Extraction of stevia

COMMERCIAL EXTRACTION OF STEVIOL GLYCOSIDES

The Stevia rebaudiana Bertoni comprises a complex mixture of compounds including eight glycosides: stevioside, steviobioside, dulcoside, and rebaudiosides A, B, C, D, and E. The most abundant substances are stevioside and rebaudioside A.

There are many patents for the commercial extraction of steviol glycosides and these patents can be classified as those based on solvent,  solvent plus a decolorizing agent,  adsorption chromatography , ion exchange, and selective precipitation of individual glycosides. The most favoured extraction processes involve four steps: aqueous or solvent extraction, ion exchange, precipitation or coagulation with filtration, then crystallization and drying.

All the conventional extraction processes follow a similar methodology ie the stevia leaves are extracted with hot water or alcohols. In some cases, the leaves are pretreated with nonpolar solvents such as chloroform or hexane to remove the essential oils, lipids, chlorophyll, and other nonpolar substances.

A Japanese patent for the production of stevia glycosides uses supercritical fluid extraction (SCFE) with CO₂ and a cosolvent. Methanol, ethanol, and acetone were used as cosolvents. The purification step is accomplished by adsorption.

The extract is clarified by precipitation with salt or alkaline solutions. The extract is concentrated and redissolved in methanol for crystallization of the glycosides. The crystals formed are almost pure stevioside.

Extracting Stevia at Home:

There are many home made instructions on how to extract Stevia from home grown Stevia plants. Here is one:

Instructions

Things You'll Need:

• Stevia
• Grain alcohol
• Vodka
• Covered container
• Cheesecloth
• Coffee filter

1.     Harvest your stevia in the morning when the essential oils peak. You must use stevia grown without pesticides, as the extract-making process concentrates undesirable chemicals. Wash the leaves and stems and remove any brown plant parts.

2.     Chop the leaves and stems coarsely. You must prepare enough fresh stevia to fill two lightly packed measuring cups.

3.     Combine the stevia with one cup of clear grain alcohol or vodka. You can use flavor-infused vodkas for variety, such as pear or citrus.

4.     Leave the stevia mixture steeping overnight in a covered container, but not more than 48 hours. Excessive steeping increases bitterness. Stir or gently shake the mixture several times while it steeps.

5.     Strain the alcohol and stevia mixture through cheesecloth or coffee filter to remove the plant matter. The mixture should appear greenish.

6.     Bring the stevia extract to a simmer over medium-low heat for 30 minutes. This evaporates the alcohol and concentrates the extract.

7.     Store the extract in the refrigerator up to three months. You must dilute the extract to taste before using with water.

 by justin lim

The health benefits that stevia offers

Health benefits of stevia
Stevia has many health benefits :

1. Calorie-free
2. Hypoglycemic action – does not cause hypoglycemia (low sugar which causes tiredness)
3. Cardiovascular action – it lowers blood pressure (unless taken at high concentrations where blood pressure increases)
4. Cardiotonic effect – given long term usage, stevia will provide mild strengthening of the heart
5. Antimicrobial effect – it inhibits the growth and reproduction of harmful organisms. Firstly, it research shows that the Streptococcus mutantss, Pseudomonas aeruginos, Proteus vulgaris and other microbes do not flourish in places where there are Stevia constituents.
6. Paraguayans say that Stevia is helpful for hypoglycemia and diabetes because it nourishes the pancreas and thereby helps to restore normal pancreatic function
7. In Brazil, Stevia ranks high among the list of plants used for centuries by the "gauchos" (a south American nomadic race) of the southern plains to flavour the bitter medicinal preparations used in their nomadic culture. After, much experimentation, these people found out that Stevia improved digestion significantly. They also discovered that it improved overall gastrointestinal function.
8. When Stevia was introduced in China, Stevia tea, made from either hot or cold water, is used as a low calorie but sweet-tasting tea. It is used to stimulate appetite and to aid digestion and weight management.
9. On the internet, a doctor suggests switching to stevia when there is fungal / yeast overgrowth in the bowels as sugar is what the yeast feeds on.
10. Stevia shows lower incidence of dental cavities than sugar
11. Female rats that consumed stevia had decreased incidence of breast cancer while the males had decreased incidence of kidney damage.
12. Stevia has been tested on rats and mice and the results show that stevia is not toxic, does not affect tissues, general appearance and organs and does not affect the 2^nd generation either. The test results show that caffine is actually 10 times as toxic as stevia.
13. The results from the test on rodents only show that the rodents that consumed stevia versus the ones that consumed sugar weighed less which is of course expected as stevia has zero calories.

Sources:http://www.stevia.net/safety.htm

            http://www.endfatigue.com/health_articles_f-n_2/Infections-          candida_eliminating_yeast_fungal_overgrowth.html

            http://www.agricultureinformation.com/forums/stevia/8089-medicinal-properties-stevia.html

Introduction to Stevia

Introduction to Stevia

Origin and History

Stevia Rebaudiana is a natural sweetener and a herb in the Asteraceae family. This family includes well-known plants such as sunflower and dandelion.  Stevia grows wild as shrubs in parts of Paraguay, Brazil and some other countries. Some South American natives had already used this plant to sweeten native beverages for centuries.

Spanish rulers first learned of the “sweetest plant of the world” in the 16^th century. Yet the commercial use of this plant did not take place quickly. During World War II, the allies thought of extracting stevioside (the chemical compound in Stevia) as an alternative for sugar, since the supplies were running out. But there was no available technology to extract the stevioside industrially. Around 1970, due to restriction of artificial sweeteners usage in Japan, there was quick progress in the technological research and usage of the plant extract. Stevia is the most used sweetener in Japan and Korea. Production now takes place mainly in Paraguay, Uruguay, Central America, USA, Israel, Thailand and China.

Description

The leaves are about 5 cm long and 2 cm wide. In the wild, the height of the plant varies from 40 to 80 cm but it can grow to about 1 metre tall when it is cultivated.  Stevia is a very hardy plant, growing even on relatively poor soil. In Paraguay and Brazil, the commercial lif e of a Stevia plant is 6 years, yielding 5 harvests a year. The roots remain in place and so the plant can regenerates

The glycosides in its leaves, including 10% Stevioside, make it incredibly sweet. The dreid leaves of Stevia are about 40 times sweeter than sugar. 1 tablespoon of Stevia extracts is about 200-300 times sweeter than a tablespoon of normal sugar. The refined product, Stevioside, is a white crystalline powder extracted from Stevia leaves. Although it is sweet, Stevia is a 100% natural sweetener that is also calorie-free. The body does not metabolize the sweet glycosides from the leaves nor any of its extracts, so there is no caloric intake. Stevia does not adversely affect blood glucose levels and thus may be used by diabetics.

Many different uses of Stevia are already well-known: as table sugar, in soft drinks, pastry, pickles, candy, jam, chewing gum, sorbets etc.

A brief summary of any possible negative side effects and principal advantages

There are no confirmed negative Stevia side effects for humans.  However, Stevia is forbidden as food additive in the European Union and some other countries.  Studies which supposedly showed some negative effects have been highly criticized on the way the data were handled and also the distilled water used appeared to be toxic. In addition, the dosage used in the experiments was way too high. To get the toxicity as in the experiment, one has to eat half his weight in stevia leaves. If one calculates the daily consumption of Stevia to replace the average daily sugar consumption, one would need to eat only 4 gram of Stevia leaves.

Instead, the principal advantages of Stevia include the following:

- 100% natural

- Calories free

- Leaves can be used in their natural state

- Only small quantities need to be used

- Non toxicity

- Leaves and extracts can be cooked, stable when heated up to 200 degrees

- Non fermentative

- Ideal, non-addictive sweetener for children

An Acronym for Stevia would be:

S weetener,

T asty,

E conomical &

VIA ble

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References:

http://www.stevia.com/,http://herbgardens.about.com

http://www.steviasideeffects.org/

http://bio.kuleuven.be/biofys/ESC/English/ESC.htm

prepared by: Edward Tan, 1A3