Authentication/discrimination, identification and quantification of cinnamon adulterants using NIR spectroscopy and different chemometric tools: A tutorial to deal with counterfeit samples

Cinnamon is one of the most consumed spices worldwide and its adulteration can pose several risks to human health. This work proposes a method for the authentication/discrimination, identification and quantification of cinnamon adulterants (Cinnamomum cassia known as false cinnamon, clove and black pepper) based on NIR spectroscopy and different chemometric tools namely, DD-SIMCA, MCR-ALS and PLS regression. In addition, this work intends to provide a guide for dealing with adulterated samples. A total of 133 samples were analysed through NIR spectroscopy and several spectral regions and pre-processing techniques were tested to optimize the respective models using only the calibration set. For the authentication/discrimination purpose using DD-SIMCA, all the testing samples were properly classified, with a sensitivity and specificity of 100%. Concerning the identification of all the samples’ constituents using MCR-ALS, the spectral profiles retrieved were very similar to the pure NIR spectra of Cinnamomum verum and each adulterant, with Pearson correlation coefficients of 0.9996, 0.9973, 0.9674 and 0.8797 for Cinnamomum verum, Cinnamomum cassia, black pepper and clove, respectively. In relation to the quantification of cinnamon adulterants, the PLS models showed a R2P, RER and RPD higher than 0.95, 12 and 4, respectively, for all the models which indicate that the developed PLS models can be considered as excellent predictive models. Globally, the obtained results reveal the suitability and accuracy of NIR spectroscopy to authenticate/discriminate, identify the adulterants and quantify their respective concentration in a rapid, robust, low-cost and environment-friendly way.