Characterization of fish oil in water emulsion produced by layer by layer deposition of soy β-conglycinin and high methoxyl pectin

Abstract

In this study we employed a layer-by-layer (LbL) deposition technique to produce fish oil in water emulsions encapsulated with a positively charged inner soy β-conglycinin (7S) layer by high shear mixing followed by deposition of a negatively charged outer high methoxyl pectin (HMP) layer using either high shear mixing or homogenization (500 or 3000 psi) and compared them with emulsions produced by 7S-HMP complex. The size, shape, morphology and wall structure of emulsion droplets were characterized by dynamic light scattering and microscopy. Emulsion produced by high shear mixing only were unstable with a droplet size of 7.48 μm. Stable emulsions were produced by high shear mixing followed by homogenization at 500 psi with significantly lower droplet size (3 μm) and uniform two layer shell thickness (80–170 nm) around the drops. The two layer shell thickness of emulsion drops produced by homogenization at 3000 psi was non uniform although it exhibited good long term storage stability. More diffuse distribution of 7S was observed in the adsorbed layer of emulsion droplets that were produced by 7S-HMP complex compared to LbL with a higher layer thickness and a lower ζ potential for the former thereby indicating a difference in morphology of adsorbed layers in the two cases. The results of this investigation seem to indicate that the mechanism of emulsion formation in the second homogenization step is closer to layer by layer deposition than stabilization by 7S-HMP complex and demonstrated a new method of LbL to utilize 7S as an emulsifier.