Protein

Denaturation

• Protein molecules are very big and formed into bundles held together by chemical bonds.

• Chemical bonds can be broken by heat, whisking, acids, air bubbles.

• If a protein molecule bundle unfolds and changes shape – it denatures.

Coagulation

• Denatured protein molecules unfold and join up with other ones to form big groups – they coagulate.

• As they coagulate, they trap air and water.

• Overcooking causes the coagulated protein molecules to tighten up and squeeze out water.

Gluten

• Protein in wheat flour formed when water is added to flour.

• Gluten makes the dough stretchy, elastic and able to be shaped.

• The dough will shrink back when it is stretched.

• Gluten sets in the oven and traps gas bubbles that have been produced in the dough.

• Pastry dough should be rested to allow the gluten to relax so it does not shrink fast in the oven.

Foams

• Air is trapped in a gas-in-liquid foam by whisking, e.g. egg whites for meringue or eggs and sugar for whisked sponges.

How micro-organisms are used to make:
Cheese

• Non-pathogenic (safe) bacteria and moulds used in cheese making.

• Bacteria culture turns lactose in the milk into lactic acid.

• Lactic acid adds flavour, texture and preserves cheese.

• Rennet added – turns milk to curds (solid) and whey (liquid).

• Whey drained off.

• Curds cut up, salt added, then curds are pressed.

• Bacteria ripen the cheese to develop flavour.

• Cheese left to mature for a few weeks.

• Blue cheeses have a safe mould added to produce blue veins and flavour.

Bread

• Yeast used to produce carbon dioxide gas to make the bread rise by fermentation.

Yogurt

• Special bacteria culture added to milk.

• Milk held at 42°C – bacteria ferment the lactose sugar to lactic acid.

• …