Influence of oil phase concentration on droplet size distribution and stability of oil-in-water emulsions

Abstract

The objective of this study was to investigate the effect of oil phase concentration, at different emulsification conditions concerning homogenization time and emulsifier content, on droplet size distribution and stability of corn oil-in-water emulsions. Emulsions were prepared with 3, 5, 10, and 20% w/w triethanolamine oleate (calculated on oil amount), 0.53% w/w carboxymethylcellulose (calculated on water amount), and 5, 10, 20, 30, or 40% w/w oil, and homogenized 5, 10, 20, and 60min. It was found that increase in oil phase concentration led to decrease in specific surface area and increase in polydispersity of emulsion at lower emulsifier concentration and less intense homogenization. At emulsifier concentrations ≤10% and homogenization time ranges of 20-60min the non-monotonous variation in droplet size parameters with oil concentration was observed, as a result of the interaction between triethanolamine oleate and carboxymethylcellulose, which were confirmed by viscosity measurements. However, at emulsifier concentration of 20% an increase in specific surface area and decrease in polydispersity with the increase in oil concentration occurred due to an increase in equilibrium concentration of emulsifier in the continuous phase. Further, influence of oil concentration on emulsion creaming stability was found to be independent on emulsifier concentration and homogenization time. Therefore, a decrease in creaming with increase in oil concentration was observed in all the examined triethanolamine oleate (TEAO) concentration and homogenization time ranges. Practical applications: Emulsions are colloidal systems which can be encountered in different industrial sectors, such as food, pharmaceutical, cosmetics, oil industry, etc. Determination of the droplet size of emulsion is probably the most important way of their characterization, since it influences the properties of emulsion such as rheology, texture, shelf life stability, appearance, taste, etc. The size of the droplets depends on a wide range of parameters. One of them is certainly the concentration of the oil phase. However, since the impact of one parameter is often influenced with the intensity of the other variable involved in the emulsion generation, the aim of the present work was to examine the effect of corn oil concentration on droplet size parameters and stability of oil-in-water emulsions at different emulsification conditions. Therefore a step toward creation of emulsions with desired final properties was made. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.