After many years of testing, in December 2011 the steviol glyclosides, which are obtained from the plant stevia rebaudiana Bertoni, were officially permitted as foodstuff additives in the EU and allocated E number 960. Their consumption is regarded as harmless if the acceptable daily intake (ADI) of 4 mg/kg is not exceeded.
When authorising its use, the European Commission established highest maximum quantities for the use of the steviol glcycosides in foodstuffs, in order to protect the consumer from excessive intake. These maximum quantities are based on approximate consumption amounts of the relevant foodstuffs, and therefore vary from product group to product group. The maximum quantities relate to the quantity of all steviol glycosides present in the finished product. These are converted into steviol equivalents using specific factors, and their totals are then stated.
Stevioside and rebaudioside A are the two main glycosides that occur in the plant stevio rebaudiana. Their sweetening power is 100 to 300 times higher than that of sucrose, they are stable when heated, are easily water-soluble and tolerable for people with diabetes. This makes them interesting as a sweetener for a wide variety of foodstuffs. Using the methods developed by the Institut Kirchhoff, valid determination of the steviol glycosides stevioside and rebaudioside A is possible in various matrices.
In the first stage, the steviol glycosides are extracted aqueously. Depending on the matrix, the sample may need to be purified and/or subjected to solid-phase purification (SPE). Measurement is by means of HPLC-UV detection, in which an external calibration quantifies the content of stevioside and rebaudioside A.