Mechanical barrier preventing the centrifugal creaming of O/W food emulsions, stabilized by proteins

Abstract In O/W emulsions, stabilized by acetylated faba bean protein isolate (AFBPI) which are stable against separation of the disperse phase (coalescence) a mechanical barrier for the separation of the continuous phase (creaming) under centrifugal forces has been detected. For any given constant centrifugal acceleration a constant amount of continuous phase is separated. This type of behaviour resembles that of coagulation structures in dispersions of solids. One possibility to determine the stability of emulsions against separation of the continuous phase (creaming) for systems stable against coalescence (separation of the disperse phase) is the use of centrifugation in many variations. Ondracek et al. [1], for example, used the speed of rotation which caused separation after a given time. In this kinetic method „stability”︁ means that during centrifugation for 10 min at a constant speed of rotation no separation of the continuous phase takes place. The reason for the stability of emulsions against creaming, may be, a mechanical barrier, which breaks down only at higher centrifugal forces, or the rate of separation of the continuous phase is extremely slow. Therefore 10 min are not sufficient to detect separation. A mechanical barrier with O/W food emulsions may arise from two mechanisms: 1. The consistency of the aqueous phase, containing the protein is gel‐like, occluding the oil droplets. 2. Oil droplets, stabilized by an adsorbed protein layer, build up a coagulation structure. The droplets act like solid particles, due to the rigid layers of the protein. The behaviour of such coagulation structures in dispersions of solids in centrifugal and shear fields has been described in [2]. The aim of this work is to examine whether there exists a mechanical barrier against the breakdown of the coagulation structure for some O/W food emulsions.