Influence of the sodium dodecyl sulphate (SDS) concentration on the disperse and rheological characteristics of oil-in-water emulsions stabilized by octenyl succinic anhydride modified starch-SDS mixtures

Stability of oil-in-water emulsions can be achieved by chemically modified starch, such as octenyl succinic anhydride (USA) starch, as an emulsifier. In order to analyse the disperse and rheological characteristics of emulsions containing two kinds of emulsifiers, part of the USA starch can be substituted with an adequate concentration of sodium dodecyl sulphate (SDS), which is a small surfactant with the same charge as USA starch. The oil contents of the examined emulsions were 5, 20 and 50 %. The selected USA starch concentration was 10 % and replacements of a part of the USA starch were realized with SDS concentrations of 1, 3 and 5 %. Dispersed droplets of emulsions were defined by determination of the Sauter mean diameter d(32) and particle size distribution. Flow curves were used to describe the rheological properties of the emulsions. In addition, the stability of the emulsion samples was observed and expressed by the creaming index. The obtained results indicated a decrease in the Sauter mean diameter of the droplets, the standard deviation and the apparent viscosity of the emulsions with increasing amounts of SDS within the emulsifier mixture USA starch-SDS. According to creaming rate, the emulsions with OSA starch were more stable than the emulsions stabilized by the USA starch and SDS combinations.