Fruit And Vegetables Pdf

Fruit and Vegetables

Key points •

The edible part of fruits and vegetables are made up of similar types of cells.

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It is recommended that we eat at least five portions of fruit and vegetables daily. A portion is approximately 80g.

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All types of fresh, frozen, canned and dried fruits and vegetables count. Fruit juice counts but only as one portion, however much is consumed in a day; likewise beans and pulses count only as one portion.

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This food group includes rich sources of a number of nutrients, e.g. carbohydrates, vitamin C, folate, dietary fibre, beta-carotene and potassium, as well as phytochemicals.

Fruit and vegetables have adapted to local climatic and geographic conditions all over the world, resulting in many different varieties. With modern distribution systems it is new easy to obtain fruit and vegetables all year round, and from many different countries.

COMPOSITION Although fruits and vegetables may look different, the edible part is made up from similar types of cells. The cell has an outer wall which is made up mostly from cellulose. Within the cell there is a jelly-like substance called cytoplasm, which carries fat droplets and colour pigments. In potatoes and yams, starch is also carried in this substance.

The major part of the cell, called the vacuole, contains cell sap. The sap is watery and contains sugar, pigments and salts. Between the cells are small pockets known as intercellular air spaces, which give raw fruits and vegetables their opaqueness.

CHARACTERISTICS •

Processing: Whether fruit and vegetables are to be canned, frozen, pickled or eaten raw, further processing is required, e.g. cleaning and trimming, peeling, chopping and washing. The processing of fruits and vegetables may alter their physical characteristics and lead to losses of nutrients. Vitamin C is the most commonly affected nutrient as it is readily oxidised and destroyed by heating in the presence of air. Cut or shredded fruit or vegetables have a shorter shelf-life than those which have not been processed.

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Spoilage: The acidic nature of fruits and vegetables acts as natural protection against spoilage by micro-organisms. Fruit and vegetables continue to live after they are picked, i.e. they absorb carbon dioxide, give off oxygen and tend to become warmer. Fruits have a higher sugar content than vegetables, which makes some varieties susceptible to mould growth. Fruits ripen and vegetables mature on storage, so changes in flavour, appearance and loss of texture may occur.

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Colour: Fruits and vegetables contain natural colour pigments which may be used to colour foods. In fruits these pigments attract animals and birds, signalling the fruit is ripe for consumption thus facilitating distribution of the seeds. The stability of the pigments is affected by pH, light and heat. Freshly cut fruit, such as bananas, apples and peaches will discolour quickly in open air. This oxidation is called enzymic browning. This may be slowed down by the use of antioxidants or prevented by adding an acidic or sugary solution to the surface of the fruit or keeping it at cold temperatures or in water. A similar reaction also occurs in some vegetables, such as potatoes.

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Cooking: During cooking the cell structure starts to break down. This is why raw fruits and vegetables become softer when cooked. Some nutrients are also lost. This is due to the loss of water and other solubles in the sap.

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Products: Many varieties of fruits and vegetables are preserved by canning, dehydration or freezing. The preservation process may alter physical, nutritional and sensory characteristics.

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Jellying: Some fruits, such as apples and blackcurrants, are rich sources of pectin. Pectin is used to set jam.

NUTRITION It is recommended that we eat at least five portions of fruit and vegetables daily. A portion is approximately 80g (e.g. 1 medium apple, 1 cereal bowl of salad or 3 heaped tablespoons of peas). Fruit juice counts too but only as one portion, however much is consumed in a day; likewise beans and pulses count as one portion however much is consumed in a day. Potatoes do not count as a portion as they belong to the starchy food group – another important group of foods for health.

This group of foods includes rich sources of a number of nutrients, e.g. carbohydrates, vitamin C, folate, dietary fibre, beta-carotene and potassium. Although not classified as a nutrient, phytochemicals are compounds commonly found in fruits and vegetables. Some phytochemicals provide colour to stems, leaves, flower and fruits and some protect against attack by insects and other predators. Some phytochemicals provide resistance to infection by mildew and other fungi, while one group of these compounds were the active ingredients in numerous potions and poisons used over the centuries and many are still in use today as prescription drugs.

It is known that diets rich in fruits and vegetables are generally associated with lower disease risks, in particular cardiovascular disease and some cancers. The search is on for the components of fruits and vegetables that convey these health benefits.

PROCESSING All types of fruit and vegetables count toward the target of at least 5 a day, including fresh, frozen, canned and dried. People often mistakenly believe that only fresh fruits and vegetables are of benefit and that processed fruits and vegetables do not provide the same levels of nutrients, due to losses during the processing procedures. This is not always the case.

Different nutrients are affected to various degrees by different food processing methods, depending on the physical properties of the nutrient. Some are fairly resistant to changes

in temperature, light and atmosphere. Others, however, such as vitamin C and folate are extremely sensitive and initial concentrations can rapidly decrease depending on how the produce is treated. Scientific studies have shown that vitamin C levels in some vegetables are actually lower in raw vegetables that have been distributed and stored at ambient or chilled temperatures than in those that had been immediately frozen after harvest when nutrient concentrations are at their highest. Other studies have shown that vegetables stored at room temperature over 2-3 days may lose 50-70% of their folate content.

In preparation for freezing, vegetables must first be blanched (heated for a short time in hot water or steam). This can result in the loss of some water-soluble and heat labile vitamins and minerals. However, losses from the conventional boiling of raw vegetables in the home can be greater as the time needed for cooking is longer. Research has shown that the vitamin C content of cooked frozen peas is comparable with raw peas that have been stored and then cooked.

TYPES There are many different types of fruits and vegetables. Below are a few examples:

Fruit Soft fruits, e.g. raspberry, blackberry, redcurrant, strawberry, bilberry. Citrus fruits, e.g. orange, lime, lemon, kumquat, grapefruit. Stone fruits, e.g. plum, apricot, peach, lychee, cherry, mango. Fleshy fruits, e.g. apple, papaya, pineapple, pear, banana Vine fruits, e.g. grape, water melon, cantaloupe

Vegetable Fruit vegetables, e.g. aubergine, marrow, plantain, tomato, cucumber Legumes, e.g. pea, bean, lentil Flower vegetables, e.g. broccoli, cauliflower, calabrese Leafy vegetables, e.g. spinach, cabbage, parsley, endive, lettuce, watercress Stem vegetables, e.g. asparagus, fennel, celery

Fungi, e.g. oyster and button mushroom Bulbs, e.g. onion, garlic, shallot, leek Roots, e.g. beetroot, swede, salsify, carrot, parsnip, radish

STORAGE Fresh fruit and vegetables should be used as soon as possible. If stored, they should be kept in a cool, dark place to prevent sprouting, mould growth and rotting.

The Foundation would like to thank Pearson Education for the reproduction of illustrations on this page from Cooking Explained (fourth edition) by Jill Davies.

© British Nutrition Foundation 2004