Sweetness and intensity of artificial sweeteners HOWARD R. MOSKOWITZ2 BAR VARD UNIVERSITY In four experiments, groups of Os saccharin) and from commercial brands magnitude estimate of each O. Thus each 0 judged either the sweetness or the entire (Domino cane sugar; "Sucaryl," "Ann Page was given a different positive number taste intensity of solutions of sucrose, Sweetener"). Solutions prepared with corresponding to his estimate of "0," with cyclamate salts, cyclamate-saccharin Cambridge tap water were made up 3 to 4 the property that it was the lowest of his mixtures, and sodium saccharin. The days prior to use. When not in use they numbers. sensory functions obtained by magnitude were stored under refrigeration at 5°C. The geometric mean has been employed estimation suggest that over the middle Different groups of Os, chosen from a as the measure of central tendency for range of concentration the sweetness and pool of 60 Harvard students, participated magnitude estimates because the intensity of the foregoing substances grow in the experiment. Each 0 sat in front of a logarithms of the judgments tend to be as power functions of concentration. As a table on which were arranged the stimulus distributed symmetrically. In the present first approximation, the exponents for solutions in a linear array. Solutions were case the presence of "0" required that the sweetness and intensity are, respectively, given in paper cups (%-oz Sweetheart median judgments be used instead, because 1.6 to 1.4 for sucrose, 1.0 to 0.8 for souffle cups), each containing 4 to 6 ml of the geometric mean of a set of numbers cyclamate salts, 0.6 to 0.85 for solution. The order of presentation was containing a zero becomes zero. cyclamate-saccharin mixtures, and 0.3 to irregular and was changed for each O. In In all the experiments reported here 0.6 for sodium saccharin. most of the experiments the 0 sampled each 0 was left free to choose the modulus between 40 and 50 solutions, usually for his scale. As a result some individuals Sugars grow in sweetness according to a taking about 30 min to complete the used numbers in the hundreds and power function of concentration, with a session. thousands, whereas others used fractions. probable exponent of 1.3 (Moskowitz, Prior to each session the 0 was given the In order to reduce the magnitude estimates 1968, 1970; Stevens, 1969). In log-log following written instructions: "In front of of all Os to a common modulus, without, coordinates this relation between sweetness you is a series of solutions in paper cups. however, changing the ratios of the (S) and concentration (C) is expressed by Your task is to tell how sweet/intense they numbers, a normalization procedure called the equation log S = 1.3 log C + log k. The seem by assigning numbers to them. If the modulus equalization was used (Lane, intercept, k, differs for different sugars and second is nineteen times as sweet/intense as Catania, & Stevens, 1961). The is a measure of relative sweetness at the the first, then assign it a number nineteen normalization required two steps. First, the concentration given by the intercept times as large. Ifthe second is one-eleventh responses of each 0 to a core set of six (Moskowitz, 1970). There are, however, as sweet/intense, then assign it a number sucrose stimuli (2%, 4%, 8%, 16%, 32%, many other sweeteners besides sugars. The one-eleventh as large, and so forth. Use 64%) were normalized by a single present study concerns the sweetness fractions, decimals, and whole numbers, multiplier so that their geometric mean functions for the artificial sweeteners, but make each assignment proportional to became to.O. The ratios of magnitude cyclamate and saccharin, whose quality of the sweetness/intensity as you perceive it. estimates were left unchanged, but the size sweetness differs markedly from the Rinse after each stimulus solution. If you of the numbers was equalized for all Os. sweetness produced by sugars. Usually the cannot taste anything in the solution then Second, the responses of each 0 to the sweet taste of cyclamate and saccharin is rinse again and try the sample once more. other stimulus concentrations in the same accompanied by a bitter off-taste (Helgren I[ you still cannot taste anything, then use experiment were also multiplied by the et al , 1955) that increases with "0" for your magnitude estimate." same constant that had been used concentration. At the higher There was no time limit on the session. previously to normalize his response to concentrations the bitter predominates and Each 0 was free to proceed at his own sucrose. Again the ratios of magnitude the artificial sweeteners no longer evoke pace. During the course of the sessions estimates were left unchanged. The only the sweet taste. several Os complained about a bitter taste change was in the absolute level of the In view of the presence of at least two that remained after rinsing. In these cases magnitude estimates, and, for each 0, that distinct tastes in artificial sweeteners, it is they were instructed to rinse thoroughly, change was identical for all his numerical important to separate the sweetness gargle, and wait a few seconds before estimates. In each experiment every 0 had component from the rest of the taste. In proceeding. a unique normalization multiplier, and the present study, functions both for when Os participated in two or more sweetness and for total taste intensity were ANALYSIS experiments they usually required two or obtained for each of four sweetening The numerical matches (magnitude more different multipliers. By this substances: sucrose, sodium and calcium estimates) were analyzed with a local normalization two sweeteners that had cyclamate, sodium and calcium Suearyl (a computer program called PSYCHOFIT been scaled in entirely different mixture of cyclamate and saccharin), and (panek & Stevens, 1965). PSYCHOFIT experiments, e.g., sodium saccharin and sodium saccharin. provided geometric means, medians, and calcium cyclamate, could be compared to measures of variability (standard deviation each other. PROCEDURE and interquartile range) for the magnitude Stimulus solutions were prepared on a estimates of each stimulus concentration. RESULTS percent-by-weight basis (grams In those instances in which Os reported In Fig. 1 the logarithms of the median solute/grams solution) from reagent-grade "0" as their magnitude estimate the "0" magnitude estimates of "sweetness" and chemicals (cyclamate salts and sodium was replaced by 0.1 X the lowest "intensity" are plotted as a function of the 40 Copyright 1970, Psychonomic Journals, Inc., Austin, Texas Perception & Psychophysics, 1970, Vol. 8 (1) 1000 .. 500 • INTENSITY • I' .OC·6 INTENSITY I' 3.8C·8~ INTENSITY I' Z& C·8 S. EETNE" S·8.5C.3 o / K / 1/ -- • o 1 [ s-r: SWEETNESS • S'9C •.0 d/~_t.~- • o o \ 0 o SWEETNESS o S. 5.4C ,E; --- \ swEETNESS 0 • S·20C·3 o o •. CALCIUM SUCARYL o O' EXP. I SODIUM SUCARYl.. .6 A• •• EXP. • CALCIUM CYCLAMATE .Z o •. xr• • ANN PAGE SwEETENER 0., SODIUM CYCLAMATE 2.0 4.0 8.0 \6.0 32D 640 ,00625 .025 .I 4 1.6 6.4 .062~ .25 1.0 4.0 16-0 4.0 5 .02~ 0.1 0.4 1.6 PERCENT SUCROSE 8"" WEIGHT PERCErIi't CYCLAMATE SALTS 8Y WEIGHT PERCENT CYCLAMATE- SACCHARIN MIXTURE 8Y WEIGHT PERCENT SODIUM SACCHARIN BY WlIG"l Fig. 1. Sweetness and intensity functions for four groups of sweet substances: sucrose, sodium and calcium cyclamate, cyclamate­ saccharin ("Sucaryl") mixtures (sodium and calcium forms), and sodium saccharin. The coordinates are log-log in each case, so that straight lines suggest power functions. logarithm of concentration. When sensory the difference between the functions is between the slopes of c-yclamate and functions are linear in these logarithmic marked, and the sweetness exponent is saccharin. coordinates, they conform to power approximately half of the intensity On the basis of the power-function functions. In most cases the sweetness exponent. exponents the sweeteners may be placed functions are linear only over a limited The three simple sweetness functions into three classes: sucrose, cyclamate salts, range of concentrations. In particular, the (sucrose, cyclamate salts, sodium and saccharin. Sucaryl mixtures appear to high concentrations of sucrose and the saccharin) differ from each other in slope be intermediate between the cyclamate extreme concentrations (at both ends) of (exponent). Sucrose grows most rapidly in salts and saccharin but resemble more the artificial sweeteners systematically sweetness with concentration, followed by closely the cyclamate salts, which depart from a straight line. The straight the cyclamate salts, and finally by sodium predominate in Sucaryl by a factor of lines in Fig. 1 were fitted only to the most saccharin. In the case of cyclamates the 10:1. linear segment of the function. Both the nature of the cation appears to make little No single exponent accounts for either slope and the intercept were calculated by difference in either the sweetness or the the sweetness or the intensity of the a least-squaresprocedure. intensity function. There are two different On the other hand, the functions that sweetness functions for sodium saccharin, resulted when the Os were instructed to both with an exponent of approximately o judge the overall intensity of the taste 0.3, but with intercepts that differ by a conform more nearly to power functions. factor of 2.5. Thus there are two separate The differences between the sweetness and estimates of the relative sweetness of the intensity functions become more sodium saccharin, differing by a factor of pronounced as the exponents decrease in 2.5. On the other hand, the growth in magnitude.