Intense sweeteners available

Enzymatic assay techniques have been developed for several additives by Merck. BIOQUANT kits are available for aspartame (intense sweetener) and nitrate (preservative). Gromes et al. (1995) applied the Bioquant kit to determination of aspartame in yoghurt, quark and confectionery. For low concentrations of aspartame a blank correction procedure was necessary. Recoveries of aspartame were in the range 93-102%. 

The available intense sweeteners belong to very different structural classes of sweeteners (Table 10.1). They were normally discovered by chance. All internationally important sweeteners are produced synthetically and only two less important products are isolated from plants. 

Metabolism via normal metabolic pathways or fast excretion without metabolism are desirable characteristics. Some intense sweeteners are excreted unchanged while others are metabolised. Bulk sweetener absorption is lower and slower than for carbohydrates and results in reduced caloric availability which is partly due to metabolites formed by intestinal bacteria. Such metabolites and osmotic effects of not fully absorbed bulk sweeteners can cause laxative effects. Generally, the calorific value of bulk sweeteners is lower than for carbohydrates. Intense and bulk sweeteners are, as far as they are metabolised, not dependent on insulin. They are therefore acceptable for diabetics as part of a suitable diet. 

Saccharin is l,2-benzisothiazol-3(2H)-on-1,1-dioxide, often also called o-benzoic acid sulfimide. Discovered in 1878, it is the oldest available intense sweetener. 

Intake estimates and calculations have been performed repeatedly for intense sweeteners for which probably the most extensive database among food additives exists. All studies and all calculations starting from reasonable assumptions indicate that only a minute proportion of consumers may come close to the ADI which may only seldom be exceeded by persons having food habits substantially different from the majority of the population. The best available data originate from a biomarker study on acesulfame and saccharin in which even the highest consumers among children consumed only a fraction of the ADI.29 Several intake studies were carried out on aspartame with the uniform result that no appreciable risk to exceed the ADI was found.14... 

In the USA the available bulk sweeteners are listed under different provisions, like food additive, interim status, GRAS (Generally Recognised As Safe) or GRAS by self-determination or self-affirmation of the manufacturers. Intense sweeteners require food additive approval which includes a listing of the approved fields of use or may be a listing as a general purpose sweetener.32... 

As in many countries where maximum levels are set for the use of intense sweeteners in foods, analytical methods for identification and quantitative determination are required. Although a wide variety of methods is described, the European Standards for sweetener analysis deserve special attention. They were based on the most widely used analytical methods available and also demonstrated applicability and reliability in collaborative studies in several laboratories. 

The sweetness of fmctose is enhanced by syneigistic combinations with sucrose (12) and high intensity sweeteners (13), eg, aspartame, saccharin, acesulfame K, and sucralose. Information on food application is available (14,15). Fmctose also reduces the starch gelatinization temperature relative to sucrose in baking applications (16—18). 

The purpose of this section is to provide a review of HPLC methods available for the determination of sweeteners in foods. First, general information of the various modes of HPLC and on sample preparation procedures available for the determination of intense sweeteners is described. Then information is given on each individual sweetener. 

Aspartame is an intense sweetener first discovered in 1965 by J. Schlatter it is available under the brand names of Nutrasweet , Equal , and Canderel . Chemically, aspartame is N-L-a-aspartyl-L-phenylalanine methyl ester (Fig. 1), withamolecularformulaofC14H 805N2 (MW = 294.30). It is a white, odorless, crystalline powder. It is slightly soluble in water and sparingly soluble in alcohol. The solubility increases as the pH is lowered (2,6,57). It has 100-200 times the sweetness of sucrose and exhibits a sweet, clean taste and a sweetness profile similar to that of sucrose, without bitter or metallic aftertaste (Table 1). However, it displays a slow onset of sweetness coupled with lingering sweet taste. It extends and intensifies tastes and enhances fruit flavors. Aspartame exhibits synergism, a superior taste profile, and improved stability when used with other sweeteners (1,4,14,55,75). 

Formulators in most markets now have a wide range of sweeteners available to use either alone or in combination. As Figures 4.1 and 4.2 show, the main intense sweeteners in use in soft drinks today are acesulfame K, aspartame, saccharin and cyclamate. Currently of less importance commercially (either because they are new to the market or because they have not found significant use in soft drinks), but still approved for use in soft drinks in some markets, are thaumatin, neohesperidin diliy-diochalcones, alitame, stevioside, sucralose and neotame. 

Chemically, these intense sweeteners are a very diverse group of substances. The early forms available were discovered serendipitously, usually by an experimenter accidentally tasting some. All of the intense sweeteners appear to be able to fit onto a particular receptor on the human tongue, and quite small chemical changes in their structures can convert a substance from sweet to bitter or vice versa. 

Artificial or intense sweeteners are often used not only to restrict the sugar intake in food and beverages but also to boost the degree of sweetness to mask bitter notes. Only few are approved for use in over 80 countries (e.g., saccharin, aspartame, sucralose, and acesulfame potassium). There is some ongoing controversy over whether artificial sweeteners are health risks despite lack of scientifically controlled peer-reviewed studies in general consistently to produce clear evidence. It is to be noted that if an acceptable daily intake (ADI) value is available, most of the time it is for a general adult population and not specifically for pediatric and geriatric population. 

Stevioside and rebaudioside A are diterpene glycosides. The sweetness is tainted with a bitter and undesirable aftertaste. The time—intensity profile is characteristic of naturally occurring sweeteners slow onset but lingering. The aglycone moiety, steviol [471 -80-7] (10), which is the principal metaboHte, has been reported to be mutagenic (79). Wide use of stevia ia Japan for over 20 years did not produce any known deleterious side effects. However, because no food additive petition has been presented to the FDA, stevioside and related materials caimot be used ia the United States. An import alert against stevia was issued by the FDA ia 1991. In 1995, however, the FDA revised this import alert to allow the importation and use of stevia as a diet supplement (80), but not as a sweetener or an ingredient for foods. Several comprehensive reviews of stevia are available (81,82). 

Intense and bulk sweeteners are endorsed by international agencies and approved in a large number of countries. Acesulfame K, aspartame and saccharin are available as sweeteners in the EU and Europe while sucralose is approved in the USA and due for approval in Europe and cyclamate, neohesperidin dihydrochalcone and thaumatin are available in Europe. As bulk sweeteners isomalt, lactitol, maltitol, mannitol, sorbitol and xylitol are commonly available. 

The chemical structure of the most important nonnutritive sweeteners is shown in Figure 11-4. Saccharin is available as the sodium or calcium salt of orthobenzosulfimide. The cyclamates are the sodium or calcium salts of cyclohexane sulfamic acid or the acid itself. Cyclamate is 30 to 40 times sweeter than sucrose, and about 300 times sweeter than saccharin. Organoleptic comparison of sweetness indicates that the medium in which the sweetener is tasted may affect the results. There is also a concentration effect. At higher concentrations, the sweetness intensity of the synthetic sweeteners increases at a lower rate than that which occurs with sugars. This has been ascribed to the bitter-... 

---