Can minerals be used as a tool to classify cinnamon samples?

Cinnamon (Cinnamomum zeylanicum) is a spice largely consumed worldwide. In spite of its high popularity, there is still restricted information about its fingerprint. This work aims to investigate the mineral composition as a possible marker for the classification of cinnamon samples. A set of 56 ground cinnamon samples were bought in different markets and regions of the State of São Paulo, Brazil. Mineral composition (P, S, Mg, Ca, K, Cu, Zn, B, Fe, Al, Mn, and Si contents) was determined by inductively coupled plasma optical emission spectroscopy (ICP OES) after cryogenic grinding) and microwave-assisted acid digestion (6.0 mL of 2.0 mol L^-1 HNO₃ + 2.0 mL of 30% v/v H₂O₂). The principal component analysis was exploited for sample classification, and the content of microelements presented the best correlation: PC1, PC2, and PC3 explained 93% of the observed variance at 95% confidence level. Si, Al, Fe, and Cu presented the most significant contribution to cluster samples, while B presented the lowest one. Samples were classified into 6 groups, in which those presenting C. zeylanicum were well clustered. Two samples, whose labeled information include traces of celery, mustard, and other spices were identified as outliers. Samples acquired in bulk as well as those whose labels declared traces of grains and/or spices presented the highest variability. Thus, it was pioneering to indicate the possibility to identify C. zeylanicum in commercial cinnamon powders, using microelements as authenticity markers.