Investigation of various shellac grades: additional analysis for identity

Abstract

Background: A number of different grades of shellac are commercially available and most of them are known only as generic shellac and are not further differentiated. The investigated grades of shellac in this study are based on different insect strains, host trees, refining methods, and products from different suppliers. Method: The Gardner/Iodine color values of alcoholic and aqueous solutions of the various shellac grades were measured. Glass transition temperatures and pK_a-values were determined. To assess chemical differences in the tested shellac grades, MALDI-TOF analysis was performed. Results: Differences were found in color, T_G, and pK_a-values and in the mass spectra by MALDI-TOF analysis. Conclusions: The results indicate that these methods can facilitate the determination of identity and are quality control parameters for shellac.