Abstract
Yellow turmeric (Curcuma longa) is widely used for culinary and medicinal purposes, and as a dietary supplement. Due to the commercial popularity of C. longa, economic adulteration and contamination with botanical additives and chemical substances has increased. This study used FT-IR spectroscopy for identifying and estimating white turmeric (Curcuma zedoaria), 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, w/w) and fifty replicates of yellow turmeric—white turmeric mixed samples (10%, 20%, 30%, 40%, 50% white turmeric, w/w) were prepared. The IR spectra of the pure compounds and mixtures were analyzed. The 748 cm−1 Sudan Red peak and the 1078 cm−1 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 (R2v) for the Sudan Red mixture model was 0.97 with a root mean square error of prediction (RMSEP) equal to 1.3%. R2v 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.
Highlights
Turmeric root (Curcuma longa) is widely used for culinary, medicinal, and cosmetic purposes and as a dietary supplement [1,2]
There is no report of contamination in whole, dry, or fresh turmeric, turmeric powder has been adulterated with other powders
We developed a simple method using Fourier Transfer-Infrared (FT-IR) spectroscopy to develop quantification models to predict the concentrations of chemical contaminant (i.e. Sudan Red G) and botanical additive in commercial yellow turmeric powder
Summary
Turmeric root (Curcuma longa) is widely used for culinary, medicinal, and cosmetic purposes and as a dietary supplement [1,2]. The vibrant yellow color and medicinal value of turmeric is mainly due to the “curcumin” (diferuloylmethane) content, which varies between 0.3% to 8.6% [3,8,9,10,11] Factors such as the soil type, cultivar, and crop fertilization affect the curcumin content in turmeric root [12,13,14,15]. There is no report of contamination in whole, dry, or fresh turmeric, turmeric powder has been adulterated with other powders Another plant in the same genus, Curcuma zedoaria (white turmeric), may be mixed with C. longa powder [18,19].
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