Paper-based arrays for geographical indication of turmerics

Abstract

Geographical indications have gained increasing importance as a powerful marketing tool for highly valuable products especially foods. In this study, a synergistic combination of chemical reaction arrays on paper and chemometric analysis was used to uncover geographical indication of turmerics, an important food ingredient in several Asian cuisines. The key to effective differentiation was from the subtle differences in the compositions of the compounds found in turmeric samples, mainly curcumin and derivatives which were preliminarily confirmed by HPLC and LC-MS experiments. In addition, the differences in the major and minor components affect the reactivity and the pattern of obtained products after reacting with various types of reagents. Our paper-based arrays were fabricated based on the reactions of curcumin with various reagents including buffer solutions, 2,4-dinitrophenylhydrazine, vanillin and some metal ion solutions. The chemical sensors reacted with various components in turmerics in different ways and resulted in different colorimetric and fluorescence profiles. The photophysical changes of the arrays were simply captured using basic tools including a document scanner and a digital camera. The images were transformed into numerical data, which were then analyzed by chemometrics. As a result, geographical prediction from 2047 combinations of sensor were investigated and our strategy could select the best combination of reagents that provided up to 94% prediction accuracy without the need for any sophisticated instruments.