Identification of ethyl 2-hydroxy-4-methylpentanoate in red wines, a compound involved in blackberry aroma

The aroma profile of Bordeaux red wines is known to be marked by blackberry and blackcurrant flavours; this study focused on the fresh blackberry aroma in Bordeaux red wines, using sensory gas chromatography-olfactometry (GC-O) and two-dimensional gas chromatography analysis (GC-GC-MS). A previous HPLC fractionation of red wine extracts on a C18 column produced four fractions with blackberry aromas that were then analysed by GC-O, GC-GC-MS and GC-MS. From these fractions, 10 esters, corresponding to red- or black-berry fruit descriptors, were characterised by GC-MS. Ethyl 2-hydroxy-4-methylpentanoate (ethyl leucate, EL) was identified for the first time in red and white table wines as a compound directly associated with a "fresh blackberry" aroma. Its perception thresholds were 900 and 300μg/l, respectively, in dearomatized red wine and model wine solution (alcohol 12%, pH 3.5), and the average concentration in the various wines was ∼400μg/l. Sensory omission tests highlighted the importance of this compound and identified a perceptive interaction with ethyl butanoate.