The majority of high-intensity sweeteners were discovered by accident rather than by deduction and structural design. In a book entitled 'Serendipity', Roberts (1989) outlines the discoveries, as a result of chance chemical experiment, of saccharin (1) by Fahlberg in 1879, cyclamate (2) by Sveda in 1937 and aspartame (3) by Schlatter in 1965, in each case by the inadvertent tasting of the intense sweetener on their fingers or hands. The early literature of organic chemistry up to the early 1900s, frequently quoted the taste of a new compound as a characteristic, a test that is no longer permitted under the safety at work code of practice, prior to toxicology on the new compound. Important observations include, for example, Emil Fischer's (1890) note that L-glucose was sweet whilst Piutti (1886) discovered that the amino acid D-asparagine was sweet and its L-isomer was not, thereby implicating the intricacies of stereochemistry in the mechanism of sweet sensation.Approximately fifty very sweet natural products, which are at least 50 times sweeter than sucrose (4), have been discovered in green plants by their taste and qualify as low-calorie sweeteners because of the much smaller quantities required to give equisweetness with sucrose. They have a diversity of chemical structures, apparently unrelated, and include a variety of terpenoids, flavonoids and proteins. A range of monosaccharides, disaccharides, hydrogenated starch hydrolysis products, polydextrose and polyols which are similar in sweetness to sucrose, but less readily metabolised, and are often utilised as bulk sweeteners in dietary and non-cariogenic products. In beverages, it is usual to add such substitutes when high-intensity sweeteners are used in order to give the products body or a similar mouthfeel to sucrose.The measurement of sweetness is arbitrary since no laboratory instrument is available to carry out the task. In assessing the relative sweetness of a substance, sucrose is invariably used as the standard reference compound, since it has a quick impact, a clean taste and rapid fall off. Sweet substances rarely have the same sweet taste characteristics, nor do they show all of the features associated with the ideal taste and mouthfeel of sucrose. They often vary in the onset time of the sweet sensation, the intensity of sweetness, the quality -sometimes involving bitter, metallic and liquorice flavours -its duration and the aftertastes.
R. Khan (ed.), Low-Calorie Foods and Food Ingredients