Investigation of Mechanisms for Perception of Astringency
Astringency has been shown to have carry-over effects which influences the perception of astringency of red wine and astringent compounds. To quantitatively measure this effect, trained judges rated intensity of astringency continuously while repeatedly sipping wine. When red wines were sipped 4 times at 25 second intervals between sips, the astringency intensity increased significantly with each sip. At each sip, astringency increased, reached a maximum intensity about 15-16 seconds after the sip was taken, then decreased slowly until the next sip was taken and again astringency increased. For two of the wines the increase with each sip was significant, whereas the other two the increase in astringency between the 3rd and 4th sip was not significant. To see what happened when more sips were taken, astringency was continuously rated over 8 sips for alum and tannic acid. The 4th sip of tannic acid was not more significantly intense than the 3rd , although the astringency continued to slowly rise. The practical consequences of these results are that most evaluations of red wines are rendered invalid due to the carry-over phenomenon demonstrated in this study. Astringency of red wines evaluated either by a winemaker during winemaking or for blending or by wine show judges is influenced by the wines tasted before it. To quantify the effects of physiological differences on perception of astringency the saliva flow rates of the judges in the red wine and alum/tannic acid studies above were determined. Individuals with low flow rates of saliva perceived astringency of red wine and of the alum and tannic acid more intensely and longer than high-flow subjects. This physiological difference in perception of astringency is of great significance in understanding how astringency is perceived. Since saliva flow rate varies with the size of the person generally speaking, the practical value of this information may lie in marketing wine, where it may account for preferences of “smaller” consumers. In evaluations of the viscosity of saliva-tannin mixtures, it was shown that viscosity of saliva decreases when tannin is added, analogous to sipping red wine. This is consistent with the observations of the effect of salivary flow status. If astringency is felt as the friction resulting from precipitation of saliva proteins by tannins, than high-flow subjects can restore lubrication better and hence perceive lower levels of astringency than low-flow individuals.