Cross-modal interactions and effects of the level of expertise on the perception of bitterness and astringency of red wines

The present study investigates the role of sensory interactions and the level of expertise of consumers on the perception of bitterness and astringency in a red wine complex matrix. In the first experiment, a commercial red wine was spiked with quinine sulphate to produce two levels of bitterness. Seven samples with high and seven with low bitterness were further spiked with one of the following aroma vectors: vegetal, herbal, spicy, roasted, animal, dried fruit or with tartaric acid to modulate sourness. In the second experiment, the wine was spiked with an astringent proanthocyanidin fraction to produce two levels of astringency and with one of the seven vectors used in the first experiment or with quinine sulphate to modulate bitterness. Fourteen and 16 spiked samples of experiments 1 and 2, respectively, were sensory evaluated together with control samples to assess the intensity of the six aroma vectors, sourness, bitterness and astringency. Evaluation was performed using a descriptive analysis technique based on intensity rating by three groups of participants with different levels of expertise. The effect of the addition of one aroma vector, sourness or bitterness on bitter or astringent intensity was evaluated by ANOVA. No significant effect of aroma, sourness or bitterness was observed for astringent intensity, confirming that in these red wines, cross-modal interactions are not relevant in astringency. Bitter-aroma interactions were demonstrated for animal aroma just for less-experienced consumers (novices) attributed to a hedonic synergism. Significant decreases in bitterness due to sour vector were observed regardless consumer expertise. This could be explained in terms of interactions at both cognitive and receptor level.