The influence of solvent viscosity on the threshold values of primary tastes

Abstract

To study the effect of viscosity on the stimulus and recognition thresholds of the four primary tastes, four thickeners which are relatively free of any specific taste and odour (methyl cellulose, guar seed flour, carob seed flour and tara seed flour) were selected from a greater number of such substances available and the stimulus and recognition thresholds at the four viscosity levels, 1, 10, 100 and 1 000 cP determined for sucrose, sodium chloride, caffeine and citric acid. It was found that with increasing viscosity also the stimulus and recognition thresholds increased which means that higher concentrations of the taste substances are necessary to produce the same taste intensity at higher viscosity. Significant differences were found particularly at the highest viscosity level of 1 000 cP as compared to 1 cP. By relating the individual values to the corresponding value at 1 cP it is possible to determine, bymeans of the so-called amplification factors, the concentration increase that is necessary toproduce the same taste intensity as at 1 cP. On the basis of regression straight lines, this amplification factor can be determined for all substances and taste qualities. It became obvious in this way that not only viscosity is important but also the kind of thickener used.