The perceptual categorisation of blended and single malt Scotch whiskies

Background: Although most Scotch whisky is blended from different casks, a firm distinction exists in the minds
of consumers and in the marketing of Scotch between single malts and blended whiskies. Consumers are offered
cultural, geographical and production reasons to treat Scotch whiskies as falling into the categories of blends and single malts. There are differences in the composition, method of distillation and origin of the two kinds of bottled spirits. But does this category distinction correspond to a perceptual difference detectable by whisky drinkers? Do experts and novices show differences in their perceptual sensitivities to the distinction between blends and single malts?
To test the sensory basis of this distinction, we conducted a series of blind tasting experiments in three countries with different levels of familiarity with the blends versus single malts distinction (the UK, the USA and France). In each country, expert and novice participants had to perform a free sorting task on nine whiskies (four blends, four single malts, one single grain, plus one repeat) first by olfaction, then by tasting.
Results: Overall, no reliable perceptual distinction was revealed in the tasting condition between blends and single malts by experts or novices when asked to group whiskies according to their similarities and differences. There was nonetheless a clear effect of expertise, with experts showing a more reliable classification of the repeat sample.
French experts came closest to a making a distinction between blends and single malts in the olfactory condition, which might be explained by a lack of familiarity with blends. Interestingly, the similarity between the blends and some of their ingredient single malts explained more of participants’ groupings than the dichotomy between blends and single malts.
Conclusions: The firmly established making and marketing distinction between blends and single malts corresponds
to no broad perceptually salient difference for whisky tasters, whether experts or novices. The present study indicates that successfully blended whiskies have their own distinctive and recognizable profiles, taking their place in a common similarity space, with groupings that can reflect their component parts.