Methods for analysis of procyanidins (condensed tannins) and their oxidation products in foods

International audienceProcyanidins, also referred as condensed tannins in their polymerised forms, correspond to very widespread oligomers and polymers of catechins found in many fruits, vegetables and their derived foods. For instance, they are the main class of polyphenols in apples both in dessert and cider varieties apples [1,2] although there are generally much more concentrated in the later. It is now admitted that they are of great importance in foods regarding their contribution to health benefits and their organoleptic roles (3).However, procyanidins are often underestimated in food composition tables because of the technical difficulties allowing their efficient extraction and detailed accurate assay. This is mainly related to their distribution under numerous polymerised forms and also their ability to establish more or less strong interactions with macromolecules (proteins and polysaccharides) which renders difficult their exhaustive extraction and purification from the raw materials. Moreover, in processed foods such as juices or dried fruits, procyanidins are sensitive to oxidation with important consequences on their chemical structures and properties. On the basis of several examples related to our experience in polyphenol analysis in fruit, juices, ciders and other plant matrixes, we propose an overview of methods adapted to procyanidins analyses from simple colorimetric assays to fine structural analysis by acidolysis methods coupled to liquid chromatography and mass spectrometry