Sweetness and Sweeteners - American Chemical Society

C h a p t e r 31

Challenges to Reducing Sugar in Foods D. Kilcast, C. den Ridder,

and C. Narain

Downloaded by CORNELL UNIV on September 4, 2016 | http://pubs.acs.org Publication Date: March 4, 2008 | doi: 10.1021/bk-2008-0979.ch031

Leatherhead Food International, Randalls Road, Leatherhead, Surrey KT22 7RY, United Kingdom

Sweetness is an important characteristic of food and drink products that at the appropriate levels receives universally positive consumer responses. In most products sweetness has traditionally been delivered by sucrose, but health and nutritional concerns have for many years obliged the food and drinks industry to find ways of reducing the sugar content of products. This has resulted in a wide range of sugar-free or reduced-sugar products on the market, but the pressure to take this process further is unrelenting. In taking this process further companies need to take a systematic approach to sugar reduction, and recognise that in addition to achieving the required sweetness level, they must also build in a range of other related characteristics. Model systems in aqueous solution can give valuable information, but do not necessarily predict responses in a typical product matrix. In addition, manufacturers should take steps to understand possible consumer segmentation patterns in their target market, and formulate modified products with this in mind. Finally, interactive effects in reducing sugar, fat and salt, either in pairs or together, should be investigated.

2008 American Chemical Society

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

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Introduction Human beings are born with the capacity to enjoy the sweetness o f foods, and this liking continues to be reinforced throughout life. This importance has provided the driving force to understand more fully the mechanism of the sweetness response, not only to sucrose, which remains the dominant sweetener of choice, but also to other sweet molecules. In addition to this positive force, however, there have emerged several important negative influences. Most important of these have been health concerns associated with high levels of sucrose consumption, and which currently focus on the issue o f obesity. These have resulted in efforts to find alternative sweeteners that will help achieve a reduction in energy consumption. One consequence has been the intensive efforts to find suitable intense sweeteners that are non-cariogenic and noncaloric, but concerns are frequently expressed that high intake of such sweeteners might also be accompanied by negative effects on health. There is, then, a need to deliver to consumers the required level and quality of perceived sweetness, but using lower quantities of sweeteners.

Problems in sucrose replacement Sucrose remains the standard sweetener in most sweet foods, which is generally regarded as a consequence of its clean sweet taste. That sucrose has a clean sweet taste is increasingly being questioned, and an alternative view that has been proposed is that sucrose has other non-sweet characteristics (such as a caramel note) that we have adapted to and recognise as the ideal profile. Sucrose also possesses other important functional properties, one of the most important of which is its bulking properties, and the ideal sucrose substitute would retain the characteristic sweet taste and functional properties, but would have none of the unhealthy connotations. However, introduction of new sucrose replacers can involve long and expensive approval procedures that are aimed primarily at ensuring consumer safety, but even sweeteners that have successfully overcome this hurdle show defects in terms of sensory characteristics when compared with sucrose. Substitution of sucrose in different food products is generally achieved via the addition of bulk sweeteners, intense sweeteners or a mixture of both. Bulk sweeteners, as the name suggests, exhibit similar bulking properties to sucrose. Their sweetness response characteristics can usually be modelled by a linear concentration-response function, but most are less sweet than sucrose, and polyols such as sorbitol and xylitol give an additional cooling effect that can limit applications. In contrast, intense sweeteners exhibit non-linear concentration-response behaviour. A n important practical consequence of this is that the equivalent concentrations of intense sweeteners to be used as sucrose



483 substitutes depend on the level of sweetness to be achieved. The range of permitted intense sweeteners is growing slowly, but the use of intense sweeteners alone cannot deliver the bulking properties of sucrose or other bulk sweeteners, and specifically in soft drinks sector, the required mouthfeel. As a consequence, there are increasing uses of combinations of bulk sweeteners and intense sweeteners: the bulk sweeteners provide the bulk but usually insufficient sweetness, with the intense sweetener providing the required sweetness. In recent years there has been increasing interest in the possible use o f combinations of sweeteners in order to maximise the potential of individual sweeteners, and often simultaneously minimising the unwanted characteristics, both sensory and physicochemical, of some sweeteners. This can be most commonly seen in the use of binary or ternary mixtures of intense sweeteners in soft drinks. A further advantage of using intense sweetener combinations lies in the potential exploitation of synergistic combinations of certain sweeteners. Such combinations exhibit sweetness levels that are greater than the sum of their components, and opens up the possibility of substantial cost savings to users. Extending the principle of combinations to bulk and intense sweeteners, however, carries the potential of realizing the high sweetening power of intense sweeteners with the mouthfeel delivery properties of the bulk sweeteners, in addition to potential quality improvements and cost-savings through synergy.

Designing sweetness quality The first step in any programme in substituting for sucrose is usually to interrogate the literature for information on the sensory and other functional characteristics of alternative sweeteners. In practice, most of the information found in the literature describes properties of sweeteners in aqueous solution. This is to be expected, both from a logical point of view - water is the most common component of food matrices - but also from a practical viewpoint, as soft drinks form one of the most common classes of sweetened products. The importance of soft drinks is emphasised even further i f the usage of intense sweeteners is considered; for example, it has estimated (1) that soft drinks represent 65% of the market for intense sweeteners. This can be seen in the reduced sugar food and drink market data for 2004 (Figure 1). One direct consequence of the dominance of the soft drink market is that the bulk of the published literature on sweeteners focuses on the sensory properties in aqueous solution and, with few exceptions (the major one being the confectionery market) pays less attention to the effect of the product matrix on the sweetener properties. Consequently, in addition to researching the basic sweetener characteristics, the product developer must also consider the effect of the product matrix. Small changes in the product matrix (equivalent to the



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Figure L Market for reduced-sugar food and drink products in the UK 2004 (LFI estimates)

external environment of the sweetener) can have a major influence on the characteristics of the sweetener. A n example of this is shown in Figure 2, which summarizes the effect of a single environmental change, that of p H , on synergistic effects in combinations of selected bulk and intense sweeteners (2). In the sucrose system, lowering the pH to 3.1 (typical of a soft drink) changes the suppressive combination of sucrose/aspartame found in neutral solution to synergistic, and the additive combination of sucrose/alitame to suppressive. Fewer changes are seen in the maltitol system, however. Most intense sweeteners ( and some bulk sweeteners) exhibit a range of nonsweet flavours that can reduce their appeal in certain product applications. For example, acesulfam-K and cyclamate show bitter and burnt flavours, whilst N H D C has a strong liquorice flavour. The detailed sensory characteristics can be identified and quantified using trained sensory profile panels. The sensory characteristics can be presented and visualised in a number of different ways, but one useful method by which the quality attributes of a number of samples can be compared and examined visually is through the use of various multivariate statistical methods, the most common being principal component analysis. Mapping of sensory profile data using principal component analysis can illustrate dramatically the sensory relationships between the sweeteners. In such



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Figure 2. Effect of pH on synergy in bulk and intense sweetener combinations.

a map, sweeteners that are closely positioned are perceived as more similar than those positioned far apart. The superimposed attribute plot shows the basis on which the sweeteners differ. A n additional problem is that the sweeteners can also show temporal responses in the mouth that are different from that of sucrose. The importance of such responses lies in the fact that chemical stimuli are not released from the food matrix, and nor are they perceived instantly once they arrive at the sweetness receptors (Figure 3). If the time-intensity profile curves of two perceptible chemical stimuli behave as shown in the figure, then an imbalance may occur. This could be an imbalance between different sweeteners, between a sweetener and another tastant (e.g. an acidulant), or between a sweetener and a volatile. In the case of sweeteners such as thaumatin and N H D C , this is manifested in an extremely long persistence time, which can limit their applications in food. However, these same properties can be of value in other applications, for example in masking bitterness and other flavours in pharmaceutical preparations and nutritional supplements. Other sweeteners might show responses different from that of sucrose, and which can give a poor harmonisation with the responses from other tastants and flavours.


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balance

imbalance

Time

•

Figure 3. Schematic tine-intensity curves showing balanced and imbalanced flavour release

Quality benefits of synergistic mixtures Synergy between bulk and intense sweeteners is less well-documented than that between intense sweeteners, but in principle can combine the desired bulk properties with the desired high sweetness levels in a cost-effective way. The summarized data in Figure 2 shows that synergistic combinations of bulk and intense sweeteners can be identified in aqueous solution. Such combinations can benefit in a number of ways. The most obvious benefit lies in cost reductions, and this has been realised for many years in the use of synergistic combinations of two or more intense sweeteners. This practice has also highlighted another major benefit, that of improved sensory quality of the combinations in comparison with the individual components. Such quality benefits can also be seen in combinations of bulk and intense sweeteners, and this effect is shown in Figure 4. This shows how the high levels of bitterness and liquorice flavour associated with cyclamate in solution can be reduced by using equisweet mixtures with either sucrose or with maltitol. The same combinations have also been shown to give improved temporal characteristics.



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Figure 4. Effect of bulk and intense sweetener combinations on improving sweetness quality characteristics

Sweeteners and mouthfeel In soft drinks and other beverages, bulk sugars contribute to a mouthfeel characteristic that has been ascribed to both the viscosity contribution and also to the density of the sweetener solution. The most likely contribution to the mouthfeel is thought to lie through the viscosity contribution, and in some markets considerable efforts are made to compensate for this effect when sucrose is replaced by intense sweeteners. This effect is illustrated in Figure 5, which shows how the sensory characteristics of a sucrose solution change when the sucrose is substituted by an aspartame/acesulfam-K combination, giving a less smooth and thinner mouthfeel, and how the characteristics can be retrieved, at least partially, when hydrocolloids are incorporated that mimic the mouthfeel properties of the sucrose. The hydrocolloid type and concentration needs to be chosen carefully in order to avoid unwanted mouthfeel characteristics, however.

Consumer segmentation Any product developer team formulating products for a diverse market must take into account probable segmentation in consumer requirements. Whilst this is commonly recognised on an international basis, such segmentation is common even on a more local scale in most markets. Optimising formulations must accept



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Figure 5. Principal component plot showing changes in the sensory characteristics of sucrose solutions on substitution by intense sweeteners, and partial compensation by hydrocolloid additions.

the possibility of segmentation, and even i f development of different formulations for these segments is not commercially feasible, then this segmentation must be understood if the major market is to be satisfied. Statistical tools are available for identifying such segmentation, and are often used in combination with experimental design techniques. As an example of such techniques, a recent study carried out at Leatherhead Food International investigated the optimisation of a fruit juice formulation using colour, sweetness, pulpiness and thickness as formulation variables. Each of these variables was manipulated at 3 levels (coded Low, Medium, High) using a d-optimal design that reduced the 81 sample treatments that would have been generated by a full 3 factorial design down to 16 sample treatments. The samples were evaluated by consumer testing and also sensory profiling by a trained panel, and the results analysed by a number of techniques such as cluster analysis, internal preference mapping, partial least squares regression and response surface modelling, the cluster analysis revealed 3 distinct clusters based on consumer liking, as shown in Table I. Whilst 76% of the respondents wanted high levels of sweetness, 2 4 % preferred low levels. Whether this size of the market is significant involves commercial judgements, any product developer would have to accept that formulating to satisfy the majority of the market is likely to alienate a significant 4


489 Table I. Cluster Analysis of Consumer Preference Data

Number of respondents


Sweetness Colour Pulpiness Thickness

94 58% High Low Medium Low

Cluster group 2 29 18% High High (Low) (Low)

3 40 24% Low Low Low Low

minority. This situation is likely to become more complex i f sweetness quality differences are introduced in sucrose substitution programmes*

Sugar reduction and reduction in other components In addition to pressures on manufacturers to reduce sugar, there are corresponding pressures to reduce both salt and fat as measures to improve healthy eating in the more affluent societies. Each of these other types of reduction carries issues that are not dissimilar to those associated with sugar reduction. Like sugar, fat has both structural and sensory functions that must be simulated. Salt has fewer structural functions, but has both sensory and microbiological functions. Many foods contain at least two of these components, and some all three, and there is little systematic information available on how reduction of two or three components simultaneously can be achieved without destroying the basic structure of the product or its desired sensory characteristics. As an example of possible interactions, it has been known for some time that additions of sodium chloride to sucrose solutions increase the intensity of sweetness (3). Investigations into the interaction of different salts with a range of bulk sweeteners shows a much more complex pattern however. As shown in Figure 6, sweetness enhancement of other bulk sweeteners is greater than with sucrose, and the pattern is highly unpredictable when potassium chloride and magnesium chloride (both potential sodium chloride replacera) are used (4).

Conclusions There is a continuing drive to extend the range of sweeteners available to food and drink manufacturers, but attaining the unique physical and sensory



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Figure 6. The effect of 2% sodium chloride addition on the sweetness of bulk sweeteners at increasing concentrations. (Reproduced with permission from reference 4. Copyright 2000 Elsevier.)



491 properties delivered by sucrose remains elusive. Consumer demands for quality are increasing in parallel with pressure to reduce sugar consumption. A small number of new sweeteners, such as sucralose, alitame and neotame are now being approved in various countries, but the costs of developing new intensive sweeteners is likely to limit any extensive future activities. The industry needs to examine more closely the potential benefits in using combinations of existing sweeteners, and the research being carried out at various centres has demonstrated the possibilities. Additionally, we need to improve the understanding of the interactive nature of flavour and texture in order to compensate for the mouthfeel changes that can occur when replacing bulk sweeteners by intense sweeteners. Increasing pressures on the food industry to contribute to healthier diets also requires a better understanding of how to achieve reductions of sugar in conjunction with other major food components successfully.

Acknowledgements The research reported in the paper was supported by European Union through two projects: The Mechanistic Understanding of the Sweetness Response, and The Optimisation of Sweet Taste Quality (TOSTQ)

References 1. 2. 3. 4.

Fry, J. C. Food Science & Technology Today 2005, 19(2), 26+28-30. Hutteau F., Mathlouthi M., Portmann M.O. and Kilcast D. Food Chemistry 1998, 63(1), 9-16. Pangborn, R. M. J. Food Sci. 1962, 26, 648-55. Kilcast D., Portmann M.-O. and Byrne, B. Food Chemistry, 2000, 70(1), 1-8.


Sweetness and Sweeteners - American Chemical Society

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