Reb A is no sugar — for better and for worse. Formulators can benefit from the advice of Greg Horn, who details how to overcome every taste challenge known to stevia
Stevia extracts have the potential to be the holy grail of sweeteners. They deliver on two key attributes that are important to consumers — being natural and having no calories.
But a third attribute that is even more important to consumers is taste. Here stevia is challenged, burdened as it is with the inherent taste issues of delayed onset of sweetness, low maximal response, bitterness and lingering sweetness. Only by correcting these issues will consumers further embrace this new sweetener. Because these are very diverse issues, the optimal solution is not a single ingredient. A combination of several tools employing different technologies is needed to deliver great-tasting food and beverages.
The World Health Organization estimates that there are more than one billion people globally who are overweight, 400 million of whom are obese. Unfortunately, these numbers are expected to nearly double by 2015. Governments are putting pressure on the food industry to offer products with reduced calories.
Using blends with stevia
Blending stevia extracts with sugars offers one solution to this epidemic. Stevia extracts are synergistic with sugar. The sugar provides the upfront sweetness and mouthfeel that stevia extracts lack. When using stevia extracts alone to sweeten a food product, proportionally more and more stevia extract must be used to increase the sweetness. Blending caloric sweeteners with stevia offsets this issue of stevia's low maximal response to sweetness and so products can be developed with high degrees of sweetness. Additionally, by using lower stevia-extract levels, the product has significantly less bitterness and licorice off-notes coming from the stevia.
Sugars add bulk and smooth mouthfeel as well as sweetnees. When sugars are replaced with stevia extracts that are typically used at only 0.02 to 0.06 percent of the sugar's original mass, the formulator needs to add back a bulking agent as well as address mouthfeel and texture issues. Sugar alcohols, such as erythritol, mannitol, xylitol and sorbitol, effectively add back mouthfeel and body to foods formulated with stevia extracts. These sugar alcohols also have varying degrees of sweetness and decrease the delayed onset of perceived sweetness in the product and mask some of the negative aftertaste of stevia extracts. But except for erythritol, sugar alcohols may cause gastrointestinal distress when consumed in large amounts, making them inappropriate for use in beverages because of their large serving sizes. Gums, pectin and fiber can also be employed as bulking agents and to increase the viscosity of products made with stevia extracts.
Benefits of lower Reb A levels
Product developers have the option of using stevia extracts with different compositions that will provide different sweetness profiles. Using more Rebaudioside A (Reb A), one of the main steviol glycosides in the stevia leaves, will deliver a cleaner flavor with less bitterness and licorice flavor, but it can be expensive. Purifying to higher Reb A levels requires more manufacturing processes and this escalates the cost of stevia extracts. Also, higher Reb A levels will have more lingering sweetness.
Considerable cost savings can be realized by using stevia extracts with lower Reb A levels. Extracts with Reb A contents of 60 percent are available that still meet EFSA's recommended specification of 95 percent steviol glycosides. Several means can be used to overcome the higher bitterness and licorice flavor of these stevia extracts with lower Reb A levels.
For some applications, this higher bitterness and licorice flavor can actually be complementary as in the case of food products that have roasted flavors like coffee or chocolate. Products with herbal or spice notes such as root beer or ketchup also benefit from the use of stevia extracts with lower Reb A levels. These lower-level Reb A extracts can be less than half the cost-in-use of the higher-level extracts, contributing to considerable overall cost savings.
The lower Reb A level stevia extracts are not limited for application in just a few types of products. A few companies specializing in extraction technologies offer bitter blockers that have the consumer-friendly label of natural flavors. These ingredients bind to the bitter taste receptors on the taste buds, thereby decreasing the bitterness of the lower Reb A extracts.
Selecting complementary flavors
Selecting flavors that are complementary to stevia extracts is an important step. Flavors with a floral note will have a lingering aftertaste that helps mask the lingering sweetness of stevia extracts. Flavors with a heavy aroma — for example, mangoes — will also provide a fuller taste sensation that compensates for the lost mouthfeel when the caloric sweeteners are replaced with high-intensity sweeteners like stevia extracts.
A sweet flavor like vanilla can help round out the sweetness profile of stevia extracts and provide more upfront sweetness. Various aroma chemicals that are typically associated with sweet flavors — for example, strawberry furanone, maltol, and ethyl maltol — can be added to the flavor at low levels to boost the upfront sweetness as well. One must be cautious when using these natural aroma chemicals at higher levels because they will alter the product to be too syrupy or cotton candylike.
Putting the package together
By using a combination of aroma chemicals, plant extracts, bitter blockers, and mouthfeel enhancers, food products with stevia extracts can have a sweetness profile that is more similar to that of sugar. Besides improving the sweetness profile, these ingredients can be used to enable the use of less expensive stevia extracts without compromising the taste.
WILD Flavors recently developed a natural flavor that optimizes the sweet taste of Reb A 60 percent, a stevia extract with 95 percent steviol glycosides and deemed safe for use as a sweetener for foods and beverages in the United States, Mexico, Australia, New Zealand and other countries. By using a trained sensory panel, many of the attributes of the much more expensive stevia extract with a Reb A content of 97 percent were matched with Reb A 60 percent when combined with the natural, sweet taste optimizers. In fact, two attributes, improved onset of sweetness perception and less sour taste, were judged to be better for Reb A 60 percent with the sweet taste optimizers than for Reb A 97 percent.
A large consumer panel of more than 300 people sampled sports drinks made with Reb A 97 percent or Reb A 60 percent with this sweet taste optimizer. The results demonstrated no significance in taste preference between the two drinks. This is a significant breakthrough because Reb A 97 percent is more than twice as expensive as the Reb A 60 percent/natural flavor blend.