FUNDAMENTALS OF FOOD TECHNOLOGY (1+1)

Physical properties of solution

A solution is a homogeneous mixture of two or more substances dissolved in a medium in which the molecules of dissolved substances are uniformly distributed in the solvent.

Solubility
The amount of solute that can be dissolved in a given amount of solvent at a given temperature is expressed as solubility.

Hydration
The attachment of molecules of the solvent to solute molecules of ions, by electrical attraction or chemical bonding. The water molecule is highly polar and so water is an excellent solvent for ionic substances. The salvation that takes place in this case is known as hydration.

Vapour Pressure
The intermolecular forces in a liquid prevent escape of most molecules from the surface.

Boiling Point
A liquid boils when its vapour pressure is equal to the external atmospheric pressure.

Freezing Point
A freezing point is the temperature at which the material changes from a liquid to a solid.

Osmotic Pressure
The flow of solvent into a solution, or from a more dilute solution to a more concentrated one, when the two liquids are separated from each other by a semi permeable membrane.

Viscosity
The internal friction which tends to bring to rest portions of the fluids moving relative to one another.

Surface and interfacial tensions
The boundary between a liquid and a gas or vapour is termed surface, whereas that of a liquid-liquid or solid-liquid junction interface.

Specific gravity
The density of one substance in relation to the density of another material is known as specific gravity.

Colloids
Colloid is classified into two groups viz., crystalloids and colloids, depending upon their ability to diffuse through parchment membrane. According to Graham, colloidal solutions contain substances whose molecular aggregates possess a diameter greater than 1 mµ and less than 100 mµ . If the particle size is greater than 100 mµ, a suspension is obtained.

Solution
The difference between true and colloidal solutions

Solution	Solute particle size
True solutions	Molecules and ions less than 1 mµ diameter.
Colloidal solutions	Molecular aggregates, diameter greater than 1 mµ but less than100 mm.
Suspenoids	Molecular aggregates – diameter greater than 100mµ