Adsorption at the oil-water interface and emulsifying properties of native granules from egg yolk: effect of aggregated state

Native and disrupted granules were used to prepare and stabilise oil-in-water emulsions containing washed sunflower oil. Native granules were in an insoluble aggregated form, whereas, after addition of sodium chloride, granules were disrupted and their proteins and lipoproteins were liberated and solubilised. Native granules were adsorbed at the oil-water interface as complex particles without dissociation of their individual proteins and lipoproteins. This aggregated state allowed a greater surface coverage than the molecular state following upon granules disruption, because of the convective mass-transport occurring during homogenisation. However, in emulsions made by means of these aggregates, the droplet size was larger, and stabilisation against creaming and coalescence were less efficient than that of emulsions made with proteins and lipoproteins liberated from disrupted granules. The electrophoretic study of emulsion droplets revealed that, whatever the native or disrupted form, all major granules proteins were adsorbed at the oil-water interface. Results suggest that it is possible to realise emulsions with native granules but that such emulsions are less fine, less homogenous and less stable than emulsions realised with disrupted granules. (C) 2000 Elsevier Science Ltd. All rights reserved.