Stevia rebaudiana Bertoni
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Stevia rebaudiana BertoniChris StothartThe Sweet Alternativerebaudiana 1OutlineOverviewHistorical Perspective BotanyEthnobotanyChemistry Extraction & Commercial UsesNutritionRegulation Controversies References
Common names include: stevia, sweet leaf, sweet herb of Paraguay, honey leaf, & sugar leafIncreasing popularity of artificial sweeteners over the past 20 yearsDemand for natural & healthier alternatives Perfect social, political, & economic climate Widespread use as a non-nutritive sweetener due to sweet leaves Much debate over its use & health implicationsStevia rebaudiana3Historical Perspective
Used extensively by native cultures of South America for centuriesFirst introduced to Europe by Spanish conquistadores in 16th centuryReintroduced in early 20th century to scientific community by Italian-Swiss botanist Dr. Moiss S. Bertoni 1905 Bertoni classified & described steviaStevia rebaudiana16th century described how Paraguays natives used the leaves of the plant to sweeten their foods and chewed on the leaves throughout the day (The National Geographic Society 2008).
4Since 1905 Stevia has been widely studiedThroughout 20th century sweet compounds in leaves have been isolated, purified, patented, & used in commercial products1970s Japan began using stevia in replace of artificial sweeteners & sugarLargest consumers: Japan, South Korea, Brazil, & South America
Historical Perspective cont.
Stevia rebaudianaNorth America and the European Union have traditionally only allowed purified extracts of S. rebaudiana to be sold in health food stores and pharmacies as dietary supplements, but recently the US Food and Drug Administration (FDA) has approved the use of highly refined stevia preparations as a sweetener in such products like soft drinks (US FDA 2011). Health Canada has recently permitted highly purified stevia extracts to be used to sweeten vitamin and mineral waters (Aquafina Plus Vitamins 10 Cal), soft drinks (Zevia), for use as a medicinal ingredient in natural health products, and for personal culinary use (Health Canada 2011).
Tropical perennial & herbaceous shrubNative to Central & South America Member of Asteraceae (Sunflower Family)Grows 65-80 cm tallTypically found in semi-dry mountainous environments & grasslandsPrefers well-drained non-saline soil with pH 6.5-7.5Stevia rebaudiana
Simple, opposite green sessile leavesStem, branches, & leaves are all green & are covered with short, fine whitish hairsAll green parts taste sweetInflorescences are tiny white & purple disk floretsDevelop achene fruits
Commercial cultivation of stevia began in 1964 in Paraguay, since then it has been cultivated in Brazil, Japan, China, Korea, Mexico, United States, Indonesia, Tanzania, and Canada (Madan 2010).
Commercial cultivationParaguay, Brazil, Japan, China, Korea, Mexico, USA, Indonesia, Tanzania, & Canada
8EthnobotanyGuarani natives (Paraguay) credited with first using the dried leaves to sweeten yerba mate (Ilex paraguariensis) & chewed the fresh leavesNatives used orally delivered concoctions as a contraceptive, to manage diabetes, and to treat stomach aches Ca h- or Ka he, which in Guaran, a local dialect, translates into sweet herb Lack of cultural & written records of steviaStevia rebaudiana
Researchers have postulated the following three explanations for the limited cultural record of stevia. First, the sweet-tasting properties of the plant have been known by indigenous cultures since the beginning of time and therefore were a closely guarded secret that they chose not to share with outsiders. Second, indigenous cultures shared the plants unique properties with the Spaniards, but the knowledge was either disregarded or overlooked by Europe at the time. Third, stevias potential as a sweetener was not discovered by natives until only a short time before its existence became known to scientists (Soejartob 2002; Lewis 1992).
9Ethnobotany cont.3 explanations for limited historical record1. Sweet-tasting properties were known since the beginning of time, but kept a secret2. Natives shared plant with Spaniards, but the knowledge was disregarded or overlooked3. Stevias potential as a sweetener was not discovered by natives until only a short time before European contact
Figure 4: Paraguayans harvest stevia. Second, indigenous cultures shared the plants unique properties with the Spaniards, but the knowledge was either disregarded or overlooked by Europe at the time. Third, stevias potential as a sweetener was not discovered by natives until only a short time before its existence became known to scientists (Soejartob 2002; Lewis 1992).
10ChemistryActive compounds: group of diterpene (steviol) glycosides dulcoside A, rebaudiosides A-E , steviolbioside, & steviosideRebaudioside A (3.8%) and stevioside (9.1%) are the sweetest, most abundant, & most important commerciallyHighest yield of these compounds in leaves just before the plant begins to flower,
Chemical structure of stevioside (left) and rebaudioside A (right) Stevia rebaudianaChemical structuresExtraction & Commercial Uses
Processing of dried leaves from Stevia produces a powdery white substance (stevioside), which is three hundred times sweeter, by weight, than sucrose derived from sugar cane Water extraction process followed by crystallization techniques to isolate the steviol glycosides NRC has patent on nanofiltration techniquescommercially available stevia products: stevioside and rebaudioside A include Truvia, Fructevia, Krisda, & PureVia.
Stevia rebaudianaThere are a variety of patented techniques used to extract the glycosides from the leaves that involve water extraction processes followed by crystallization techniques to isolate the steviol glycosides (Madan 2010). The National Research Council in Canada currently holds the patent on a technique that uses column extraction and purification, using nanofiltration, to isolate the desired compound (United States Patent and Trademark Office 1998). Examples of commercially available stevia products containing stevioside and rebaudioside A include Truvia, Fructevia, Krisda, and PureVia.
13Commercial productsStevia rebaudiana
The dried leaves are 30 to 45 times as sweet as sucroseNon-nutritive, three hundred times sweeter than sugar, heat stable, non-fermentable, as well as an anti-plaque and anti-carieMore studies must be conducted on bulking agents to make it easy to replace it for sugar
Stevia rebaudianaTable from Goyal 2010, Stevias properties of being a natural food extract, non-nutritive, three hundred times sweeter than sugar, heat stable, non-fermentable, as well as an anti-plaque and anti-carie, has made it a popular non-caloric sweetener around the world (Goyal 2010). Another interesting characteristic of stevia is its potential to replace sugar in recipes without altering the visual acceptability and physical characteristics of the food product (Madan 2010). However, more studies must be conducted on combing stevia with various bulking agents to determine the most efficient way to substitute sugar with stevia in baked goods and confectionaries at a one-to-one ratio. Presently, Health Canada has set the acceptable daily intake guideline for steviol glycosides at 10 mg/kg(body weight)/day, which for a 75 kg person would be approximately 750 mg/day (Health Canada 2011). On average, a one-gram package of commercial stevia extract preparation contains less than a thousandth of a gram of rebaudioside A or stevioside. To illustrate the intense sweetening power of stevia, a one-gram packet of Krisda, a premium brand of stevia extract with a inulin bulking agent that is available in Canada, is equivalent to 2 teaspoons of sugar (8.4 grams) (Krisda 2011).
15Traditionally, North America & EU have only permitted use of highly purified extracts for sale in health food stores & pharmaciesLeaves classified as a dietary supplement, but not as a sweetener (Health Canada 2011)FDA & Health Canada has approved use of stevia derivatives as a sweetener in some products (FDA 2011; Health Canada 2011)Marketed as medicinal, non-medicinal ingredients & for personal culinary useRegulationStevia rebaudiana16ControversiesFew conclusive results verifying negative health claimsInvestigated effect of stevia on energy & carbohydrate metabolism, on the cardiovascular & renal systems, & reproductionDiabetes mellitus: helps with proper blood glucose control, as antihyperglycemic by stimulating the release of insulin, & to help prevent insulin intolerance in diabetic patients Need for further clinical trials to ensure safety of stevia for widespread human consumption
Stevia rebaudianaThough indigenous cultures of Paraguay have been using stevia for centuries, its widespread use has been greatly restricted due to reports claiming that it cause harm to human health. Few studies have found conclusive results verifying this to be true, but several have investigated the effect stevia extracts have on energy and carbohydrate metabolism, on the cardiovascular and renal systems, and on reproduction (Huxtable 2002).
No significant findings from these studies indicated that stevia extracts are harmful to human health (Wheeler 2008). In individuals with diabetes mellitus, stevia extracts are thought to help with proper blood glucose control, to act as antihyperglycemic by stimulating the release of insulin, and to help prevent insulin intolerance in diabetic patients (Jeppesen 2003