Bread, cereals, flour and potatoes as a food commodity group: their nutritional value, the value of starchy carbohydrates in the diet, the main types, their working characteristics, and how they are stored.

What this dot point is asking

This is the first commodity group in WJEC Food Preparation and Nutrition. You need to know what bread, cereals, flour and potatoes provide in the diet, the main types, how they behave when prepared and cooked (their working characteristics), and how to store them safely.

What this group gives us in the diet

These foods are valued mainly as a source of energy. Their main nutrient is starch, a complex carbohydrate that is digested to glucose. They are the largest section of the Eatwell Guide, so starchy foods should fill about a third of the plate at each meal.

Wholegrain versions (wholemeal bread, brown rice, wholewheat pasta, jacket potatoes with skin) are an important source of dietary fibre (NSP), which keeps the digestive system working, helps prevent constipation and bowel disease, and helps you feel full. The group also provides B vitamins (for releasing energy from food) and some protein, and is naturally low in fat.

The main types

• Cereals are grains: wheat, rice, oats, maize (corn), barley and rye. Wheat is milled into flour; rice and oats are eaten as grains; maize gives cornflour and breakfast cereals.
• Flour is milled from wheat. Strong (bread) flour is high in protein for bread; plain and self-raising flour are softer flours for cakes and pastry; wholemeal flour contains the whole grain.
• Bread is made from flour, water, yeast and salt. It can be white, brown or wholemeal, and shaped many ways.
• Potatoes are starchy vegetables (counted here as a starchy staple, not as one of the five-a-day). Floury (maincrop) varieties are best for baking and mashing; waxy (new) potatoes hold their shape for boiling and salads.

Working characteristics

These foods behave in distinctive ways when prepared and cooked, and the exam often tests these properties.

Gelatinisation

When starch (for example flour or cornflour) is heated in liquid, the starch grains absorb the liquid, swell and burst at about 80 to 90 degrees Celsius, thickening the mixture. This is how a roux or a cornflour sauce thickens.

Gluten formation

When water is added to wheat flour and the dough is worked, the proteins form gluten, an elastic network that traps gas and gives bread and pastry their structure. Strong flour has more protein, so it forms more gluten, which is why it is used for bread.

Dextrinisation

When starchy food is cooked with dry heat (toasting bread, baking a crust), the starch on the surface browns and changes flavour. This is why toast and bread crusts turn golden.

Storing these foods

• Flour and dried cereals: keep cool, dry and in a sealed container to keep out moisture and pests, and use within the date mark.
• Bread: store in a bread bin or sealed bag at room temperature, or freeze; do not keep bread in the fridge, as it goes stale faster.
• Potatoes: keep cool, dark and dry (a paper sack, not plastic), away from light. Light turns potatoes green and produces a bitter, slightly toxic substance, so green parts should be cut away.