ANALYSIS OF POLYPHENOLIC COMPOUNDS OF DIFFERENT VINEGAR SAMPLES

A method for the determination of low-molecular-mass polyphenolic compounds in vinegars has been optimized and applied to different samples. Ethyl acetate has been used for the extraction of the polyphenolic compounds in a continuous rotatory system, furnished with a special device that allows for the simultaneous extraction of twelve samples. The extracts obtained were submitted to HPLC separation using a C18 reversed-phase column and gradient elution. The identification of polyphenolic compounds was carried out using a photodiode detector. Important differences were found in the phenolic content of the different samples. Best extraction yields were obtained when using 80 ml ethyl acetate and 300 steps (2 h 5 min) at a velocity of 0.8 rpm. The reproducibility of the method may be considered quite good. The method has been successfully applied to the analysis of real samples of very different kinds of vinegar. There are very interesting differences between the low-molecular-mass phenolic fraction of the vinegar analysed. Some interesting low-molecular-mass phenolic compounds have been identified. Their concentration, as well as the concentrations of other so far non-identified substances, depend upon the type of sample. The individual investigation of these phenolic compounds may furnish hints enabling the origin and type of vinegar to be traced. The elaboration type used in connection with the starting wine can be ascertained and differentiated, together with the ageing system used, through inference from the analytical data obtained from different vinegars.