Development of an accurate and direct method for the green food colorants detection

Color impression represents between 60 and 90% of the final acceptance/rejection choice made by consumers. Consequently, color additives are attribute standards for our daily life in any market and any culture. Currently, authorized natural green food colorants comprise several copper-chelated chlorophyll derivatives. Both the raw materials and the manufacturing processes for the acquisition of these green food colorants are numerous and diverse. Hence, each producer applies its own know-how to obtain 'signature' green colorant products. Indeed, the chlorophyll profile of these products is partially known and may substantially differ among batches, while their identification just by HPLC-UV-Vis is not complete. Native chlorophylls do not chelate copper. Therefore, we propose a fast and specific method for copper chlorophyll detection, as indicative (except in a few fermented foods) of probable green food colorant addition or "re-greening" with copper salts. The new method is based on the characteristic isotopic pattern of the copper chlorophyll derivatives and does not require the precise characterization of the corresponding chlorophyll structure. This accurate methodology, based on a specific HPLC-ESI/APCI-HRMS method assisted with powerful post-processing software, is versatile as it can be used for other metallo-chlorophyll complexes also applied to improve the green coloration of food products.