Ecofriendly shiitake authentication using bulk and amino acid-specific stable isotope models

Accurate authentication of ecofriendly shiitake, such as organic and pesticide-free shiitake, is required to improve food safety and to increase reliability of the national agrofood certification system; however, this is a challenging task. Therefore, this study examined the feasibility of bulk and compound-specific isotope analyses to discriminate ecofriendly shiitake against conventional counterparts. Using the compound-specific isotope model, the classification accuracy was greater (100%) than that of the bulk isotope model (74.5%) for each original sample set. In the compound-specific model, a cutting score of -4.42 discriminated organic shiitake from pesticide-free shiitake and a cutting score of 4.87 discriminated organic shiitake from conventional shiitake. The isotope fractionation trend was less influenced by shiitake type and the amino acid synthetic pathway. Thus, the compound-specific isotope model of amino acids may be a good complementary authentication tool to overcome the limitations of bulk stable isotopes or a pesticide residue test.