Perceptual interactions and characterisation of odour quality of binary mixtures of volatile phenols and 2-isobutyl-3-methoxypyrazine in a red wine matrix

The qualitative perceptual interactions of single and binary mixtures of four compounds: guaiacol (‘burnt/smoky’), o-cresol (‘phenolic/tar’), 4-ethylphenol (4-EP, ‘leather/barnyard’), and 2-isobutyl-3-methoxypyrazine (IBMP, ‘green pepper/herbaceous’), were studied in a partially de-aromatised red wine matrix. Using Descriptive Analysis, each compound was characterised individually by a trained panel of eleven judges at peri- and sub-threshold levels. Binary mixtures of all four compounds were subsequently characterised in the same matrix using a D-optimal fractional statistical design. The data show that the olfactory outcome of binary mixtures of these compounds in red wine cannot be predicted from the attributes of the single compounds, with some ‘single compound’ attributes absent in binary mixtures, and new attributes emerging when two compounds are present together. This work adds to our understanding of the sensory impact of low levels of volatile phenols and IBMP in wine.