CEREALS AND LEGUMES
CEREALS:
This are plant foods which are derived from seeds of the grass family. Cereals provide most of the world's food energy and more than one-third of its proteins (plant proteins).
Cereal grains are used in various forms. They can be consumed as they are for food, or in slightly modified forms. They can further be processed into flour, starch, oil, bran, sugar syrup, and numerous additional ingredients used in the manufacture of other foods. Moreover, they are fed to livestock which convert them to animal protein of meat, milk and eggs.
The three most important cereals in the world are wheat, rice and corn. Other important ones include sorghum, oats, barley, millet, beniseed and rye.
Generally, in cereals, the limiting amino acid is lysine. For example in corn meal, the lysine content is 167mg/gN while that of egg is 346mg/gN.
COMPOSITION AND USEFULNESS OF SOME CEREALS
1. RICE
COMPOSITION:
Rice contains 11% moisture, 65% carbohydrate, 8% protein, 2% fat, 9% firbre, 0.3% ash and 360 calories pre 100g. These values are average values of the different varieties of rice.
USEFULNESS
Rice is mostly consumed whole (without hull and bran) boiled or cooked in various forms with stew (containing meat, fish, oil and sometimes vegetables) in West Africa.
In China, it is eaten with pork, chicken or vegetables. in India as curry, in Spain as paella and in Italy as risotto.
It is sometimes parboiled, dried and processed into flour for baby foods and for people who are allergic to wheat flour.
Rice puddings are also made from boiled rice. A popular rice pudding in Northern Nigeria is 'Tuwo-shinkafa'. Rice is also used in Japan to brew an alcoholic beverage called Sake. The by-product of rice processing such as hull, bran and germ are used as animal feeds.
2. MAIZE OR CORN
COMPOSITION:
Corn is composed of 11.5% moisture, 72% carbohydrates, 10% protein, 4% fat, 2% fibre and 352 calories per 100g. As was stated earlier, the values of composition are average values. These values can vary depending on varieties, stage of maturity, geographical and weather conditions, soil and other factors.
Corn or maize flour is lower in protein content when compared to wheat but it has higher iron and vitamin A contents than wheat.
The protein type found in corn is Zein hence corn flour is not good in bread making.
USEFULNESS:
Corn is consumed in various forms. It is eaten green, that is, when matured, it is harvested green and boiled or roasted for consumption. It is also described as eating corn on the cob. This is a very popular way of eating corn in Nigeria and in the coast of West Africa.
Corn may be converted to products such as syrup, sugar or pap. These are products of wet milling of corn. Wet milling process involves soaking the kernel overnight to allow them imbibe water. The swollen and softened kernels are milled thereby loosening the hull and the germ. The germ is separated by floatation.
The ground corn is suspended in water and passed over a bolting cloth to remove the hulls. The hulls, pressed cake from germ and proteins are used as animal feeds.
Corn sugar is made by hydrolysis of the starch leading to the production of hydrated dextrose.
Dry milling of corn also leads to production of different food items, chief among which is semovita.
Corn flour is used also for making pastries. In north central part of Nigeria, particularly among the Igalas, cassava flour is mixed with corn flour to prepare a popular corn meal locally referred to as 'ojeakpa' - a variant of semovita.
3. WHEAT
COMPOSITION:
The gross composition of wheat is as follows:- Moisture - 11%, carbohydrate - 69%, protein - 13%, indigestible fibre - 2%, ash - 2% and calories - 340 per 100g.
The above values are average values, therefore, these compositions may vary slightly depending on varieties, stage of maturity, geographical and weather conditions and soil or edaphic factors.
Wheat protein is called gluten. It is gum-like and makes the wheat flour suitable for bread making. It holds the dough together and retains the gas to make the bread porous. Gluten is a mixture of two proteins, glutenin and gliadin.
USEFULNESS:
Wheat flour is used tremendously in baking industries including bread making, sweet doughs, cakes, biscuits, dough nuts, crackers, etc.
It is also used in making some breakfast cereals, gravies, soups, confections, etc.
Another major use of wheat flour is in the making of alimentary pastes such as macaroni, spaghetti and other type of noodles.
LEGUMES:
Legumes are widely distributed world-wide and generally referred to as pulses. Every zone of the world has some legumes peculiar to them.
For example, in France, groundnuts are found, in South America, lima and runner beans, in the United States, soya beans and in Africa, cowpeas, bambara nut, broad beans, in India, lentils and chick peas, etc. All of these and many more can now be cultivated in many parts of the world.
There are two main types of legumes:
i). Those containing high-protein and high oil content. Examples include; soya bean, groundnut, lupin and winged beans.
ii). Those containing moderate protein and low oil content. Examples include; cowpea, gram, pea, bambara groundnut, lentil and the different varieties of the phaseolus group.
LEGUMES COMPOSITION AND USEFULNESS
Legumes are generally high in B vitamins but low in sulphur containing amino acids (methionine and cystine).
They have high content of lysine which makes legumes a good complement to cereals (cereals are low in lysine but high in methionine).
Legumes have some nutritional disadvantages apart from being deficient in methionine and cystine. These are of low digestibility and the consumption of high proportion of legumes in the diet can cause flatulence.
In some cases, it is very fatal to eat some legumes if not properly cooked and the cooking water discarded.
For example, sword bean is highly toxic except the water for cooking it is changed at least twice to remove the leached toxins.
Moreover, butter beans contain hydrogen cyanide which must be removed by steeping the beans in water over night.
Fava beans causes haemolytic anemia (favism). Yet another disease caused by a species, tare(Lathyrus Sativus) is lathyrism which leads to serious paralysis of the legs.
It is very important to follow the laid down procedure for cooking some of these legumes.
REFERENCES
Adeyemi, I. A, Balogh, E. (1985)
Biotechnology in food processing: prospects in Nigeria. Nig. Food J vol 2 and 3
Egbekun, M. K. (1997)
Food Biotechnology in sustenable food production and food security in Nigeria. Proc 28th Annual conf. Nutr. Soc. Nigeria
Ihekoronye, A. I. and Ngoddy, P. O. (1985)
Integrated Food Science and Technology for the Tropics. Macmillan Publishers, London.
Ignatius, A. O. and Matthew, K. E. (1998)
Comprehensive Food Science and Nutrition. Ambik press (ltd) Publishers, Nigeria.
