Starch (6105) n is a polysaccharide that consists of two fractions: 25% linear amylose and 75% branched amylopectin. It is formed in the light in plants during photosynthesis.
This substance is a white powder that does not dissolve in cold water, forming a suspension. After settling the suspension, a white precipitate is deposited at the bottom of the tank, and water can be easily drained. After drying, starch restores all its properties.
In hot water, this substance forms a colloidal solution - this is such a sticky liquid, which is also called starch paste and is often used in everyday life as a bonding agent. And also on this property cooking of jelly and some desserts is based.
Starch is a chemically inert substance. In order for it to enter into a reaction, the participation of catalysts in this process is necessary.
The use of this substance is based on its physical and chemical properties. So, starch and its derivatives are often used in the food, textile and paper industries. And for living organisms, it plays an important role.
To use this organic substance for industrial purposes, it is subjected to chemical exposure. Hydrolysis of starch is a process of exchange between the ions of a substance and water, which can be enzymatic or acidic.
Chemical starch hydrolysis is a catalytic reaction, as it occurs when heated in the presence of inorganic acids. During this chemical reaction , glucose is formed, which can be expressed by the equation:
(C6H10O5) n + nH2O + (cat. H2SO4 + t °) = nC6H12O6.
But recently, enzymatic hydrolysis of starch has become very popular. Using special technologies, ethyl alcohol, molasses and glucose are obtained from it in the same way as in chemical hydrolysis.
The advantage of this process is that for it, starch-containing plants, for example, rye, potatoes, corn, rice and some others, are taken as starting material. These sources, in addition, contain amylolytic enzymes, which are used in the process of hydrolysis.
For example, such enzymes are isoamylases and pullulanases, glucolinases. Enzymes are natural catalysts that accelerate chemical reactions. Schematically, the process of starch degradation by enzymes is as follows: starch → soluble starch (amylose) → oligosaccharides (dextrins) → disaccharide (maltose = malt) → α-glucose. It can also be expressed by the equation:
(C6H10O5) n + nH2O + (cat. Enzyme) = nC6H12O6
You can clearly see that there was a chemical hydrolysis by conducting an experiment. We boil a mixture of starch paste with sulfuric acid. Check if hydrolysis has occurred - drip iodine. If the reaction is negative, that is, there is no blue or purple color, then hydrolysis has occurred.
Now we prove that the hydrolysis product is glucose. Add alkali and copper (II) sulfate (CuSO4) to the resulting solution. The precipitate of copper hydroxide does not precipitate, the solution acquires a bright blue color. We heat and we see the formation of a precipitate of terracotta (brick) color - this means that there is glucose in the solution, which was formed during hydrolysis.
Enzymatic hydrolysis of starch also occurs in the human body. This process is very important, as carbohydrates are formed, in particular glucose. It is oxidized in every cell of the body, forming water and carbon dioxide, while releasing the energy that is necessary for the normal functioning of the body.
Hydrolysis of starch by enzymes begins in the mouth when chewing food. Human saliva contains an enzyme - amylase, under the action of which starch is broken down into simpler components - dextrins. This process a person can even feel. After all, if you chew bread for a long time, then a sweetish taste appears in the mouth, which indicates that the process of hydrolysis of starch has begun. Excess glucose, which is formed during hydrolysis, is deposited in the liver as a reserve nutrient - glycogen.