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Clean-Label & Cost Effective Sweetener Taste Modulators

NAFFS Staff Report

“Consumers want the taste of sugar,” said Grant DuBois during the NAFFS 103rd Annual Convention. A “biologically-oriented” organic chemist and Chief Scientific Officer for Almendra, DuBois said good taste, manageable manufacturing costs and consumer acceptability are key factors in making a product commercially successful, including those with stevia sweeteners.

DuBois shared his extensive background in the study and improvement of sugar substitutes, which included 20 years with the Coca-Cola Co., where he was responsible for new sweetener technology development. He said that while working there, he initiated a program in collaboration with Senomyx to find enhancers of carbohydrate sweeteners such as sucrose, fructose and glucose.

The idea was that since the sweetener remained a carbohydrate sweetener, it would still have great taste. The first set identified were synthetic organic compounds; being synthetic, they required labeling as artificial flavors. The company wanted only naturally occurring compounds, which could be commercialized as natural flavors. “After 15 plus years of intensive research by Senomyx as well as other companies, to this day, natural enhancers with significant enhancement effects have not been found,” he said.

DuBois said carbohydrate-sweetened beverages (with sugar) have a different mouthfeel than sweeteners. In 2000, Coca-Cola was spending $6 billion on sugar and high-fructose corn syrups. Finding a two-fold enhancer would offer astronomical savings, he said, adding that he created a list of metrics of commercial viability of a sweetener to help with this project. As part of that list, he said the new technology had to be safe or it would fail at the regulatory stage. The most-important metric, he added, is “the need for taste quality because”, he said, “if you don’t have good taste quality, you don’t have a product.” 

DuBois said taste quality metrics include stability, solubility, cost-effectiveness and consumer acceptability. “The product has to carry sufficient stability to modulate the conditions as well as sufficient solubility - rapid dissolution in water. Also, in order to compete with other technologies, the technology must be cost-effective and patentable. After investing millions of dollars and resources into the development, he said, a manufacturer has to be sure of a period of exclusivity,” he said.

When considering the costs, calculations are done on a cost-per-unit basis. DuBois said high fructose corn syrup, used in the Coca-Cola Classic recipe, costs ~54 cents. In contrast, U.S. Diet Coke is sweetened with aspartame with a cost per unit case of ~3 cents. In the mid-1980s, Diet Coke was sweetened with a saccharin/aspartame blend and a cancer warning label was required due some evidence that saccharin caused cancer. So, to avoid the cancer warning label, the company moved to 100% aspartame. Once the patent expired on aspartame, the price came down significantly, to its current beverage application cost per unit case of ~3 cents.

Almendra, DuBois said, experimented with its ultra-pure REBA in beverages but the cost per unit case was too high at ~34 cents per unit case and the taste was not good enough, he said. There was need to create a modulator which would increase sweetness intensity, accelerate rate of sweetness onset, reduce sweetness-linger and provide mouthfeel, DuBois said. “There’s a great need for a cost-effective taste modulator.”

DuBois said the manufacturer must finally be sure to create a product technology that is acceptable to consumers, citing GMO issues as an example.

DuBois said the combination of four aspects of taste quality – maximal response, flavor profile, temporal profile and sweetness desensitization – has been the greatest challenge of his career. 

He provided maximal response data on four non-caloric sweeteners:
a. Saccharin 9.1: “This is limited because no matter what concentration is achieved, saccharin will never get sweeter than 9.1%,” at least in a citrate buffer; you cannot reach a 10% sucrose equivalency of sweetness.”
b. Cyclamate 18.4: “You can easily reach a 10% sucrose equivalency with cyclamate.”
c. Aspartame 24.7: “You can easily reach a 10% sucrose equivalency with aspartame and this is why aspartame can be used all by itself without blending.”
d. “Rebaudioside A 9.7: “Reb A, like saccharin, is limited by a maximal response < the intensity of 10% sucrose,” he said. When considering the flavor profile of the sweeteners, DuBois discussed six sweeteners. He said to get to 7% sucrose level of sweetness with Saccharin, one will get a lot of bitter off-taste. The rest of the sweeteners, he said, are like Rebaudioside A and can carry a licorice off-taste.  

DuBois said the other major challenge with non-caloric sweeteners, whether they are synthetic or natural, is the temporal profile. He looked at the same list of six sweeteners and said the sweetness of sucrose rises quickly. He said Cyclamate was similar but was banned by the FDA in 1969. He said compared to sweeteners such as aspartame, it rises relatively quickly and lingers considerably compared to sucrose. Rebaudioside A, he said, lingers even longer. With Reb A, he said, “you can even discern some delay in onset of sweetness.”

Thaumatin, the protein sweetener, has a marked delayed onset and then “long, long, long sweetness-linger,” he said, “And this is the major problem to solve in making non-caloric sweeteners tastes more like sugar.” 

Moving to sweetness desensitization, DuBois spoke about a study done on three cola products. With the use of high-fructose corn syrup, he said, the sweetness stays about the same in taking sips of a beverage every 30 seconds. Using Aspartame, the sweetness drops off over time, causing some desensitization. The cola with the synthetic flavor CPU had its sweetness drop off much more, on iterative tasting, than aspartame. 

In providing a brief history of innovation in sweetness technology, DuBois said that for decades chemists have been trying to get high-potency synthetic non-caloric sweeteners to taste more like sugar. “Although aspartame and sucralose are good after many years of development, they’re still not going to fool anybody,” DuBois said.  

The goal, he said, was to achieve a zero-caloric beverage but when it was determined that only a two-fold enhancer was possible, that meant only a 50% calorie reduction was possible. “On top of this, these were all synthetic molecules, so they had to be labeled as artificial flavors. This meant that it was never much of a commercial success,” he said.

In the 1990s, he said, Coca-Cola moved to all-natural ingredients. After a long search for the best natural non-caloric sweeteners, DuBois said the best option found was REB A stevia sweetener but the taste was still a “long way from sugar.” So that lead them to search for modulators of sweet taste, which were more useful by themselves. 

As part of DuBois’ career-long challenge to find an enhancer that would taste like sucrose, he said he’s been helped by lots of empirical observations done by his teams and industry colleagues over the past 35 years. During that time, many different chemicals including ordinary salt, potassium chloride, erythritol and osmolytes were seen to increase maximal response, accelerate sweetness onset, reduce sweetness-linger and add mouthfeel to non-caloric sweetener formulations. In 2016, DuBois said, the team was able to connect all these observations to the mechanistic rationale that the sweetness-linger and intensity had something to do with the mucus in the mouth.

The roof of the mouth, he said, is slippery because of salivary mucus. “This is what causes the onset and lingering after taste. But, if you rinse with astringent substance, the sweetness of a sweetener like Reb A is enhanced; sweetness develops more rapidly and sweetness-linger is reduced,” he said. This empirical observation led them, he said, to “dramatic improvement in the taste of sweeteners.”

DuBois said a hydrogel covers tastebuds, due to a salivary glycoprotein called mucin. Sweet molecules must diffuse through this gel to get to the sweetener receptor on taste buds. Carbohydrate sweeteners diffuse right through this gel very rapidly, while non-caloric sweeteners bind to the mucin instead, slowing the onset, he said. Since the noncaloric sweetener arrives at the receptor over a protracted period, the apparent sweetness maximal intensity is lower. As the sweetener binds again in the mucous hydrogel as it diffuses away from the receptor, the sweetener is able to diffuse back to the receptor over and over, thereby iteratively activating the receptor. This is observed as sweetness linger, he said. 

Salivary mucin is maintained in a very compact form by binding to calcium while inside the salivary gland, DuBois said. “And then on secretion of saliva, the calcium is retained in the salivary gland cells and mucin expands to form the hydrogel coating the tongue.” Thus, DuBois and his team began to formulate Reb A with calcium salts, thinking that calcium ion would bind to the mucin to create pores or channels in the mucous hydrogel, thereby enabling a more-rapid diffusion to and from the receptor. “Later,” he said, “we found that a mixture of magnesium and calcium salts was more effective than calcium alone. In fact we found that calcium and magnesium were synergistic with each other.

“But as we started experimenting with calcium salts as well as with calcium/magnesium salt blends, we noticed that they also introduced a marked mouthfeel increase,” DuBois said.  Japanese scientists at Ajinomoto, he said, had earlier found that the calcium-sensing receptor is expressed in a subset of taste bud cells and their activation leads to “kokumi taste,” which they translate as “mouthfulness.” 

Thus, since our taste modulator system is a mixture of calcium and magnesium salts, both being agonists at the calcium sensing receptor, it was clear as to why we were observing sugar-like mouthfeel. Finally, in our ongoing research to find effective taste modulation systems for Reb A and other noncaloric sweeteners, we found that mixtures of calcium, magnesium and potassium salts were even better than the binary blend of a calcium and a magnesium salt."

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