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Lesson Note

Subject: Food And Nutrition

Topic: Food Study
Sub Topic: Vegetables

Lesson Objectives: By the end of the lesson, the learners should be able to:

  1. Define vegetables;
  2. Classify vegetables;
  3. Describe the nutritive value of vegetables;
  4. State the factors to be considered when choosing vegetables;
  5. Mention the different ways of preparing or cooking vegetables;
  6. State the methods or guidelines for preparing leafy vegetables.

Lesson Summary / Discussion

Vegetable can be defined as a plant cultivated for an edible part or parts, roots stems leaves or flowers. vegetables are more clearly perishable foodstuffs and are seasonal. However, through the advancement in technology and science, they can now be kept for a reasonable long-term and are made available during the off-season.

Classification of vegetables

  • Vegetables can be classified into the following groups:
  • Roots examples are carrot turnip parsnips
  • Tubers examples are potatoes
  • Green leaves examples are water leaf, cabbage, spinach, amaranths, lettuce etc.
  • Swollen leaves such as bulbs like onion.
  • Miscellaneous vegetables, examples are cucumber, pumpkins, Pepper, garden eggs, okra etc.
  • Examples of different types of vegetables are shown in the chart below:

Value Of Vegetables

Vegetables especially the leafy vegetables are rich in the B-complex vitamins and also contain a fair amount of vitamin C. Vegetables are also rich in carotene which is a precursor to vitamin A. They are good sources of crude fibre. The crude fibre has the property of absorbing water. They therefore add bulk to stool and assist in easy defecation. Thus vegetables often serve as a mild laxative. vegetables are in addition good source of the mineral elements, notably iron, calcium, phosphorus, sodium and sulphur. However the presence of phytic acid and oxalates in vegetables often interfere with the proper utilisation of iron and calcium found in them. They are low in energy content being deficient in fat and carbohydrates especially the leafy vegetables. They are not highly proteinous so they should not be complemented with other sources of protein.

Factors To Be Considered When Choosing Vegetables

  • The colour should be attractive and they should look crispy and fresh.
  • The midrib of large leaves such as cocoyam leaves should snap sharply when broken across.
  • They should be free from insect attack.
  • When the bunch of vegetables are shaken, beliefs should not drop. If the leaves should drop when shaken, it shows that the vegetable is not fresh.

Factors to consider when choosing miscellaneous vegetables

  • They should not be over ripe and should be free from insect attack such as maggots.
  • They should be fresh. Okra for example should snap sharply when broken.
  • Onions should be firm and well covered with skins.

Factors To Consider When Choosing Root Vegetables

  • They should be free from soil.
  • They should be free from bruises caused by cuts or spades.
  • medium-sized vegetables should be chosen in preference to very small or very large ones.
  • They should be free from signs of decay.
  • Root vegetables should be smooth, unwrinkled and firm.

Cooking / Preparation of Vegetables

There are different ways by which vegetables can be cooked. Vegetables can be boiled, steamed or cooked in a pressure sauce pan and stewed. Leafy vegetables are usually cooked in conjunction with melon. This type is usually referred to as ‘efo elegusi’ (meaning vegetable with melon) in Yoruba language.
Alternatively, the vegetable can be cooked with additional seasonings and spices. The method chosen will depend on the purpose for which the vegetable is to serve and the type of dish to go with it.

Methods of cooking vegetable

A. Root vegetables
Root vegetables can be cooked by any of the following methods: boiling, frying, baking, roasting, or steaming. The method of cooking depends on the types of vegetables and purpose it is meant to serve. However, when cooking root vegetables the following precautions and steps should be taken since most of the food value contained in them may be lost through bad choice of preparation and cooking;
  1. Peeling should be done very carefully and thinly to prevent loss of the edible parts.
  2. They should be soaked in salted water immediately after peeling so as to prevent discolouration.
  3. the peeled vegetables should not be soaked in water for a long time before cooking.
  4. Sweet potatoes cocoyam and yams may be cooked with their peels on. This method saves the loss of some of the nutrients that may occur with peeled ones.
  5. When cooked, the vegetables should be removed from the water immediately else they may become sodden and watery and lose their flavour and colour.
  6. vegetable should be served immediately if possible as cold vegetables are rather insipid to the test.
  7. Root vegetables should be boiled gently to prevent them from breaking up.
  8. As much as possible conservative method of cooking should be used for vegetables. This conservative method help to conserve the nutrients, retain the flavour, maintain the shape and size and little heat is required. These conservative methods are:
  • Baking- only moisture is lost.
  • Stewing: the liquid used for cooking should be used in the sauce.
  • Steaming.
9. An iron pot should be avoided in cooking as this tends to discolour white root vegetables. Aluminium and enamel pans are more suitable.

Methods Of Preparing Leafy Vegetables

  • The following rules should be observed when cooking leafy vegetables.
  • Trim well, discard leaves and pluck fresh leaves from stalk.
  • Wash very well severally without breaking so as to remove soil particles and other dirt.
  • Cut cabbage into four and soak for a short time to crisp the pieces, add a little salt for the last 15 minutes to remove grubs.
  • Shred cabbage just before cooking. large green vegetable may be threaded but small ones may be cooked whole.
  • Pound bitter leaves in a mortar to break up the leaves. Wash several times to remove bitter taste.
  • avoid overcooking vegetables in stews and soups as overcooking a colour and flavour and destroys vitamin C present in the vegetable.

Effect of Heat On Vegetables

  • Heat has the following effect on vegetables:
  • The cellulose and hemicellulose in cell walls get softened with heat.
  • The starch grains swell and burst.
  • Vitamins and soluble mineral salts are leached out by water in boiling.
  • The addition of bicarbonate of soda to green vegetable destroy vitamin C.
  • Vitamin A is soluble at high temperature under pressure and can be destroyed in pressure cooking. This is the reason while pressure cooker is not a good option for cooking vegetables.

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Lesson Evaluation /Test

  1. What are vegetables?
  2. What are classes of vegetables?
  3. Describe the nutritive value of vegetables.
  4. What are the factors to be considered when choosing vegetables?
  5. Mention the different ways of preparing or cooking vegetables.
  6. State the methods or guidelines for preparing leafy vegetables.
  7. Mention vegetables that are peculiar to your locality. Share your knowledge in the comment section.
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