Pendant drop tensiometry for the evaluation of the foaming properties of milk-derived proteins

Aim of the present study was to investigate the relationship between parameters derived from pendant drop tensiometry and foaming properties of milk-derived proteins. Foaming time and foam stability of solutions of whey protein isolate and two different whey protein hydrolysates with varying protein content were analysed. Pendant drop tensiometry was used to determine the surface elasticity and different parameters from a modified dynamic surface tension measurement to characterise protein adsorption to the air-water interface. A modified pendant drop technique allowed the characterisation of the surface occupation of proteins for very fast processes like air bubble stabilisation during foaming. Principal component analysis revealed a close relation between foaming time and parameters from dynamic surface tension measurement (lag time for protein adsorption to the interface, slope of the regression line for the change in surface tension) as well as foam stability with parameters derived from interfacial rheology (surface dilatational modulus as well as elastic and viscous components, phase angle). Therefore pendant drop tensiometry proved to be a valuable tool for the characterisation and prediction of the foaming properties and foam stability of protein solutions.

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