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

摘要

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.