| Summary: | Yellow turmeric (<i>Curcuma longa</i>) is widely used for culinary and medicinal purposes, and as a dietary supplement. Due to the commercial popularity of <i>C. longa</i>, economic adulteration and contamination with botanical additives and chemical substances has increased. This study used FT-IR spectroscopy for identifying and estimating white turmeric (<i>Curcuma zedoaria</i>), and Sudan Red G dye mixed with yellow turmeric powder. Fifty replicates of yellow turmeric—Sudan Red mixed samples (1%, 5%, 10%, 15%, 20%, 25% Sudan Red, <i>w</i>/<i>w</i>) and fifty replicates of yellow turmeric—white turmeric mixed samples (10%, 20%, 30%, 40%, 50% white turmeric, <i>w</i>/<i>w</i>) were prepared. The IR spectra of the pure compounds and mixtures were analyzed. The 748 cm<sup>−1</sup> Sudan Red peak and the 1078 cm<sup>−1</sup> white turmeric peak were used as spectral fingerprints. A partial least square regression (PLSR) model was developed for each mixture type to estimate adulteration concentrations. The coefficient of determination (R<sup>2</sup><sub>v</sub>) for the Sudan Red mixture model was 0.97 with a root mean square error of prediction (RMSEP) equal to 1.3%. R<sup>2</sup><sub>v</sub> and RMSEP for the white turmeric model were 0.95 and 3.0%, respectively. Our results indicate that the method developed in this study can be used to identify and quantify yellow turmeric powder adulteration.
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