Aspartame, sweetness

Aspartame, sweetness production, 28-30 Aspartic acid, as food material, 138-147 Aspartic acid dipeptides, taste, 141-142r Astringpncy, sensation based on generalized membrane responses, 16-18 Automated data analysis and pattern recognition tool kit, 102... 

L-Aspartyl-L-phenylalanine methyl ester (aspartame) (sweet)... 

Saccharin sucralose and aspartame illustrate the diversity of structural types that taste sweet and the vitality and continuing development of the in dustry of which they are a part ... 

Fmctose is sweeter than sucrose at low temperatures (- S C) at higher temperatures, the reverse is tme. At 40°C, they have equal sweetness, the result of a temperature-induced shift in the percentages of a- and P-fmctose anomers. The taste of sucrose is synergistic with high intensity sweeteners (eg, sucralose and aspartame) and can be enhanced or prolonged by substances like glycerol monostearate, lecithin, and maltol (19). 

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). 

The rate of aspartame degradation in dry mixes is more dependent on the water activity than on the temperature (23). In dry mixes, aspartame may also engage ia Maillard reactions with the aldehyde moieties of flavoting agents, resulting ia the loss of sweetness and flavor. Use of the corresponding acetals of the flavor compounds to avoid this reaction has been reported (24). 

Acesulfame-K is a white crystalline powder having a long (six years or more) shelf life. It readily dissolves in water (270 g/L at 20°C). Like saccharin, acesulfame-K is stable to heat over a wide range of pH. At higher concentrations, there is a detectable bitter and metallic off-taste similar to saccharin. Use of the sodium salt of feruHc acid [437-98-4] (FEMA no. 3812) to reduce the bitter aftertaste of acesulfame-K has been described (64). The sweetness potency of acesulfame-K (100 to 200x, depending on the matching sucrose concentration) (63) is considered to be about half that of saccharin, which is about the same as that of aspartame. 

Saccharin imparts a sweetness that is pleasant at the onset but is followed by a lingering, bitter aftertaste. Sensitivity to this bitterness varies from person to person. At high concentration, however, most people can detect the rather unpleasant aftertaste. Saccharin is synergistic with other sweeteners of different chemical classes. For example, saccharin—cyclamate, saccharin—aspartame, saccharin—sucralose, and saccharin—aUtame combinations all exert synergy to various degrees. The blends, as a rule, exhibit less aftertaste than each of the component sweeteners by themselves. 

The disaccharide stmcture of (12) (trade name SPLENDA) is emphasized by the manufacturer as responsible for a taste quaUty and time—intensity profile closer to that of sucrose than any other high potency sweetener. The sweetness potency at the 10% sucrose solution sweetness equivalence is between 450 and 500X, or about two and one-half times that of aspartame. When compared to a 2% sugar solution, the potency of sucralose can be as high as 750X. A moderate degree of synergy between sucralose and other nonnutritive (91) or nutritive (92) sweeteners has been reported. 

Alitame (trade name Adame) is a water-soluble, crystalline powder of high sweetness potency (2000X, 10% sucrose solution sweetness equivalence). The sweet taste is clean, and the time—intensity profile is similar to that of aspartame. Because it is a stericaHy hindered amide rather than an ester, ahtame is expected to be more stable than aspartame. At pH 2 to 4, the half-life of aUtame in solution is reported to be twice that of aspartame. The main decomposition pathways (Fig. 6) include conversion to the unsweet P-aspartic isomer (17) and hydrolysis to aspartic acid and alanine amide (96). No cyclization to diketopiperazine or hydrolysis of the alanine amide bond has been reported. AUtame-sweetened beverages, particularly colas, that have a pH below 4.0 can develop an off-flavor which can be avoided or minimized by the addition of edetic acid (EDTA) [60-00-4] (97). 

Lactisole [13794-15-5] the sodium salt of racemic 2(4-methoxyphenoxy)propionic acid, is a sweet-taste inhibitor marketed by Domino Sugar. It was affirmed as a GRAS flavor (FEMA no. 3773). At a concentration of 100 to 150 ppm, lactisole strongly reduces or eliminates the sweet taste of a 10% sugar solution. This inhibition appears to be receptor-related because lactisole also inhibits the sweet taste of aspartame. The 5 -( —)-enantiomer [4276-74-8] (38), isolated from roasted coffee beans, is the active isomer the i -(+)-enantiomer is inert (127). 

Aspartame, a nonnutritive sweetener marketed under the trade name Nutra-Sweet (among others), is the methyl ester of a simple dipeptide, Asp-Phe-OCH.3. 

Different optical enantiomers of amino acids also have different properties. L-asparagine, for example, tastes bitter while D-asparagine tastes sweet (see Figure 8.3). L-Phenylalanine is a constituent of the artificial sweetener aspartame (Figure 8.3). When one uses D-phenylalanine the same compound tastes bitter. These examples clearly demonstrate the importance of the use of homochiral compounds. 

Sweeteners can be anything from simple sugars to fragments of proteins, such as aspartame, that trigger the sweet receptors on our tongues, sometimes up to two hundred times as strongly as sugar itself. 

Acesulfame potassium is used with other sweeteners such as aspartame because it has a long shelf life, and tastes sweet right away. It also has a synergistic effect with other sweeteners, so less of each is necessary to achieve the same sweetness. 

In acidic solutions at high temperatures, aspartame degrades and loses its sweetness. 

Fig. 10.1. Synergistic sweetness enhancement in acesulfame K-aspartame blends.

The other source of modem dmgs was the European dyestuff industry of the nineteenth and early twentieth centuries. The goal of this industry was to make useful dyes, principally for fabrics. In the course of handling novel molecules, scientists occasionally make unexpected observations (serendipity) that suggest novel utilities. For example, the commonly used sweetener aspartame was discovered by accident when a scientist licked a finger containing a bit of this substance. It turned out to be surprisingly sweet. 

Aspartame is the most successful and widely used artificial sweetener. It is roughly 100 times as sweet as cane sugar. It is methyl ester of dipeptide formed from aspartic acid and phenylalanine. Use of aspartame is limited to cold foods and soft drinks because it is unstable at cooking temperature. 

Alitame is high potency sweetener, although it is more stable than aspartame, the control of sweetness of food is difficult while using it. 

Other Food Industries. Aspartame is a synthetic dipeptide ester, L-asp-L-phe-OMe which is about 200 times as sweet as sucrose. It has recently been released for sale in North America and Europe by G. D. Searle. It was originally synthesized chemically and reported by Mazur et al. 38). Subsequent improved methods of synthesis have been developed which involve the use of metalloproteases such as thermolysin in reverse . Metalloproteases are used because, unlike the more common proteases, they have no esterase activity. 

During work on a series of aspartyl dipeptides containing ACC 71 (vide supra, Eq. (28), Sect. 4) at the carboxyl terminus, it was reported that dispartame Asp-ACC-OMe had a distinct sweet taste [302] and that the corresponding n-propyl ester had 250-300 times the sweetness of sucrose [303]. However, replacement of phenylalanine by 2,3-methanophenylalanine gave tasteless analogues of aspartame [293, 304], and some dimethyl-ACC 214 (methanovaline) and tri-methyl-ACC 215 aspartame analogues [Asp-(Me)n-ACC-OMe] have a bitter taste. These taste properties, which depend on the number and position of the methyl substituents, have been explained on the basis of topochemical models thus, a L-shaped conformation of the dipeptide is necessary for sweet taste, Eq. (86) [3051. 

Most of the food and feed additives are commoditized. This is also the case for the artificial sweeteners. The main products are Saccharin (550), Aspartame (Canderel, 200), Acesulfam K (Sunnett, 200), and Cyclamate (35). The figures in brackets are the sweetness intensity, whereby sucrose = 1. Sucra-lose, discovered in the 1980s by Tate Lyle, now taken over by Johnson Johnson s formidable marketing machine, is enjoying a revival as Spenda. 

Aspartame is a high intensity dipeptide sweetener, ca. 200 times as sweet as sncrose. It was originally developed by G.D.Searle Co. prior to their acqnisition by Monsanto. Chemically synthesised aspartame has rapidly acqnired a major share of the world high intensity sweetener market, particnlarly in soft drinks. Until recently it has all been snpplied by a monopoly snpplier, the Nntrasweet Corp (a Monsanto-AJinomoto joint ventnre) protected by prodnct patents. Recently biocatalytic methods... 

In the future aspartame can expect to encounter competition from new high intensity sweeteners such as sucralose which is produced by Tate Lyle/Johnson Johnson and alitame (Pfizer), which have advantages such as even higher sweetness and, in the case of sucralose, heat stability. In response Nutrasweet are busy developing a new very high intensity sweetener (Sweetener 2000), which is reputed to be 10,000 times as sweet as sucrose. 

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