Ground cinnamon bark (Ceylon cinnamon or “true” cinnamon) is vulnerable to substitution with the related species cinnamon camphora (cassia cinnamon) or to bulking with different parts of the plant such as roots and leaves. There are a number of test methods, both published and proprietary, including some based on spectroscopic classification chemometrics.
This paper (open access), from the Joint Research Centre of the European Commission, gives a robust justification for a recommended FT-Raman spectroscopic screening method. The researchers based their reference database on a much wider variety of “true” cinnamon samples on the market than other published methods. They purchased over 100 market samples of cinnamon bark from a variety of countries and ground their own reference samples. They also investigated the chemical explanation for all spectral features that underpinned their discriminatory models
They compared all results with complementary techniques, including GC-MS and XRF, to ensure robustness and reliability. Both of these orthogonal techniques supported the FT-Raman classification results. XRF is based on discriminatory features independent of FT-Raman i.e. the fact that the elemental content of cassia samples is generally lower than that of Ceylon cinnamon. The detection of certain elements (e.g., Al, Si, Ti, Cr, Fe, Zr, and Pb) was also used as an indication of substitution with organic matter and/or effect by the material used to mill the cinnamon sticks. GC-MS is based on the analysis of several volatile compounds (e.g., camphor, cinnamaldehyde, eugenol, coumarin, cinnamyl acetate) for the detection of substitution of Ceylon cinnamon with cassia as well as the substitution of bark with other parts of the cinnamon plant (leaves, flowers, roots, seeds), based on the difference in relative abundances of the selected compounds.
The authors conclude that FT-Raman combined with Principal Component Analysis provides a very efficient and fast approach to detect the substitution of Ceylon and cassia species by Cinnamon camphora, other parts of the plant (e.g., root), and/or inorganic matter, using only cinnamaldehyde as the main marker along p1. Complementary techniques such as GC-MS and XRF can then be used to confirm the type of substitution.
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