STARCH

About

Starch is a tasteless and fluffy white powder which is insoluble in cold water, alcohol, and other solvents.

It is a non-reducing sugar which means it does not test positive for reducing sugars.

Structure and formula

It is a polysaccharide made up of 1,4 linkages between glucose monomers.

The chemical formula of starch is (C6H10O5)n.

Composition

Starch is made up of two major components: 

Amylose: The linear polymer, the basic form of starch.

Amylopectin: The branched form.

The ratio of amylose to amylopectin varies by the source of the starch.

It can range from 17–70% amylose and 30–83% amylopectin. 

The type of starch is determined by the ratio of amylose to amylopectin: 

• Waxy starches: They contain less than 15% amylose 
• Normal starches: Contain 20–35% amylose 
• High amylose starches: Contain more than 40% amylose.

Role of starches

Energy Storage: The starch helps plants store energy. Plants use the glucose produced by photosynthesis for immediate energy and convert the excess glucose into starch for storage.

Dietary Source: In animals, starch primarily serves as a source of sugar.

Enzymatic Breakdown: Amylase which is found in saliva and pancreas breaks down starch for energy.

Uses

Nutritional Benefits: Starch is broken down into glucose, and provides essential nutrients such as B vitamins, iron, calcium, and folate and serves as fuel for the body.

Pharmaceutical Applications: They are used as a binder in wet granulation processes for tablets and capsules.

Dietary Function: Starch converts glucose into energy and glucose is the primary carbohydrate utilized by the body.

Culinary Uses: They act as a thickener and stabilizer in foods (e.g., puddings, soups, sauces, gravies, pie fillings) and in noodle and pasta production.

PRACTICE QUESTION

Q.Consider the following statements about the Starch:

1. They are insoluble in cold water, alcohol, and other solvents.
2. Amylose is the basic form of starch.
3. Plants convert the excess starch into glucose for storage.

Which of the above  statements are correct? 

A. 1 and 2 only

B. 2 and 3 only

C. 1, 2 and 3 only

D. None

Answer: A

Explanation:

Statement 1 is correct: 

Starch is a tasteless and fluffy white powder which is insoluble in cold water, alcohol, and other solvents.

It is a non-reducing sugar which means it does not test positive for reducing sugars.

Statement 2 is correct: 

Starch is made up of two major components: 

Amylose: The linear polymer, the basic form of starch.

Amylopectin: The branched form.

The ratio of amylose to amylopectin varies by the source of the starch.

It can range from 17–70% amylose and 30–83% amylopectin. 

The type of starch is determined by the ratio of amylose to amylopectin: 

• Waxy starches: They contain less than 15% amylose 
• Normal starches: Contain 20–35% amylose 
• High amylose starches: Contain more than 40% amylose

Statement 3 is incorrect: 

The starch helps plants store energy. Plants use the glucose produced by photosynthesis for immediate energy and convert the excess glucose into starch for storage.