Protein Properties

Denaturation

A change in the nature of the protein, unfolding of the protein chains results in irreversible loss in both shape and structure

What causes denaturation?

Heat, chemicals, mechanical action

Heat

Protein coagulates when heated, heat causes protein chains to unfold and bond together resulting in hardening or setting of the protein food

Chemicals

Acid lowers the pH, lemon juice added to milk causes the milk protein caseinogen to curdle

Mechanical action

Whisking egg white causes the protein chains to unfold resulting in partial coagulation forming foam

Culinary applications of denaturation

Moist heat converts collagen to gelatine, dry heat , whisking

Elasticity

Some proteins such as gluten in flour are very elastic

Culinary applications of elasticity

The presence of gluten allows bread to rise during cooking by making yeast dough elastic so it can trap CO2

Solubility

Proteins are generally insoluble in water apart from egg white which is soluble in cold water and collagen which is soluble in warm water

Culinary applications of solubility

Moist heat converts collagen in meat to gelatine making meat more tender

Maillard reaction

The non-enzymic browning of food when dry heat is applied, under dry heat a reaction occurs between amino acids and carbohydrates resulting in browning of food

Culinary applications of Maillard reaction

Roast beef, roast potatoes, toast

Gel formation

The protein collagen present in bones and skin of meat is converted to gelatine on heating, gelatine has the ability to absorb large amounts of water when heated, as protein chains uncoil and water becomes trapped, a sol is formed which on cooking firms a gel

What is a sol

A solution with evenly dispersed particles

What is a gel

A semi solid thickened solution with a 3D network in which water molecules can be trapped

Culinary applications of gel formation

Setting cheesecakes, souffles

Foam formation

Whisking an egg causes protein chains to unfold and air bubbles form which entrap air creating a temporary foam, heat is generated which coagulates the egg albumin slightly, foam will collapse in time unless heated so it sets to form a permanent foam

Culinary applications of foam formation

Making meringues