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

This study explored the interactive effects of temperature, pH, viscosity a nd quinic acid in modifying astringency of cranberry juice. A panel of 17 t rained judges rated astringency of nine samples, in duplicate, at 10 and 20 s after ingestion. Astringency intensity at both times showed the same tre nds, although the ratings were lower at 20 s. Addition of 1.5 g/l quinic ac id lowered the pH to 2.59 and failed to produce a difference in astringency from the base juice (pH 2.65) at 5 degrees C and 25 degrees 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 i ncrease of about 2 cp in viscosity and lowered the perceived astringency at all pH levels. Increasing the viscosity by 1.5 cp using CMC (carboxymethyl cellulose, medium viscosity, Sigma Chemical) lowered the perceived astringe ncy for all pHs but the effect was only significant at 25 degrees C. Thus, without varying the concentration of astringent compounds, astringency inte nsity could be significantly modified by altering viscosity or pH. (C) 1999 Elsevier Science Ltd. All rights reserved.