Food & Drink: Food for thought - What is modified starch?

Look at almost any label on prepared food, from pizzas to jelly beans, from yoghurt to gravy mixes and you will find the curious ingredient "modified starch". But what exactly is it? What does it do? And "Modified" how?

There are many types, each with unique properties and functions depending on the way it's been modified. The starch in some canned soups, for example, is bonded with phosphate, which allows it to absorb more water and so the soup from does not separate. Fish batter contains an oxidised starch to make it "stickier" to adhere to the sides of the fish better. Instant desserts, such as blancmange, use a pre-gelatinised starch which has been thickened by heat, then dried and added to the product. So, when liquid is then added, it reverts to its original gelatinised form, and hardens.

As for pizza - to stop the tomato sauce spilling off during baking, a starch treated with a chlorine solution is often added to the topping. This produces a gel that thickens during cooking, but goes runny when cooled.