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New Sweetener - Stevia rebaudiana Bertoni: Chemical Characteristics and Comparison of Classic and Ultrasound Assisted Extraction Techniques

The exceptional sweetness of stevia, is hidden in its leaf and is natural defense mechanism that protects plant against natural pests (repellent characteristic). Natural sweeteners isolated from the stevia leaves are diterpene glycosides identified as stevioside, steviolbioside, rebaudioside A, B, C, D, E, F and dulcoside. In the stevia leaves, stevioside is the most common (4-20% w/w), and followed by rebaudioside A (2-4% w/w), rebaudioside C and dulcoside. Above mentioned diterpene glycosides are specific for its extreme sweetness, even 300 times sweeter than sucrose without any caloric value, glycemic index is zero, and it is a sweetener with zero calories. It is important to emphasize that apart from exceptional sweetness, stevia is characteristic in rich nutritional composition with significant antioxidant capacity, which differs this plant greatly from other popular sweeteners thus indicating a high potential for use in functional food category. The leaves of stevia which are used as a raw material for production of sweetener in food products, on the market are present as a green powder, a white powder and a solution which are obtained by different extraction methods of sweet glycosides from green powder. Still, on the market, the mostly applied stevia product is white powder. In order to produce a white stevia powder, the classical method of extraction of stevioside by process of maceration and heat extraction is usually applied. Mentioned classical methods of extraction show numerous disadvantages of which the most important being a longer time period, relatively low efficiency of the extraction process, higher energy consumption, increased solvent usage and more released heat as well. High intensity ultrasound found its important application in the catalysis of the compounds extraction from organic materials. Mechanical effects of ultrasound will provide greater penetration of solvent into cellular materials and substantially improve the mass transfer of compounds that dissolve in the solvent. The ultrasound energy alone will enable the disruption of the plant cell walls, and thus facilitate the release of cell contents into the solvent. The application of high intensity ultrasound has proven to be extremely effective in the extraction of various types of compounds out of various plants, on account of shorter processing time, higher extraction yield, less solvent usage, lower energy consumption and cost effective maintenance of the facility.

Stevia rebaudiana Bertoni ; Glycosides ; Extraction methods ; Ultrasound

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