Instruments for Physical/ Rheological Properties

These instruments can be used to determine the physical/ rheological properties of milk and milk products although these are the general-purpose instruments.Physical properties like viscosity, surface tension, melting point and freezing point electrical conductance; heat capacity refractive Index etc. are some of the important physical properties which are used to determine the richness or purity of milk and milk products. Whearess springiness, gumminess, cohesiveness etc are the rheological properties, which are determined to judge the texture profile of different dairy products. The important instrument used to determine the physical/ rheological properties of milk and milk products are discussed below.

i. Viscometer: This instrument is used to measure the viscosity/ consistency of milk and milk products. Number of instrument are available in the market for this purpose. Ostwald viscometer is generally used to measure the viscosity of fluid milk while the hoppeler or some other viscometers are used to determine the viscosity of semi liquid products like condensed milk, ice-cream mix etc.

ii. Refrectometer: This instrument is used for both qualitative and quantative analysis such as identification of oils and fats, concentration of sugar solutions and determination of total solids of products (condensed milk etc). There are number of instrument used to determine the refractor index of the solution. In the dairy industry the refrectometer is used to determine the desired concentration of total solids during the manufacturing of sweetened condensed milk and to determine the purity of ghee using a special refrectometer (butyro-refrectometer).

iii. Polarimeter: The polarimeter is used to determine the concentration of those substances in solution which are optically active and are capable to rotate the plane of polarized light examples are amino acids, sugars, steroids, terpenes etc. As the extent to which the plane of polarized light is rotated by an optically active compound is dependent on the concentration of its solution the instrument can be used to determine the concentration of these substances. Whereas the direction (levo or dextro) of rotation is used to identify the optically active substance.

iv. Cryscope/ Cryostar: It is used for the determination of freezing point of liquids such as milk and can reveal the purity of the liquid as the addition or removal of any substance in it can lead to a change in its freezing point.

v. Instron: It is a very sophisticated instrument which is used to determine the rheological properties like springiness, guminess co-hesivoness etc. This instrument is very useful in judging the texture profile of butter, shrikhand, khoa, panee,r, chhana and cheese etc.