In June 2008, the FAO/WHO’s Joint Expert Committee on Food Additives (JECFA) convened to consider and evaluate various steviol glycosides and concluded that high-purity Reb A, containing 95% steviol glycosides, is safe for human use. It allocated a permanent Acceptable Daily Intake (ADI) of 0 mg to 4 mg per kg body weight. The importance of the JECFA conclusions should not be underestimated. It paved the way for global clearance of Reb A, and approvals have subsequently been granted in Switzerland, Australia and New Zealand.
Stevia was accepted in Australia and New Zealand following an application made by the Plant Science Group at Central Queensland University and Australian Stevia Mills. In a judgement based on numerous studies from around the world, the plant was approved for commercial use in Australian food and beverage manufacture by the country’s food safety authority, FSANZ, in Oct. 2008. Approvals have subsequently been given in Switzerland, the first European country to do so, and Russia.
Approvals are also expected in the EU, following a Sept. 2007 submission made to the European Food Safety Authority (EFSA).
How Reb A is processed
The stevia plant has been used for many years throughout the world as a natural sweetener. Stevia is a member of the Chrysanthemum family. It grows wild in any warm climate where there are large temperature variations during the day. The plant is hardy, requires little water and has few natural pests. Its cultivation provides significant economic benefits to the local farming communities in which it is grown, because it can be harvested up to four times per year.
After the stevia plants are harvested, they are dried and put through an extraction process. The extraction process follows traditional methods using a freshwater brewing method to unlock the plant’s natural sweeteners, including Reb A. To minimize waste, once the extraction process is complete, the unwanted mulch and processed leaf is used as fertilizer for the crops.
The crude extract is then refined to isolate out the Reb A. Using proprietary natural crystallization and separation technology, the constituent glycoside molecules in the extract (Table 1) are separated, isolating pure Reb A. The crude extract is made up of about 50% Reb A, the balance or coproduct that is refined out is either recycled or used in the production of other products.
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Molecular Structure of Steviol |
Table 1: Molecular structure, sweetening power and amount of Steviol glycosides in stevia leaves
Na = Not available. a: may be an artifact of the extraction process (Geuns, 2004) The high-pressure liquid chromatography of Reb A 97% and stevia extract points out the main difference in purity between them, which contributes to sweetness quality in different applications.
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| HPLC Diagram for Raw Stevia Extract & Rebaudioside A 97% |
Sensory evaluation of Reb A shows a significant improvement in sweetness and reduction in bitterness and sourness against stevia raw extract, and stevioside.
Using Reb A
Reb A offers a number of tangible benefits both to food producers and their customers, making it an ideal mainstream food ingredient. It is 100% natural and is about 350 to 450 times sweeter than sugar, yet has no calories, giving manufacturers the ability to lower the caloric content of their products without adversely affecting taste.