News | April 28, 1999

Sweet Without the Sugar - Part Two

By: Kimberly J. Decker, Contributing Editor

From Food Product Design Magazine

Click here to read Sweet Without the Sugar - Part One.

Table of Contents
Ace of a sweeteer
Sweetening with sucralose
All about alitame
On the horizon

Ace of a sweetener

At 200 times sucrose's sweetness, acesulfame-potassium - acesulfame-K or ace-K - has an intensity along the lines of aspartame. Ace-K has sweetened American food products since 1988, when the FDA approved its use in certain foods. Marketed as Sunett brand sweetener by Somerset, NJ-based Nutrinova, Inc., a member of the Hoechst Group, ace-K is the potassium salt of the cyclic sulfonamide 6-methyl-1,2,3-oxathiazine-4(3H)-1,2,2-dioxide. Studies have found that the 6-methyl dioxide ring gives rise to ace-K's sweetness, a quickly perceptible taste that resembles sucrose, with no bitter aftertaste. According to Robert Baron, Ph.D., senior food technologist at Nutrinova, "Sunett's sweetness onset is very rapid, followed by a short decrease in sweetness - leaving no lingering sweet aftertaste. This impact sweetness is just one reason that it blends well with other sweeteners to provide a sugar-like profile."

Ace-K exhibits a significant synergy with other nutritive and non-nutritive sweeteners, particularly aspartame. Researchers evaluating 1:1 blends of ace-K and aspartame have found that both sweeteners in combination can lead to a sweetness intensity as high as 280% that of sucrose. This allows a 30% to 50% reduction in the total amount of sweetener. Furthermore, the blend has a more sucrose-like taste than either sweetener on its own and can extend the finished product's shelf life by maintaining acceptable sweetness levels longer. Blending ace-K with traditional sweeteners like sucrose and fructose and with polyols like sorbitol also has a synergistic effect, as the combinations enhance sweetness and play down any artificial notes that ace-K might contribute.

Ace-K contributes nothing to caloric content. The human body cannot metabolize this odorless, free-flowing white crystalline powder, allowing the kidneys to excrete it unchanged. This distinction warrants its FDA classification as a non-nutritive sweetener. Like most other synthetic sweeteners, ace-K exhibits non-cariogenicity and its negligible effect on blood glucose levels makes it safe for inclusion in foods meant for diabetics.

Processing advantages focus on stability. Ace-K lacks a defined melting point, although studies have detected thermal decomposition at around 437°F - a higher temperature than normally reached by foods and beverages. This permits its use in cakes and cookies - where studies have shown an ace-K recovery rate after baking of more than 99% - and high-temperature processed beverages, among other items. Its stability also manifests itself in the lack of off-flavors or diminished sweetness that high temperatures can produce in some high-intensity sweeteners. It also resists decomposition over a wide range of pH values, even while exposed to higher temperatures. Only extreme pH and temperature combinations atypical of food processing conditions adversely affect its stability. Ready solubility also works in ace-K's favor, making preparation of liquid concentrates and uniform distribution during product mixing much easier. Its ability to withstand the test of time, having a shelf life of over five years at room temperature, is yet another positive attribute.

Nonetheless, like most other non-carbohydrate sweeteners, ace-K cannot participate in fermentation or Maillard browning reactions; it has no effect on water activity or freezing and boiling points of solutions; and it contributes little or no viscosity, often requiring use of bulking agents.

How'd You Get So Sweet?

  Given the universal appeal of sweetness, an understanding of what gives certain compounds that characteristic should prove valuable, especially as the search for alternative sweetener options continues. And while the scientific community believed for years that the hydroxyl (-OH) groups common to sugar molecules gave them their characteristic taste, during the mid-1960s researchers proposed the "AH/B/g theory to explain what makes sweet things sweet. According to this theory, all sweet compounds share a common "saporous" (taste-eliciting) unit composed of "A" and "B" - two negatively charged atoms, often oxygen, nitrogen or chlorine - positioned about 3Å from one another; "H," a hydrogen-bonding proton; and y, a lipophilic region. The theory proposes that the "AH/B" portions of the site hydrogen-bond to corresponding structures on the sweetness taste receptor, and that the compound's lipophilic y site - usually a methylene, methyl or phenyl group - associates itself closely with similar non-polar spots on the receptor as well. This somewhat triangular arrangement between the molecule and the receptor initiates the sweetness response.
  The non-polar y site appears to play a role in potentiating the sweetness of high-intensity sweeteners to a much greater extent than it does for common sugars. This is not surprising, considering the largely polar nature of most sugars. Since the non-polar site differs with each sweet substance, its affinity for the sweetness receptor also changes, eliciting a stronger or less-intense sweetness response and also affecting the time intensity and temporal aspects of the compound's sweetness. Although researchers have a ways to go in detailing this interaction for all sweet compounds, it certainly gives them a start in understanding how foods interact with our taste buds to bring about the response we all seem to enjoy so much.

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Sweetening with sucralose

In contrast to most high-intensity sweeteners, sucralose - a trichloro derivative of sucrose produced from selective chlorination of the sugar's hydroxyl groups - actually comes from sugar. Developed and marketed by McNeil Specialty Products Company, New Brunswick, NJ, through a licensing agreement with Tate & Lyle, PLC, sucralose has found success as Splenda in Canada, Australia and Mexico. In the United States, the FDA announced its approval of sucralose in April 1998. Its makers note that since it comes from sucrose, it has a sucrose-like taste with no unpleasant aftertaste. It's rated at 600 times its parent compound's sweetness, although that value will vary from formulation to formulation. A non-caloric and non-nutritive sweetener, sucralose is excreted from the body unchanged, provides no calories, makes no contribution to tooth decay and has no effect on blood-sugar levels.

Sucralose's excellent heat- and acid-stability makes it perfect for a wide range of products. Stable in the neat form for 18 months at 75°F, it shows its first signs of breakdown as a pink discoloration and a light release of the compound's chlorine as hydrochloric acid. After holding sucralose at 212°F and pHs of 3, 5 and 7 for up to 2 hours, the greatest sweetener loss occurred at pH 7, and only 4%. Not bad, considering that a perceptible decline in sweetness occurs only upon loss of 10% to 15% of the sweetener. Its ability to withstand a range of temperatures also makes it effective in pasteurized, retorted, UHT-processed, baked and extruded products. It readily dissolves in both water and ethanol at a variety of temperatures to yield a uniformly sweet product.

Even though sucralose comes from sugar, its high intensity still means that small enough amounts are used to require bulking agents. Additionally, it has no measurable effect on viscosity, humectancy or water activity, and cannot participate in fermentation or browning reactions. But its clean, sugary-sweet taste, non-nutritive nature and powerful sweetness make it ideal for inclusion in formulations that require sweetness without the calories that often come along for the ride. Given the recent FDA approval, we will likely soon see sucralose used in products such as baking mixes and baked goods, beverages and beverage mixes, confections, dairy products, puddings and fillings, jams, syrups, and even as a home-use sweetener.

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All about alitame

Alitame, although still pending FDA approval, has sweetened products in Australia and Mexico since 1993 and 1994, respectively. This protein-based sweetener belongs to a class of compounds called the L-a-aspartyl-D-alanine amide series in which the alanine carboxyl group serves as an amide in 2,2,4,4-tetramethyl-3-thietanyl amine amide - a compound thankfully called a "novel amine" by Pfizer, the company that developed the sweetener. Alitame's clean, sweet, sugar-like taste reportedly owes itself to this novel amine. It has been used in a broad range of applications including baked goods, fruit beverages and home-use sweeteners.

At an estimated 2000 times sucrose's sweetness, tiny amounts of alitame provide the same sweet taste as considerably larger amounts of other sweeteners - even the high-intensity ones. Furthermore, although FDA will likely classify it as a nutritive sweetener along with other protein-based sweeteners, the human body only partially metabolizes alitame's alanine amide, resulting in a calorie contribution of just 1.4 kcal/g.

This obviously means that bulking agents must accompany alitame in formulations, and that the sweetener only makes a negligible contribution to viscosity and mouthfeel. As a humectant, water-activity reducer and substrate for fermentation and browning reactions, alitame also falls short, but most developers of artificially sweetened products believe that the low-calorie/high-sweetness level of these sweeteners more than makes up for the other functionalities they lack.

And while alitame may not give the brown notes or thicker mouthfeel of sugar, its solution stability nears the maximum for aspartic acid dipeptides. At a neutral pH range - from 6 to 8 - it remains stable for about one year at room temperature. However, in acidic conditions, alitame may develop off-flavors. Though holding it at higher temperatures in the neutral range will reduce the shelf life somewhat, alitame still exhibits enough stability at elevated temperatures to allow its use in confections, heat-pasteurized products and bakery goods. Its high solubility and stability in solution mean that concentrated solutions of alitame can increase production flexibility. Because alitame is a white, odorless, non-hygroscopic powder, those in both product development and production can appreciate its easy incorporation into products.

Consumers will appreciate its safety as well. Extensive safety studies have found alitame "safe for its intended use as a component of the diet of man." Its three major decomposition products - an a-aspartic isomer of alitame, aspartic acid and alanine amide - all have no detectable taste of their own and, more importantly to the oft-leery public, pose no apparent health risks.

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On the horizon

All the action in high-intensity sweetener research and development should leave product designers hungry for a taste of the sweeteners to come, and a number of options are currently in the works.

The Monsanto Company has submitted a petition to FDA to approve neotame for use as a sweetener in any food or beverage sold in the United States. The FDA got its first taste of neotame in 1997 when Monsanto asked it to approve the sweetener for home use, and the company hopes to introduce their new product to other areas of the world in 1999 as well.

Although the company has remained tight-lipped about the product, it reportedly has a naturally sweet, sugar-like taste; provides no calories; and, at about 8000 times sucrose's sweetness, requires significantly lower usage levels than all other current sweeteners. The company also cites its ability to enhance some food and beverage flavors, giving product designers more formulation flexibility and potentially leading to entirely new-tasting products.

Another sweetener, thaumatin (brand name Talin), comes from the Sudanese katemfe fruit, also known as the "miraculous fruit." Thaumatin has 750% to 1600% sucrose's sweetness, according to some estimates. The small protein contributes 4 kcal/g, but its intense sweetness means that sweetening levels of thaumatin contribute essentially no calories.

Thaumatin's protein has disulfide bridges that confer stability at pHs ranging from 2 to 8 and under canning, pasteurization and UHT temperatures. When freeze- or spray-dried, it can remain stable indefinitely under ambient conditions. However, its electrostatic activity causes undesirable instability in colors, and its combination with the anionic polysaccharides in fruit juices leads to coagulation, precipitation and fading. To forestall these reactions, a form of thaumatin crystallized with gum arabic has proven relatively effective.

In addition to synergizing with sugars and other high-intensity sweeteners, thaumatin has the unique property of enhancing both sweet and savory flavors and smoothing sharp and bitter coffee and peppermint notes at concentrations as low as 0.1 to 0.5 ppm. It can also mask bitter, metallic aftertastes associated with vitamins, minerals and even other high-intensity sweeteners like saccharin. However, thaumatin itself can have an unusual licorice aftertaste that may require its own masking ingredient. While processors in the United Kingdom, Europe, Australia, Canada, New Zealand, South Africa and Japan already use thaumatin in a wide variety of applications, the United States currently permits its use only as a flavor enhancer in chewing gums.

Another sweetener, stevioside, is championed by natural-foods advocates in the United States and is used in several countries, most notably Japan. Stevioside comes from the leaves of the stevia plant (Stevia rebaudiana Bertoni), a perennial shrub of the Asteraceae (Compositae) family native to Brazil and Paraguay. Stevia contains sweet-tasting glycosides, mainly stevioside; but also rebaudiosides A, B, C, D, and E; dulcoside A; and steviolbioside. Stevioside has a slight bitter aftertaste and provides 250 to 300 times the sweetness of sugar. It is stable to 200°C (392°F), but it is not fermentable and does not act in browning reactions.

In the 1970s, the Japanese government approved the plant for use in food. Japanese food processors use stevioside in a wide range of foods: pickled vegetables, dried seafood, soy sauce and miso, beverages, candy, gums, baked goods and cereals, yogurt, ice cream, and as a tabletop sweetener. In salty applications, stevioside modifies the harshness of sodium chloride. Combining it with other natural and synthetic sweeteners improves taste and functionality.

FDA considers stevia leaves and stevioside as unapproved, non-GRAS food additives. In 1992, the American Herbal Products Association (AHPA) petitioned the FDA to declare stevia as GRAS, citing historical usage and referring to numerous toxicology studies conducted in Japan and other countries. The FDA rejected AHPA's petition, contending inadequate evidence to approve the product. The agency does allow the herb to be used in dietary supplements as covered by DSHEA (Dietary Supplement Health and Education Act).

Given the growth in intense sweetener use, we may soon see these new sweeteners popping up in many more products and product categories. As consumers learn more about their sweetener options, and about the benefits that those options provide, product designers can count on a growing demand for the sweet things in life.

Kimberly Decker, a California-based technical writer, has a bachelor's degree in consumer food science with a minor in English from the University of California-Davis. She lives in the San Francisco Bay Area, and enjoys cooking and eating food in addition to writing about it.

© 1999 by Weeks Publishing Company

Used with permission from Food Product Design Magazine

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