Detailed LC-UV-MS quantification of native and oxidized phenolic compounds in experimental and commercial apple juices revealed highly contrasting compositions

Abstract

During apple juice production, phenolic compounds undergo enzymatic oxidation leading to newly formed molecules. More quantitative information is needed concerning these oxidized phenolic compounds (OP) that contribute to the organoleptic and nutritional properties of apple juices. Firstly, a new HPLC-UV-MS method was developed to simultaneously quantify native phenolic compounds and two families of OP (i.e. 5-O-caffeoylquinic acid dehydrodimers and epicatechin-5-O-caffeoylquinic acid heterodimers). Secondly, the method was applied to 54 commercial and experimental apple juices. Then, statistical cluster analysis (Euclidian Ward’s method) was performed on all the phenolic compound data sets. To the best of our knowledge, it is the first time that two families of OP have been successfully quantified in a large series of apple juices revealing that they may represent up to 14% of the total phenolic compounds quantified (TPQ). Furthermore, the statistical classification of the juices based on their native and oxidized polyphenol compositions clearly underlined the great discrepancies in polyphenol composition observed in this panel of juices available on the French market. Interestingly, the polyphenol concentration in most of the juices made from cider apple varieties (experimental juices and local cider producers) was on average 8-fold higher than in most of the juices found in supermarkets.