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Determination of ellagitannins in extracts of oak wood and in distilled beverages matured in oak barrels.

A method is described for determination of ellagitannins in ethanol-water extracts of oak wood and in distilled alcoholic beverages matured in oak barrels. It is based on the combined ellagic acid content according to ellagitannin structure. Hydrolysis was carried out in the presence of hydrochloric acid under reflux in a 100 degrees C oil bath for 3 h. Total ellagic acid was thus determined by liquid chromatography (LC), and the free ellagic acid content present in the ethanol-water media was subtracted, the difference being the combined ellagic acid content corresponding to ellagitannins. A 5 micron C18 column was used with detection at 254 nm. The method is specific for ellagitannins, which is an advantage over other analytical techniques for overall evaluation of these substances extracted from wood. Results for spirits distilled from wine, grain, and sugarcane were highly variable.