Determination of equivalence between intensity scales by means of paired comparison

Duineveld, C.; Arents, P. K. ng, B.

doi:10.1016/s0950-3293(03)00019-3

The equivalency of intensity scales used for different sensory descriptors by panelists during profiling with the audio method has been shown by comparing profiling data with data from paired comparisons. Sucrose-sweetness and lactic acid-sourness were chosen as examples of sensory stimulus-response relationships. Dose-response curves were measured for aqueous solutions of these compounds. Data were fitted with fourth order polynomial models that can be seen as power series expansions of Fechner's law. Expected scores and the zero-difference in (expected) scores for any descriptor pair, along with their standard deviations, were determined from the models. The respective sweetness/sourness of these solutions was also measured by 2-alternative forced choice (2-AFC) tests. A model with logit link and binomial distribution was used to fit the proportion wins as a function of the log concentrations of sucrose or lactic acid. The function representing an equal proportion of wins was plotted with 95% confidence intervals. Thus, regions of equal sweetness/sourness intensity could be compared graphically for both profiling data and 2-AFC data in a plot of lactic acid concentration versus sucrose concentration. The overlap of these two regions of equivalent concentrations supports the conclusion that the sweetness and sourness intensity scales as measured by the audio method are equivalent.