Analytical profiling of food-grade extracts from grape ( Vitis vinifera sp.) seeds and skins, green tea ( Camellia sinensis ) leaves and Limousin oak ( Quercus robur ) heartwood using MALDI-TOF-MS, ICP-MS and spectrophotometric methods

Tannins are food additives widely used due to their antioxidant and antimicrobial activities, and flavouring properties. Nevertheless, the information provided by the manufacturers are often generic, and data on the presence of specific phenolic compounds and potentially toxic elements are needed. In this work a selection of food-grade plant extracts – also called ‘commercial tannins’ – from different botanical sources: Vitis vinifera sp., Camellia Sinensis, Quercus robur, were profiled using UV–vis spectrophotometry, matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS), and inductively coupled plasma-mass spectrometry (ICP-MS). The combined analytical approach was suitable for quality control of the polyphenolic fraction to highlight authenticity markers (e.g. galloylated flavonoids, glycosides, ellagitannins), and to ascertain the content of toxic elements (Cu, Sr, As, Co, Cr, Fe, Zn, Li, Ba and Pb) respect to their legal and/or recommended limits.