WEEK 3
Agricultural Science. S.S.S 1 First Term
TOPIC: Nutrition and health
In everyday usage, a vegetable is any part of a plant that is consumed by humans as food as part of a savoury course or meal. The term “vegetable” is somewhat arbitrary, and largely defined through culinary and cultural tradition. It normally excludes other main types of plant food, fruits, nuts and cereal grains but includes seeds such as pulses. The original meaning of the word vegetable, still used in biology, was to describe all types of plant, as in the terms “vegetable kingdom” and “vegetable matter”.
Nutrition and health
Vegetables play an important role in human nutrition. Most are low in fat and calories but are bulky and filling. They supply dietary fibre and are important sources of essential vitamins, minerals and trace elements. Particularly important are the antioxidant vitamins A, C and E. When vegetables are included in the diet, there is found to be a reduction in the incidence of cancer, stroke, cardiovascular disease and other chronic ailments. Research has shown that, compared with individuals who eat less than three servings of fruits and vegetables each day, those that eat more than five servings have an approximately twenty percent lower risk of developing coronary heart disease or stroke.
When a vegetable is harvested, it is cut off from its source of water and nourishment. It continues to transpire and loses moisture as it does so, a process most noticeable in the wilting of green leafy crops. Harvesting root vegetables when they are fully mature improves their storage life, but alternatively, these root crops can be left in the ground and harvested over an extended period. The harvesting process should seek to minimise damage and bruising to the crop. Onions and garlic can be dried for a few days in the field and root crops such as potatoes benefit from a short maturation period in warm moist surroundings during which time wounds heal and the skin thickens up and hardens. Before marketing or storage, grading needs to be done to remove damaged goods and select produce according to its quality, size, ripeness and colour
Storage
All vegetables benefit from proper post harvest care. A large proportion of vegetables and perishable foods are lost after harvest during the storage period. These losses may be as high as thirty to fifty percent in developing countries where adequate cold storage facilities are not available. The main causes of loss include spoilage caused by moisture, moulds, micro-organisms and vermin.
Preservation
The objective of preserving vegetables is to extend their availability for consumption or marketing purposes. The aim is to harvest the food at its maximum state of palatability and nutritional value, and preserve these qualities for an extended period. The main causes of deterioration in vegetables after they are gathered are the actions of naturally-occurring enzymes and the spoilage caused by micro-organisms. Canning and freezing are the most commonly used techniques, and vegetables preserved by these methods are generally similar in nutritional value to comparable fresh products with regards to carotenoids, vitamin E, minerals and dietary fibre.
| Some common vegetables | ||||
| Image | Description | Parts used | Origin | Related cultivars |
| Cabbage Brassica oleracea |
Leaves, axillary buds, stems, flowerheads | Europe | Cabbage, red cabbage Savoy cabbage, kale Brussels sprouts, kohlrabi, cauliflower, broccoli Chinese broccoli |
|
| Turnip Brassica rapa |
Tubers, leaves | Asia | Turnip, rutabaga (swede) Chinese cabbage napa cabbage bok choy, collard greens |
|
| Radish Raphanus sativus |
Roots, leaves, seed pods, seed oil, sprouting | Southeastern Asia | Radish daikon seedpod varieties |
|
| Carrot Daucus carota |
Root tubers | Persia | Carrot | |
| Parsnip Pastinaca sativa |
Root tubers | Eurasia | Parsnip | |
| Beetroot Beta vulgaris |
Tubers, leaves | Europe, Near East and India | Beetroot sea beet Swiss chard sugar beet |
|
| Lettuce Lactuca sativa |
Leaves, stems, seed oil | Egypt | Lettuce celtuce |
|
| Beans Phaseolus vulgaris Phaseolus coccineus Phaseolus lunatus |
Pods, seeds | Central and South America | Green bean French bean runner bean haricot bean Lima bean |
|
| Broad beans Vicia faba |
Pods, seeds | North Africa South and southwest Asia |
Broad bean | |
| Peas Pisum sativum |
Pods, seeds, sprouting | Mediterranean area and Middle East | Pea snap pea snow pea split pea |
|
| Potato Solanum tuberosum |
Root tubers | South America | Potato | |
| Eggplant Solanum melongena |
Fruits | South and East Asia | Eggplant (aubergine) | |
| Tomato Solanum lycopersicum |
Fruits | South America | Tomato | |
| Cucumber Cucumis sativus |
Fruits | Southern Asia | Cucumber | |
| Squashes Cucurbita spp. |
Fruits, flowers | MesoAmerica | Pumpkin, squash, marrow, zucchini (courgette), gherkin, gourd | |
| Onion Allium cepa |
Bulbs, leaves | Asia | Onion spring onion scallion shallot |
|
| Garlic Allium sativum |
Bulbs | Asia | Garlic | |
| Leek Allium ampeloprasum |
Leaf sheaths | Europe and Middle East | Leek elephant garlic |
|
| Capsicum annuum | Fruits | North and South America | Pepper bell pepper sweet pepper |
|
| Spinach Spinacia oleracea) |
Leaves | Central and southwestern Asia | Spinach | |
| Yam Dioscorea spp. |
Tubers | Tropical Africa | Yam | |
| Sweet potato Ipomoea batatas |
Tubers leaves shoots |
Central and South America | Sweet potato | |
| Cassava Manihot esculenta |
Tubers | South America | Cassava | |
Exercise
- Explain how to store vegetables
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