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Chemistry of cereals

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Cereals:

Cereals form the major source of food.
The composition of cereal grains varies greatly due to

The genetic makeup of the plant
Soil factors
Climatic factors
Cultural practices


Cereals include rice, wheat, maize, sorghum, barley, etc
They comes under the family gramineae, i.e grass family.







Chemistry of cereal crops deals about chemical constituents :
Carbohydrates
Fats
Proteins
Ash
Nutrients like Ca,P
Vitamins
Toxins
Cereals are the major part of Indian diet so also known as staple foods.

The 80% percent of the dry matter in grains is carbohydrate, mainly the starch therefore, they are considered as the main energy providing crops.

Cereals provide 350 kcal of energy per 100 grams to the body.

Cereals contain 6-12% of protein

The whole grain form of cereal is more nutritious than milled one as it contains greater levels of B-complex vitamins, dietary fibre and essential fatty acids.
Cereals low in proteins.

High in Nitrogen Free Extract which includes the carbohydrates such as starch, dextrin, soluble sugars.

Starch constitutes more than 90% of NFE.


Grains, hulls and bran – rich in cellulose, pentosans and ash constituents.

germ or embryo – higher oil content, crude protein, sugar and minerals.

Endosperm – starch.
Abundant constituent of cereal plant system (80-95%).
With maturity water content decreases in plant.



CARBOHYDRATES:

Generally cereals rich in carbohydrates.

It ranges from 70-80%.

83% of total dry matter of wheat, barley, rye, maize, sorghum
and rice and 79% of oats.

Carbohydrates in cereal grains include more than 90% of starch.

Dextrin occurs in small amounts.

Bran chiefly contains pentosans and some cellulose and lignin.

Germ tissues have sucrose.

PROTEINS:

Cereal proteins are simple proteins in composition.

Conjugated proteins like nucleoproteins are concentrated mostly in the germ.

The simple proteins yield α- amino acids on hydrolysis.

Among simple proteins, cereal grains found to have
1) water soluble proteins (albumins)
2) salt soluble proteins (globulins)
3) alcohol soluble proteins (prolamines)
4) acids and alkali soluble proteins (glutuleins)

In cereals 6-12%




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Chemistry of cereals

  1. 1. B.R. INIYA LAKSHIMI Ph.D. Scholar TNAU
  2. 2. Cereals: Cereals form the major source of food. The composition of cereal grains varies greatly due to The genetic makeup of the plant Soil factors Climatic factors Cultural practices Cereals include rice, wheat, maize, sorghum, barley, etc They comes under the family gramineae, i.e grass family.
  3. 3. Chemistry of cereal crops deals about chemical constituents : Carbohydrates Fats Proteins Ash Nutrients like Ca,P Vitamins Toxins
  4. 4.  Cereals are the major part of Indian diet so also known as staple foods.  The 80% percent of the dry matter in grains is carbohydrate, mainly the starch therefore, they are considered as the main energy providing crops.  Cereals provide 350 kcal of energy per 100 grams to the body.  Cereals contain 6-12% of protein  The whole grain form of cereal is more nutritious than milled one as it contains greater levels of B-complex vitamins, dietary fibre and essential fatty acids.
  5. 5. Cereals low in proteins. High in Nitrogen Free Extract which includes the carbohydrates such as starch, dextrin, soluble sugars. Starch constitutes more than 90% of NFE. Grains, hulls and bran – rich in cellulose, pentosans and ash constituents. germ or embryo – higher oil content, crude protein, sugar and minerals. Endosperm – starch.
  6. 6.  Abundant constituent of cereal plant system (80-95%).  With maturity water content decreases in plant. Water
  7. 7. CARBOHYDRATES: Generally cereals rich in carbohydrates. It ranges from 70-80%.  83% of total dry matter of wheat, barley, rye, maize, sorghum and rice and 79% of oats. Carbohydrates in cereal grains include more than 90% of starch. Dextrin occurs in small amounts. Bran chiefly contains pentosans and some cellulose and lignin. Germ tissues have sucrose.
  8. 8. PROTEINS: o Cereal proteins are simple proteins in composition. o Conjugated proteins like nucleoproteins are concentrated mostly in the germ. o The simple proteins yield α- amino acids on hydrolysis. o Among simple proteins, cereal grains found to have 1) water soluble proteins (albumins) 2) salt soluble proteins (globulins) 3) alcohol soluble proteins (prolamines) 4) acids and alkali soluble proteins (glutuleins) o In cereals 6-12%
  9. 9. Prolamines are the characteristics of grass family. Cereal proteins are poor in one or more essential amino acids. Zein – maize protein lacks lysine and trptophan. Wheat protein poor in lysine and threonine. proteins: Rice – oryzenin Wheat – gliadine and glutenin. Maize – zeatin
  10. 10. LIPIDS: 1- 5% in cereal plant. Lipids are present in the embryo of seeds. They include fatty oils, phosphatides like lecithin and sterols like sitosterols. Tocopherols ( vitamin E) are found in larger amount in the unsaponifiable fraction of germ oils. The iodine value of cereal oils varies from 100 – 125 and they are classed as semidrying oils. This is a measure of degree of unsaturation of fats and oils.
  11. 11. ENZYMES: The most important cereal enzyme is amylases. Other enzymes present in cereals are proteases, lipases, oxidases. Also contains fermentation enzymes such as maltases, diastases, etc.,
  12. 12. VITAMINS: All the cereal grains are fairly rich in vitamin B but low in vitamin C & D. The endosperm has the lowest amount of vitamin B. About 63% of thiamine content of wheat is found in scutellum. Golden rice rich in vitamin A, containing carotenoids. Vitamin A activity in yellow rice is primarily due to coloring substances “cryptoxanthin”.
  13. 13. MINERALS: Inorganic constituent . Occurrence- free state, ions, salts, organically bound form. 2- 5% The dominant ash constituents of cereals are K , P and Mg. The other minerals are S, Cl, Ca and Na which are present in small volumes.
  14. 14. Silicon is found to present in higher proportions in closed cereal grains like rice and barley (4-6%). The other trace elements are Al, Ca, Cu, Li, Ni, Se, Sn, Ti and I. P content is uniformly distributed in different cereals and in many cases higher than that of Ca. It is mainly present as Ca or Mg salt of phytic acid.
  15. 15. TOXINS: Some cereals contains toxins in their forage: Sorghum – HCN/ dhurin/ prussic acid Pearl millet – oxalic acid
  16. 16. CRUDE FIBER  Defined as the sum of all those organic components remain after removal of crude protein, crude fibre, and nitrogen-free extractives.  insoluble in dilute acid and alkali  represents about 50-80% of cellulose, 10-15% of lignin, and 20% of the hemicellulose of the original food. Cereal grains are good sources of water-soluble dietary fibres. In cereals crude fibre content used for evaluating milling efficiency .
  17. 17. King - wheat Queen – maize – backbone of America. King of coarse cereals – sorghum Know this

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