Comparison of procedures for reducing astringency carry-over effects in evaluation of red wines

The intensity of astringency of red wine increases when a single wine is sipped repeatedly or during evaluation of several red wines in one session. The effectiveness of different rinses in reducing or preventing the build-up of astringency was evaluated using time-intensity (TI) methodology. Trained subjects continuously rated the intensity of an astringent red wine using a sip and spit protocol. Ten s after the wine was sipped, it was expectorated. Ten s later, a rinse was sipped, which was spat out after another 10 s. Judges rated until astringency was no longer perceived. Between wine-rinse combinations, subjects rinsed twice with de-ionised water for 20 s. Intensity ratings at maximum intensity and at 5 s intervals were extracted from the TI curves and subjected to analysis of variance. Pectin (1 g/L) reduced astringency more effectively than water, polyvinylpyrrolidone (PVP) (4 g/L), gelatin (6 g/L), or ovalbumin (4 g/L) (Experiment 1). Low (1g/L) and high (5 g/L) concentrations of pectin and a high (1 g/L) concentration of carboxymethylcellulose (CMC) decreased astringency significantly more than rinses of Polycose, (5 and 40 g/L), CMC (0.01 g/L) or water (Experiment 2). In a third Experiment, unsalted crackers were shown to be more effective in decreasing astringency than water, although the pectin (5 g/L) rinse was superior to crackers and water. For the inter-stimulus rinse protocol to be most effective, it was found to be important to remove the residuals from each 'rinse' by extensive water rinses before tasting the next wine.