Sweetness and Sweeteners

Chapter 26

Evaluation of High-Intensity Sweetener Modulators Cheryl R. Mitchell, Richard Ray, and Marian Schwartz

Downloaded by IOWA STATE UNIV on April 19, 2017 | http://pubs.acs.org Publication Date: March 4, 2008 | doi: 10.1021/bk-2008-0979.ch026

Creative Research Management, 2029 East Harding Way, Stockton, CA 95205

Different compounds have been sought to function as modulators that stimulate sweetness perception, diminish lingering sweetness, or diminish off tastes that characterize most of the popular synthetic sweeteners. Sensory evaluation and determination of effectiveness of modulators is very difficult due to the cross-over or residual effects that characterize high intensity sweeteners. Using a three-way light switch as the model for the sweetness receptor circuit and sweetness perception, blocking and modulation, a protocol for testing the modulating effect of different compounds was developed. This sensory evaluation protocol enabled panelists to better evaluate and distinguish between and among different flavored beverage systems containing high intensity sweeteners that are not readily "cleared" and normally inhibit a panelist's ability to characterize and distinguish specific samples. The study provides an evaluation and summary of the effectiveness of Sucramask® (a natural flavoring) and acelsulfame-K as modulators for sucralose in beverage systems of neutral and high pH.

410

© 2008 American Chemical Society

Weerasinghe and DuBois; Sweetness and Sweeteners ACS Symposium Series; American Chemical Society: Washington, DC, 2008.


411 The symposium has provided research in the area of structure and modeling of taste receptors, taste transduction, and quantifying the sweetener response. In the area of current product formulation, manufacturing and packaging, the application of sweetener modulation is of primary concern in the current efforts to utilize existing high intensity sweeteners. Current manufacturers do not have the luxury of waiting for the proposed new and improved sweeteners. Food formulators must work with what they have and become aware of what modulators will improve the already existing high intensity sweeteners. The food industry works with complex systems of foods and beverages having a multitude of taste responses of which sweetness or perceived sweetness is a key element. Perceived texture, flavor and sweetness will dictate the success or failure of a product. However, of these three, the intensity and quality of the sweetness, is the most significant. As a sweetener, sucrose is the gold standard. Sucrose does not have any off tastes and is perceived as an example of "natural" sweetness. It is the primary or first ingredient in many foods and most beverages, providing both sweetness and texture or body. Significantly, sucrose works in harmony with many flavors and food systems including those of varying p H . Sucrose works in concert, like a classical string quartet, and does not stand out. It is a team player and provides homogenous and integrated sweetness along with texture and flavor. Food compositions should produce a taste sensation that is balanced, rather than being segregated or producing "spikes". Sucrose works well to accomplish this task. However, since it is desirable to produce low calorie foods and beverages, sucrose must be replaced with a low calorie high intensity sweetener. Unfortunately, high intensity sweeteners for the most part do not integrate well with either the flavor or texture of the food product system. While work is being done to improve the quality of these high intensity sweeteners, because of the approval process, one can anticipate that the approval for use will not be in the immediate friture. Since food formulators are producing products right now with the currently available high intensity sweeteners, the food formulator has no choice but to select and find appropriate modulators that will make the high intensity sweetener perform in the food system similar to the way sucrose would perform. To select appropriate modulators, it is important to understand the organoleptic issues associated with high intensity sweeteners. High intensity sweeteners differ from sucrose in the quality and intensity of sweetness as well as the texture. Aftertastes such as bitter, cardboard, lingering sweetness, chemical, as well as textural sensations of coolness, powderiness, or a watery sensation may be associated with these non-sucrose sweeteners in food or beverage systems. Additionally, the sweet taste itself many times does not integrate well with the flavors at different p H of the system. Consequently, instead of getting an integrated sweet/sour for example, one is hit with flashes of spiking "sweet/sour/sweet/sour, etc." Sucrose on the other hand, is homogenous,



412 working together with other flavor and p H elements of a food system. The incongruous sweetness and flavor profiles produced by food systems containing high intensity sweeteners is a little like trying to get a rock and roll group to integrate homogenously with the classical string quartet. There are a lot of issues to resolve. However, it is the responsibility of the food scientist, to make the system work. Since at this point in time, there are limitations to the choice of high intensity sweeteners, and any food ingredients added as modulators must be an approved food additive or G R A S (generally recognized as safe), the challenge is to use food approved substances to modulate the currently accepted high intensity sweetener. The most popular and acceptable high intensity sweetener as of the writing of this paper is sucralose. Sucralose is a high intensity sweetener that performs very well at neutral p H and in systems that undergo high heat processing such as beverage systems. Aspartame, is not as stable when subjected to the high temperatures and time necessary for product pasteurization or for aseptic commercial sterilization, Sucralose, while very heat stable, does not behave well in systems with low pH. In these systems, the sweetness and flavor profiles become erratic and it becomes very difficult to balance pH, sweetness level, and flavor. Consequently, it is necessary to perform numerous taste panels to determine the differences and perceived improvements of the formulations. However, these evaluations are flawed because of the lingering sweetness of sucralose which goes from one sample to another blinding the panelists taste from any perceived improvement in the formulation that may result from a modulator and the impact the modulator may have especially in its ability to diminish the lingering sweetness inherent to sucralose. Panelists trained in sweeteners, flavors, and sourness, describe the incongruities of sucralose in beverage systems as: (a) Flavors: Intensity varies with p H (spiking); (b) Homogeneity: Lingering sweetness; and (c) Mouthfeel: Watery

Modulators The food formulators' objective is to find the right modulators) that would impact the undesirable attributes of sucralose as well as a methodology that could correctly indicate the impact of the modulator when being evaluated from sample to sample. Specifically, in the case of sucralose, the food formulator is looking for modulators) that can impact the stabilization of the food/beverage system containing sucralose with regard to the incongruities of lingering sweetness, watery mouth feel, and the spiking or non integration of the acidity, sweetness and flavor. To determine evaluation methodology, one might first want to deliberate on the causes of the incongruities of sucralose. The incongruities of spiking and



413 lingering may be associated with binding times of the sucralose to the receptor site. The incongruity of watery mouthfeel results from the differences in solids when using ppm of high intensity sweeteners versus grams of sucrose to achieve the same sweetness intensity. Regarding the latter, a thickening agent such as gums, would increase the viscosity and improve the mouthfeel. Unfortunately, it also reduces flavor impact. A gum that does not have viscosity but produces mouthfeel is the most desirable, and there are now modified pectins, that perform this action without increasing viscosity or reducing flavor impact With regard to the binding and "release" of the sucralose, two modulators are actively considered with regard to the modulation in current food systems; Acelsulfame Κ (ASK) and Sucramask® (SM)(1). Both modulators appear to have an impact on sucralose, but it is difficult to understand exactly how and where they have their modulation effect as well as evaluating their effects using taste panels. First, a proposed binding/activation model will be provided to assist in an understanding of how these modulators may be impacting the sweetener receptor site, and then sensory evaluation methodologies and results using A S K and S M will be reviewed. Binding/Activation Model Sometimes it is much easier for the food formulator to work with easy conceptual models that are very familiar and help one to understand how systems are behaving and why they are having so much difficulty. In our laboratories, we have found the 3-way switch model to be very helpful and appropriate in understanding the binding of sucralose so that we could later target and look for modulators that target or impact that binding. To that end, Figure 1 represents the electrical schematic of a three-way switch and a possible representation of the sweetness receptors and their binding and impact on the sweetness signal. Many people have three way switches in their homes and offices. They are designed such the light in a room for example, can be activated by either one of two different switches such that a person can enter or leave through two different doors and still turn on or off the same light. We believe that the binding of sucrose and sucralose as well as other molecules that impact the sweetness response can be simply considered in terms of this three-way mechanism. There are believed to be two different active receptor sites that control sweetness. The T1R2 and the T1R3. (2) Our model assumes that these represent the two switches in the room. The receptor site can be either filled or empty. When it is empty or filled, it is like flipping one of the switches. There is also a consideration as to the intensity with which these molecules bind or fill the switch. In Figure 1, neither receptor site is filled and the light is off (no sweetness). In Figure 2 and Figure 3, when one or the other receptor site is filled, the light is activated (sweetness), in Figure 4, both receptor sites are filled, and the light is



414 off (no sweetness). The molecules that bind in the first receptor site may be considered to be sucrose, or analogous to sucrose such as sucralose. Interestingly, molecules like lactisole would have to then be able to bind to both sites, and apparently adhere to one site very tightly. Consequently, when lactisole is present alone or in combination with sucrose, (both receptor sites are filled), there is no apparent sweetness. (3) However, when the lactisole in the beverage is gone, sweetness is observed in water or liquids that do not contain other sugars or lactisole. The remaining binding lactisole keeps one switch filled and activates the sweetness response. In the case of sucralose, it apparently binds more tightly to the same receptor as sucrose (hence the lingering sweetness). Consequently, it is a matter of simply making sure one can remove the sucralose from the site. Modulators such as A S K and S M impact the binding of the sucrose site by either binding themselves or removing the sucrose or sucralose molecule from that site. They do not interfere with the second site

Figure 1. Three way switch model. Both receptor sites empty (no sweetness is perceived).

Sucrose (Sweetener) only

iTxwa 1Ο

IT I R S I ·

Figure 2. Three way switch model. Sucrose only filling one receptor site (perceived sweetness).


415


Residual Lactisole

Figure 3. Three way switch model. Sucrose and lactisole filling both receptor sites (no sweetness is perceived).

Figure 4. Three way switch model. Residual lactisole remaining in receptor site (perceived sweetness).

as the sweetness is not eliminated as is the case of lactisole. When developing test protocols to evaluate the impact of modulators on the sucralose system, keeping the above model in mind is helpful in understanding some of the test results.

Sensory Evaluations Sensory evaluations were conducted with trained panelists from the National Food Laboratories.(4) These panelists have been extensively trained in the use of standardized vocabulary to describe the appearance, aroma, flavor and texture of a variety of products and are used on a regular basis to support contract research.


416


Lactisole Rinse Evaluation The impact of both A S K and S M was evaluated in the lactisole system. That is the impact, of these modulators in a lactisole solution, that was perceived following a water rinse. For the lactisole rinse descriptive test, panelists rinsed with a 30 ml portion of a rinse, and then rated a sample of water which was coded with a three-digit random number. The panelists were unaware that the liquid they were rating was water. Four sets of rinses with water samples to rate (water rinse, lactisole rinse, lactisole/ASK and lactisole/SM rinse) were evaluated during each session. Two sessions were conducted with a 1-hour break between sessions. Two evaluations (replicates) were obtained from each panelist for each product; therefore, a total of 18 judgments were obtained for each product. Panelists placed a slash mark on 15-cm line scales to indicate the intensity of the sensory characteristics. Unsalted soda crackers were provided for cleansing the palate between samples. For data analysis, the slash marks on the line scales were converted to numbers ranging from 0 to 15 using a digitizer. The mean intensities were calculated for each sensory characteristic. Analysis of Variance and Duncan's Multiple Range Test, where appropriate, were used to determine significant differences among the samples for each attribute. When panelists-by-product interactions were significant, the mean square of the interaction term, instead of the mean square of the error term, was used in calculation of the product F values. Results of this test are presented in Table I. Essentially, while there was significant difference between lactisole solution followed by water rinse versus a water followed by water rinse as anticipated, there was only a trending difference between lactisole solutions containing A S K or S M . The lactisole solutions containing the S M , followed by a water rinse, indicated a higher level of sweetness and sugar character. The latter would be expected i f S M was dislodging the lactisole from the first site a bit more rapidly. A S K , produced a trending difference in the sugar character indicating that it was potentially in a competitive binding with the lactisole in the first site. More studies need to be performed to support these trending differences.

Triangle Test The impact or binding of the sweetness receptor sites would also be a problem when one considers triangle tests which are very commonly used to determine the impact of modulators on high intensity sweetener systems. A s indicated above, i f the modulator clears the site or binds the site preferentially, the rate of release or binding is going to impact the system. The panelists were given three coded samples (two of die same product and one of the other product) and asked to indicate which sample was different from the other two.


417 Table I. Lactisole- Sweetener Rinses on Flavor Impact

Lactisole Rinses Quantitative Descriptive QUANTITATIVE DESCRIPTIVE EVALUATIONS OF RINSES (n»18,9 Panelists, 2 Evaluations Each)


Water after Water/ Rinse FLAVOR: Total Flavor Sweet Sugar Character Chemical/Artificial Bitter Soft Water Cardboard Plastic TEXTURE: Astringent

2.62» 0.94" 0.13» 1.76 1.28 0.93 0.66 0.37 2.13»

Water After Water/ Lactisole Rinse

Water After Water After Water/ Water/ Lactisole/ Lactisole/ AceK SucraMask™ Rinse Rinse

3.20» 2.26· 0.74· 2.04 1.07 1.21 0.89 0.40

3.27· 2.26· 0.69· 2.07 1.16 1.07 0.64 0.67

3.60· 2.69· 0.74· 2.06 1.16 1.17 0.68 0.68

2.69·

2.80»

2.67·

Conf. Level 96% 96% 96% N8D NSD NSD NSD NSD 96%

NSD: Net significantly different at confidence lavais of 8 0 % or higher

The triangle test was conducted using a balanced reference (i.e. half of the time the two samples were the control product and half of the time the two samples were the test product). Each panelist repeated the test three times (i.e. replications) for a total of 30 evaluations within each set of samples. Serving order was balanced (i.e. each sample was seen approximately an equal number of times in each position). A ten minute break was given between trials. Ambient drinking water and unsalted soda crackers were provided for cleansing the palate between samples. The numbers of correct responses were tallied. A binomial test was used to determine i f a significant difference was found between the samples in each set. Table II provides tallies of correct responses for the sucralose vs. sucraloseASK and sucralose vs. sucralose/SM triangle tests. In the sucralose vs. sucralose / A S K test, the panelists chose the correct sample 15 out of 30 times (p=0.043). The descriptive panel was able to perceive a difference between the two samples at the 95% confidence level. In the sucralose vs. sucralose/SM test, the panelists chose the correct sample 10 out of 30 times (p=0.568). The descriptive panel was not able to perceive a difference between the two samples at the 90% confidence level However, in the triangle containing 2 sucralose vs. 1 sucralose/SM sets, the panelists chose the correct sample 5 out of 10 times (p=0.213). In the triangle tests utilizing 1 sucralose vs. 2 sucralose/SM sets, the panelists chose the correct sample 1 out of 10 times (p=0.983). Basically, the latter would indicate that there was a significant difference in the ability for panelists to distinguish during a triangle test with


418 sucralose and a modulator, as long as the modulator samples or the predominant samples If the sucralose samples without modulator are the predominant samples, the lingering is so significant that they cannot distinguish the samples from each other.


Table II. Triangle Taste Evaluation Results Sucralose vs. Sucralose with Modifier

Triangle Test - Number of Correct Responses Panelist 1 2 3 4 6 6 7 8 9 10 Total Correct Ρ

Sucralose vs. Sucralose/ AceK i3/oanaflst) 3 2 1 1

Sucralose vs. Sucralose SucraMask 13/Banellstl

2 0 0 0

2 Sucralose vs. 1 Sucralose/ SucraMask™ (1 viewing only) H/oaneDst) 1 0 0 0 st

1 Sucralose vs. 2 Sucralose/ SucraMask™ (1* viewing only) H/oanaOstl 0

0 0 0

0

1

1

1 1 2 3 1

2 0 1

1 0 0

1

1

0

3 10 O f 30 0.568

1 6 o f 10 0.213

1 1Of10 0.983

16 o f 30 0.043

β 0 0 0

Summary Sucralose is a popular high intensity sweetener that is being used by food and beverage formulators. Certain incongruities resulting from the use of this sweetener such as wateriness, p H impact and lingering sweetness require that the food formulator use modulators to reduce or eliminate these incongruities. As such certain modulators such as gums, acelsulfame-K (ASK) and Sucramask® (SM) are used to modulate the texture and flavor of the food beverage system. The understanding of the binding of sucralose can be easily understood by relating to a 3 way switch model. The function of a modulator that impacts the binding of sucralose can be understood using this model. The potential of S M to remove lactisole is indicated but requires further evaluation. S M is a modulator that displaces the sucralose but at a relatively slow rate such that the intensity of sweetness is perceived but not the lingering. A S K apparently modulates by sharing the sucralose binding site providing a different type o f sweetness


419 character. Care must be taken in selecting the order of triangle testing in that the modulator may be readily overcome by the sucralose only samples and hence the perceived difference with respect to lingering sweetness is very difficult to ascertain.

References SucraMask® is a product of Creative Research Management, 2029 E. Harding Way, Stockton, California 95205 www.crmcorp.net. 2. Munger, Steven D.; Vigas, Stephan; Nie, Yling; Hobbs, Jeanette R.; Conn, Graeme L. TIR2, TIR3 and the Detection of Sweet Stimuli, presented at the 231 ACS National Meeting, Atlanta, GA, March 26-30, 2006. 3. Schiffman, Susan S.; Booth, Barbara J.; Sattely-Milller, Elizabeth Α.; Graham, Brevick G.; Gibes, Kernon M. Selective Inhibition of Sweetness by the Sodium Salt of ±2-(4-Methoxyphenoxy)-propanoic acid. Chem. Senses 1999, 24, 439-447 4. The National Food Laboratories, 6363 Clark Avenue, Dublin, California 94568-3097.


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Sweetness and Sweeteners

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