Identification of Turmeric and Revelation of Adulterations by Digital Colorimetry and Near-IR Spectrometry

Abstract

A possibility of identifying turmeric and establishing its adulterations by simple and available methods using IR spectrometry, digital colorimetry, and chemometric spectral data processing is shown. Near-IR spectrometry enabled the differentiation of samples of turmeric powder purchased in India and prepared by grinding roots and commercial samples, and also their distinguishing from samples containing flour, starch, bread crumb, and chalk impurities by analyzing diffuse reflection spectra using principal component analysis, hierarchical cluster analysis, and soft independent modelling of class analogy. The same approaches were applied to a simpler and a less expensive colorimetry method. Chemometric processing of the data obtained confirmed the absence of similarity between the analyzed turmeric samples and samples with additives and made it possible to determine impurities using multivariate regression analysis algorithms. A comparison of the results obtained by IR spectrometry and digital colorimetry demonstrated their equivalent efficiency, so that a more available colorimetry method can be recommended for the routine quality control and the detection of turmeric adulterations.