A novel method for determining vitamin B1 in a wide variety of foodstuffs with or without polyphenols.

Certain foodstuffs exhibit matrix interference effects on the vitamin B(1) analysis prescribed in the official methods of the European Union, AOAC International, and Japan. In this study, we demonstrated that one of the problematic polyphenols in green tea or cocoa was tannin. For these matrices, thiamine was found to interact with tannin in the extraction step and was thus removed by filtration as a residue.