Thickening properties, often measured by viscosity, which is the resistance of a fluid being deformed by either shear stress or tensile stress. Viscosity can be scientifically measured by equipments like Viscometers and Rheometers. However, close temperature control of the fluid is needed to acquire an accurate and repeated readings, since the viscosity is dependent on temperature.
The common measurement unit is pascal-second (Pa·s) or centipoise (cP). 1 cP = 1 mPa·s = 0.001 Pa·s.
On the human sensory perspective, the mouth is sensitive to the physical viscosity, an aspect of food rheology. Often it is been define as mouthfeel or texture. It is a concept used to define and evaluate the quality of the food while eating or drinking. The thickening effect will increase the viscosity of the media, therefore, enriching the mouthfeel of the products. Until today, there is no clear equation of using analytical equipment to measure texture and sensation we experience when eating and drinking. Therefore, texture will remains as a combination of both science and arts.
On the basic science principal, thickening of solution happens when the macromolecules does not cross-link. The level of vicosity depends on the concentration of the product,electrostatic interaction, steric forces and molecular weight. Function of the viscosity is to trap or immobilized the water in the solution or media where the hydrocolloids dissolved.
Some example of product that forms thickener are : xanthan gum, carboxymethyl cellulose, locust bean gum, carrageenan, gelatine.