PHYSICAL AND CHEMICAL PROPERTIES OF CEREAL GRAINS

• Components or Parts of Cereals

  • Hull
  • Bran
  • Endosperm
  • Embryo/Germ
• Hull


  • Protects the grain during germinating process and protects from mechanical damage during malting process
  • Restricts excessive seedling growth without adversely affecting the desirable enzymatic-degradation of insoluble high molecular weight materials
  • Can slow the attack of storage in cereals
• Bran


  • Affords little protection against insect infestations
  • Large quantities of lipid and protein are present in aleurone part of the bran
  • Fiber-rich outer layer that supplies B vitamins, iron, zinc, magnesium, antioxidants, and phytochemicals

  
• Endosperm


  • Two main components are starch and protein
  • Two-dimensional parameters, perimeter and surface area, of starch granules are used to describe the endosperm

  
• Germ


  • A separate structure and generally can be easily separated from the rest of the cereal grain
  • The core part where growth occurs, which is rich in healthy fats, vitamin E, B vitamins, phytochemicals, and antioxidants
• Chemical Compositions of Cereals

  • 12-14% of water
  • 65-75% carbohydrates
  • 2-6% lipids
  • 7-12% protein

  
• Moisture content of initial flour is higher than the moisture content of grain due to tempering
• The chemical composition or components of cereals are not uniformly distributed in the grain
• Carbohydrates


  • Constitute about 75% of the solid content of cereals
  • Endosperm contains starch granules, which are the grain's essential part
  • The principal carbohydrate of all cereals is starch, representing 56% (oats) to 80% (maize) of the grain dry matter
  • Cereal starches are similar in composition, having 74-79% amylopectin, 25-30% amylose, and 1% lipids

  
• Proteins


  • The distribution of these protein fractions varies among different cereals
  • Protein content varies by variety, environment, and laboratory extraction
  • Protein content in cereals ranges from 6–15%
• Osborne fractions in cereals

  • Wheat has gliadins and glutenins
  • Rice and Maize have glutelin (oryzenin) and prolamin (zein), respectively
  • Oats have albumins and globulins, avenin
  • Barley has hordeins and glutelins
  • Rye has secalin
• There is considerable variation in the solubility classes among the cereals and also to some extent within each species of cereal
• Notwithstanding the way that cereals contain a different scope of amino acids, which are the blocks for building proteins, a few are just present in the following amount
• Lipid


  • In most cereals the lipid fraction is concentrated in the germ and in the bran milling fractions
  • Oats and maize: unique amongst the cereals; may contain a relatively high lipid content, e.g., >10 percent for oats and as high as 17 percent for some maize cultivars compared to about 2-3 percent for wheat and most other cereals

  
• Vitamins


  • Cereals lack vitamins C, B12, A, and beta-carotene, except yellow maize
  • Cereals provide an excellent source of thiamin, riboflavin, and niacin, among other B vitamins
  • Grains also have a large amount of nutrients,such as vitamin E
• Minerals


  • Grains have high potassium content level
  • Grains have low salt level
  • Grains have significant levels of magnesium, iron, and zinc
  • Grains have lower quantity of a variety of trace minerals, including selenium
• Physical Properties


  • Grain color
  • Grain shape
  • Grain weight
  • Grain size

  
• Wheat

  • Color: light buff or yellow to red brown; depends upon the absence or presence of red pigment
  • Shape: considered like spheres or ellipse because of their irregular shapes; round approaching to spheroid
  • Vitreous wheat: is of higher quality and gives more semolina content
  • Non-vitreous wheat: is opaque and starchy in appearance
• Wheat chemical properties


  • Moisture content: wheat grains contain 10-12% moisture; wheat flour contains less than or equal to 15%
  • Starch content: 70-75% starch content, majority is extracted in the endosperm part of the grain
  • Protein content: 10-13%; 75-80% of the protein content is due to gluten
  • Glutenin contributes to the hydration and elasticity of dough
  • Gliadin contributes to the stickiness and extensibility
• Corn/Maize


  • Color: blackish, bluish-gray, green, white, red and yellow; yellow variety is most common among all colors of corn
  • Shape: flattened cylindrical in shape
  • Size/weight: the size of peas and has maximum size of 2.5cm; standard weight of 56 pounds per bushel
• Corn/Maize chemical properties


  • Starch content: 28-80%; located in the endosperm portion of the grain
  • Protein content: 10-15% (Zeins Protein)
  • Sugar content: approximately 18%
  • Fiber content: in dry weight, fiber content of corn ranges from 9-15%
  • Fat content: 5%; corn oil; linoleic acid
• Rice


  • Color: range of color of white, brown and black
  • Size/weight: consist of short, medium, and long grain size
• Rice chemical properties


  • Moisture content: estimated to have 13% moisture in total
  • Amylose content: 80% of the total dry weight
• Maize/Corn Color


  • blackish
  • bluish-gray
  • green
  • white
  • red
  • yellow
• Yellow variety of corn is most common among all colors
• Maize/Corn Shape


  • Flattened cylindrical in shape
• Maize/Corn Size/Weight


  • Size of peas and has maximum size of 2.5cm
  • Standard weight of 56 pounds per bushel
• Physical Properties of Rice

  • Color: range of color of white, brown and black
  • Size/Weight: consist of short, medium, and long grain size
• Chemical Properties of Rice

  • Moisture content: estimated to have 13% moisture in total
  • Amylose content: 80% of the total dry weight
  • High amylose: difficult to digest
  • Low amylose: quick to digest, higher palatability; mostly sticky rice
• Physical Properties of Barley

  • Color: ranges from light tan to yellowish hue
  • Shape: elongated shape towards more rounded or spherical ones
  • Size/Weight: ranges from as short as 4-7mm to as long as 12-15mm and has weight of 0.6g per cubic meter
• Chemical Properties of Barley

  • Starch content: 70% of its dry weight
  • Amylose content: >35% High-Amylose Barley, 25-27% Medium-Amylose Barley, Below 5% Low-Amylose Barley

  
• Physical Properties of Rye

  • Color: very similar to color of wheat grain but it is slightly darker due to anthocyanin pigment
  • Shape: moves from spheroid towards a more ellipse or spindle shape
  • Size/Weight: single rye grain has size of approximately 7-10mm long
• Chemical Properties of Rye

  • Starch content: estimated 16%
  • Protein content: a decent source of protein; make up 18%
  • Fiber content: around 24%; makes it capable of fulfilling the human body requirements

  
• Physical Properties of Oats

  • Color: ranges in pale gray to yellowish hue with white undertone
  • Shape: differs as it can be rolled out or groats

  Rolled out oats: flattened with their husk removed

  Groats: unflattened with the husk removed

  • Size/Weight: length: 0.5inch width: 0.125 or less, one metric of oats have the weight measurements of 88.1g

  
• Chemical Properties of Oats

  • Carbohydrate content: 66% of total dry weight
  • Protein content: ranges from 11-17%; only cereal that has avenalin protein
  • Fiber content: 11%; fiber of oats has its major part called beta-glucan

  
• Physical Properties of Sorghum

  • Color: present in color of ivory shade to brown or radish black
  • Shape: round or spherical towards broad conic shape
  • Size/Weight: upon milling they give medium particle size of 0.5- 1.0mm. In terms of weight, 1000 sorghum is mostly between 20-30g
• Chemical Properties of Sorghum

  • Starch content: 84%
  • Protein content: 9-12%
  • Fat content: 4%

  
• Physical Properties of Millet

  • Color: ranging from white to yellowish and also darker grains
  • Shape: millet grains are small, round and spherical
  • Size/Weight: a cubic meter of millet grains is measured to have the weight of 780 kg
• Chemical Properties of Millet

  • Carbohydrate content: 70.4%
  • Protein content: 12.4%
  • Fat content: 3.4%
  • Fiber content: 14.2%
• Cereal grains are composed of three major components: starches, proteins, and lipids, with other minor albeit important ingredients, such as minerals, fibers, vitamins, and bioactive metabolites