Aggregation behavior of partially crystalline oil-in-water emulsions: Part I – Characterization under steady shear

• Partially crystalline O/W emulsions were designed to “jam” under steady shear.
• Jamming was induced by displacing sodium caseinate with Tween 20.
• Interfacial protein load affected the strength of fat globule aggregates.
• Interfacial protein load controls the dependency of aggregation time on shear rate.
• Solid fat content plays a secondary role in the aggregation process.

Shear-induced aggregation of 35 wt% partially crystalline oil-in-water emulsions was investigated under conditions causing jamming of partially coalesced fat globule aggregates formed under steady shear. Emulsions with different interfacial compositions and solid fat content (∼25–90%) were studied to probe their effect on the generation of a jamming transition over a range of shear rates (500–2000 s−1). Shear stable, sodium caseinate stabilized emulsions were rendered shear sensitive by the addition of Tween 20. Partial displacement of adsorbed sodium caseinate by Tween 20 prior to shear generally resulted in the formation of relatively stable aggregates whereas high displacement of protein led to the formation of less stable aggregates under shear. Evaluation of the dependency of aggregation time on shear rate revealed that interfacial composition primarily controlled aggregate formation rather than solid fat content. These findings show that interfacial protein functions both to regulate the formation of partially crystalline aggregates as well as the aggregate stability under shear. Furthermore, the steady shear method utilized here provides excellent utility for the study of a notoriously complex type of shear-induced colloidal aggregation.

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