December 20, 2017 belezza 0Comment

All You Need To Know About Cereals


Cereals

Cereal crops or grains are mostly grasses  cultivated for their edible grains or a fruit seeds

Principle crops

  • Rice
  • Wheat
  • Maize or corn
  • Jowar
  • Ragi
  • Bajra

Nutritive Value

  • Cereals provides
  • Carbohydrate- starch (80%)
  • Fiber
  • Protein (6-12%)
  • EFA
  • Minerals (phsphates & sulphates of K, Mg & Ca
  •  B-Complex vitamins

 

Starch

Starch consist of linear polymers of glucose which are tightly coiled in form of granules

Have a characteristic shape & size depending upon  plant from which they are derived

Two different types of chains:

  • Linear – Amylose
  • Branched-Amylopectin

Amylose

  • Contribute to gel formation
  • Linear chains can orient parallel to each other, moving close enough together to bond
  • Probably due to ease with which they can slip past each other in the cooked paste, they do not contribute significantly to viscosity

Amylopectin

  • Give viscosity to cooked paste
  • Side chains & bulky shape keep them from orienting closely enough to bond together, so they do not usually contribute to gel formation
  • Different plants have different relative amounts of amylose & amylopectin

Protein-Gluten

  • Glutenin or glutelin
  • Gives toughness & rubberiness to gluten
  • Gliadin gives elasticity
  • Glutenin is a much larger molecule than gliadin.

 

Factors affecting  gluten formation

Mechanical Action:

Under mixing, enough gluten is not developed to  retain the gas well. With the result the loaf is heavy & poor in volume

Over-kneading declines elasticity of gluten & dough becomes sticky leading to poor volume of loaf

Oxidising agents:

  • Like potassium bromate, potassium iodate, when added increases strength of gluten
  • If large amounts are added gluten becomes tough with little elasticity
  • Reducing agents have opposite effect making it more extensible & sticky

Other factors:

  • Calcium salts present in  hard water tend to increase elasticity of gluten
  • NACL likewise affects gluten
  • Fats in small amounts increase  ability of dough to retain gas

Effect of Moist Heat

Gelatinization

Starch Granules

H20 +Heat

Breaking of intramolecular H-bonding

Absorb H20

Swell &   Viscosity

Thickness  &  translucency

Factors affecting Gelatinization

Mechanical Action:

  • In early stages , stirring while cooking a starch mixture is desirable for obtaining uniform consistency
  • If agitation is too intense or continued too long, it accelerates breakdown or rupturing thereby decreases viscosity & may give a pasty mouth feel

Types of starches:

  • Wheat starches gelatinize earlier compared to rice, sorghum or corn starch

Proportions of starch:

  • More concentrated dispersions of starch show higher viscosity at lower temperatures than do less concentrated mixtures because of larger number of granules that can swell in early stages

Temperature & time of heating:

Starch pastes may be prepared most quickly by bringing them to a boiling temperature over direct heat, constantly stirring as they thicken & simmering them for approximately one minute

Addition of other substances:

  • Sugar competes with water & decreases gelatinization & lump formation
  • Fats & proteins coat starch granules & thereby delay hydration also lower  rate of viscosity development
  • Acid -vinegar or lime juice reduces thickness of hot starch paste & firmness of  cooled paste

 

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