quantitative and qualitative evaluation of high-intensity sweeteners and sweetener mixtures

Chemical Senses Vol.17 no.3 pp.245-259, 1992

Quantitative and qualitative evaluation of high-intensitysweeteners and sweetener mixtures

Nalini Ayya and Harry T.Lawless1

Cornell University, Ithaca, New York, USA,

Correspondence: Harry T. Lawless, Department of Food Science,Stocking Hall, Cornell University, Ithaca, NY 14853, USA

Abstract. High intensity sweeteners were evaluated for sweetness and bitterness intensity using time-intensityscaling. Mean intensities of 50:50 mixtures as well as the single sweeteners were used to compute predictedscores which were compared to the observed scores as a means of evaluating additivity in the mixtures.Concentration-dependent effects of subadditivity, additivity and hyperadditivity were observed within somesweetener pairs, but these did not follow any consistent pattern across sweeteners. Synergy, a special caseof hyperadditivity evaluated by comparing predicted to observed scores, was seen in mixtures of aspartameand acesulfame-K at all concentrations. Aspartame/saccharin blends were synergistic only at the lowestconcentration tested, despite the structural similarity between acesulfamc-K and saccharin. Blends ofsucrose/aspartame and accsulfame-K/saccharin did not exhibit synergy. Comparisons based on ratings ofinitial sweetness rather than the whole time-intensity curve, reflected previous findings of synergy in somesweetener pairs.

Introduction

The existence of synergism in taste mixtures has been of interest in psychophysicsbecause the phenomenon may help us understand the peripheral mechanisms of tastereception and help evaluate single and multiple site models of taste (Lawless and Stevens,1983; Frijters and de Graaf, 1987; Frank et al., 1989). Practically, it is of value tothe foods industry in the potential for reducing additives such as sweeteners in foodsand beverages. Superadditivity is an intensity response to a mix that is greater thanthe intensity response predicted from the individual components of the mixture. Thus,if a combination of sweeteners can potentiate sweetness, lower concentrations of eachwould be used to achieve the same sweetness as the individual sweeteners. The studyof sweeteners has remained of interest with the discovery and approval for food useof high intensity sweeteners that are as acceptable as sucrose (O'Brien and Gelardi,1981).

Two approaches to the study of sweetness have dominated the literature. In themolecular approach various stimuli have been studied that are recognizably sweet, buthave vastly differing molecular structures and possibly sweetness qualities. Therefore,the structure of a molecule does not accurately predict the nature and intensity ofsweetness. The AH-B theory (Shallenberger and Acree, 1967) describes a structuralsub-unit to describe sweet-taste reception with an H-bonding proton (A-H) and an electro-negative atom (B) 3 angstroms away. The AH-B components have a stereochemicalrequirement imposed so that molecules will be suitably aligned with the receptor sitewhich also has a complementary AH-B pair, suggesting that at least one other additionalbonding site may be required (Solms, 1969; Deutsch and Hansch, 1966). A hydrophobic

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bonding area or a dispersion site (gamma) has been added to this theory to extend itsvalidity to high-intensity sweeteners to complete the receptor-site model (Shallenbergerand Birch, 1975). However, the theory is still not definitive because Pronase-E, semi-alkaline protease and gymnemic acid all selectively inhibit sweetness for somecompounds but not others, evidence that the sweetness receptor site may not be fullyexplained by a simple AH-B site-model. Pronase-E and semi alkaline protease are bothproteolytic enzymes. Topical application of these enzymes to rat taste cells and the humantongue inhibits sweetness because presumably the receptor site is hydrolysed (Hiji, 1975;Hiji and Ito, 1977). This effect is selective in that partial inhibition is seen—glycineand D-alanine are not affected. Also pyschophysical cross adaptation data suggest thatmore than one receptor site may be involved. Failures to cross adapt and assymetricpatterns of cross adaptation are difficult to reconcile with a single receptor type forsweetness (Lawless and Stevens, 1983. Schiffman et al., 1981; Faurion et al., 1980).

Psychophysical approaches to the study of mixture synergism have included functionalmeasurement, an equi-ratio mixture model and studies of the applicability of the Beidlermixture equation. Functional measurement (Anderson, 1962, 1970, 1977) focuses onevaluating responses in factorial designs. Parallel functions are interpreted as evidencefor both linear response functions as well as independence of stimulus effects. The goalof the equiratio mixture model (Frijters and Oude Ouphius, 1983; Frijters and de Graaf,1987) was to predict the exponents of mixtures given the exponents of individualcomponents. A limitation of this approach is that it assumes a single receptor mechanism(Frijters and de Graaf, 1987). Since there is evidence that different sweeteners maystimulate independent or at least partially independent receptor sites (Faurion, 1980,1987; McBurney, 1972; Schiffman etal., 1979, 1985; Lawless and Stevens, 1983)the model is limited to the study of molecularly similar sweeteners. According to themodel sucrose would overwhelmingly dominate a mixture of sucrose (effective in themolar range) and aspartame (effective in the millimolar), and this is implausible.

The Beidler mixture equation (Beidler, 1962) assumes a common receptor site thatthe components of a mixture would compete for, later corrected for receptor site affinityand intrinsic activity of the components. However, even with these refinements thecorrected equation has a response maximum (Rj^ in the denominator that is the samefor single sweeteners as well as mixtures. Thus, if the /?„,„ of a mixture is less thanthat of the single components, predicted sweetness may never be reached (see Figure2 in McBride, 1988).

A recent evaluation of binary mixtures was made with both carbohydrate and highintensity sweeteners in factorial designs using simple category scaling (Frank et al.,1989). The authors differentiate between synergy and superadditivity since super-additivity can be an artifact of the pyschophysical function. Bartoshuk (1975) andBartoshuk and Cleveland (1977) have demonstrated that the observed interaction(suppression, addition, synergism) may be related to the forms of the psychophysicalfunctions of the mixture's components. Suppression is seen if the function is negativelyaccelerating and synergism of the psychophysical function is positively accelerating.

Frank and colleagues made predictions of mixture synergies using a simple summationof responses and these theoretical values were compared to observed ratings of mixturesweetness. For instance, Component A receiving a score of 10 and B receiving a score

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Synergy in sweeteners

of 9 would predict a score of 19 for mixture AB. Synergy was evaluated by comparingthe ratios of the areas under the curve of the predicted mixture responses vs. observedresponses to the corresponding areas under self-mixture curves. The self-mixture curvespresumably reflect the curvature inherent in the psychophysical functions of the singlecomponent compounds. Some sweetener pairs demonstrated marked synergy. Theauthors found a consistent pattern of superadditivity at low concentrations, additivityat intermediate concentrations and subadditivity at the highest concentations. Theysuggested that release from bitter suppression may account for the reported synergies.The inclusion of the variety of high intensity sweeteners was valuable as was the useof areas-under-the-(dose-response)- curve as the parameter for comparsion, since neitherslopes or intercepts convey a complete picture. This study was a useful step forwardin its separation of true synergies from simple hyperadditive relations expected as afunction of self-mixing. However, one difficulty with this approach was the functionallimit of the bounded category scale. On a 15-point category scale observed evaluationsof mixture AB would not permit the value of 19, forcing results of subadditivity athigher concentrations.

Classical research on sweeteners has focused on intensity ratings, iso-sweetnessmatches or threshold measurements. Recently, methods have evolved to track the time-course of sweet tastes (Larso-Powers and Pangborn, 1978; Lawless and Skinner, 1979;Birch and Munton, 1981; Ott, Edwards and Palmer, 1991). Although there is quantitativedata on the comparison of time-intensity profiles to single-point intensity measurements,it is widely held that measuring the rise and fall of a taste sensation over time providesa more detailed and therefore potentially more informative picture of the psychophysicalcharacteristics of a chemical stimulus (Birch and Munton, 1981; Lee, 1989; Ott et al.,1991). The general goal of out study was to evaluate whether Frank's model of assessingsynergy could be extended to the study of synergy in the time domain. Time intensityprofiles are quantitatively richer and provide potentially useful information in theunderstanding of sweetness quality. Intensive sweeteners may be more persistent thancarbohydrate sweeteners and this difference may be examined in the decay function.Time-intensity data may also better approximate conditions of consumption and be moresuitable for examining the functionality of these sweeteners. One specific objective wasto evaluate whether existing reports of synergy would hold even when examined overtime.

In addition to the extension of Frank et al. 's methods of evaluating synergy into thetime domain, we introduced an additional basis for comparison of mixture to components.A logically simple comparison of additivity involves comparsions of equi-intensecomponents to their 50:50 concentration in mixtures (Lawless and Stevens, 1986). Whilethis method is based on the addition of concentrations, rather than responses, it doesavoid the problem Frank et al. faced in their predicted response measures, i.e. thataddition of observed responses to the (halved) component concentrations could producevalues beyond the ceiling of the bounded response scale.

The taste qualities and intensities of five sweeteners were examined in aqueous systemsin order to describe the pyschophysical profiles of these sweeteners. Sweeteners andsweetener mixtures were compared for sweetness and bitterness intensity and the changein intensity over time.

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Materials and methods

Stimuli

The sweeteners, sucrose, aspartame, acesulfame-K, and saccharin were tested in binaryconcentration steps over a range of four levels (Table 1). These sweeteners were selecteddue to their use in the study of Frank et at. (1989) and because they met with the approvalof our institutional human subjects review board. Solutions were made up in springwater (Chemung, NY). Spring water also served as an interstimulus rinse as it wasfound to have little, if any, taste. Solutions were prepared at least 24 hours in advanceto allow mutarotation of sucrose. Mixtures were prepared by combining the solutesand then making up to volume. This resulted in only three comparsions as combiningthe two concentrations of level 1 (the most dilute of any given range) was comparedwith level 2 of the single sweeteners (Table 1). Samples were served at 22°C in plasticcups and sample volume was 15 ml. Subjects were instructed to swallow the samples.

Subjects

Ten to 13 volunteers from the university, ages ranging from 18 to 35, were paid forparticipation. Informed consents were obtained and subjects were screened for tasteacuity, discrimination ability and PTC taster status. A group of subjects that completedthe evaluation of a sweetener pair were called a panel; panels were recruited anew foreach pair of sweetener combinations. All subjects completed the evaluation of a sweetenerpair and served as their own controls in a repeated measures design.

Terminology development

The subjects on the first panel developed a vocabulary to describe the sensations ofthe sweeteners in a technique similar to focus-group testing used in market researchand commonly used in the applied sensory testing for preliminary terminology develop-ment (Stone and Sidel, 1986). Redundancies in the descriptors were resolved throughdiscussion and some references were provided to assist the panelists in focusing ona particular sensation. Ways of evaluating a sensation were also standardized. Sixattributes were found to be important in describing the tastes of the sweeteners, however,only sweetness and bitterness are reported here.

Table I. Experimental design of study

Sweetener 1

Sweetener 2 C,D,

•Arbitrary units representing binary dilutions.Am—high mix; Bm—medium mix; Cm—low mix.Percentage concentration tested: sucrose—2.5, 5, 10 and 20; aspartame—0.025, 0.05, 0.1 and 0.2;acesulfame-K—0.03, 0.06, 0.12 and 0.24; saccharin—0.015, 0.03, 0.06 and 0.12.

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Quantitative scaling of sensations

Nine to 13 subjects were recruited per panel for discrete point time intensity scaling(Gordin, 1987). Concentrations of sweeteners were adjusted for iso-sweetness informallyby a group of experienced subjects. Concentrations previously used in the literaturewere screened to arrive at a four concentration series of binary steps for each sweetener.A warm-up session was conducted at the start of each panel to familiarize the subjectswith the scaling procedure, range of intensities that would be encountered and answerany other questions. All ratings were made on a 15-point category scale, anchoredverbally at each end of the scale, by marking the appropriate box for each attributeat each time. This scale was an approximation of a visual analogue scale in that itprovided sufficient scale range, equal sensitivity to differences, but minimised the effortof data transcription (Lawless and Malone, 1986). Each page of the ballot containedall the six attributes to be evaluated in their order of appearance; bitterness alwaysfollowed sweetness. Scales for each time interval were placed on a separate page inorder to minimize the influence of the previous rating on the rating currently beingmade. Ratings were made every 15 seconds for the first minute and every 30 secondsthereafter for a total of 5 minutues. Subjects rinsed twice with spring water betweeneach sample. The inter-stimulus interval was at least 1 minute.

Analyses

Proportional changes in sweetness were computed by dividing the area of the mixtureby the averaged area of the comparison self-mixture, subtracting one and calculatingthe percentage change. Responses to water, collected for two of the sweetener pairs,were not zero and have been subtracted from the predicted response to the mixtures,so that the water response would not be counted twice in predicting, an adjustmentused by Frank et al. (1989). Synergies reported (Figure 10) reflect this adjustment.

Results

General

Data from each attribute were submitted to a repeated measures analyses for eachsweetener pair and corresponding mixtures with sweetener, time, replicate andconcentration as factors. All listed effects are significant at P < 0.05 unless statedotherwise. The general pattern of results showed a decrement of sensation over time(P < 0.001). As expected, differences in concentration were also seen. Main effectsof sweetener type and concentration (level) were observed for all the sweetener pairs.Bitterness also differed among sweetener types and concentrations except for acesulfame-K/saccharin comparisons which did not show an effect of sweetener type, but only con-centration effects. Figure 1 shows the overall pattern of additivity for initial sweetnessratings for all pairs. Discussion of each of the sweetener pairs follows.

Sucrose/aspartame

No significant differences in sweetness were seen between sucrose and aspartamesuggesting successful matching for isosweetness. As Figure 2 depicts the mixture fellbetween sweetness intensity of aspartame and sucrose and at lower concentrations was

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coincident with the profile for sucrose. Figure 3 shows the ratings for bitterness ofthe mixtures relative to sucrose and aspartame solutions. The differences in bitternessprofiles may be attributed to molecular differences between sucrose and aspartame.

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Synergy In sweeteners

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Fig. 3. Means of perceived bitterness rated over time of APM, sucrose and APM/sucrose mixtures.

Aspartame/acesulfame-K

As seen in the plot of initial sweetness, Figure 1, the mixtures received consistentlyhigher scores compared to doubled concentrations of single sweeteners. In addition,all three concentrations of mixtures received ratings at the high end of the scale anddid not show the more typical ratings that began around 5 and rose to a scale valuearound 10. This pattern of superadditivity held across time (Figure 4) and this wasthe only pair of sweeteners that exhibited synergy as evaluated in the percent changein the area under the time-intensity curve (Table II). Bitter ratings of the mixtures wereequivalent to or lower than bitterness ratings of the single sweeteners (Figure 5).

Saccharin/aspartame

The mixtures showed a dose related effect of subadditivity and additivity (Figure 1).The presence of saccharin dominated the behaviour of the mixtures—the mixture elicitedsweetness responses more like the saccharin solutions than the aspartame (Figure 6).Paradoxically, bitterness ratings resembled the bitterness of the aspartame solutionsbut this did not potentiate the perceived sweetness intensity (Figure 7). Althoughbitterness was not pronounced sweetness was not potentiated.

Accsulfame-KIsaccharin

The mixtures did not show synergy but received ratings less than the single sweeteners(subadditivity, Figure 8). Bitterness ratings were comparable with other sweetener pairsevaluated, typically receiving ratings in the low end of the scale (Figure 9).

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Table II. Comparisons of sweetness additivity

This study Frank et al.

Initial Sweetness Areas

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Linear and exponential functions were fit to the decay curves. Exponential fits gavehigher /f2 ranging from 0.985 to 0.884. Calculating proportional increases in sweetnessby companng areas under the curve would be important in comparing these data tosynergies reported in the literature. Areas under the time-intensity curves were comparedby two different methods, as follows:(1) A planimeter (Keuffel—Esser) was used to compute both the actual areas as well

as the areas under the best-fit curve. Despite the good exponential fits obtained(R? 0.985-0.884) areas under these fitted curves differed from those obtained bycomputing areas under the connected time points. No systematic effect was apparent

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in terms of overestimating or underestimating the areas. This points out a pitfallof using fitted data, i.e. derived values that are steps removed from raw data.

(2) Areas were compared by cutting out the area under the curve and comparing theproportional change in weights. This method was the most reliable and all subsequentanalyses was done by this method. Table II reports the percent change in areasfor sweetness and bitterness for the four sweetener pairs.

Discussion

The phenomenon of mixture interactions is complex and no single effect pervades allthe pairs of sweeteners tested. Figure 1 shows the initial sweetness of the sweeteners.Other studies that have evaluated synergies have done so using single point estimatesof intensity. The most recent evaluation of binary mixtures (Frank et al., 1989) includedboth carbohydrate and high intensity sweeteners. The authors proposed that synergycould be evaluated by comparing observed sweeteness to predictions of mixturesweetness, based on a simple additive model, to minimise artifacts of measurement.This work was designed to extend this proposed method of assessing synergy to thetime domain. Thus, our study evaluated intensity over time but also abstracted time-zero ratings of intensity to make comparisons between observed and predicted responsesto mixtures, as in the previous work. Time intensity data might better aid food scientistsin their selection of sweeteners as time-intensity profiles are quantitatively richer andmay better approximate conditions of consumption.

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Fig. 6. Means of perceived sweetness rated over time of APM, saccharin and APM/saccharin.

Initial sweetness

Assuming for the sake of argument that time-zero evaluation, defined as the time pointat which the first evaluation is made, are equivalent to single-point estimates of intensity,we see that there are differences in the responses to sweetness among the sweetenerpairs, as well as the levels within a sweetener pair. Saccharin/aspartame shows hyper-additivity at the lowest concentration, additivity at the middle concentration andsubadditivity at the highest concentration. This dose response relationship is reversedin the case of acesulfame-K and saccharin which shows subadditivity at the lowestconcentration and hyperadditivity at the highest concentration. Structural similaritiesbetween saccharin and acesulfame-K would suggest a correspondence when mixed withaspartame (the most sucrose-like sweetener). However, initial sweetness (time-zeroestimates) showed hyperadditivity at all the concentrations of the aspartame/acesulfame-Kmixtures, but hyperadditivity only at the lowest concentration of aspartame/saccharinmixtures. Sucrose/aspartame mixtures showed a modest, consistent additivity response(Figure 1). There is no systematic relationship suggesting any effect of bitternesssuppressing the sweetness response, since there are no significant changes in the areasfor bitterness in any of the sweetener pairs. Furthermore, the saccharin/acesulfame-Kmixture did not potentiate bitterness.

Frank et al. (1989) evaluated the mixtures by single point measures of intensity andcompared mixture dose-response functions to 'self-mixture' dose-response functions.

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Using this type of comparison, observed versus predicted data from our study are plottedin Figure 10. Predicted data are the sum of the mean intensity score at time-zero ofthe component sweeteners of the preceding concentration in the case of the mixtures(A| + B[ = Mix2; see Table I). Comparison plots of the sweetener series were alsomade, i.e. B2 predicted is the sum of B, + B,. We see that the position of the mixturesrelative to the single components (Figure 10) parallels the results as computed for initialsweetness (Figure 1). For example, in the case of sucrose/aspartame the mixes fallbetween the plots for sucrose and aspartame series. Similarly, in the case ofaspartame/acesulfame-K comparisons, the mixtures remain elevated relative to the plotsof aspartame or acesulfame-K. Differences in the degree of synergy of saccharin/aspartame mixtures compared to the results of Frank's study may be attributed todifferences in concentrations in the two studies. Frank et aL use saccharin concentrationsof 0.007,0.036 and 0.089%, while this study used concentrations of 0.03, 0.06 and0.12%. The concentrations used in this study are high enough, relative to Frank's study,that we did not see synergy at the intermediate and higher concentrations, but onlyat the lowest concentration tested. This is further supported by the domination ofsaccharin in the response to sweetness in the mixtures (Figure 6). In the case ofaspartame/acesulfame-K, concentrations of acesulfame-K are more comparable in thetwo studies and the reports of synergy in aspartame/acelsulfame-K (Figure 10,D)mixtures are in agreement with the findings of Frank et al..

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Fig. 8. Means of perceived sweetness rated over time of acesulfam-K, saccharin and acesulfain-K/saccharinmixtures.

The frequent observation of hypoadditivity by Frank et al. especially at highconcentrations is seen in the current results. This is, in part, because predictions ofsweetness responses result in values greater than 15 (the upper scale value of the categoryscale used in this study) and are plotted on a 30-point scale while observed values arebased on a 15-point scale. That is, the addition of responses to components to predictthe responses to mixtures produces values beyond the ceiling of the bounded responsescale, necessitating some hypoadditivity.

Frank et al. (1989) reported 11% synergy for sucrose/aspartame mixtures atcomparable concentations to those tested in this study. This study did not see apotentiation of sweetness of sucrose/aspartame mixtures. Cross-adaptation date in theliterature (Lawless and Stevens, 1983) showed mutual, if partial cross-adaptation ofsucrose and aspartame. This is appropriate as aspartame is perceived to be the mostsucrose-like of the high intensity sweeteners and these two sweeteners may share receptorsite mechanisms. However, partial cross-adaptation might suggest that low levels ofsynergy have been expected (but were not observed in this study).

Area under the time-intensity curve

Comparisons of the change in areas under the time-intensity curves show that only inthe case of aspartame/acesulfame-K do the patterns of initial sweetness additivity persist

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across time, at all concentrations. In other words the sweeteners appear to fulfil theexpectations of synergy as evidenced in time-zero estimates of sweetness. In the caseof the three other sweetener pairs the initial synergistic effects of sweetness becomeaveraged or integrated to form a unitary sweetness. This study provides an alternativeprocedure to the approach of Frank et al. by using stimulus substitution as a way ofevaluating synergy.

There are some differences in the nature of the decay curves that need to be betterdescribed. For example, in the case of aspartame/acesulfame-K that there is a steepinitial decline followed by a persistence of sweetness. Such details of the time-intensityprofile may have practical implications. For example, persistent sweetness may besuitable for products such as chewing gum, but not desirable in a product such as wine-cooler where the persistence of sweetness may interfere with the enjoyment of otherfoods. The question remains as to how we can best describe time intensity curves andquantify operating characteristics that provide a shorthand insight into the details oftemporal profiles.

Certain other important methodological issues are raised by the study. Do time-zeroestimates of intensity equal single-point measures of intensity? Does a time intensityprocedure better approximate actual conditions of consumption and is it, therefore, amore appropriate measure of additive interactions? Other questions have to do withthe nature of the subject's task. In the evaluation of many different attributes do subjectsapply an informal system where they weight their ratings on one or another attribute(perhaps based on the order of appearance) to compensate for earlier ratings that mayhave been more hurried? How will ratings change if ratings are made on one attributeat a time, in separate trials? Finally, how will the patterns of mixture additivity changewhen multiple sips are allowed, as occurs in real ingestion of foods?

References

Anderson, N.H. (1962) Applications of an additive model to impression information. Science, 138,817-818.Anderson.N.H. (1970) Functional measurement and psychophysical judgement. Psychol. Rev.,T7, 153-170.Anderson.N.H. (1977) Note on functional measurement and data analysis. Percept. Psychophys., 21, 202-215.Bartoshuk.L.M. (1975) Taste mixtures: is mixture suppression related to compression? Physiol. Behav.,

14, 643-649.Bartoshuk.L.M. and Cleveland.C.T. (1977) Mixtures of substances with similar tastes: a test of a new model

of taste mixture interactions. Sen. Proc. 1, 177-186.Beidler.L.M. (1962) Taste receptor stimulation. Prog. Biophys., 12, 109-151.Birch.G.G. and Munton.S.L. (1981) Use of the 'SMURF' in taste analysis. Chem. Senses, 6, 45-49.Deutsch.E.W. and Hansch.C. (1966) Dependence of relative sweetness on hydrophobic bonding. Nature,

5044, 75.Faurion.A., Saito.S. and MacLeod,P. (1980) Sweet taste involves several distinct receptor mechanisms.

Chem. Senses, 5, 107-121.Faurion.A. (1987) Physiology of the Sweet Taste. Progress in Sensory Physiology. Springer Verlag, Berlin.Frank.R.A., Mize.SJ. andCarter.R. (1989) An assessment of binary mixture interactions for nine sweeteners.

Chem. Senses, 14, 621-632.FrijtersJ.E.R. and de Graaf.C. (1987) The equiratio mixture model successfully predicts the sensory response

to the sweetness intensity of complex mixtures of sugars and sugar alcohols. Perception, 16, 615—628.FrijtersJ.E.R. andOudeOuphius.P.A.M. (1983) The construction and prediction of psychophysical power

functions for the sweetness of equiratio sugar mixtures. Perception, 12, 753;767.Goidin,H.H. (1987) Intensity variation descriptive methodology: development and application of a new sensory

evaluation technique. J. Sensory Stud., 2, 187 — 198.

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Hiji,Y. and Ito.J. (1977) Removal of sweetness by proteases and its recovery mechanism in rat taste cellsComp. Biochem. Physiol., 58, 109-113.

Hiji,Y. (1975) Selective elimination of taste responses to sugars by proteolytic enzymes. Nature, 256,427-429.Larson-Powers.N. and Pangbom.R.M. (1978) Paired comparisons and time-intensity measurements of the

sensory properties of beverages and gelatins containing sucrose or synthetic sweeteners. J. Food Sci.,43, 41-48 .

Lawless,H.T. and Malone.G.J. (1986) A comparison of rating scales: sensitivity, replicates, and relativemeasurements. J. Sensory Stud., 1, 155-174.

Lawless,H.T. and Skinner.E.Z. (1979) The duration of perceived intensity and sucrose taste. Percep.Psychophys., 25, 180.

Lawless,H.T. and Stevens,D. A. (1983) Cross adaptation of sucrose and intensive sweeteners. Chem. Senses,7, 309-315.

Lawless.H.T. and Stevens, D. A. (1986) Mixtures of oral chemical irritants. In Perception of Complex Smellsand Tastes. Academic Press, Australia, pp. 297-309.

McBride.R.L. (1988) Taste reception of binary sugar mixtures: Psychophysical comparison of two models.Percept. Psychophys., 44, 167-171.

McBurney.D.H. (1972) Gustatory cross adaptation between sweet tasting compounds. Percept. Psychophys.,11, 225-227.

Solms.J. (1969) The taste of amino acids. Peptides and Proteins, 17, 686-688.O'Brien,L. and Gclardi.R.C. (1981) Alternative sweeteners. Chemtech., 11, 274-278.Ott.D.B., Edwards.C.L. and Palmer.S.J. (1991) Perceived taste intensity and duration of nutritive and non-

nutritive sweeteners in water using time-intensity (T-I) evaluations. J. Food Sci., 56, 535-542.Schiffman.S.S., Reilly.D.A. and Clark.T.B. (1979) Qualitative differences among sweeteners. Physiol. Behav.,

23, 119.Schiffman.S.S., Crofton.V.A. and Beeker.T.G. (1985) Sensory evaluation of soft drinks with various

sweeteners. Physiol. Behav., 34, 369-377.Schiffman.S.S., Cahn.H. and Lindley.M.G. (1981) Multiple receptor sites and mediate sweetness: evidence

from cross adaptation. Pharm. Biochem, Behav , 15, 377-388.Shallenberger.R.S. and Acree.T.E. (1967) Molecular theory of sweet taste. Nature, 216, 480-482.Shallenberger.R.S. and Birch,G.G. (1975) Sugar Chemistry. AVI Publishing, Westport.Stone,H. and Sidel J. (1986) Descriptive Analysis. Sensory Evaluation Practices. Academic Press, San Diego

Received April 29, 1991; accepted February 5, 1992

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