Quantitative determination of beta-ionone in red wines and grapes of Bordeaux using a stable isotope dilution assay.

Quantitative analysis of beta-ionone has been developed, using a stable isotope dilution assay. This was applied to red wines from different cultivars and regions. The Burgundy Pinot noir wines exhibited the highest levels of beta-ionone. The variation in the levels of beta-ionone in grape samples and in their corresponding wines, of Merlot, Cabernet Sauvignon and Cabernet franc from Bordeaux regions was monitored at four different stages towards the end of maturation: the levels of beta-ionone were almost similar, exhibiting only a slight decrease during maturation. beta-Ionone occurred in all the grapes and wines samples analysed at levels higher than, or close to its odour threshold which was determined in a model wine solution and was found to be of 90 ng l-1. In a previously supplemented model wine solution with beta-ionone (250 ng l-1), the odour threshold was found to be of 980 ng l-1 (total levels).