E420 (INS 420) is sorbitol, a sugar alcohol or polyol. It occurs naturally in fruits such as apples, pears and prunes, and is made commercially by hydrogenating glucose obtained from corn or wheat starch. It comes as a powder, sorbitol (420(i)), or as sorbitol syrup (420(ii)).
Sorbitol is about 60% as sweet as sugar, with a mild, slightly cool taste. Besides sweetening, it is a humectant: it holds on to water, so sponge cakes and creams stay soft and moist during storage instead of drying out. In soft cakes such as the Shoei Tokyo Sweet Banana Gift Box, which also contains reduced starch syrup, it is typically used for this moisture-keeping effect.
Sorbitol is an approved food additive that has been evaluated by JECFA. Like other polyols it is only partly absorbed, and large amounts can have a laxative effect; in the EU, foods with more than 10% added polyols must carry a warning about this.
