Fruit and vegetables as a food commodity group: their nutritional value, the five-a-day message, how they are classified, enzymic browning, how preparation and cooking affect vitamin C, and storage.

What this dot point is asking

You need to know what fruit and vegetables provide in the diet, how they are grouped, why they brown when cut, and how to prepare, cook and store them so they keep their nutrients, especially the easily lost vitamin C.

What this group gives us in the diet

Fruit and vegetables are valued for their vitamins, minerals, dietary fibre (NSP) and water, and for being low in fat. Important nutrients include vitamin C (for healthy skin, gums and wound healing, and to help iron absorption) and beta-carotene, which the body turns into vitamin A. They also add colour, flavour and texture to meals.

The public health message is to eat at least five portions a day (five-a-day). One portion is about 80 g of fresh, frozen or canned produce, or 30 g of dried fruit, or 150 ml of juice (juice counts only once a day).

How fruit and vegetables are classified

Vegetables are usually grouped by the part of the plant that is eaten:

• roots (carrots, parsnips), tubers (potatoes, although potatoes are a starchy staple), bulbs (onions),
• stems (celery), leaves (cabbage, spinach), flowers (broccoli, cauliflower),
• fruits used as vegetables (tomatoes, peppers), seeds and pods (peas, beans).

Fruits are the part of the plant that contains the seeds, and include soft fruit (berries), hard fruit (apples, pears), stone fruit (peaches, plums), and citrus fruit (oranges, lemons).

Enzymic browning

It is common in apples, pears, bananas, avocados and potatoes. It can be slowed or stopped by:

• coating the cut surface with acid such as lemon juice (the low pH stops the enzyme),
• excluding air (covering the surface or keeping pieces under water),
• blanching (a short heat treatment that destroys the enzyme).

Keeping vitamin C during preparation and cooking

Vitamin C is water-soluble and easily destroyed by exposure to air, heat and long cooking, and it dissolves into cooking water. To keep as much as possible:

• prepare and cut produce just before it is needed,
• cut into larger pieces to reduce the surface exposed,
• cook in a small amount of boiling water, or steam, microwave or stir-fry,
• cook for the shortest time and serve immediately.

Storing fruit and vegetables

• Most fresh produce keeps best cool, for example in the salad drawer of the fridge, which slows wilting and spoilage.
• Some fruit (bananas, tomatoes, avocados) is kept at room temperature to ripen, then can be chilled.
• Keep produce dry and use within a few days, as fruit and vegetables lose vitamin C steadily after harvest.
• Frozen and canned fruit and vegetables keep their value well and count towards five-a-day.