Premix membrane emulsification to produce oil-in-water emulsions stabilized with various interfacial structures of whey protein and carboxymethyl cellulose

• Complex-layered emulsions can be produced by premix membrane emulsification.
• Although SPR confirmed multi-layer structures, these O/W emulsion were not stable.
• Oxidation rate of O/W emulsions strongly depends on the layer composition.

Premix Membrane Emulsification (ME) with Shirasu Porous Glass membranes of 10 μm pore size enabled to produce oil-in-water (O/W) emulsions with different interfacial structures made of whey protein isolate (WPI) and carboxymethyl cellulose (CMC). Emulsions were stabilized by one interfacial layer, made of WPI (mono-layer emulsion) or 0.5 %wt WPI–0.25 %wt CMC complex (complex emulsion), or by two interfacial layers: one layer made of WPI and the second made of CMC (bi-layer emulsion) or WPI–CMC complex (sequential emulsion). Although the adsorption between the several layers was confirmed by Surface Plasmon Resonance (SPR), only O/W emulsions stabilized by one interfacial layer did not coalescence after homogenization. Mono-layer and complex emulsions were stable after emulsification with a 8.7 μm and 14.4 μm mean droplet size, respectively, although a significant amount of much smaller droplets contributed to increase droplet dispersion giving span values of 1.8 and 3.2 for mono-layer and complex emulsions, respectively.Regarding oxidation rate, TBARS in complex emulsions increased much faster than in mono-layer emulsions. Adsorption data at a hydrophobic interface and the electrical charge of the WPI–CMC complex suggested that it formed a thick (2.2 nm) but less dense (1.40 g cm−3) interface than WPI (2.59 g cm−3) with a negative charge able to attract any transition metal ion and promote lipid oxidation. Premix ME should be further optimized to obtain multi-layered interfaces with an external positive layer, e.g. made of WPI.

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