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 Starch | The structure of starch and how it is used in the food industry

Starch | The structure of starch and how it is used in the food industry

What is starch؟

Starch is extracted from many sources such as wheat, rice, corn and potatoes
  • Corn is one of the most important sources of starch, and potatoes come in second place
  • The shape of the starch grain varies according to the source, taking the shape of an oval, round, or polygonal shape, and thus the specifications of the starch differ according to the source from which it is extracted

The corn grain consists of the following sections:

The outer husk ( 5-6% of the whole grain) and this part is rich in fiber, and during the manufacturing process it is completely removed

Endosperm: (80-85% of the whole grain), and this section  subjects to all manufacturing processes to extract the starch (we get it in the form of a fine white powder)

The fetus (10-13% of the whole grain) It is removed in order to extract fetal oil for medical treatments, and this part does not enter into the manufacturing processes.


Benefits of starch industrially:

There are different types of starch as each type specializes in performing a specific industrial function  in a specific product

For example, some products need a certain viscosity at the lowest rate of heating like milk products need high heat to obtain the required viscosity, but there are other products that require a certain viscosity without being exposed to high heat, so the starch has been modified to conform with the manufacturing requirements.  we modified starch through chemical reaction that affect the glycosidic bond or affect the oxidation of hydroxyl groups within the starch

The phenomenon of swelling of starch grains in hot water can be reduced by inserting chemical elements into the starch molecule using specific reagents that interact with hydroxyl groups, as these reactions cause the transformation and modification of the starch composition to become suitable for manufacturing processes.

That is, the processes of physical and chemical modification of the natural types of starch vary to reach new properties that were not previously present, which helps to increase the range of their uses in food.

And by using some enzymes or by heating  with an acid solution or both together, the starch turns into dextrins, maltose and dextrose. The starch is also converted to corn syrup, which is high percentage of fructose, and by enzymes corn syrup turns into fructose sugar.  when starch is dissolved by the action of acids it is converted into glucose sugar. This is observed in all types of starch such as corn, potatoes or rice.


Starch as a molecule is made of

Amylose and amylopectin (the basic unit of both compounds is glucose)

Amylose 

  • constitutes 20%. It is composed of unbranched chains of glucose linked to each other by alpha1-4 linkages. It is pyrolysed by the enzyme beta-amylase.
  • It gives a dark blue color as a result of its union with iodine
  • it is completely crystallized with the presence of butanol alcohol,and this property is used to separate amylose from starch and adsorb it to cellulose, this facilitates the separation process


Amylopectin

  • It constitutes 80%, which are branched chains of glucose linked at the branching points by alpha 1-6
  • And within the chain by alpha 1-4 links
  • It is not completely hydrolyzed using beta-amylase enzyme,and it is not adsorbed on cellulose such as amylose, and also does not crystallize completely in the presence of butanol alcohol and gives a reddish-pink color with iodine.
  • Previous contrasts between amylose and amylopectin make them easy to distinguish and separate from the starch solution

Natural starch has the following physical properties

  • White substance that is odorless and tasteless
  • It does not dissolve in cold water because the starch grains swell in the water  and it does not dissolve  in hot solutions too, but rather forms a gelatin state
  • It has a hygroscopic feature, that means it quickly absorbs moisture
  • The shapes of starch differ according to the plant source, and these shapes are round, oval, polygonal, compound, or clustered, and conical.


Uses of starch in various applications:

In the food industry:

  •  starch is used in the baking industry because it helps to produce an easy-to-chew product without adding sugar or fat.
  • It is used as a filler if it is added to wheat flour by 40%, and this leads to an apparent improvement in the shape and properties of bread.
  • Starch is used to increase viscosity  of canning products and ice creams
  • Starch is  used to prepare  types of cooking milk products
  • The glucose resulting from the hydrolysis of starch, at a rate of not less than 43%, is used in the manufacture of various flavored crystalline sugars.

It is used in the pharmaceutical industries: as a carrier or a sweetener materials 

Chemical industries: especially in the manufacture of paper, gums, textile and packaging industries


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