Cultivation and Harvesting
The artificial sweetener stevia has been used in foods and beverages in the U.S. as a calorie-free sweetener since the Food and Drug Administration proclaimed in 2008 that it's generally safe. Its extract can be hundreds of times sweeter than regular table sugar. But unlike sugar, it doesn't raise blood sugar levels. According to the Mayo Clinic, stevia is an herb that is cultivated primarily in China, Japan, Brazil and Paraguay.
According to UnderutilizedSpecies.org. some 800 hectares (1,976 acres) were cultivated for commercial use in stevia's country of origin, Paraguay, in 2006. During harvesting, stevia leaves are cut at ground level and placed in a drying wagon. It typically takes a day or two for the leaves to dry out completely. The dry leaves are placed in cardboard boxes with plastic liners and sealed for processing.
Processing
Dried stevia leaves from Paraguay and other locations in South America, China, Japan and Brazil, are purchased by the United States and other countries where they are processed into sweeteners. According to HealthSweet.com, commercial processing includes water extraction, purification and decoloration.
Water Extraction
Once stevia plants are dried, they undergo a water extraction process. About half of this crude extract contains Rebaudioside A (Reb A). According to Food ProductDesign.com, Reb A is the sweetest and most flavorful of the many sugar-like substances (steviol-glycosides) contained in the stevia plant.
Reb A is refined through crystallization and with the use of specialized equipment that separates the many glycoside molecules in the stevia extract. This process permits manufacturers to select only pure Reb A for commercial use.
Purification
The Berkeley Electronic Press says crude stevia extract is brown in color and has a bitter taste accompanied by an unpleasant smell. These unappealing traits necessitate a purification process of the extract for the final product to satisfy commercial quality standards. According to HealthSweet.com, purification measures can include ion-exchange resins (separating out certain elements) and decoloration (removal of the brown color, bleaching).
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