β-lactoglobulin as food grade surfactant for clove oil-in-water and limonene-in-water emulsion droplets produced by microchannel emulsification

Unheated and heat-aggregated beta-lactoglobulin (beta-Ig) solutions were used to stabilize clove oil-in-water emulsion and limonene-in-water emulsion prepared by microchannel (MC) emulsification. The size of the MC array plate was 15 x 15 mm(2) consisting of 100 parallel MCs fabricated on each side of the plate. The channels were 4 mu m depth, 71 mu m length, and 8.2 mu m width, with the terrace length of 29.1 mu um. Unheated and heat-aggregated beta-Ig effectively stabilized clove oil-in-water and limonene-in-water emulsions during production using MC emulsification. The emulsion droplets were steadily produced by the channels. The average diameter of clove oil droplets was around 17 mu m, with both unheated and heat-aggregated beta-lg, regardless of the concentration of beta-mu g. The average diameter of the limonene droplets was 18-26 mu m depending on the conditions (unheated or heat-aggregated) and the concentration of beta-lg. The coefficient of variation for all average droplet diameters was <8%, which was an indication of monodisperse droplets. Clove oil-in-water emulsion droplets became polydisperse within 2 h observation, whilst limonene-in-water emulsion droplets remained monodisperse over time. The stability of the oil droplets over time related to the solubility of the oil phases rather than the effects of beta-lg as the surfactant. In addition, the droplet sizes at different surfactant concentrations seemed to relate to the viscosity ratio between the dispersed phase and the continuous phase rather than the effects of the surfactant. (C) 2016 Elsevier Ltd. All rights reserved.