Functional properties of food

1. Functional properties of food • Food designers need to understand the properties of foods when they are designing new dishes, to make sure they match the product profile.

2. Solutions Examples of a solution are • Fruit juices • Sugar and water syrups • Salt and water brine A solution is formed when • A liquid is dissolved in another liquid, for example fruit squash in water • A solid is dissolved in a liquid like sugar in a cup of tea. Solutions will not separate when left to stand.

3. Suspensions • A suspension forms when solid particles are added to liquid but do not dissolve • Starch particles such as flour do not dissolve in a liquid but they form a suspension. • If the suspension is not agitated the solid particles fall to the bottom . One example is when a sauce pan is not stirred when heated and lumps form at the bottom of the pan.

4. Gels • A gel is a solid jelly-like substance. Gels are mostly liquid but behave like a solid due to the gelling agent holding the liquid in place. • Gels form when starch is heated in a liquid and cooled(gelatinisation). Examples include • White sauce • Lemon meringue pie filling • Jam • Flan glaze

5. Smart starches • Manufacturers use a large number of starches which have been altered to change their working properties. These are known a modified starches or smart starches. • Some modified starches are pre-gelatinised. This allows them to thicken instantly such as cup a soups or pot noodles • Some modified starches allow sauces to be reheated with no synerisis • Some modified starches are not affected by acidity so can be used to thicken salad dressings.

6. Emulsions • Liquids that will not mix together are immiscible such as oils and water. • When shaken together they form an unstable emulsion which separates if left standing. • A mixture only remains stable if an emulsifier is used. Lecithin in egg yolk is an emulsifier. • Egg yolk is used in the preparation of mayonnaise where it holds oil and vinegar together. • It helps the fat in the cake mix with the egg white.

7. Foams • Foams are gas mixed into a liquid giving a light texture like in ice cream. • Meringues are a foam made by whisking air (gas) into egg white (liquid). • When you bake then the air expands and the egg white coagulates to give a solid structure.

8. Elasticity • Wheat contains two proteins glutenin and gliadin. When water is added to wheat flour they form gluten. • Gluten is very stretchy or elastic it allows food made from wheat flour such as bread and cakes to rise.

9. Plasticity • Plasticity describes how fats change shape under pressure such as rubbing in or spreading • You can easily rub in • Soft margarine • Butter • Lard • Oil cannot be easily rubbed in • Plasticity allows fat to coat each flour particle in rubbed in products like short crust pastry or shortbread.

10. Shortening • Fats make cakes and biscuits crumbly and melt in the mouth by forming a coating around the starch and protein molecules in the flour. • This stops the liquid coming into contact with the flour and helps stop gluten forming. • Any gluten that does form is in short lengths not the long elastic strands found in bread. • These short gluten strands give us the term shortening.