Abstract:

Surfactants contg. sugar components and fatty acids satisfy the quality stds. for food application. The food grade sugar ester in this study is a com. sucrose monoester of stearic acid (abbreviated SES), the oil phase consists of a 1:1 mixt. of n-tetradecane and l-butanol. The originally planned food grade oil, a medium chain triglyceride, is substituted by tetradecane because tetradecane is available as a fully deuterated product, which is necessary for some structural investigations. The investigated system is solid at room temp., but liquefies and structures into a homogeneous microemulsion when heated to above 37°C. The structural characterization of the microemulsions was studied. The established methods for this purpose are scattering methods, such as small-angle scattering of X-rays and neutrons and dynamic light scattering. These scattering techniques can be used to obtain valuable information on the size, shape, and internal structure of colloids and complex fluids. The authors started the investigation with the pseudobinary system SES, tetradecane and l-butanol, varying the SES content. The scattering results show that the sugar ester forms inverse globular micelles in the oil phase. The size of these micelles is about 6 nm. While the size is nearly const. in a wide SES concn. regime (5 up to 40% surfactant), the vol. or aggregation no. increases significantly with SES. This is explained by an increasing replacement of l-butanol mols. by sugar-ester mols. in the micelles formed. Moreover, it can be shown that these micelles strongly overlap. Their center-to-center distance is about 3.8 nm at 40% SES at a micellar diam. of 6 nm. The micellar overlap leads to a highly reduced diffusion of the micelles as was found with dynamic light scattering. When incorporating water in the micellar core, the micelles swell up to about 10 nm and the shape of the aggregates becomes more and more elongated with higher water content. (c) 2001 Academic Press. [on SciFinder(R)]