Taste of Stevia

Introduction

Indigenous populations in Paraguay and Brazil have been using the leaves of the stevia plant, Stevia rebaudiana (Bertoni), as a sweetener since before recorded history (Lee, 1979; Soejarto, 2002). The ancient Guarani people of Paraguay referred to stevia as “kaa he-he”, which means “sweet herb” (Ranjan, 2011).

Stevia is a naturally derived, high potency sweetener that can be up to 250-300 times sweeter than sucrose, or table sugar. It is similar in sweetness intensity to many of the artificial sweeteners currently on the market (U.S. Food and Drug Administration, 2015).

Steviol Glycosides

Unlike artificial sweeteners, stevia’s sweetness is naturally derived from over 40 compounds, known as steviol glycosides. Of these, the eleven most common range from 50-350 times the sweetness of sugar (table 2) (Ashwell, 2015; Prakash, 2008). Stevioside (figure 1) and rebaudioside A (figure 2) are the most prevalent and generally make up about 75% of the total steviol glycoside content in stevia.

In addition to varying sweetening powers, each steviol glycoside has a unique set of sensory and functional properties. Some, such as rebaudioside D, have a relatively clean sweet taste. Others, such as stevioside, are higher in negative sensory characteristics such as bitter, metallic, astringent and licorice-like (DuBois, 1985). Whole leaf stevia extracts, which can contain a full array of steviol glycosides, are usually a poor substitute for the singular sweet taste of sucrose or sugar because they contain compounds such as polyphenols, fibrous matter, proteins, carbohydrates etc. that contribute to color, texture and taste characteristics that are distinctly different from sucrose.

Purified Stevia Extracts 

Identification and isolation of specific steviol glycosides found in whole leaf stevia extracts began early in the twentieth century but was not accomplished until 1955 with the discovery of the complete structure of stevioside (Mosettig, 1955). This new development allowed for the creation of purified stevia extracts containing a specific blend of one or more steviol glycosides. It is important to note that the structure of steviol glycosides are in no way altered during the extraction and purification process to make high-purity stevia extract. Purified stevia extracts can achieve maximum sugar reduction while imparting a more sugar-like taste without adding calories or bitter off notes.

Purified stevia extracts were adopted by the Japanese in the 1970s and are widely used around the world today. Most are sold in single serve packages for consumer use in beverages such as coffee or tea. In 2008, sweeteners containing rebaudioside A (also referred to as Reb A or Rebiana) became widely available in the US under the brand name of PureVia®. Global brands include Diabetasol (Indonesia), Finn (Brazil), Suganon (South Africa) and Spike (Malaysia).

While purified stevia extracts generally taste better than their whole leaf counterparts, there is still is room for improvement to make them closer to sucrose. Many stevia based sweeteners made with stevioside and rebaudioside A can contain bitter and licorice-like “off” tastes, more notable for stevioside than rebaudioside A (Prakash, 2008). Most consumers still prefer the taste of sucrose and most food scientists and product developers try to closely replicate the taste and functionality of sucrose when combining nutritive and/or non-nutritive sweeteners.

Formulating with Stevia

When compared to sugar, the four main challenges for high potency sweeteners are that they have (1) low maximal sweetness intensities, (2) “off” tastes such as bitter and metallic, (3) slow-onset sweet tastes that linger, and (4) a desensitizing sweet taste (DuBois, 2012). Blending sweeteners, nutritive as well as non-nutritive, can have a synergistic effect on sweetness. Such blends are also largely advantageous and exhibit improvements in sensory profile, reduced costs and improved stability (Prakash, 2008).

When compared to sugar, most high potency sweeteners take longer to develop a sweet taste but tend to have a sustained aftertaste. This can be desirable in some products such as chewing gum were prolonged sweetness is desirable (Prakash, 2014) or in products where sour or bitter aftertastes are improved by adding sweetness. Sweetness perception relative to sugar is also affected by temperature. For instance, rebaudioside A can be significantly more potent in some cold applications (Fry, 2011).

Conclusion

Stevia is an age old naturally derived sweetener with a bright future. Food scientists at companies like PureCircle are constantly discovering new ways to leverage individual and proprietary blends of steviol glycosides to achieve the desired sensory attributes. This evolution of the science and taste of stevia will continuously benefit consumers as well as food and beverage companies seeking to reduce sugar.

REFERENCES

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