Whisky is a popular grain-based spirit originating allegedly from Ireland in the 7 th century . It has a distinctive aromatic profile that varies by brand, dependant on the choice and quality of grains, their fermentation, choice of barrel and its treatment, and the duration of the ageing process. The variety and concentrations of alcohols, aldehydes, esters, fatty acids, fermentation products from yeast and other local microbes, phenolics and lactones are subject to the variables mentioned above .