"With the growing trend in the commercial market towards the use of sweetener blends in a variety of media, putting emphasis on designing a sweetener blend that yields the best possible temporal profile for a given medium is of increasing importance," wrote the researchers in the journal Food Quality and Preference (doi: 10.1016/j.foodqual.2006.04.007).
A number of sweeteners, both natural and artificial, are available to food formulators. Indeed, the sweetener industry is enjoying considerable growth above the industry average as consumers with growing health and weight concerns turn away from sugar-heavy foods and beverages to 'lite' versions.
According to market analysts Freedonia, the sweetener market is set to grow at around 8.3 per cent year on year until 2008: considerably higher than growth in the ingredients industry currently at about 3 to 4 per cent.
Previous studies, said the researchers, have focused on individual sweeteners, or limited combinations, and were more interested on the temporal profile than on measuring the so-called "time to maximum sweetness" - a measure of how quickly the sweet taste is experienced in the mouth.
"While time to maximum sweetness intensity is a standard timeintensity parameter and has been shown to be an important variable in the perception of many oral stimuli, it has not been studied previously for a broad range of binary and ternary sweetener blends," wrote lead author of the study, Susan Schiffman from Duke University Medical Center.
Sixteen different sweeteners were considered, including protein sweeteners, such as thaumatin, dipeptide sweeteners, such as neotame and aspartame, carbohydrate sweeteners (sugars), such as fructose and sucrose, and sugar alcohols, such as mannitol and sorbitol.
The full list tested is as follows: sucralose, neotame, mannitol, acesulfame-K, sorbitol, saccharin, fructose, sucrose, cyclamate, stevioside, aspartame, rebaudioside-A, neohesperidin dihydrochalcone (NeoDHC), alitame, thaumatin.
Three different sweetness levels were examined for each binary blend, and the blends were formulated to be equally sweet as 3, 5, and 7 per cent sucrose solutions.
The binary blends that were reported by the trained panelists as being 'synergistic' were further evaluated with addition of a third sweetener to produce ternary blends.
The researchers report that sweetener blends that contained the protein thaumatin were associated with the latest time to maximum sweetness intensity.
Blends containing stevioside, neotame, NeoDHC, alitame, or rebauadioside-A had later times to maximum sweetness intensity compared to blends with sugars and sugar alcohols, reported the researchers.
The explanation for these later times to experience maximum sweetness may be the size and complexity of the chemical structures of these particular sweeteners, since thaumatin and neoDHC in particular are relatively large molecules.
This indicates three things, said Schiffman: "Their size may (a) slow the rate of diffusion to the receptor, (b) cause them to require more time to orient properly relative to the receptor, and (c) require a multi-step process in order to make all of the binding interactions between the sweetener and the receptor."
It was also found that many of the blends displayed times to maximum sweetness intensity that were in-between the earliest and latest of its constituent parts.
"These data indicate that the time to maximum sweetness intensity of "late" sweeteners can be shortened by blending with earlier onset sweeteners," said the researchers.
Such basic research on sweetener blends could be of interest to a wide range of food formulators, but the researchers called for further work to better understand the time properties of the sweeteners in other media. In this study only solutions in water were studied.
"Providing the consumer with a product that is both early in onset and time to maximum sweetness intensity like sucrose, the standard for sweetness, is clearly a task that is essential in sweetener and sweetener blend development," said Schiffman.
The scientists said that they had already started looking at the effect of specific blends in a cola soft drink, and preliminary data (which were not presented) suggests that the time to maximum sweetness is further influenced by other ingredients in the beverage.