A new colorimetric method to quantify β-1,3-1,6-glucans in comparison with total β-1,3-glucans and a method to quantify chitin in edible mushrooms.

Mushrooms contain high amounts of substances like chitin and glucans, which can be used for medical purposes and nutrient matter. Therefore, an easy quantification method for chitin and for glucans, with high precision, is a matter of particular importance. For this purpose, we developed an easy and unique photometric method for the determination of -1,3-1,6 glucans in mushrooms. This method is specific for -glucans with a triple-helix tertiary structure. The used dye, congo red, forms a complex with the triple-helix, which causes a specific bathochromic shift of the absorption maximum from 483 nm to 523 nm. For the specific determination of total -1,3 glucans a fluorimetric method was adapted, too, which easily can be performed. By the combination of both methods, it was possible to compare the amount of -1,3-1,6 glucans with the total -glucan content. Furthermore, we developed a new colorimetric method for the quantification of chitin and chitosan, which is based on the specific reaction of polyiodide anions and chitosan. After deacetylation, chitin can also be quantified by this method. With this new spot assay, the chitin content of mycelia and fruiting bodies from several basidiomycetes and an ascomycete was analysed. The presented method can be used for determination in other samples, too.