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Cereals - Grains we eat!
Cereals are seeds of domesticated grasses which had been included in man’s diet for centuries. The principal cereals are rice, wheat, maize, millets, oats and rye. The choice of cereal for any population depends on the availability, climate of that area, economy of the population, culture and customs of that society. For example rice is grown in moist, damp tropical areas and wheat is grown in temperate drier climates.
What are the advantages of eating cereals?
Advantages of using cereals as a main meal are as follows:
· They supply a wide range of nutrients at low cost
· It is the major source of energy and protein as they supply
o 70% of the total energy
o 25- 60% of the total protein intake
· Grow almost anywhere on earth
· Easy to store and transport
· Can be readily processed into highly refined food
What are the cereals made of?
It is important to know the parts of a cereal grain so as to know the nutritional value. Outer most part of the grain is called husk/ hullwhich consist of cellulose and is not useful that part is thrown away as barn. Next layer is pericarp which is 2-4 fibrous layers containing some nutrients. Testa is the fibrous layer between pericarp and aleurone layer which is nutritious. Germ or embryolocated inside these layers has 3 structures named scutellum, plumule, radicle; which is also has a nutritional value. Endosperm is the greater part of grain; which is the store house of the grain; contains carbohydrate. Outer layers of other than husk are of high nutritional value with regard to protein and vitamins.
Nutritional value of Cereals!!
Regarding nutritional characteristics of cereals; there are some basic points to consider i.e. the amount of nutrients varies considerably from species to species; soil and climate. Added fertilizer also affects their composition and processing can reduce the nutritive content of the grain.
Energy content in cereals is high because of the high carbohydrate content [1.00 – 1.63 MJ (240- 390 kcal) per 100 g]. Here starch is the principal carbohydrate mainly seen in endosperm and sucrose is high in germ.
Protein content is 6.5-14% and generally deficient in one or more following essential amino acids i.e. Lysine, Threonine, Tryptopan; but still it contains a wide variety of the non essential amino acids. Regarding composition of proteins; Prolamines and Glutelins are chief proteins. In wheat endosperm gliadin (a prolamine) and glutenin (a glutelin) are present and these proteins are important in bread making as these proteins make a tough elastic complex called gluten which is medically important since some develop allergy against gluten.
Lipid content is 1 – 5% which is low; therefore cereals can be used as a source of protein for low fat diets. In general, diets mainly based on cereals will be deficient in fat soluble vitamins, but wheat germ oil is a particularly rich source of vitamin E.
There is a wide variation regarding mineral content; which is influenced by soil, storage conditions and processing method. Most are good sources of phosphorus, but are poor in calcium and sodium.
Cereals are also an important source of vitamins in the diet. Cereals are good source of thiamin (vitamin B1), riboflavin(vitaminB2), niacin (belong to vitamin B complex); nevertheless it is low in retinol (vitamin A) and Calciferol (vitamin D); also practically devoid of ascorbic acid (vitamin C).But still it is an important source of Pyridoxine (vitamin B6), but great deal may be lost during processing.
Rice - the cereal of the tropics!
Rice is the most important staple food of more than half the human race but it is not a complete food. Value is further reduced between harvesting and consumption as most nutrients are lost during the processing. Milling removes outer portions of the seed, including the embryo, leading to insufficiency of the B complex of vitamins, as vitamins are concentrated on the outer portions of the grain. Washing the milled rice further reduce the content of vitamins as it exposes the aleurone layer and endosperm to water.
Alternative for this is parboiling which is practice in some countries like China, India; where paddy is soaked, steamed, dried and milled. Here water soluble nutrients diffuse from the germ and aleurone layer into the endosperm, so milling doesn’t diminish their concentration in the grain to a greater extent; but since this is not a standard procedure the end product is variable; and there can be disagreeable color and odor as a result of prolonged soaking.
Wheat - from West to East!
The cultivation of wheat is pre-historic. The grain of wheat is a seed with a structure similar to that of rice; here outer coverings, pericarp and testa are hard, fibrous and indigestible; while the aleurone layer is rich in protein. Distribution of nutrients in the grain is not uniform unlike in rice.
Wheat is usually ground into flour before being prepared as food. Proportion of the whole grain that is used for making flour is called extraction rate; here flours of low extraction rate have lost most of the aleurone layer and outer endosperm; which consist mainly starch with little vitamin and it is white in color; while high extraction flour contain most of the scutellum and aleurone layer, in addition to the endosperm
Some products prepared by wheat flour are bread, biscuits, macaroni, spaghetti and noodles. In 1 lb of bread made with 80% extraction flour contains 1140 kcal of energy, 40 g of protein, 480 mg of calcium, 6.5 mg of iron, 0.6 mg of thiamin (vitamin B1) and 0.3 mg of riboflavin (vitamin B2).
Maize or corn grows in localities not particularly suitable for other cereals but it has higher protein content than rice or wheat. There is more niacin (Belong to B complex vitamins) content than rice but the vitamin is present in bound form (niacytin), so they are unavailable for the absorption.
Oats is the most nutritious of cereals, containing 14% protein and 8% fat. It is difficult to remove the husk so it has high fiber content.
So there is enough evidence to have cereals as chief article of diet of humans since it provides most of the nutrients quite easily. Even the base of the food guide pyramid is comprises 2-4 servings of cereals.