TASTE THRESHOLDS OF PHENOLIC EXTRACTS OF FRENCH AND AMERICAN OAKWOOD - THE INFLUENCE OF OAK PHENOLS ON WINE FLAVOR

The concentration of the total phenol fraction in extracts of both gre en and seasoned oakwood from Ohio in the USA and from the Limousin and Vosges regions and the Troncais forest in France was measured by both UV absorbance at 280 nm and by the Folin-Ciocalteu reagent. The conce ntration of phenols in both white wine and model wines stored in barre ls made from the same wood samples was also measured. Taste thresholds of the aroma-stripped extracts in a white wine and in a model wine we re determined by duo-trio difference testing. The concentration of the phenolic fraction in the extracts varied with oak source, but not wit h seasoning (i.e., wood drying). Taste thresholds varied with both of these parameters. The concentration of phenols in the barrel-aged wine s was near to or below their sensory thresholds, indicating that the c ontribution of oak polyphenols to the taste of a wine is likely to be no more than a subtle one and to depend on the training and sensory ac uity of an individual observer. The sensory thresholds of extracts con taining aroma volatiles were much lower than those of the aroma-stripp ed extracts, suggesting that it is the oak-derived volatiles that prov ide the primary sensory cue that a wine has received oak-treatment.