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C1f) Cooking and food additives
Cooking is a chemical change because a new substance is made.
The process cannot be reversed, an energy change takes place in the food and new
substances are made.
The chemical changes happen when the chemicals in food are heated.
Proteins are large molecules that have a definite shape.
The white part of the egg is called albumin. The albumin molecules change shape when the
egg is cooked.
When a protein molecule changes, it is called denaturing.
Denaturing causes changes in the appearance and texture of the meat and eggs when they
are cooked. For example:
Meat becomes firmer and turns from red to brown
Egg white solidifies and becomes white instead of transparent.
When a potato is cooked, the cells wall breaks down and loses its structure.
The starch grains swell up and burst and spread. This makes potato easy to digest.
Bread and cakes made from flour. Flour is made of wheat and must be cooked.
Baking powder makes cake rise. Carbon dioxide is made when it is heated in the oven.