Headspace Congeners of Blended Scotch Whiskies of Different Product Categories from SPME Analysis

Flavour congeners in headspaces of 40 blended Scotch whiskies, of 4 different product categories (Deluxe, standard, retailer and West Highland), were collected by solid phase micro extraction (SPME) over 10 ml diluted (23% abv) whisky. Fibres (100 μm diameter) were thermally desorbed for 5 min in a split/splitless injection port and congeners quantified by high resolution gas chromatography. Two bonded SPME phases (polydimethylsiloxane and polyacrylate) were evaluated: exposure time was varied between 5 and 30 min; with whisky at either nosing (25°C) or tasting (37°C) temperature. Optimal analysis was with polyacrylate fibres at 37°C for 15 min but extraction at 25°C generated data relevant to sensory (nosing) data. Principal component (PCA) and discriminant partial least square (DPLS) analyses of mean % peak areas for all 57 resolved HRGC components and congeners (38) common to all whiskies gave product spaces showing clear separation of Deluxe, retailer and West Highland blends, but dispersed standard blends. In DPLS2 product clustering was similar whether relative (%) or absolute peak area was used in analyses but congeners loadings differed. From product spaces it was possible to assess contributions of flavour congeners, mainly esters and alcohols, to headspaces of individual blends and product categories.