Guaiacol

A whiff of antiseptic in whisky or wine may be guaiacol, the phenol-group member with a medicinal-type aroma that numbers among the aromatic constituents of beer, wine and whisky. At low levels it adds smoky complexity; as a taint in fruit juices from bacterial spoilage it ruins the product. Analysts also use it as a substrate for measuring peroxidase activity. Its dual nature makes it a compound flavourists respect and microbiologists watch. Alicyclobacillus species are the usual culprits behind guaiacol taints in juices.