Pendant Drop Tensiometer: A Valuable Tool for the Characterization of the Foaming Properties and the Interfacial Behavior of Protein Solutions.

Pendant drop tensiometry was usually used to determine the surface elasticity and different kinetic parameters from a modified dynamic surface tension measurement in order to characterize milk protein adsorption behavior to the air/water interface. During manufacturing of various dairy products, milk proteins undergo significant changes due to the application of technological and preservation processing including enzymatic hydrolysis, heat treatment and the change of the pH level. The aim of the present chapter was to investigate the relationship between parameters, which are derived from pendant drop tensiometry (dynamic surface tension and interfacial rheology via volume oscillation) and foaming properties (foam capacity and foam stability) of milk proteins (caseins and whey proteins) as a function of protein composition, heating processes and variation of pH level. As an example, the results of the interfacial properties of sodium caseinates revealed that the initial adsorption rate values of caseinates proteins were reduced and longer time to reach equilibrium conditions was needed when pH decreased and after heating treatment at 70°C and 90°C for 30 min. These findings confirmed the pronounced caseins precipitation at low pH and at high temperature values.