H.E GCSE revision

Starch: a polysaccharide made up of glucose units.

Sugar: including sucrose, glucose, fructose, maltose and lactose. 

Sources:

• Starches: bread, pasta, rice, potatoes, pulses and breakfast cereals.
• Sugars: fruits, sof drinks, table sugar, sweets and cakes.

Starchy foods should make up at least 50% of our food energy intake. Starchy foods fill you up. 

Glycaemic index

GI is a measure of the effects of carbs on blood glucose levels.

Low GI foods: fruit +veg, grainy breads, pasta and milk

High GI foods: Cornflakes, baked potato, watermelon, croissant, white bread and sweets.

Non-milk extrinsic sugars (NMES): sugars found in sweets and cakes etc.

Insoluble fibre: absorbs water and helps the faeces. Also keeps the gut healthy 

Soluble fibre: slows down digestion and absorption of carbohydrates. Helps to control blood sugar which stops us feeling hungry. 

dietary fibre;

• prevents constipation 
• helps to lower blood cholesterol and glucose levels
• decreases the rise in blood glucose after a meal. 

Low fibre diets cause constipation and gut diseases such as bowel cancer. You should have 12g of fibre a day.

Ways to increase fibre:

• wholegrain breakfast products
• use nuts and seeds
• beans, lentils and peas added to savoury dishes
• dried fruit

We cook food to make it more attractive, tastier and easier to eat. Cooking also makes food safer to eat because it gets rid of harmful bacteria. Cooked food keeps longer than fresh food. Cooking also improves the flavour of many foods.

• Convection: Heat travels round by convection currentsHot air rises and the cool air falls. Methods that involve this are boiling food in a saucepan and baking cakes in an oven. 
• Conduction: a method of heat transfer where a piece of food is heated through direct contact with a hotter object like a hot pan.
• Radiation: Heat travels in waves or rays that heat up food. Food that is grilled or toasted is cooked by radiation. 

Most food is cooked by a combination of methods of heat transfer. E.g. a baked potato is cooked in an oven by convection currents carrying the heat around the oven to the potato. The heat is then conducted through the potato to cook it.