Stevia: The Plant and the Term
Stevia is a broad term that can refer to several things, leading to common consumer confusion. Primarily, it refers to the plant species Stevia rebaudiana, a leafy shrub native to South America. For centuries, indigenous peoples have used its leaves to sweeten foods and beverages. The term "stevia" is also colloquially used to describe the processed, zero-calorie sweeteners derived from this plant.
The stevia plant contains various compounds, but the ones responsible for its sweet taste are called steviol glycosides. Because stevia products can range from dried whole leaves to highly purified extracts, understanding the specific form you are consuming is crucial. The U.S. Food and Drug Administration (FDA), for instance, has approved high-purity steviol glycosides as generally recognized as safe (GRAS), but has not approved the use of whole-leaf stevia or crude stevia extracts as food additives.
Steviol Glycosides: The Sweet Components
Steviol glycosides are the specific, intensely sweet chemical compounds found within the stevia plant's leaves. These molecules are what make stevia-based sweeteners sweet, and they are typically 150 to 300 times sweeter than sucrose (table sugar). There are numerous types of steviol glycosides, each with a different taste profile. Two of the most common are:
- Stevioside: Historically the most abundant steviol glycoside, but often associated with a slightly bitter or licorice-like aftertaste, especially in higher concentrations.
- Rebaudioside A (Reb A): Another major glycoside, valued for its cleaner, more sugar-like taste with less bitterness. Many commercial stevia sweeteners focus on maximizing Reb A content for a better flavor.
The Purification Process
The extraction of steviol glycosides from the stevia leaf is a multi-step process that moves from a raw plant to a refined product. It generally involves:
- Harvesting and Drying: Stevia leaves are harvested and dried, similar to how herbal teas are processed.
- Water Extraction: The dried leaves are steeped in hot water to extract the sweet compounds.
- Purification: The resulting liquid extract is filtered to remove plant matter and other impurities, and the steviol glycosides are then isolated and concentrated, often using techniques like ion-exchange chromatography.
- Crystallization: The purified solution is dried to produce a white, crystalline powder of steviol glycosides.
Advanced methods also exist, such as enzymatic modification and fermentation, which can produce specific steviol glycosides like Reb M and Reb D in larger quantities, often with improved taste profiles.
Comparison Table: Stevia vs. Steviol Glycosides
| Feature | Stevia (Whole Leaf/Crude Extract) | Steviol Glycosides (Purified Extract) |
|---|---|---|
| Nature | The plant itself or a minimally processed version. | The specific sweet compounds isolated from the plant. |
| Composition | A complex mixture of compounds, including steviol glycosides, other plant materials, and flavorings. | A highly purified and concentrated form of sweet glycoside molecules. |
| Regulation | Not approved as a food additive in many countries, including the U.S. and EU. | Widely approved as a food additive for use as a sweetener. |
| Taste Profile | Can have a more intense, sometimes bitter or lingering aftertaste, depending on the concentration of different glycosides. | Often has a cleaner, less bitter, and more sugar-like taste, especially in products high in Reb A or Reb M. |
| Uses | Primarily used as a dietary supplement or in homemade recipes like herbal teas. | Used commercially as a zero-calorie sweetener in a vast range of foods and beverages, from diet sodas to yogurt. |
Why the Distinction Matters for Consumers
For a consumer, knowing this distinction is important for several reasons. First, it helps to interpret product labels accurately. A product labeled “natural stevia” may contain a mix of compounds, while one listing “steviol glycosides” or “Reb A” indicates a higher level of purification. This affects taste, as the purity level directly impacts the likelihood of a bitter aftertaste. For instance, Steviala's blog notes that their use of high-quality Reb A 98% and 99% results in a non-bitter sugar substitute.
Furthermore, the regulatory status of purified steviol glycosides gives consumers confidence in the safety profile of these specific, concentrated sweeteners, as they have undergone rigorous testing. Whole-leaf stevia, while a natural product, has not received the same level of approval from regulatory bodies for use in food products. Therefore, making an informed choice relies on understanding whether you are purchasing the unprocessed plant or the refined sweetening components.
Conclusion: From Plant to Purified Sweetener
In summary, the core difference between stevia and steviol glycosides is the distinction between the source and the product. Stevia is the plant, Stevia rebaudiana, while steviol glycosides are the specific, naturally occurring compounds within the plant that are responsible for its sweetness. When a food or drink is sweetened with “stevia,” it is most often the high-purity steviol glycosides that have been extracted, filtered, and purified, a process akin to extracting sugar from sugarcane. This purification removes the other compounds that can contribute to an undesirable aftertaste, resulting in a cleaner-tasting, zero-calorie sweetener. By understanding this key difference, consumers can make more informed choices about the sweeteners they choose for their diet, balancing their desire for natural origins with their expectations for taste and regulatory safety. For additional reading on the nutritional science behind sweeteners, the Academy of Nutrition and Dietetics is a useful resource.
Keypoints
- Source vs. Compound: Stevia is the name of the plant, while steviol glycosides are the sweet-tasting compounds extracted from its leaves.
- Purity Varies: Whole-leaf stevia contains a mix of compounds, whereas commercial sweeteners use purified steviol glycosides for a better taste.
- Regulation Matters: Regulatory bodies like the FDA have approved high-purity steviol glycosides, but not whole-leaf stevia, for use in food.
- Taste Profile: Different glycosides have varying taste profiles; Rebaudioside A is prized for its cleaner, less bitter flavor compared to Stevioside.
- Processing: Steviol glycosides are obtained through a multi-step extraction and purification process, which can involve water extraction, filtration, and crystallization.
- Commercial Use: The purified form, steviol glycosides, is used widely in packaged foods and beverages as a zero-calorie sweetener.
Faqs
What are steviol glycosides? Steviol glycosides are the specific chemical compounds found in the leaves of the stevia plant that provide its intense sweetness. They are purified extracts used as zero-calorie sweeteners.
Is whole-leaf stevia the same as steviol glycosides? No. Whole-leaf stevia is the unprocessed plant leaf, while steviol glycosides are the refined, isolated sweetening compounds extracted from those leaves. Most commercial products use purified steviol glycosides.
Why do some stevia products have a bitter aftertaste? The bitter aftertaste is often associated with less purified extracts that contain higher concentrations of certain steviol glycosides, like stevioside, compared to cleaner-tasting ones like Rebaudioside A.
Are stevia-based sweeteners safe to consume? Yes, when consumed within the established acceptable daily intake (ADI). High-purity steviol glycoside extracts have been rigorously tested and deemed safe by major regulatory bodies.
How are steviol glycosides extracted from the plant? The extraction process involves steeping dried stevia leaves in hot water, filtering and purifying the liquid extract, and then concentrating and drying it to produce a crystalline powder.
Can stevia be produced without the stevia plant? Yes. While traditional steviol glycosides are extracted from the plant, new methods like fermentation and bioconversion use microorganisms to produce them, often targeting specific glycosides like Reb M.
Which type of steviol glycoside is considered the best tasting? Rebaudioside M (Reb M) is widely regarded as having the cleanest, most sugar-like taste profile with minimal bitterness or aftertaste, though it is one of the more expensive options to produce.
