Food technologists now have more sweeteners from which to choose than ever before. With the obesity epidemic and the public attention it currently receives, plus the increasing interest in foods with added benefits, sweeteners that allow for consumer-appealing labeling are of particular interest.
These sweeteners fall into two basic categories: those which are essentially calorie free, often referred to as low-calorie or intense sweeteners, and those which are significantly reduced in calories, which may be referred to as reduced calorie-sweeteners, bulk sweeteners, or sugar replacers. These sweeteners when used alone or in combination may permit such labeling as “low-calorie,” “reduced-calorie,” “light,” “sugar-free,” and “does not promote tooth decay.”
The ideal sweetener does not exist. It would be at least as sweet as sucrose and provide the same properties to a product as sucrose, with processing parameters similar to those of sucrose so that existing equipment can be used. It would be colorless, odorless, and noncariogenic, with a clean, pleasant taste, and have immediate onset and not much lingering. Solubility and stability are important. The ideal sweetener must be compatible with a wide range of food ingredients because sweetness is but one element of a complex food flavor system. Even sucrose is not perfect, being unsuitable for some applications.
There are therefore real advantages to having a number of sweeteners available. With several available, food manufacturers can use sweeteners in the applications for which they are best suited, and limitations of individual sweeteners can be overcome by using them in blends. Most sweeteners, including the polyols, are synergistic, so the sweetness of sweetener blends is greater than the sum of the individual parts. In addition, there is considerable research, including a soon-to-be published study by Duke University’s Susan Schiffman, demonstrating that blends of multiple sweeteners present improved flavor profiles.
The first commercial sweetener blend was saccharin and cyclamate. The primary advantage of this blend was that saccharin (300 times sweeter than sucrose) boosted the sweetening power of cyclamate (30 times sweeter than sucrose), while cyclamate masked the aftertaste some people associate with saccharin.
Today, blends are frequently used. For example, in the United States, diet fountain soft drinks are generally sweetened with a combination of aspartame and saccharin, while in other parts of the world soft drinks may contain as many as four sweeteners. Sugar-free gums and candies contain combinations such as saccharin/sorbitol and acesulfame potassium/isomalt.
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When choosing a sweeteners, many things need to be considered. What is the goal? For example, are you trying to reduce calories, increase sweetness, reduce sweetness, or replace the sugar in a product? Is labeling, such as “reduced calorie” or “sugar free,” important? Do you want the finished product to have essentially the same taste and appearance as a traditional product? If so, not only taste, but also texture and bulk are especially important. How long a shelf life is required? Some sweeteners may not hold up well in an acidic product over time. Will the product require baking or heating? Some sweeteners may break down at prolonged high temperatures, while others may develop a metallic taste when heated. What other ingredients does the product contain that might interact with the sweetener? Some sweeteners enhance fruit flavors. Is this important to your new product?
It is important to remember that in developing low-calorie products, low-calorie sweeteners cannot be simply substituted for sugar. Products must be reformulated. The various sweeteners interact differently with other food ingredients, so the flavoring acid/sweetness ratio may require modification. And, of course, low-calorie sweeteners do not provide bulk.
Approved Low-Calorie Sweeteners
Four low-calorie sweeteners are currently approved by the Food and Drug Administration for use in the U.S.
• Acesulfame potassium (acesulfame K) is approved for use in a wide range of products, including tabletop sweeteners, desserts, puddings, baked goods, candies, and soft drinks. A petition was recently filed with FDA for its use as a general purpose sweetener and flavor enhancer. It dissolves readily in water, even at room temperature, and is very stable, with virtually no change in concentration observed in the pH range common for foods and beverages after several months. Beverages containing acesulfame K can be pasteurized under normal pasteurization conditions without loss of sweetness. Decomposition in baked goods is only found at temperatures well over 200°C. It blends well with other sweeteners and is especially synergistic with aspartame and sodium cyclamate but less so with saccharin. Prior to approval, acesulfame K was the subject of a comprehensive safety evaluation program that confirmed its safety.
• Aspartame is approved for general use in the U.S. and therefore may be used in any product where a standard of identity does not preclude its use. For example, if a standard called for a “nutritive carbohydrate sweetener,” aspartame would not be appropriate. However, it could be used in a product whose standard calls for a “nutritive sweetener”—although it technically has 0.4 kcal/g, as used it provides essentially no calories because it is 200 times sweeter than sugar.
Studies have demonstrated that the taste profile of aspartame closely resembles that of sucrose. It enhances various food and beverage flavors, especially fruit flavors. Although aspartame may hydrolyze with excessive heat, it can withstand the heat processing used for dairy products and juices, aseptic processing, and other processes in which high-temperature, short-time and ultra-high-temperatures are used.
Aspartame is slightly soluble in water, sparingly soluble in alcohol, but not soluble in fats or oils. Under dry conditions, it has good stability. In liquids under certain conditions of moisture, temperature, and pH, it may hydrolyze, resulting in loss of sweetness.
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No adverse health effects related to aspartame have been demonstrated, but this has not stopped its critics. Inaccurate information about aspartame has been circulating, especially on the Internet, associating aspartame with any number of diseases. This misinformation has prompted a number of responses. FDA has stated that aspartame is one of the most thoroughly tested food additives ever submitted to the agency and “All of the early testing in animals and human subjects conducted to support the safety of aspartame as well as the well-designed and conducted studies subsequently performed to assess whether aspartame might mediate a number of anecdotally reported symptoms have reinforced the appropriateness of FDA’s approval and regulation of aspartame as a safe food additive.”
Most recently, the French Food Safety Agency conducted an extensive review of aspartame, prompted by negative allegations about it, and determined that there is no scientific data to support these allegations.
• Saccharin is approved in the U.S. as a special dietary sweetener. It is commercially available in three forms: acid saccharin, sodium saccharin, and calcium saccharin. Sodium saccharin is the most commonly used form because of its high solubility and stability. Calcium saccharin, however, might be chosen for a “sodium-free” product. In its bulk form, saccharin and its salts have been shown to be stable for several years. In aqueous solutions, saccharin demonstrates high stability over a wide pH range.
Saccharin has been available for more than 100 years. In 1977, FDA proposed banning it, on the basis of controversial high-dose rat studies in which rats fed the human equivalent of sodium saccharin in hundreds of cans of diet soft drinks each day for a lifetime developed bladder tumors. Congress placed a moratorium on the proposed ban but required saccharin-containing products to bear a warning label indicating that saccharin had been shown to cause tumors in laboratory animals. In 1991, FDA withdrew its proposal to ban. In 2000, the U.S. National Toxicology Program delisted saccharin from its list of potential carcinogens, and, as a result, Congress removed the saccharin warning label requirement.
• Sucralose also has been granted U.S. approval as a general-purpose sweetener. The sweetest of the currently approved sweeteners (600 times sweeter than sucrose), it has a clean, quickly perceptible sweet taste. Its excellent chemical and biological stability, both dry and in aqueous solution, allows for its use essentially anywhere sugar is used, including cooking and baking. The solubility and aqueous stability of the sweetener allow for sucralose to be provided as a liquid concentrate for industrial use. This product provides an extremely stable ingredient system compatible with most food operations. Studies in model food systems, confirmed by actual product use, demonstrate that sucralose can be used in dry food applications, with no expectation of discoloration when food products are handled in normal food distribution systems.
Sucralose is being used in a broad range of products. The actual use level varies with the sweetness level desired and the other ingredients and flavor system used in the specific formulation. It has been thoroughly tested in more than 100 studies over a 20-year period and found to be safe. It passes rapidly through the body virtually unchanged.
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Low-Calorie Sweeteners Pending Approval
Three additional low-calorie sweeteners—alitame, cyclamate, and neotame—are pending approval by FDA. Of the three, neotame is expected to be approved first.
• Neotame is a both a low-calorie sweetener and a flavor enhancer. It is structurally similar to aspartame but 30–60 times sweeter—or 7,000–13,000 times sweeter than sucrose. Neotame is stable across a wide range of applications. It is similar in stability to aspartame but has greater stability in baked and dairy products. Neotame’s clean, sweet taste is maintained over the range of concentrations required for numerous food and beverage applications. It extends both sweetness and flavor in confectionery applications, such as sugar-free chewing gum, and its onset and linger are similar to those of sucrose in applications such as powdered soft drinks. It is soluble in ethanol, and its solubility increases in both water and ethyl acetate with increasing temperature. It dissolves rapidly in aqueous solutions, since very little is needed as a result of its intense sweetness.
Extensive research has been conducted confirming neotame’s safety for human consumption. FDA is evaluating neotame for general use and may approve it as a sweetener and flavor enhancer in the not-too-distant future.
• Alitame is formed from the amino acids L-aspartic acid and D-alanine, with a novel amide moiety (formed from 2,2,4,4-tetramethylthienanylamine). This novel amide is responsible for the intense sweetness of alitame, 2,000 times that of sucrose. Alitame’s sweetness is described as sucrose-like, without bitterness or metallic notes. It is a crystalline, odorless, nonhygroscopic powder that is very soluble in water at the isoelectric pH. Excellent solubility is seen in other polar solvents, as well. This sweetener is sufficiently stable for use in hard and soft candies, heat-pasteurized foods, and neutral-pH foods processed at high temperatures, such as sweet baked goods.
Alitame is compatible with a wide variety of freshly prepared foods. It can undergo chemical reactions with certain food components. For example, high levels of reducing sugars, such as glucose and lactose, may react with alitame in heated liquid and semiliquid systems, such as baked goods, to form Maillard reaction products. Similar reactions may be observed when high levels of aldehydes are present. Prolonged storage in liquid beverages may result in off-flavors in the presence of hydrogen peroxide, sodium bisulfite, ascorbic acid, and some type of caramel color at pH values below 4.0. Research is underway to resolve these issues.
• Cyclamate is available for use in more than 50 countries but not currently in the U.S. It is almost always used in combination with other sweeteners. It has a favorable flavor profile and is better able to mask bitterness than sugar. It is compatible with most food ingredients, natural and artificial flavoring agents (enhancing fruit flavors), and chemical preservatives. It is extremely stable at both high and low temperatures, over a wide pH range, as well as in the presence of light, oxygen, and other food ingredients.
Cyclamate is particularly well suited for fruit products because it enhances fruit flavors and even at low concentrations can mask the tartness of some citrus fruits. Canned fruit is one product in which it has been used as the sole sweetener. Cyclamate solutions used for such products have a lower specific gravity and osmotic pressure than sucrose syrups and therefore do not pull water out of the fruit. It is suitable for tabletop sweeteners and beverages. Before it was banned in the U.S., cyclamate was responsible for the popularity of several brands of diet soft drink.
Cyclamate can also be used in gelatins, jams, jellies, and low-calorie salad dressings. With the proper combination of other ingredients to provide bulk and texture, it can be used in baked goods. It also has been used in cured meats. It has a higher melting point than sugar and does not caramelize when fried. For example, cyclamate-cured ham and bacon have improved flavor and color and do not scorch or stick to the frying pan.
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• Stevioside is mentioned here because of the considerable attention it receives from those promoting “natural.” Stevioside may be used as a dietary supplement in the U.S., but it is not approved as a sweetener and no reference to sweetness should be made. Although it is approved in Japan, South Korea, Brazil, Argentina, and Paraguay, both the Food and Agriculture Organization/World Health Organization’s Joint Expert Committee on Food Additives (JECFA) and the European Union’s Scientific Committee for Food have reviewed stevioside and determined that it is not acceptable as a sweetener on the basis of presently available data, which are considered insufficient.
As noted above, the low-calorie sweeteners lack the bulk needed for many products in which they are used. Polyols are often used in combination with the low-calorie sweeteners to provide bulk and improve texture and mouthfeel. There are currently eight polyols available for use in the U.S.
JECFA has evaluated the available data—chemical, biochemical, toxicological, and other—on polyols and determined that the total daily intake of each polyol, arising from its use at the levels necessary to achieve the desired effect, does not represent a hazard to health. For that reason and for reasons stated in the individual evaluations, the committee deemed it not necessary to assign an numerical value for Acceptable Daily Intake (ADI) but instead assigned the most favorable term, “not specified.”
Sugar-free products sweetened with polyols or sugar replacers are reduced in calories but are not calorie free. Based on an evaluation of a large number of studies by the Federation of American Societies for Experimental Biology’s Life Sciences Research Office, FDA allows the use of the following caloric values: 0.2 kcal/g for erythritol, 1.6 for mannitol, 2.0 for isomalt and lactitol, 2.1 for maltitol, 2.4 for xylitol, 2.6 for sorbitol, and 3.0 for hydrogenated starch hydrolysates—compared to 4 kcal/g for sucrose.
These reduced values for polyols are important to the manufacturers of polyol-containing products. Under current regulations, reduced calorie foods must have a 25% caloric reduction from their full-calorie counterparts. In many polyol-containing products, the polyol or a combination of polyols constitutes the principal ingredient. Therefore, with a caloric value of 3 kcal/g or less, the product may be able to make a reduced-calorie claim. For example, products sweetened exclusively with polyols or a combination of polyols and low-calorie sweeteners may bear a “sugar-free” claim. However, unless the product is reduced-calorie (i.e., has at least 25% fewer calories than its traditional full-calorie counterpart), the label must also state that the food is not a reduced-calorie food.
FDA also has authorized the use of the “does not promote tooth decay” health claim for sugar-free food products sweetened with polyols. And the American Dental Association has approved a position statement acknowledging the “Role of Sugar-Free Foods and Medications in Maintaining Good Oral Health.” ADA recognizes that “it is neither advisable nor appropriate to eliminate from the American diet sugar-containing foods that provide necessary energy value for optimal nutrition.” The association recommends, however, “that major efforts be made to promote the use of sugar-free foods or chewing substances in place of sugar-containing foods that involve a frequent intake or repeated oral use. . . . Use of these sugar-free products will contribute to improved oral health.”
• Erythritol is the newest polyol. It is an odorless white crystalline powder with a clean sweet taste. It is approximately 70% as sweet as sugar but provides only 0.2 kcal/g. It is nonhygroscopic and moderately soluble in water. It is stable at high temperatures and over a wide pH range and has a mild cooling effect in the mouth. It is suitable for use in a number of food products, including chewing gum, candies, chocolate, lozenges, fondant, fudge, bakery products, beverages, and tabletop sweeteners.
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• Hydrogenated starch hydrolysates, including maltitol syrups, sorbitol syrups, and hydrogenated glucose syrups, are a family of products found in a wide variety of foods. The term hydrogenated starch hydrolysate can correctly be applied to any polyol produced by the hydrogenation of the saccharide products of starch hydrolysis. In practice, however, certain polyols such as sorbitol, mannitol, and maltitol are referred to by their common chemical names. The term hydrogenated starch hydrolysate is more commonly used to describe the broad group of polyols that contain substantial quantities of hydrogenated oligo- and polysaccharides in addition to any monomeric polyols (e.g., sorbitol or mannitol) or dimeric polyols (e.g., maltitol).
The broad term does not differentiate polyols with different sweetness levels, and it does not identify the principal polyol in the hydrogenated starch hydrolysate. Common names have, therefore, been developed for major subgroups. These common names are usually based on the most common polyol in the hydrogenated starch hydrolysate. For example, polyols that are 50% or more sorbitol are known as sorbitol syrups, and those that are 50% or more maltitol are called maltitol syrups. Polyols that do not have a majority component are referred to by the general term hydrogenated starch hydrolysate.
Hydrogenated starch hydrolysates are 40–90% as sweet as sugar and serve a number of functional roles, including use as bulk sweeteners, viscosity and bodying agents, humectants, crystallization modifiers, cryoprotectants, and rehydration aids. They can also carry flavors, colors, and enzymes. Since they are excellent humectants which do not crystallize, they can be used in the production of sugar-free confections with the same cooking and handling systems used to produce sugar candies. Their excellent humectancy also makes them suitable for baked goods. Also, they do not have reducing groups, thereby minimizing Maillard browning reactions. They are also used to replace sugar in a variety of frozen desserts, since they do not form crystals.
• Isomalt has a sweet taste similar to sucrose and reinforces flavor transfer in foods. It is 0.45–0.6 times as sweet as sucrose and, unlike most polyols, does not produce a cooling effect. Isomalt can replace sugar in many foods, using existing processing equipment without major changes. Hard-boiled candies made with it, for example, can be stamped, filled, pulled, combed, and molded and have very good shelf life. Minor changes in the production of these products are required, since isomalt has lower solubility, a higher melting point, lower viscosity of the melt, and a higher specific heat capacity than sucrose or corn syrup.
Isomalt can also be used in pan-coated products, chewing gum, chocolate, low-boiled candies, ice cream, jams and preserves, fillings, fondant, and baked goods. “Light” baked goods with isomalt require only minimal formulation modifications. Isomalt’s low solubility, low hygroscopicity, and browning reaction should be considered. The final baked product containing isomalt has a sugar-like taste with a long shelf life. Isomalt cookies absorb less water than sugar formulations, so are crisper.
• Lactitol has a clean taste about 0.4 times as sweet as sucrose, without an aftertaste. A low-calorie sweetener also may be needed in some applications to provide the desired sweetness. Lactitol is nonhygroscopic, making it suitable for all applications in which water absorption is a critical issue, such as bakery products, tablets, and panned confections. Since its molecular weight is similar to that of sucrose, its influence on water activity is also similar to that of sucrose (on a dry-weight basis). It is stable in acidic and alkaline conditions and under the high temperatures of food processing. Lactitol is suitable for a wide range of products, from baked goods to frozen dairy desserts.
The prebiotic effects of lactitol have been studied. Lactitol reaches the colon untouched and can be used as an energy source by intestinal microflora. In-vitro studies show that lactitol stimulates the growth of Lactobacillus and Bifidobacteria.
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• Maltitol has many attributes that allow its use in a wide variety of food applications. It is a white crystalline powder with a sweetness profile similar to that of sugar, is substantially nonhygroscopic, and is thermostable. It exhibits a negligible cooling effect and can be used to replace fat as well as sugar, since it provides a creamy texture to brownies, cakes, and cookies. This attribute also facilitates its use in sucrose-free chocolate. Maltitol’s anhydrous crystalline form, low hygroscopicity, high melting point, and stability allow it to replace sucrose in high-quality chocolate coatings, confectionery, bakery chocolate, and ice cream. It is also suitable for granola bars, jams with no added sugar, pie fillings, salad dressings, and spreads. Although maltitol works well with other sweeteners, the use of a low-calorie sweetener is not required because maltitol is nearly as sweet as sucrose.
• Mannitol has long been used in food and pharmaceutical products. It is nonhygroscopic, so it is often used as a dusting powder for chewing gum to prevent the gum from sticking to the manufacturing equipment and wrappers. It also is used a part of the plasticizer system to help maintain the soft texture of the gum. Because of its high melting point (165–169°C), it is used in chocolate-flavored coating agents for ice cream and confections. It has a pleasant taste and does not discolor at high temperatures. FDA requires the statement “Excess consumption may have a laxative effect” on the label of a food if the daily consumption of mannitol in the food might exceed 20 g.
Mannitol is used in tableting applications as a diluent or filler. Because of its chemical inertness, it is one of the most stable tablet diluents available and is most often used in chewable tablets because of its pleasant taste and mouthfeel, as well as its ability to mask the bitter taste of vitamins and minerals, herbs, or active pharmaceutical ingredients.
• Sorbitol has been used in processed foods for half a century as a sweetener, humectant, and texturizing agent. It has a smooth mouthfeel, is 0.6 times as sweet as sucrose, and has a cool, pleasant taste. Its moisture-stabilizing and textural properties are important to the production of confectionery, baked goods, and chocolate, where products tend to become dry or harden. It is very stable and chemically unreactive. It can withstand high temperatures and does not participate in Maillard reactions. It combines well with other food ingredients, including sugars, gelling agents, proteins, and vegetable fats. In addition to the products mentioned above, it functions well in chewing gums, frozen desserts, icings, and fillings.
Sorbitol is affirmed by FDA as Generally Recognized As Safe (GRAS). However, FDA requires that the statement “Excess consumption may have a laxative effect” on the label of a food if the daily consumption of sorbitol in the food might exceed 50 g. Although laxative statements are not required in the U.S. on products containing polyols other than mannitol and sorbitol, polyol manufacturers may recommend that their customers place a similar statement on products the daily consumption of which might be expected to exceed a specified limit.
• Xylitol is used mainly in noncariogenic confections such as chewing gum, candies, chocolates, and gum drops. In both clinical and field studies, xylitol use between meals is associated with significantly reduced formation of new caries, even when participants were already practicing good oral hygiene. It is approved as a direct food additive for foods for special dietary purposes in the U.S.
Xylitol is as sweet as sucrose. Crystalline xylitol provides a significant cooling effect. The cooling effect enhances the perception of mint flavor but is most notable in sugar-free chewing gum, compressed candies, and chewable vitamins. The cooling effect is not perceived in jellies or boiled, transparent candies. Xylitol’s solubility is similar to that of sucrose. It is chemically inert and does not participate in Maillard reactions.
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Other New Sweeteners
There are two new sweeteners also of interest—tagatose and trehalose.
• Tagatose occurs naturally in dairy products, but the commercial product is made via a patented process. It has the bulk of sugar, is almost as sweet, but provides only 1.5 kcal/g. It has the potential for use in many products where sucrose is currently used, such as confections, ice cream, soft drinks, cereals, and meal replacements. It is synergistic with other sweeteners and can be used with low-calorie sweeteners to improve texture and mouthfeel. Its solubility in water is similar to that of sucrose. It is nonhygroscopic, with lower water activity than sucrose. Tagatose-containing products “brown” more readily than sucrose-containing baked goods. It has also been shown to have prebiotic properties.
Under FDA’s GRAS notification system, manufacturers may make a self-determination that a substance is Generally Recognized As Safe, claiming exemption from the premarket or food additive approval requirements. After evaluating the GRAS notification submitted for tagatose, FDA told the manufacturer that it does not object to the manufacturer’s determination of GRAS and that tagatose may therfore be used in the U.S. food supply.
• Trehalose is a multifunctional sweetener found naturally in honey, mushrooms, lobster, shrimp and food produced using baker’s and brewer’s yeast. It is commercially made from starch by an enzymatic process. It is metabolized much like other disaccharides. Trehalose protects and preserves cell structure in foods and may aid in the freezing and thawing process of many food products by assisting in maintaining the desired texture. It is also heat stable. It may be used in beverages, purees and fillings, nutrition bars, surimi, dehydrated fruits and vegetables, and white chocolate for cookies or chips. Because it provides 4 kcal/g and is only half as sweet as sucrose, it is more likely to be used for cell preservation than for sweetness. FDA has issued a letter of no objection to the manufacturer’s self-determination of GRAS status for trehalose.
A Multitude of Choices
As indicated above, there are many sweeteners from which to choose. Most sweetener suppliers are pleased to provide information on how to best use their products, and some provide model formulations and/or blends or customized products for specific applications.
The information in this article is based on chapters in the author’s book, Alternative Sweeteners, 3rd ed., published in 2001 by Marcel Dekker, Inc., New York, N.Y
by Lyn O’Brien Nabors
The author, a Professional Member of IFT, is Executive Vice President, Calorie Control Council, Bldg. G, Suite 500, 5775 Peachtree-Dunwoody Rd., Atlanta, GA 30342