NANCY LARSON-POWERS’ and ROSE MARIE PANGBORN Food Science & Technology, University of California, Davis, CA 95616

PAIRED COMPARISON AND TIME-INTENSITY MEASUREMENTS OF THE SENSORY PROPERTIES OF BEVERAGES AND GELATINS

CONTAINING SUCROSE OR SYNTHETIC SWEETENERS

ABSTRACT By paired comparison methods, concentrations of 0.75% and 0.86% calcium cyclamate and of 0.17% and 0.19% aspartame were equivalent in sweetness to 10% sucrose in distilled water at 3” and 22”C, respec- tively. Inherent bitterness of the compounds prevented precise assess- ment of relative sweetness for sodium saccharin in distilled water, and for the saccharin and cyclamate in flavored drinks. By application of linear regression to the paired comparison data, 0.07% aspartame was calculated as equal in sweetness to 10% sucrose in lemon, strawberry and orange drinks. Because the underlying bitterness of saccharin inter- fered with assessment of its sweetness, a time-intensity technique was applied. Using a chart recorder to monitor time, time-intensity (T-l) measurements were made of the intensity and the duration of sweet- ness, bitterness, sourness and flavor in distilled water, and the same characteristics, plus flavor in three flavored drinks, and two flavored gelatins, sweetened with sucrose, cyclamate, or saccharin. T-l curves for the sensory properties of aspartame closely resembled those for sucrose in all media. Cyclamate and saccharin imparted a marked, persistent bitterness to all carriers. In gelatin, samples containing 18% sucrose were firmer initially and took longer to manipulate to a liquid in the mouth than did gelatins containing 0.105% aspartame, 0.55% cycla- mate, or 0.05% saccharin.

INTRODUCTION THE DEVELOPMENT and testing of synthetic sweeteners in- volves a lengthly sequential procedure. First, it must be estab- lished that the new ingredient is safe for human consumption, that it is stable under normal conditions of handling and stor- age, and that it is not detrimental to the physical or functional attributes of the products in which it is to be used. Of prime importance are the sensory properties - appearance, aroma, texture, taste and aftertaste. Traditionally, a single sensory parameter is measured - sweetness equivalence to sucrose, usually by paired comparison methods, In the interest of expediency and efficiency, most investigations are conducted using model systems (compounds dispersed in distilled water), with the hope that similar relationships would hold in more complex food and beverage systems. We felt that measure- ments of perceived intensity, sensory quality, and stimulus duration in several systems would be useful supplements to the conventional, unidimensional “relative sweetness” measure-

’ ment. The present investigation was undertaken to compare the relative taste properties of aspartame, sodium saccharin and calcium cyclamate with those of sucrose in distilled water, in lemon, orange and strawberry drinks, and in orange- and strawberry-f lavored gelatins, using both paired comparison and a new approach to time-intensity (T-I), wherein time is con- tinuously monitored by a strip chart recorder (Larson, 1975).

Stock solutions of the two gelatins were prepared by mixing the base with 3/4 of the total volume of boiling, distilled water and stirring for 2 min by hand. After mixing for 10 min with a magnetic stirrer, the gelatin was cooled to room temperature and brought to volume. Ali- quots of the sweetener, which had been dissolved in distilled water (w/v) to a specific volume, dependent upon the desired concentration, were combined with the gelatin solution, brought to volume, and poured into enamel pans to a height of 2 cm. Any surface foam was removed, and the pans were covered with a plastic wrap and stored at 3°C +_ 1°C for 18 hr. All gelatins were tested within 24 hr of prepara- tion, at which time they were served as 2 cm cubes at 7” * 1°C. Sensory procedures

The paired comparison, constant stimulus, forcedchoice method (Amerine et al., 1965) was used to compare seven concentrations of each of the three synthetic sweeteners with solutions of 10% sucrose, at 3” and at 22°C. In the three flavored drinks, five concentrations of each synthetic sweetener were compared with samples containing 10% su- crose. Judges selected the sweeter sample within each pair, with a total of three replications obtained per judge per paired concentration. The percentage of the responses selecting the 10% sucrose sample as sweeter

Table l-Composition of powdered bases used for drinks andgelatins

Drinks (w/w%)

Strawberry Orange Lemon

Citric acid 52.36 48.71 69 98 Monocalcium phosphate 43.64 42.35 22.07 Flavoring 0.74 6.61 290 FD&C color 1.49 0.61 0.01 Vitamin C 1.80 1.55 0.81 Vitamin A 0.17 0.17 0.09 Clouding agent 4.23

MATERIALS&METHODS Gelatins (w/w%)

Ingredients Strawberry Orange The sweeteners used were: sucrose (99% pure, C & H Sugar Co.),

sodium saccharin (Sherwin Williams, lot x5768), calcium cyclohexyl- sulfamate (Searle Biochemics, lot x5735), and aspartame (L-aspartyl-L-

Gelatin 70.9 70.7 Adipic/fumaric acid 20.3 20.1 -Sodium citrate 6.7 6.6 Flavoring 1.7 2.4 Color 0.4 0.2 I - ’ Present address: 1015 Campbell, Presser, WA 99350

phenylalanine methyl ester, Searle Biochemics, lot 5270-7). Drinks and gelatins were prepared from powdered bases supplied by General Foods Corp., Tarrytown, NY (Table 1). Sample preparation

The water solutions were prepared (w/v) using doubledistilled water and sweetener, covered, and allowed to stand at 22°C for 16 hr prior to tests conducted at room temperature, and at 3°C for 16 hr prior to tests conducted with solutions at refrigerator temperature. The chilled samples were poured into the test beakers 1 hr before the test session, covered, and replaced in the refrigerator to allow the temperature to equilibrate to 3°C.

The three flavored drinks were prepared from a stock solution of the powdered base and doubledistilled water. The stock was added to the solid sweeteners, agitated to dissolve them, diluted to volume at 22”C, and stored at 3°C for approximately 12 hr.

Volume 43 (1978kJOURNAL OF FOOD SCIENCE- 41

Fig. l-Time intensity method. Judge places sample in mouth, acti- vates strip-chart and records perceived intensity on moving chart until extinction point.

ASPARTAME W

Fig. 2-Sweetness of aspartame relative to 10% sucrose in distilled water at 3” and 22°C. showing both linear and parabolic lines fitted to the data.

-0 0.4 0.5 0.6 0.7 0.8 0.9 1.0 CYCLAMATE ("lo)

Fig. 3-Sweetness of calcium cyclamate relative to 70% sucrose in distilled water at 3 and 22’C, showing both linear and parabolic fines fitted to the data.

42 -JOURNAL OF FOOD SCIENCE- Volume 43 (1978)

was plotted against the concentration of the synthetic sweetener, and a regression line fitted to the data. Equisweetness was defined as that concentration of synthetic sweetener at which 50% of the responses indicated the synthetic was sweeter than sucrose, as read from the linear regression line. For the water solutions, only, parabolic lines were fitted to the data by computer, also. Gelatins were not evaluated by paired comparison due to difficulties encountered with the liquids.

Judges consisted of nine females and four males, students and employees, selected on the basis of interest in participation and consis- tency of response to perceived sweetness and bitterness in paired pre- sentation of test solutions. Within all test series, samples of approxi- mately 35 ml of solution were served in randomized order in 50-ml beakers coded randomly with numbers from l-999. Distilled water was provided for oral rinsing and judges were instructed not to swallow samples. Test sessions were conducted three to four times per week, between 10:00 am and noon, in individually partitioned booths main- tained at 21” + 2°C.

For the T-I measurements, time was monitored by a strip chart recorder (Heathkit Multi-speed Servo Chart Recorder, Model lR-18M). The paper was set to advance at a rate of 0.05 in/set when liquids were being tested, and at’ 0.1 in/set for testing gelatin. Perceived intensity was recorded manually with a felt-tip pen on the moving chart, using a lOOdivision, unstructured scale labeled “none” to “extreme” on the stationary paper-cutter bar (Fig. 1). The bar served both as a guideline for marking intensity, and to cover the previous response, forcing judges to concentrate on the immediate intensity. Samples were presented in 50-ml beakers identified with small, gummed labels marked with the sequence and with the single sensation being meas- ured, e.g., “l-sweet,” or “2-bitter.” The gummed label was transferred from the beaker onto the chart paper to identify the curve, and to focus the judge’s attention on the single sensation under consideration. The judge placed the entire sample into the mouth, retaining the IO ml of liquid for 20 set, or the 2-cm cube of gelatin for 10 set before expectoration, while recording the intensity on the moving chart. For sweetness measurements in distilled water (Fig. 2, 3, and 4), judges first recorded initial intensity on the stationary chart. Then, a second sample of the same stimulus was placed in the mouth while simultaneously initiating the advancement of the chart paper. Beginning from the initial intensity point, the judge marked perceived intensity on the moving chart, expectorating at the designated times, and continuing to mark the moving chart until the sensation was no longer perceived, i.e., to the extinction point (Fig. 1).

In addition to recording taste and flavor intensities, hardness and rate of breakdown of the gelatins were assessed by the T-I method. First the judge placed the gelatin cube between the molar teeth, bit down and expectorated, recording the initial hardness or f irmness on the stationary chart. Next, the second sample of the same gelatin was placed between the molars, bitten and manipulated between the tongue and palate to a complete liquid, recording the perceived rate of break- down on the moving chart. For both liquids and gelatin, a total of eight samples were tested per session, with distilled water provided for oral rinsing.

For evaluation of the water solutions and the three drinks by the T-l method, nine judges, with experience on the previous paired tests, par- ticipated. For evaluation of gelatins, a new group of subjects was screened and trained, with ten being selected on the basis of repro- ducibility of judgment, two of whom had participated in the previous taste studies.

To tabulate the T-I data, points on the graphs were joined to form a smooth curve, with mean intensities calculated for the entire panel at 47%~ intervals for the liquids, and at 2-set intervals for the gelatins. These mean intensities were then replotted against time for each sen- sation for each sweetener. The total area under the curve was estimated using third-order exponential smoothing, based on an input of points from a digitizing table to a calculator (Hewlett-Packard, 9810). Analysis of variance was applied to the initial intensity values read from the individual charts, and to the values representing areas under the curves.

RESULTS & DISCUSSION Paired comparison method

Sensory responses to the sweetness of aspartame, cycla- mate and saccharin compared to 10% sucrose in distilled water are plotted in Figures 2, 3, and 4, respectively. For aspartame, it was necessary to test a different concentration series at each solution temperature to bracket the sweetness match (Fig. 2).

SENSORY PROPERTIES OF BEVERAGESAND GELATINS.. .

Table 2-Concentration range, equisweet concentrations and correlation coefficients for solutions of synthetic sweeteners compared to 10% sucrose, paired comparison method

Medium of dispersion

Aspartame Cyclamate Saccharin++

Cone range Equiv. Cont. range Equiv. Cone range

tested sweetnessa tested sweetnessa tested

% % r % % r 36

Distilled water 22°C

3°C

Drinks Strawberry Orange Lemon

0.075-0.290 0.190 0.903X” 0.15-l .o 0.86 0.818” 0.03-0.50 0.065-0.290 0.170 0.955”“” 0.04-I .o 0.75 0.9371” 0.05-0.35

0.05-0.15 0.069 0.955” 0.25-0.85 ++b - 0.05-0.25 0.05-0.270 0.068 0.986’” 0.20-I .25 ++ - 0.02-0.30 0.05-0.10 0.066 0.963** 0.45-l .15 -I+ - 0.05-0.15

*Significant at p < 0.05 l * Significant at p < 0.01 * * * Significant at p < 0.001 a Values determined from linear regression line. b++Equivalent sweetness concentration point was not determinable.

The aspartame data fit more closely to a parabolic (r = 0.965 at 22°C and r = 0.990 at 3’C, p < 0.01) than a linear regres- sion (r = 0.903 and 0.955, respectively, p < 0.01 and 0.001). The cyclamate data (Fig. 3) also fit more closely to a parabolic (r = 0.962, p < 0.01) than a linear regression (r = 0.818, p < 0.05). Using the conventional measurement of reading values from a linear regression line, 10% sucrose was determined to be equivalent to 0.190% aspartame and 0.86% cyclamate in solutions tested at 22’C, and to 0.170% aspartame and 0.75% cyclamate at 3°C (Table 2). Lower aspartame values have been reported in the literature, e.g., a 10% sucrose match of 0.075% aspartame (Beck, 1974) and 0.050% aspartame (Guadagni et al., 1974). The latter investigators did not specify solution temperatures, but we presume samples were served at room temperature. Although sucrose and cyclamate have been tested by several investigators (Vincent et al., 1955; Schutz and Pilgrim, 1957; Kamen, 1959; Hellaur, 1966; Stone and Oliver, 1969; Yamaguchi et al., 1970a, b none compared cycla- mate directly to 10% sucrose. The best estimate of the sweet- ness of calcium cyclamate from these literature values can be expressed as a relative sweetness of 30-80 compared to su- crose being equal to 1.

The linear regression lines in Figure 3 are highly question- able, particularly for solutions tested at 22’C, because of the obvious plateauing of responses at the 50% mark for concen- trations ranging from 0.6-1.0% cyclamate. An inspection of the individual data showed a time-order bias for the cyclamate- sucrose comparison, only. The second sample within a paired set was significantly selected as sweeter 226 times in 364 trials, or 62% of the time (p < O.OOl), compared to the chance selection of 50%. This overselection of the second sample, despite random presentation, strongly suggests mutual synergism of the two compounds, agreeing with Kamen (1959) and Yamaguchi et al. (1970b) who reported sweetness synergism of intermediate concentrations of sucrose and cycla- mate. It should also be pointed out that several investigators have observed a bitter off-taste in cyclamate solutions, starting with concentrations of 1.3% (Helgren et al., 1955). Vincent et al. (1955) found a linear relationship between the percentage of their 76 judges reporting off-taste and the log of the con- centration of sodium cyclamate. Twenty percent detected an off-taste at 0.42%, and 50% at 0.66% cyclamate. The off-taste was perceived at higher levels of relative sweetness for the sodium salt than for the calcium salt of cyclamate. Using 150 female testers, Tiwald (197 1) reported significant differences between equisweet solutions of 0.17% sodium cyclamate and

n l 13 026

1 039

4 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

(T, SODIUM SACCHARIN (%I

Fig. 4-Sweetness of sodium saccharin relative to 10% sucrose in distilled water at 22”C, demonstrating the impossibility of fitting a line to the data to determine the relative sweetness.

7.5% sucrose, which he attributed to the bitter aftertaste of the former.

Figure 4 dramatically illustrates the impossibility of using the paired comparison technique to establish the concentra- tion of saccharin equivalent to 10% sucrose. A 20increment concentration series, ranging from 0.03-0.05% saccharin re- sulted in a tracking-type response pattern which never approxi- mated the 50% response criteria. A second concentration series of three levels of saccharin, 0.10, 0.20 and 0.30%, fared no better, despite the increased number of replications. A re- appraisal of the recent literature proved futile, as a 10% su- crose standard was not tested by paired comparison. The closest concentration values were 9.12% sucrose Z 0.03% saccharin (Schutz and Pilgrim, 1957) determined by a single stimulus, 9-point intensity scale, and 9.18% sucrose g 0.08% saccharin (Yamaguchi et al., 1970a) established by paired com- parison. Neither investigator reported difficulty in testing the relative sweetness of this compound. In his review of a large number of early articles on relative sweetness, Nieman (1958) reported a summary value of 30,000 for saccharin relative to 100 for 10% sucrose. As shown by Amerine et al. (1965), TZufel and Klemm (1925) reported a value of 18,900 for sac- charin relative to 100 for 10% sucrose.

Vincent et al. (1955) calculated that sodium saccharin was 240-350 times sweeter than sucrose at a level of

Volume 43 (1978)-JOURNAL OF FOOD SCIENCE- 43

Dislllled Water At 22°C

TINE (SEC) TIME (SEC)

Fig. 5-Time-intensity curves for sourness, bitterness, and sweetness of four sweeteners in distilled water at 22OC.

0.007-0.0 125%, but at higher concentrations the sweetness dropped rapidly due to increasing bitterness of the saccharin. This was substantiated by Moskowitz (1970), using magnitude estimation. Although we did not quantitate the bitterness intensity in the paired comparisons, we concur with Mosko- witz (1970) that the bitterness of the saccharin concentrations increases at a faster rate than does the sweetness. These changes in sweetness-bitterness functions with increasing con- centration -preclude the establishment by paired comparison of a concentration at which 50% of the responses would indi- cate the saccharin solution was sweeter than 10% sucrose.

No difficulty was encountered in calculating sweetness equivalence by paired comparison for aspartame in the three flavored drinks. The aspartame values equivalent to 10% su- crose were so similar for the three drinks, that a single concen- tration of 0.07% aspartame was used for subsequent testing of all drinks.

STRAWBERRY DRINK AT 3°C

64 FLAVOR

50 - BITTER

. . . . . . . . . .

a()- 1

SOUR -sucrose 10% _--. AlpOrfome 0.07% -- -Cyclomote 0.65%

.- ‘saccharin 0.10%

TIME (set) TIME hxl

Fig. 7a-Time-intensity curves for flavor, bitterness, sourness and sweetness in strawberry drink at 3°C.

Fig. 7b-Time-intensity curves for flavor, bitterness, sourness and sweetness in lemon drink at 3” C.

20 .\ BITTER \

Distilled Water 22'C - Sucrose 10% 4n2

60 ‘\ SWEET t \ -.- ---- ‘......’ Asporlomr 0.075% 2 I

Arportomc Asporlomc 0.13% 0 177X 21 21

TIMEfsecl 20 40 60 80

TIME(secl

Fig. &Time-intensity curves for sourness, bitterness, and sweetness for 10% sucrose and three concentrations of aspartame in distilled water at 22DC.

Our experience with paired comparison testing of cycla- mate, and particularly with saccharin, emphasized the need for a sensitive, indirect estimate of the multiple sensory properties of these compounds, hence the development of the T-I tech- nique. For the T-I method the final concentrations selected for each sweetener are specified on the individual graphs (Fig. 5-9).

Time-Intensity method Average T-I curves for the four sweeteners dispersed in

distilled water and tested at 22’C are shown in Figure 5. Simi- lar curves were obtained with solutions tested at 3’C, except that sourness of the three synthetic sweeteners was signifi- cantly lower (p < 0.001) at the lower temperature, as were sweetness and sourness for all compounds. Bitterness intensity was the same, possibly because solutions may have been closer to mouth temperature when they made contact with the bitter

LEMON DRINK AT 3°C

2 5. .-'"'.<,,~~~ BITTER t '. t

SWEET

44 -JOURNAL OF FOOD SCIENCE-Volume 43 (1978)

Fig. 8a-Time-intensity curves for strawberry gelatin with four sweeteners: In = 30 for hard- ness and flavor; n = 24 for bitterness; n = 27 for sweetness).

TIME Irecl

SENSORY PROPERTIES OF BEVERAGES AND GELATINS.. .

TIME (seconds)

Fig. 8b-Time-intensity curves for orange gela- Fig. g--Average T-l curves for strawberry flavor tin with four sweeteners: (n = 30 for hardness in gelatin for each of ten judges, demonstrating and flavor; n = 24 for bitterness; n = 27 for variation in initial intensity, maximum intensity sweetness).

receptors at the base of the tongue. At both temperatures, the greater sourness and bitterness of saccharin and of cyclamate, compared to sucrose was quite evident. Also, it is very obvious that 0.10% saccharin was considerably less sweet initially, with a shorter sweetness duration, compared to the other sweet- eners. The aspartame samples were initially sweeter than the sucrose solutions, but at the lower temperature, the sweetness duration of both solutions was identical. The persistence of all taste sensations in the synthetic sweeteners tested at 22’C is striking, particularly the bitterness and sourness of saccharin. Table 3 presents values in cm* for the total areas under the curves, with the corresponding LSD values.

Since the concentration of 0.177% aspartame, calculated from the paired comparison experiment as equivalent to 10% sucrose proved to be sweeter, two lower concentrations were compared to sucrose using the T-I method (Fig. 6). The con- centration of 0.075% was taken from a literature value (Beck, 1974), while the level of 0.13% was derived arithmetically from the data in Figure 5, i.e., 0.177% aspartame /64 initial intensity = 0.13% aspartame/49 initial intensity (the starting point for 10% sucrose). The latter aspartame concentration gave sweetness, sourness, and bitterness curves remarkably similar to those for 10% sucrose when tested experimentally (Fig. 6). This demonstrates the use of T-I data to interpolate and match sweetness intensities for compounds with no inter- fering secondary tastes.

T-I curves for the orange and strawberry drinks were al- most identical, hence only the latter data are shown (Fig. 7a), contrasted with curves from the lemon drink (Fig. 7b). The main difference in the curves for strawberry (pH 3.0) and lemon (pH 2.75 was the greater perceived sourness of the latter. The data suggest that sourness supressed perceived sweetness intensity, which agrees with previous findings (Pangborn, 1963). Flavor intensity curves were similar in both drinks for sucrose, aspartame, and cyclamate, with signifi- cantly less initial flavor for drinks sweetened with saccharin. In both drinks, the saccharin samples were very bitter, cyclamate samples were moderately bitter, and the sucrose and aspartame samples had a slight, transient bitterness. Bitterness curves for samples containing saccharin and for those containing cycla- mate suggest a slight increase in intensity up to the time of expectoration (20 set), then a pronounced drop. This slight delay in perception of maximum bitterness, only, might be related to the delay in the stimuli reaching the circumvallate

and duration In = 3).

Table d--Mean areas under the curve (cm’ ) for solutions, drinks end gelatins sweetened with sucrose or three synthetic sweeteners, T-l methoda

SUC APM WC SAC LSD”

Distilled water

Sour

Bitter

Sweet

Drinks Flavor

Bitter

Sour

Sweet

Gelatins Hardness

Bitter

Flavor

Sweet

3°C 5.5 10.7 14.6 17.0 7.1 22Oc 6.5 14.4 22.7 28.1 7.1

3°C 7.3 15.7 43.1 57.3 13.3 22” c 6.0 20.3 41.5 65.6 13.3

3°C 37.1 61.9 44.0 22.6 13.1 22°C 38.1 76.2 53.7 26.7 13.1

Strawberry 43.4 53.5 61.7 35.3 8.2 Orange 36.9 47.5 48.8 37.1 9.1 Lemon 49.6 62.0 71.7 37.5 8.3 Strawberry 7.1 10.4 40.9 51.7 9.5 Orange 13.6 7.8 36.4 53.3 10.7 Lemon 16.9 20.2 41.3 65.3 11 .l Strawberry 17.7 18.3 17.7 30.9 8.1 Orange 20.0 20.4 26.1 33.2 6.7 Lemon 64.9 59.4 56.0 75.1 10.1 Strawberry 31.2 44.6 56.3 16.2 10.0 Orange 30.2 43.3 51.3 20.4 10.9 Lemon 23.4 39.6 48.6 11.0 10.1

Strawberry 53.4 25.5 26.0 29.7 6.3 Orange 56.8 32.4 25.9 33.5 7.6 Strawberry 0.8 6.0 20.5 30.3 7.5 Orange 0.7 8.8 la.4 35.4 11.7 Strawberry 48.6 52.7 63.2 47.1 11.5 Orange 49.3 56.1 73.1 59.9 13.9 Strawberry 68.9 77.9 82.0 55.3 17.5 Orange 57.0 82.1 70.0 48.8 16.4

=SUC, APM, CYC and SAC are, respectively. sucrose, aspartame, cyclamate, and saccharin. For concentration, consult Fig. 6-8.

b least significant difference among sweetener means at p < 0.05.

papillae at the base of the tongue, the receptors primarily responsive to bitter compounds.

Marked differences can be seen in sweetness intensity and in duration, with aspartame and cyclamate being the greatest

Volume 43 /1978)-JOURNAL OF FOOD SCIENCE- 45

and saccharin being the least. Quantification of areas under the curve in cm* and the corresponding LSD values (Table 3) emphasize the magnitudes of greater bitterness and sourness, and of lesser sweetness and flavor of the saccharin samples.

The data indicate that lower concentrations of aspartame and of cyclamate should be used to match the initial sweetness intensity of 10% sucrose. Applying the ratio described pre- viously, one could predict that the initial sweetness intensity of sucrose in these drinks would be equivalent to 0.06% aspartame, and to 0.45-0.47% cyclamate. Due to the un- availability of the same judges, we were unable to verify these predicted concentration matches.

Despite the almost identical curves obtained for T-I measurements of orange and of strawberry gelatin;both fig- ures are included to illustrate the reproducibility of the panel using this method (Figs. 8a and 8b). As would be anticipated, gelatins sweetened with sucrose were firmer (p < 0.001) and broke down in the mouth more slowly than did the syntheti- cally-sweetened samples. Maximum firmness was perceived at “0” time, whereas maximum flavor and sweetness were per- ceived after 10 set of oral manipulation, and maximum bitter- ness after approximately 15 sec. Again, greater bitterness and less flavor and sweetness were assigned to samples containing saccharin. A good matching of curves was obtained for flavor and for sweetness of samples with 0.55% cyclamate, 0.105% aspartame, and 18% sucrose, also demonstrated in Table 3. An increase in the amount of saccharin would definitely have in- creased bitterness, but might not have increased sweetness, due to the interference of bitterness.

Figure 9 is included to illustrate the typical range of in- dividual judge responses to gelatin samples, using the T-I method. Although all ten judges were requested to begin marking the moving chart at the same time (2 set after placing the gelatin cube in the mouth), they differed markedly in their perception of initial flavor intensity, maximum flavor inten- sity, and extinction point. Most likely these differences are caused by variations in sensory sensitivity to the stimulus and to variations in the usage of the scalar points. Despite the large between-judge variation, observed in all sensory tests, there was excellent within-judge reproducibility of response. The latter was demonstrated by the general lack of significant F-ratios for the judge X replication interactions in the analysis of variance of these T-I data.

We feel that the T-I technique described herein for liquids and gelatins has considerable potential for testing sensory attributes of a variety of foods and beverages, after trained judges master the mechanics of marking intensity on a moving chart. The use of a recorder to monitor time is an improve- ment over the T-I methods described by Nielson (1957) and by Jellinek (1964) in which judges watch the second hand of a clock, by Todd et al. (197 1) where judges used a stop-watch to time duration of bitterness of beer, and by McNulty and Moskowitz (1974) where 1-set auditory signals indicated the time intervals.

In conclusion, it should be emphasized that paired compar- ison methods could be inappropriate with stimuli which exhibit masking or synergistic effects, or with stimuli which differ in more than one parameter.

REFERENCES

Amerine, M.A.. Pangborn, R.M. and Roessler, E.B. 1965. “Principles of Sensory Evaluation of Food.” Academic Press, New York.

Beck, C.I. 1974. Sweetness, character and applications of aspartic acid based sweeteners. In “Symposium: Sweeteners,” Ed. Inglett, G.E., Avi Publishing Co., Inc.. Westport, CT.

Beck, K.M. 1975. Practical considerations for synthetic sweeteners. Food Product Dev. g(4): 47.

Guadagni, D.G., Maier, V.P. and Turnbaugh, J.G. 1974. Effect of subthreshold concentrations of l imonin. naringin and sweeteners on bitterness perception. J. Sci. Food & Agric. 25(11): 1349.

Helgren, F.J., Lynch, M.J. and Kirchmeyer. F.J. 1955. A taste panel study of the saccharin“off-taste. ” J. Amer. Pharm. Assoc. 44(6): 353.

HeBarn, D. 1966. Sweetness of cyclamate. sodium cyclohexyl sulfam- ate, Z. Biol. 115: 313.

JeIIinek, G. 1964. Introduction to and critical review of modern methods of sensory analysis (odour. taste and flavour evaluation) with special emuhasis on descriutive analvais (Flavour Profile meth- od). J..Nutr. & Diet. l(3): 219.

Kanien, J. 1959. Interaction of sucrose and calcium cyclamate on per- ceived intensity of sweetness. Food Research 24(3): 279.

Larson, N.L. 1975. Sensory Properties of Flavored Beverages and Gela- tins Containing Sucrose or Synthetic Sweeteners. MS. thesis, University of California. Davis.

McNuItv, P.B. and Moskowitz. H.R. 1974. Time-intensity curves for flavored oil-in-water emulsions. J. Food Sci. 39(l): 55.

Moskowitz. H.R. 1970. Sweetness and mtensitv of artificial sweeteners Perception &-Psychophysics 8(l): 40. -

Nielson, A.J. 1958. Time-intensity studies. In “Flavor Research and Food Acceptance.” Reinhold Publ. Corp., New York.

Nieman. C. 1958. Relative Susskraft van Zuckerarten. Zucker- u. Siisswarewirthsch. ll(9): 420. 465. 505, 632. 610, 752, 791, 840, 878,933,974.1051,1088.

Pangborn. R.M. 1963. Relative taste intensities of selected sugars and organic acids J. Food Sci. 28(6): 726.

Schulz, H.G. and Pilgrim. F.J. 1957. Sweetness of various compounds. and its measurement. Food Research 22(2): 206.

Stone, H. and Oliver, S. 1969. Measurement of the relative sweetness of selected sweeteners and sweetener mixtures. J. Food Sci. 35(2): 215.

Taufel, K. and Klemm. B. 1925. Untersuchungen iiber natilrliche und kiinstliche Siistoffe. 1. Studien iiber den Siissungsgrad van Saccha- rin und DuIcin. Z. Untersuch. Nahr. Genussm. 50: 264.

Tiwam. H. 1971. eber den geschmack van natrium&lamai m vergleich zu sucker. Zucker 24(8): 227.

Todd, P.H., Bensinger, M.G., Johnson, P.A. and Worden, L.R. 1971. Organoleptic evaluation of iso-alpha-acids and other hop bittering substances. Proc. Amer. Sot. Brewing Chem. 9.

Vincent, H.C.. Lynch, M.J., Pohley, F.M., Helgren, F.J. and Kirch- meyer, F.J. .1955. A taste panel study of cyclamate-saccharin mix- tu;; and of its components. Amer. Pharm. Assoc. J., Sci. Ed. 44(6):

Yama&chi. S.. Yoshikawa. T., Ikeda. S. and Ninomiya. T. 1970a. Studies on the taste of some sweet substances. 1. Measurement of ielative sweetness. Agric. & Bio. Chem. 34(2): 181.

Yamaguchi, S., Yoshikawa. T.. Ikeda, S. and Ninomiya, T. 1970b. Studies on the taste of some sweet substances. 2. Interrelationships among them. Agric. & Bio. Chem. 34(2): 187.

M S received 512177; revised 814177; accepted 8112177.

Based on a thesis submitted by the senior author to the Univ. of California in partial fulfil lment of the MS. degree.

The technical assistance of Mrs. Cathy Tassan is gratefully ac- knowledged. The research was supported, in part, by Searle Biochemics. Arlington Heights, IBinois.

46 -JOURNAL OF FOOD SCIENCE-Volume 43 (19781