One of the more common sweeteners used in sugar free sweets is Maltitol. It tends to be used in Toffee and Jelly sugar free sweets rather than boiled sweets.
It can be found in Werther's sugar free toffees as well as the Thornes toffees.
What is Maltitol?
It is a sugar alcohol made by the conversion of a sugar in starch from maize or wheat.
Oral bacteria cannot metabolise it so does not cause tooth decay.
It is metabolised more slowly than sugar so can be consumed by diabetics (glycaemic index of 45).
Taste and other Properties
It is very similar to sugar in terms of sweetness and unlike some other sweeteners does not have a cooling effect. It can be made in a crystalline form like sugar and when heated it can brown and caramelize just as sugar does(which is why it is used for toffees). A maltitol syrup is often used in pharmaceutical products such as cough syrups where it not only replaces sugar but has another advantage in that it doesn't crystalize round the bottle top and make it stick.
In common with some other sugar free sweeteners, excessive consumption of Maltitol can have a laxative effect. Some people seem to be particularly sensitive to Maltitol.