Aspartame relative

Aspartame is a methyl ester of a dipeptide, unrelated to any carbohydrate. An aspartame relative, neotame, is even sweeter. 

The sweetness of fmctose is enhanced by synergistic combiaations with sucrose (12) and high iatensity sweeteners (13), eg, aspartame, sacchatin, acesulfame K, and sucralose. Information on food appHcation is available (14,15). Fmctose also reduces the starch gelatinization temperature relative to sucrose ia baking appHcations (16—18). 

Finally, some amphiphilic sweeteners, eg, aspartame, saccharin, and neohesperidin dihydrochalcone, have been shown to be capable of stimulating a purified G-protein direcdy in an in vitro assay (136). This suggests some sweeteners may be able to cross the plasma membrane and stimulate the G-protein without first binding to a receptor. This type of action could explain the relatively longer response times and the lingering of taste associated with many high potency sweeteners. 

Aspartame is relatively unstable in solution, undergoing cyclisation by intramolecular self-aminolysis at pH values in excess of 2.0 [91]. This follows nucleophilic attack of the free base N-terminal amino group on the phenylalanine carboxyl group resulting in the formation of 3-methylenecarboxyl-6-benzyl-2, 5-diketopiperazine (DKP). The DKP further hydrolyses to L-aspartyl-L-phenyl-alanine and to L-phenylalanine-L-aspartate [92]. Grant and co-workers [93] have extensively investigated the solid-state stability of aspartame. At elevated temperatures, dehydration followed by loss of methanol and the resultant cyclisation to DKP were observed. The solid-state reaction mechanism was described as Prout-Tompkins kinetics (via nucleation control mechanism). 

Every patient with diabetes requires some form of dietary assessment, and often therapy. This is important to allocate the relative amounts of energy derived from carbohydrate, protein and fat of total recommended daily calories in proportion to the patient s body weight and height and daily requirements, while avoiding atherogenic diets. Diets with high carbohydrate content (50-60%), low fat (30-35%) and adequate protein (10-15%) is recommended. Fibre-rich foods are preferable. The use of non-nutritive sweeteners (saccharin, aspartame, ace-sulfame K and sucralose) are acceptable. Alcohol intake should be assessed since excess consumption... 

Sweet Taste. The mechanism of sweetness perception has been extensively studied because of its commercial importance. Many substances that vary in chemical structure have been discovered which are similar to the taste of sucrose. Commercial sweeteners include sucralose, acesulfame-K, saccharin, aspartame, cyclamate (Canada) and the protein thaumatin 4), Each sweetener is unique in its perceived sensation because of the time to the onset of sweetness and to maximum sweetness, ability to mask other sensations, persistence, aftertaste and intensity relative to sucrose [TABLE IT. For example, the saccharides, sorbitol and... 

Aspartame has been quantified by UV detection at 254 nm and at 200-217 nm. However, because aspartame has a relatively low extinction at 254 nm, quantification at lower wavelengths provides increased response. Detection can also be performed with increased specificity by fluorescence after postcolumn derivatization with o-phthaldehyde (76). 

HY Aboul-Enein, AS Bakr. Comparative study of the separation and determination of aspartame and its decomposition products in bulk material and diet soft drinks by HPLC and CE. J Liq Chromatogr Rel Technol 20(9) 1437-1444, 1997. 

Salt of aspartame and acesulfame. A salt of aspartame and acesul-fame is now available. The product is a chemical combination of aspartame and acesulfame in a ratio of 64 36 on a weight basis. This product was given 2 years temporary national approval in the United Kingdom (Statutory Instrument 2003 number 1182). It also has temporary approval in The Netherlands (Staatscourant, 17 July 2002), and it can be used in the United States, Canada, China, Mexico and Russia. In 2004, amendment of the EU Sweetener Regulation saw extension of the approval to all EU markets. In solution, the salt breaks up to form aspartame and acesulfame. The relative sweetness is 350 (HSC, 2003). 

With the general name of cyclohexylsulphamate, this sweetener was discovered in 1937 by Michael Sveda at the University of Illinois. The sodium salt is the most commonly used form. It is a white crystalline salt with good solubility. The relative sweetness of cyclamate is comparatively low, at approximately 35, in most food systems (Bakal, 1983). The taste quality of cyclamate as a sole sweetener has a slow onset time and can have a sweet/sour aftertaste at high concentrations (Franta et al., 1986). Sweetness quality is greatly unproved in combination with other sweeteners. Cyclamate is synergistic with acesulfame K (Von Rymon Lipinsky, 1985), aspartame (Searle, 1971), saccharin (Von Rymon Lipinsky, 1987) and sucralose (Tate Lyle Pic, 2002). 

It has been reported to be synergistic with intense sweeteners such as aspartame and acesulfame K and, when used at low levels (0.2%), improves certain flavour profiles (Eriknauer, 2003 LFRA, 2001). The relative sweetness of tagatose is 0.92. On ingestion, 20% of tagatose is absorbed in the small intestine and the rest is metabolised by the microflora of the colon. Dose-response studies indicate a prebiotic effect at 10 g/day (Eriknauer, 2003). 

Acesulfame K was intr oduced as a high-intensity sweetener at around the same time as aspartame. It too is much sweeter than sucrose but is also stable under the low pH conditions of soft drinks. Its analysis in a soft drink is relatively straightforward and an HPLC procedure is given by Grosspietsch and Hachenburg (1980). 

Nutritional ingredients (e.g., relatively small molecules, such as carotenoids, (pro)vitamins, anti-oxidants, preservatives, polyunsaturated fatty acids, aspartame, and tailored peptide mixes). 

Aspartame has been reported in a variety of solvatomorphic forms, namely one anhydrous form, two hemihydrate forms (Forms I and II) and a di-hemihydrate [8]. The structural details of the crystal properties have been discussed earlier, and will also be addressed in the discussion on thermal analysis. The room temperature transition between the hemihydrate and di-hemihydrate forms occurs between relative humidities of 40% and 60%. 

Several kinetic studies have been performed on aspartame, which is relatively unstable in solution [24-30], The half-life at pH 4.3 (the pH of maximum stability) is about 260 days at 25°C [30]. The shelf life (t%) at this temperature and pH 4.0 is about 53 days [28]. Degradation is more rapid at other pH values e.g. shelf-life 12 days at pH 1, and 1 day at pH 7 [30],... 

Additives that specifically interact with an analyte component are also very useful in altering the electrophoretic mobility of that component. For example, the addition of copper(II)-L-histidine (12) or copper(II)-aspartame (54) complexes to the buffer system allows racemic mixtures of derivatized amino acids to resolve into its component enantiomers. Similarly, cyclodextrins have proven to be useful additives for improving selectivity. Cyclodextrins are non-ionic cyclic polysaccharides of glucose with a shape like a hollow truncated torus. The cavity is relatively hydrophobic while the external faces are hydrophilic, with one edge of the torus containing chiral secondary hydroxyl groups (55). These substances form inclusion complexes with guest compounds that fit well into their cavity. The use of cyclodextrins has been successfully applied to the separation of isomeric compounds (56), and to the optical resolution of racemic amino acid derivatives (57). 

Sometimes the natural products that are needed are immediately obvious from the structure of the target molecule. An apparently trivial example is the artificial sweetener aspartame (marketed as Nutrasweet), which is a dipeptide. Clearly, an asymmetric synthesis of this compound will start with the two members of the chiral pool, the constituent (natural) (S)-amino acids, aspartic acid and phenylalanine. In fact, because phenylalanine is relatively expensive for an amino acid, significant quantities of aspartame derive from synthetic (S)-phenylalanine made by one of the methods discussed later in the chapter. 

Another example of a protease-catalyzed commercial process, which in this case uses the enzyme in a synthetic mode, is the completely regio- and stereoselective production of the low-caloric sweetener aspartame developed by DSM-TOSOH [15] (Fig. 7.9). Aspartame is a dipeptide consisting of the amino acids phenylalanine and aspartic acid, which are coupled by the enzyme thermolysin from Bacillus thermoproteolyticus. For an efficient coupling, relatively high temperatures are required and the amount of water in the system must be kept low to drive the reaction in the desired direction. Thermolysin, which is a metallo-endoprotease, meets these two requirements. It is thermostable, and it works in an organic solvent, which is required to keep the water activity low. In practice, however, organic solvents were not necessary, since the product aspartame forms an insoluble complex with unreacted D-Phe-OMe, which crystallizes out of the aqueous medium. 

Acquiring Information In a reference book, find a table comparing the relative sweetness of various sugars and artificial sweeteners. How do the following artificial sweeteners compare in sweetness with sucrose (table sugar) sucralose, aspartame, saccharin, and acesulfame-K ... 

Hydrolyzed starch products, such as maltodextrins, are produced by the partial hydrolysis of cereal (e.g., com) or root (such as potato) base starches and are commercially available in spray dried, particulate form. As manufactured it has a relatively low sweetness level and, if used alone as a sweetener, the food product can not be characterized as 100% artificially sweetened, a characterization that is often desired from a marketing standpoint. However, maltodextrins can be used as a bulking agent or carrier for synthetic sweeteners, such as aspartame, and then, the resulting product can be characterized as 100% artificially sweetened. 

Aspartame is made by a relatively simple procedure in which two amino acids, aspartic acid and phenylalanine, are reacted with each other to form a two-amino-acid product, called a dipeptide. The carboxylic acid group in the dipeptide is then reacted with methanol (methyl alcohol CH3OH) to obtain the methyl ester of the compound. One problem that makes the preparation somewhat more difficult is that hoth aspartic acid and phenylalanine have stereoisomers. The term stereoisomer refers to two forms of a compound that contain the same kind and number of atoms, hut differ in the orientation in space ( stereo ) of some of the atoms. Because of these stereoisomers, four different kinds of aspartame are formed during the preparation described above — D D L L D L L D (the latter two are different from each other). Only one is the desired product, the one that contains only L stereoisomers. 

Fortunately, PKU can be easily detected in newborns, and all 50 states and the District of Columbia mandate that such a test be performed because it is cheaper to treat the disease with a modified diet than to cope with the costs of a mentally retarded individual who is usually institutionalized for life. The dietary changes are relatively simple. Phenylalanine must be limited to the amount needed for protein synthesis, and tyrosine must now be supplemented, because phenylalanine is no longer a source. You may have noticed that foods containing aspartame carry a warning about the phenylalanine portion of that artificial sweetener. A substitute for aspartame, which carries the trade name Alatame, contains alanine rather than phenylalanine. It has been introduced to retain the benefits of aspartame without the dangers associated with phenylalanine. 

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