Effect of viscosity, temperature and pH on astringency in cranberry juice

This study explored the interactive effects of temperature, pH, viscosity and quinic acid in modifying astringency of cranberry juice. A panel of 17 trained judges rated astringency of nine samples, in duplicate, at 10 and 20 s after ingestion. Astringency intensity at both times showed the same trends, although the ratings were lower at 20 s. Addition of 1.5 g/l quinic acid lowered the pH to 2.59 and failed to produce a difference in astringency from the base juice (pH 2.65) at 5°C and 25°C. Astringency of juice adjusted to pH 3 was significantly lower than either the base or quinic acid juices at both temperatures. Decreasing temperature caused an increase of about 2 cp in viscosity and lowered the perceived astringency at all pH levels. Increasing the viscosity by 1.5 cp using CMC (carboxymethylcellulose, medium viscosity, Sigma Chemical) lowered the perceived astringency for all pHs but the effect was only significant at 25°C. Thus, without varying the concentration of astringent compounds, astringency intensity could be significantly modified by altering viscosity or pH.