that cannot be differentiated analytically from the mushroom-derived beta glucans.
Using sample preparation steps that are appropriate for our unextracted, whole food mushroom powders, we get beta glucan contents in our mushroom powders that are greater than 20% (DW). Although there is a diversity of opinions, it is generally thought that somewhere between 250 and 500 mg/day of beta glucans is sufficient to trigger the host-mediated immune responses to beta glucans that result in the support and balancing of immune function. At a 20% beta glucan content, our recommended daily serving does provide sufficient beta glucans to trigger a cascade of host-mediated immune responses and cell-signaling events. More is not always better.
It is important to note that while beta glucans do get the most attention regarding the immune support provided by mushrooms, beta glucans are by no means the only constituents that are present in unextracted, functional mushroom powders that work together to support immune function. Other immunity-supporting constituents include fungal alpha glucans, prebiotic dietary fibers, antioxidants (glutathione, ergothioneine, polyphenols, SOD), triterpenes, sterols, peptides, vitamins and minerals.