Extraction of Hydroxycinnamoyltartaric Acids from Berries of Different Grape Varieties

Abstract

The concentrations of the hydroxycinnamoyltartaric acids (caftaric, cis- and trans-coutaric, and fertaric acid) were determined in berries of six white grapevine cultivars and compared with their concentrations in oxidation-protected juices. The analyses were performed by direct injection in a reverse phase HPLC-DAD system. Differences among the cultivars in extraction yield appear to be independent of absolute amount. The extraction of fertaric acid was steadily the highest (average = 70.9%), followed by caftaric acid (average = 59.0%) and both p-coutaric isomers (average = 36.2% for cis- and 33.6% for trans-). Four different technologies of juice preparation were performed (in pilot-scale press) to verify the influence of technology on the extraction yield of hydroxycinnamoyltartaric acids and their enzymatic oxidation during the pressing. Losses during juice preparation depended strongly on pressing management. The lowest recovery of all examined compounds occurred in must obtained by whole cluster pressing. Overnight settling of the juice caused further oxidative losses only in the treatments in which the juice had been left on skins before pressing, irrespective of SO2 addition. Keywords: White grape; hydroxycinnamoyltartaric acids; extraction yield; enzymatic oxidation