Serum separation and structure of depletion- and bridging-flocculated emulsions: a comparison

Stability against demixing, rheology and microstructure of emulsions that were flocculated by depletion or bridging were compared. Flocculation by depletion and bridging was induced by addition of the polysaccharide carboxy-methylcellulose (CMC) to emulsions that were stabilised by beta-lactoglobulin (beta-1g) at pH 6.7 and 3.0, respectively. Depletion-flocculated emulsions generally have a lower initial demixing rates than bridging-flocculated emulsions, but after long times they are compressed to a higher oil content by gravity. Differences in the initial demixing rate are shown to be caused by differences in porosity between the gels. In bridging-flocculated emulsions, large irreversible flocs are formed by flow during mixing, resulting in larger permeability than in depletion-flocculated emulsions. Rheological measurements showed that bridging-flocculated emulsions could withstand larger stresses than depletion-flocculated emulsions. Greater network strength and a lower probability of rearrangements explain why bridging-flocculation systems can retain more water at longer times. (C) 2004 Elsevier B.V. All rights reserved.