The unique flavoring compounds found in the leaves of the stevia plant have been growing in popularity. Datamonitor, New York, reported that, of the more than 600 stevia-sweetened products launched worldwide between October 2010 and September 2011, more than 300 of them were in the United States. And, according to an August, 2011, report from Mintel, Chicago, sales of stevia-extract-containing products are projected to reach $1.2 billion by the end of 2013.
Wade Schmelzer, principal food scientist, health and nutrition, Cargill, Minneapolis, suggests three main trends driving growth in stevia use. “First is the natural ingredient benefit that offers food and beverage manufacturers the ability to make ‘naturally sweetened with’ claims on their products," he says. "Second, with rising obesity and diabetes rates, nearly every manufacturer is looking for solutions to reduce sugar without sacrificing taste. Finally, as the economics of stevia products have improved, there has been a greater uptake among customers in a range of brands."
A sweet discovery
The term “stevia" has come to be used as a general term for sweetening agents derived from a South American plant called ka'a he'ê (sweet herb). Used for centuries to sweeten yerba-mate teas and medicinal beverages, and chewed for a sweet treat, it was not until the 1900s that the plant was scientifically classified as Stevia rebaudiana Bertoni, after the Swiss scientist who “discovered" it, Moises Santiago Bertoni.
Stevia’s sweetening power comes from a family of compounds called steviol glycosides—sugar molecules (glucose, rhamanose and/or xylose) connected in varying numbers and configurations around a steviol core. The several known steviol glycosides provide variations in taste profiles and sweetness levels from 50 to 400 times that of sucrose. The most prominent steviol glycosides in stevia leaves are stevioside and rebaudioside A (reb A). And, while stevioside is the most predominant, at approximately 9%, an additional sugar moiety makes reb A the sweetest. Other steviol glycosides include rebaudioside B, C, D, E and F, steviolbioside and rubusoside.
Modern steviol glycoside extraction mirrors traditional use. “In general, stevia is extracted from the leaves by a steeping process in water, then purified through an alcohol crystallization process, then further clarified and dried," says Ron Deis, Ph.D., director, global sweetener development, Ingredion Incorporated, Westchester, IL,
Stevia extracts consist of one or more steviol glycosides. “The first stevia products allowed on the market in the United States (via GRAS or self-GRAS process) were equal or greater than 95%, and equal or greater than 97% reb A, with the remaining percentage as stevioside and other steviol glycosides," Deis says. “Secondary petitions were added for use of equal or greater than 95% steviol glycosides for certain applications, with the majority of this being stevioside and reb A."
Modern stevia extracts provide clean, sugar-like taste without the subtle licorice notes associated with less-refined products of the past. In addition, stevia-extract powders offer excellent shelf life and stability to pH, temperature and light.
Stevia wonder
Most frequently used in powdered form, stevia extracts exhibit good stability under storage and processing conditions. Reb A has been shown to remain stable through dairy-product pasteurization processes and baking processes as high as 390F. Stability in acidic beverages is good through typical commercial processes, with degradation being observed only when pH is less than 3, and temperature exceeded 40C. Reb A is also stable to light.
“Reb A is usually used to reduce sugar and calories in formulations, so it is often used in combination with nutritive sweeteners, such as sucrose and fructose," Deis says. “For most of the beverage and dairy applications we have worked with, reb A is generally used in the less than 100 to 300 ppm range. Keep in mind that we are generally replacing 25% to 50% of the sugar in formulations. At the levels used, we have not encountered any adverse ingredient interactions."
In fact, stevia is more commonly used in conjunction with other sweeteners than as a single sweetness source. “Stevia extracts, like other high-potency sweeteners, can work well with other high-potency sweeteners or bulk sweeteners to modify the overall sweetness profile," Deis says. "Combinations can change peak sweetness timing or modulate lingering sweetness, and combinations can attenuate any off-flavors or bitterness."
Stevia extracts partner well with polyols, especially in systems where removing sugar can affect texture, as well as taste. Erythritol, at approximately half the sweetness of sugar, gets a flavor boost from stevia, while masking potential off-notes and lingering sweetness, and providing bulk replacement. Similarly, the combination of stevia and isomalt yields a distinct sugarlike taste and mouthfeel.
Stevia is also finding synergy with mogrosides, the sweet elements found in monk fruit. Around 200 to 250 times sweeter than sugar, monk fruit extracts are gaining popularity due to consumer-friendly labeling options such as “monk fruit concentrate," or “sweetened with fruit extract." Working in tandem, reb A’s intense initial sweetness is complemented by mogroside-V’s weak initial flavor and pleasant late taste.
Leafing through the regs
As with any relatively new ingredient, the regulatory guidelines can be confusing, especially when considering products for export. “In 2008, in response to Generally Recognized as Safe (GRAS) notifications submitted to the U.S. Food and Drug Administration (FDA), the FDA stated it has no questions regarding the conclusion of expert panels that rebaudioside A is GRAS for use as a general purpose sweetener in foods and beverages, excluding meat and poultry. In 2011 the EU authorized the use of steviol glycosides as a sweetener in foods and beverages," Deis says. “Stevia sweeteners are approved for use in many other countries, including Korea, Mexico, Taiwan, China, Russia, Australia, Argentina, New Zealand, Colombia, Peru, Uruguay, Brazil and Malaysia."
