Steviol glycosides are normally 200 to 300 times sweeter than sugar and are used in a range of foods.
Steviol glycosides are extracted and purified from the South American plant Stevia rebaudiana Bertoni (stevia) but can also be produced using other methods. There are a large number of individual steviol glycosides that have similar chemical structures and properties that can make up a steviol glycosides preparation. The Food Standards Code currently permits foods to contain steviol glycosides that are either sourced from the leaves of the stevia plant or produced by chemical conversion of the plant extract, known as 'bioconversion'. This conversion process is driven by enzymes which may be made from microorganisms that are genetically modified. The steviol glycosides produced in this way are chemically equivalent to the same steviol glycosides extracted directly from the stevia leaf.
When added to a food, steviol glycosides must be declared in the ingredient list by the appropriate food additive class name, for example, 'sweetener', followed by the food additive code number '960' or the name 'steviol glycosides'.
If you would like to know how the steviol glycosides in a particular food are produced (i.e. whether they are sourced from the leaves of the stevia plant or are made using bioconversion) you can ask the manufacturer of the food for that information.