Assessment of Flavor Compounds in Blended Malt Whisky Aged with Acacia, Cedar and Oak Wood Using Liquid Chromatography Hyphenated to Electrospray Ionization and Tandem Mass Spectrometry (LC-ESI-MS/MS)

Abstract

Selected flavor compounds from wood were quantified, with liquid chromatography hyphenated to electrospray ionization and tandem mass spectrometry (LC-ESI-MS/MS), in four samples of base spirit matured with acacia, cedar, virgin oak, and used port wine oak wood cubes and the results were used to describe and differentiate their different wood congener profiles. ESI-MS/MS parameters were optimized in terms of capillary voltage, cone- and desolvation gas flow, source- and desolvation temperature, cone voltage, and collision energy. The method was validated in terms of linearity (R2 > 0.995), limit of detection, limit of quantification, recovery, and repeatability. One-way analysis of variance (ANOVA) showed that for most compounds there were no significant differences (α = 0.05) between seven to 30 days of aging plus a heat treatment at 40 °C, but wood type did significantly influence the wood congener profile. Principal component analysis discriminated the spirits based on relative amounts of wood congeners extracted, and the chemical profile. Aging with cedar wood led to a less pronounced chemical profile, not very distinct from the base spirit. Aging with acacia and virgin oak wood produced a second chemical profile with relatively higher levels of synapaldehyde, syringaldehyde, scopoletin, and coniferyl aldehyde. Aging with port oak wood produced a third chemical profile with relatively higher levels of 5-HMF, gallic acid, furfural, vanillic acid, and syringic acid.