Sweet Without the Sugar - Part One
From Food Product Design Magazine
Table of Contents
Not just a sweet taste
Polyfunctional polyols
The high road
Aspartame and associates
Give a child the choice between snacking on steamed Brussels sprouts or a candy bar, and you can safely guess which item the child will choose. And although as health-conscious adults, we may feel obligated to choose the sprouts, we really want the candy just as much as we did years ago. The expanding choice in sweeteners makes sinfully sweet products much less sinful, with fewer calories and other health benefits. But product designers must examine their needs closely, as a sweetener's role in foods only begins with imparting a sweet taste. Sweeteners add color, structure and bulk, viscosity, water-activity control or fermentation fuel, just to name a few possibilities.
Formulations not only benefit from the sweetness, but from the color development that some sweeteners - particularly sugars - produce. In "Functionality and Use of Bulk Sweeteners in Food and Drink," Andrè Rapaille and Peter de Cock of Cerestar Europe's Food Center in Belgium note that: "Browning, an important functional property, is the result of the reaction between the reducing groups of carbohydrates and amino acids (Maillard reaction), and affects the application's taste and colour." The extent of browning depends on the reducing sugars involved in the reaction, and this makes sweetener choice critical in determining whether a product develops caramelized colors and flavors. Furthermore, the higher the product's pH, the more rapidly sugars brown, making it wise to keep the reaction in check by acidifying the formulation. Because many of the new breed of sweeteners do not contain reducing sugars, or in fact, any sugars at all, such a reaction will not take place. Finished products will then lack the characteristic color and flavor of a sucrose-containing formula.
In addition to providing color and flavor, some sweeteners help build a product's structural foundation and add bulk. Low-moisture cookies made with a synthetic sweetener instead of sugar are fragile and crumble easily, because normally a sugar matrix encases the starch and fat droplets to hold the cookie together. As for bulk, sugar can represent up to 50% of the dry weight of some cakes, so replacing it with a high-intensity sweetener leaves a significant deficiency in mass.
Just think of the thick, smooth consistency of items such as syrups, shakes and icings - the sweetener plays a critical role in making that viscous mouthfeel possible. Related to its viscosity, a sweetener's humectant properties also serve an important purpose. Many of the same sugar syrups that give products their thick mouthfeel have long polysaccharide chains that resist water evaporation in even the driest atmospheres. As such, these humectant sweeteners maintain the product's soft, moist texture. This adds up to an extended shelf life both organoleptically - it keeps its fresh texture longer - and microbially, since the water binds with the sugars to lower water activity and forestall microbial growth.
For alcoholic beverages and yeast-leavened baked goods, sugar provides an ideal source of fermentable carbohydrates. Since yeasts preferentially ferment some carbohydrates over others, processors must carefully select which sweeteners to use. Obviously, yeasts cannot ferment non-carbohydrate artificial sweeteners, but perhaps less obvious is their inability to ferment sugar alcohols or lactose. This narrows the sweetener choices, but it does not mean product designers cannot successfully devise a creatively sweetened product.
The polyols, or sugar alcohols, include: xylitol, derived from xylose; lactitol from lactose; mannitol from mannose; and others. Each is produced by the catalytic hydrogenation to alcohols of the parent sugar's reducing groups. According to Graeme Locke, technical manager, Cultor Food Science, England, "The structure is virtually exactly the same as the original sugar, except you have -OH groups instead of the reducing groups you would have on the sugar." While this gives sugar alcohols a strong functional resemblance to their parent saccharides, their lower caloric values and non-sugar nature make them suitable for use in reduced-calorie or sugar-free applications.
Taste intensity of this sweetener class ranges from relatively low to equivalent with sucrose. Xylitol has the same sweetness intensity as sucrose and a very similar sweetness profile, with just a slightly earlier onset and demise of sweetness. Maltitol follows xylitol with an intensity of about 75% that of sucrose. Sorbitol, mannitol and isomalt (the latter composed of both sorbitol and mannitol) check in at around 50% to 60% of the standard. Lactitol, on the other hand, only has about 30% to 40% sucrose's sweetness. But, Locke says, this can be of benefit when formulating reduced-sweetness products, such as some jams and confections. And in other applications, combining lactitol with high-intensity sweeteners provides the correct intensity. However, this combination does not create a synergy, just a simple additive sweetness.
Sugar alcohols stand apart from sucrose and most other sweeteners due to their negative heats of solution, which leave a pleasant cooling feeling in the mouth. Xylitol, with the highest negative heat of solution, enhances cool flavors to make it particularly applicable in chewing gums and mints. In comparison, lactitol's and isomalt's more positive heats of solution reduce the cooling effect. Anhydrous lactitol, lacking the water of crystallization associated with lactitol monohydrate, has such a slight cooling effect that it works well in chocolates, sweetening the product without a strong cooling sensation that might seem unusual.
Product designers using sugar alcohols need not stop at chocolates and mints, especially since many exhibit the same functionalities as sugars, and have improved stability characteristics to boot. For instance, Locke notes that "Lactitol really is quite universal. Use it anywhere you'd be using sugar. Its actual properties, its viscosity, its solubility, and the effect it has on the freezing point and boiling point of water or sugar solutions are very similar to sugar." Five-carbon xylitol, on the other hand, has a lower molecular weight than sugar and thus a lower viscosity and diminished effect on freezing and boiling points. But for the most part, as bulk sweeteners, polyols can replace sugar's volume in a formula without added bulking agents.
While individual viscosities vary with molecular weight, larger molecules, such as lactitol, contribute the same texture and mouthfeel to products as do traditional sweeteners. As humectants, the ability of some polyols to retain moisture makes them efficient plasticizers in gums and chewy candies, and they also maintain moisture in baked goods. In addition to lowering freezing points in frozen desserts, polyols such as sorbitol have long served as cryoprotectants in protein products like surimi, where they prevent low-temperature protein denaturation. Sugar alcohols also increase a product's osmotic pressure, thus reducing water activity and microbial load. The degree depends on the individual polyol, as does the tendency to crystallize out of solution. Some polyols, such as mannitol, have very limited solubility.
Food-manufacturing microorganisms ferment polyols to a negligible degree because of the latter's hydrogenated nature. This makes them poor choices for yeast-leavened items or alcoholic fermentations. And since hydrogenation removes polyols' reducing groups, they do not contribute to Maillard reactions to any extent - actually a plus for lightly baked foods and brightly colored candies.
When stability issues limit the variety of sugars used in certain high-temperature or low-pH systems, the lack of reducing carbonyl groups on polyols renders them chemically and physically more stable than their related saccharides. "They are therefore not sensitive to pH, temperature or light unless heated to very high temperatures that you usually don't find in food applications," notes Locke. So even high-boil candies produced with polyols can reach elevated temperatures without taking part in unwanted reactions or incurring caramelized notes.
Sugar alcohols also possess unique health benefits. They sweeten products while allowing for "no sugar added" claims on ingredient legends. And the same hydrogenation that bars them from food fermentations also makes them unsuitable for fermentation by plaque-causing bacteria in the mouth. Their non-cariogenicity makes them perfect for tooth-friendly applications. In particular, according to Locke, "Xylitol itself is actually what is known as cariostatic. So when it's used in chewing gums or in mouthwashes, it actually helps to prevent dental caries caused by Streptococcus mutens - not just stop them, but prevent them."
Their incomplete absorption and metabolism in the human body give polyols lower caloric values than carbohydrates, although the exact value assigned depends on which government you ask. The United States and Japan assign specific caloric values to each polyol: xylitol has 2.4 kcal/g and lactitol has 2.0 kcal/g, compared to 4.0 kcal/g for sugar, for example. However, the European Union considers all sugar alcohols as contributing 2.4 kcal/g. In any case, this adds up to a considerable caloric savings, making the sweeteners winning choices in consumers' and product developers' eyes. One note of caution for product developers: When consumed at levels above 50 grams per day, polyols have a laxative effect, so remember - moderation!
| The Incredible Bulk When substituting sugar in a formula with a high-intensity sweetener calls for a bulking agent to make up for sugar's lost volume, formulators have a number of choices. One option, polydextrose, has the distinct advantage of having only 1 kcal/g, making it appropriate for addition to reduced-calorie products. A polymer of long-chain dextrose with sorbitol as either some or all of its end groups, its low caloric value results from partial fermentation by microorganisms in the large intestine to volatile fatty acids. The human body can derive energy from these fatty acids in only the most inefficient way, allowing this form of polydextrose to contribute just 1/4 the calories of an equal amount of any other carbohydrate. In this respect, polydextrose resembles a typical dietary fiber, and some markets in the world do legally consider it a fiber, according to Jim Kappas, business manager, bulking agents, Cultor Food Science, England. But it serves mainly as a more functional ingredient. "There are uses for polydextrose that are what we call 'functional uses,' where it's not there to make a label claim per se, but just to be present as a humectant, a moisture barrier, or a cryoprotectant," says Kappas. And these functions relate to polydextrose's ability to hold water within a system. As a very large-molecular-weight molecule, it can also contribute noticeable viscosity to products. Since it adds no sweetness of its own, "It can be easily incorporated into applications that require less sweetness, such as savory products and less-sweet confections," notes Graeme Locke, technical manager, Cultor Food Science. And its lack of sweetness makes it compatible with both high-intensity sweeteners and polyols. When combined with the latter, its positive heat of solution and mild palate-warming help balance the polyols' cooling effect. This effect improves the flavor of sugar-free chocolates sweetened with lactitol or other sugar alcohols, with the balanced flavor similar to that of traditionally sweetened chocolate. In combination with non-browning ingredients like sugar alcohols and high-intensity sweeteners, the residual reducing groups in some of Cultor's Litesse; polydextrose products will participate in the Maillard reaction, making it useful in baked goods, sugar-free caramels and toffees, and other items that benefit from the caramelized colors and flavors that the Maillard reaction brings. Incredible bulk, indeed! |
A number of new sweeteners have begun vying for the regulatory approval to satisfy America's somewhat conflicted calorie-conscious sweet tooth. The earliest high-intensity sweeteners often fell short of sugar in taste, stability and consumer favor. Indeed, that "saccharine" has become synonymous with "cloyingly sweet and artificial" must have something to do with how people perceive it and other synthetic sweeteners.
Not until the introduction of NutraSweet; brand aspartame in the early '80s did the real sweetener revolution begin in earnest. This and other high-intensity sweeteners have the distinct advantage in today's weight-concerned society of providing sugar's sweetness without its calories. Some non-nutritive sweeteners escape the body's metabolism to yield no caloric energy, while others have such a high sweetness intensity that the amount needed to sweeten a product adds essentially negligible calories.
While artificial sweeteners provide many of sugar's taste benefits, they still cannot mimic some of sugar's functionalities. Many product developers have found that non-carbohydrate sweeteners have a hard time imitating sugar's more viscous mouthfeel. But fortunately, texture does not play as important a role in some products as it does in others. Angela Miraglio, manager, trade/marketing communications, Monsanto Nutrition and Consumer Sector, Chicago, notes that, for example, diet soda users can actually develop a preference for the "thinner" effect that results from using high-intensity sweeteners in those products.
Despite some functional drawbacks to using high-intensity sweeteners as substitutes for sugar, product developers cannot ignore their many advantages - not the least of which is their ability to sweeten products without adding significant calories. And in terms of nutritional and health benefits, the range of choices for those on restricted diets has undoubtedly changed the lives of many who previously could not enjoy the sweet life. Studies have shown that artificial sweeteners, such as aspartame, do not interfere with blood glucose concentration, making them a boon to diabetics.
Like sugar alcohols, most high-intensity sweeteners have minimal or no cariogenic effect. And although artificially sweetened foods cannot turn a heretofore unhealthy diet into a balanced one, when consumed as part of a healthy eating plan, they can facilitate and help maintain weight loss in obese individuals. "So if you've done a good job of formulating a product, you can end up with reduced-calorie claims as well as claims of being sugar-free or reduced-sugar depending again on the food system," says Miraglio.
Consumers now generally perceive these products as posing no real health threat. Whereas not too long ago, artificial sweeteners had the stigma of causing cancer in laboratory animals (due to studies on saccharin and some others that are under question on cyclamates) most people are aware of the rigorous safety-testing required before achieving FDA approval. Save for danger to phenylketonurics from consuming the phenylalanine in aspartame, high-intensity sweetener users need not worry about any health risks.
Although not so popular in the United States as abroad, the combination of some high-intensity sweeteners with others or with sugar itself proves that those sweeteners add up to more than just the sum of their parts. Indeed, some combine in very synergistic ways, by enhancing the other's sweetness, balancing out any bitter aftertaste or picking up sweetness intensity at the point when the other leaves off.
Of all the high-intensity sweeteners, aspartame has enjoyed some of the widest success since the real surge in the category's popularity began. It has found its way into more than 5000 products worldwide to date. Aspartame - a methyl ester of the dipeptide L-aspartyl-L-phenylalanine - is actually a nutritive sweetener and, like other proteins, contributes approximately 4 kcal/g. But its high-potency sweetness lets a little go a long way without adding many calories.
Just how sweet is aspartame? According to Miraglio, "The bottom line is that the potency is a range that we don't even quote anymore." Many factors in the whole food system enter into the equation, but for product developers' purposes, most sources rate aspartame at around 200 times as sweet as sucrose, although that figure varies with the formulation. With a sweet, clean taste that lacks bitter or metallic notes, aspartame can successfully sweeten many products, from cold cereals, chewing gums and yogurts to frozen desserts, soft drinks and even baked goods. In addition to potency, a sweetener's temporal profile also comes into play, and aspartame's involves a slower onset and a sweet aftertaste that make it an improvement over more-bitter options. Its ability to enhance and extend tart fruit flavors makes it great for fruity beverages and yogurts.
When it comes to serving as a substrate for browning or fermentation, lowering water activity, or contributing to a product's structure, aspartame simply does not cut it. "Since the sweetener intensity permits its inclusion in products at very low usage levels, depending on the food system, that lack of bulk you have when substituting intense sweeteners for sugar forces you to find some replacement," Miraglio says. Developers can turn to polydextrose or maltodextrins to build structure. These compounds also often enhance the product's textural characteristics. But when used in large enough amounts, many bulking agents have flavors and caloric contents that can significantly alter the product's profile. "So, depending on the food system, you might find yourself having to overcome a taste profile that's being given by one of the ingredients that you're adding simply for bulk," says Miraglio.
It might be difficult to evenly disperse such small amounts of sweetener throughout the product, so agglomeration and coating systems can facilitate aspartame's incorporation into the system.
Product developers once only dreamed about subjecting aspartame to high heat, since it breaks down and loses sweetness at high temperatures. However, the early 1990s saw FDA approval for the encapsulated form of the sweetener, NutraSweet Encapsulated 20, in baked goods. "It protects the aspartame during the heating process so that it does not break down, and then it releases it toward the end of baking so that you get the sweetness that you want," Miraglio says.
Aspartame's stability also varies with time, moisture and pH as well as with temperature. As pH moves above or below 4.2, aspartame's stability declines. Encapsulation protects it somewhat, but upon release from the coating, it gets exposed to the pH and moisture in the system.
Click here to read Sweet Without the Sugar - Part Two.
© 1999 by Weeks Publishing Company
Used with permission from Food Product Design Magazine
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