GRANT DUBOIS, PH.D., Consultant, Sweetness Technologies, LLC, reviewed the progress made on natural high-potency (HP) sweetener systems for food and beverages by offering tantalizing insights on how to resolve some of their negative taste and flavor attributes, in his presentation titled “Replication of Sugar Taste Enabled by Taste Modulators and Enhancers.”
Earlier work with HP sweeteners and sweetness enhancers recognized the importance of both maximal sweetness intensity and taste quality. However, DuBois listed six additional criteria for use in determining the commercial viability of such ingredients: safety, stability, solubility, cost, patentability and consumer acceptability.
A major research focus today is the search for all-natural HP sweeteners and sweetness enhancers. Interest in these ingredients began to grow at The Coca-Cola Company in the 1990s, recalled DuBois. This led to the development and commercialization of rebaudioside A (REBA)—a sweet-tasting diterpenoid glycoside isolated from South American stevia plant leaves. “One challenge with REBA was a maximal sweetness response at ambient temperature of <10% sucrose equivalency (SE). However, in cold solutions, that maxima increased to 18% SE, so it wasn’t as bad as it first looked, explained DuBois.
Unfortunately, as with other natural HP sweeteners, off-tastes were an issue: Most commercial REBA products exhibit distinctive bitter and licorice-like notes. DuBois explained that the REBA under study in early work was 97% (min) purity and that “batch-to-batch bitterness and licorice-like taste variability suggested the culpability of contaminants.” Today, REBA of higher purity is available with negligible off-tastes, albeit somewhat more expensive. (See sidebar “The Cost of Sweetness”).
Additionally, the challenge of social perspectives exists. For example, new ingredients must weather reflexive and hostile social media storms. When aspartame was first introduced, activists charged that the breakdown of aspartame into phenylalanine (Phe) and methanol posed severe public health threats. However, perspective matters: “If I eat 100g of roasted chicken, I ingest 13x the Phe that I get from the aspartame in a 12oz Diet Coke, while 12oz of tomato juice provides 5.9x the amount of methanol generated from the aspartame in a single Diet Coke,” countered DuBois.
More than 40 sweet diterpenoid glycosides have been isolated from the stevia plant of which REBA was one of the first to be brought to the market. In recent years, rebaudiosides D (REBD) and M (REBM) have been commercialized, although they are present only at very low levels in the plant. Because of their low natural abundances, REBD and REBM are manufactured in bioconversion or fermentation processes and therefore cannot be labeled as “stevia leaf extracts,” as is the case for REBA.
Another commercialized terpenoid-type sweetener is the triterpenoid monk fruit sweetener group, members of which are known as mogrosides. The monk fruit sweeteners are very challenging to purify and are available in a range of purities.
Other categories of natural HP sweeteners are on the market or in development and include proteins (e.g., thaumatin and brazzein) and amino acids (e.g., monatin). Each has its own problems, ranging from licorice flavors (thaumatin); lingering sweetness profiles (thaumatin, brazzein and monatin); to rapid-degradation into foul-smelling derivatives (monatin). Neohesperidin dihydrochalcone, a flavonoid-type sweetener, is commercially available and claimed by some to be natural but does not occur in nature.
DuBois equivocated on the opportunities presented by flavors with modifying properties (FMPs) of the positive allosteric modulator (PAM) type. PAM FMPs significantly enhance the sweetness intensities of carbohydrate sweeteners. Dihydroxybenzoic acid, for example, will increase the sweetness perception of sucrose by 1.3-fold and fructose. by 1.2-fold he noted.
“While PAMs were hoped to be a big deal for us when I was with The Coca-Cola Company, they ultimately were not,” said DuBois. The reason? In vivo, “the probability of sucrose and PAMs binding at a taste receptor at the same time, as required to enable this synergistic response, is far too low; and so, the hoped-for 10-20-fold “enhancements were never found.
While PAM FMPs have not realized significant commercial success, sweetener FMPs such as glucosylated steviol glycosides (GSGs) have realized success as natural flavors which enable reduction of caloric sweetener levels. These FMPs are used below their sweetness detection thresholds and thereby enhance sweetness by 1.1-1.2-fold.
One area in which very significant progress has been made is in the identification of taste modulators for HP sweeteners. “In early work, we noticed that osmolytes worked well at eliminating the lingering sweet aftertastes of HP sweeteners.” As example, adding salt at 500 mg/L to REBA “eliminated the lingering sweetness effect; however, such formulations were too salty.” Erythritol was also found to be very effective in elimination of the REBA sweetness lingering aftertaste, but cost remains the challenge with REBA/erythritol formulations.
In closing, DuBois hinted at major developments in taste modulation technology on the verge of disclosure. Stay tuned.
The Cost of Sweetness
A key metric for commercial viability is cost. Beverage companies measure ingredient cost impacts in terms of cost/unit case. “If we use HFCS as a benchmark, the sweetener cost is about US$0.51/unit case for a beverage like Coca-Cola. In contrast, the cost/unit case for a beverage like Diet Coke sweetened with aspartame today is ca. US$0.03-0.04 (ca. US$0.33 in 1985 when aspartame was under patent protection),” noted Grant DuBois.
Currently, a blend of REBA with erythritol to balance the sugar taste pro?le and which tastes pretty good, incurs a cost of about US$0.99/unit case. In his opinion, the cost threshold for viability should be ca. US$0.40/unit case, so there is work to be done.
“Replication of Sugar Taste enabled by Taste Modulators and Enhancers,” Grant DuBois, Ph.D., Consultant, Sweetness Technologies, LLC
This presentation was given at the 2018 Sweetener Systems Conference. To download presentations from this event, go to: https://sweeteners.globalfoodforums.com/category/sweetener-systems-rd-academy/
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