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The Rim of this work was to carry out a rheologicai study of aqueous systems containing a noniouic surfaetant derived from sugar. The compositions studied ranged from the micellar region up to the occurrence of fully developed liquid crystals. This study was tailed out at 50°C.Systems up to 2% {wt) sucrose stearate exhibited a powezqaw decrease in the steady-state apparent viscosity with shear rate. At higher sucrose stearate concentrations, the flow curves exhibited two well~lefined regions depending on shear rate, so that the apparent viscosities fitted the Carreau model A [Carreau, P.J., D. De Kee and M. Daroux, Can. J. Chem. Eng. 57:135 (1979)]. The existence of three composition ranges is proposed. An increasingly stronger micellar structure, as surfactant concentration rises, extends up to 10% {wt) sucrose stearate. Between 15% and 35% (wt) sucrose stearate, the results obtained are consistent with the occurrence of a lamellar liquid-crystai dispersion in an isotropie micellar solution. The Hquid crystalline content in the dispersion steadily increases with surfactant concentration up to reaching a fully developed lamellar liquid crystal at 40% {wt) sucrose stearate.KEY WORD~ Flow behavior, food emulsifier, food surfaetant, liquid crystal, mieeile, phase behavior, rheology, sucrose esters, viscoelasticity, viscosity.

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ResumenUna sepiolita procedente de Toledo (España) se ha activado por tratamiento con disoluciones 0·25, 0·50 y 0·75 n de NO3H, seguido de calentamiento durante 10 h a 110, 200, 300, 400 y 500°C. Para cualquier concentración ácida, un calentamiento de 110, 200 y, a veces, 300°C, produce un aumento del número de poros mientras que las temperaturas superiores significan un cierre de los mismos tanto mayor cuanto más elevada es la temperatura de tratamiento. El máximo desarrollo de la superficie accesible al N2 tiene lugar con una disolución 0·50 n de NO3Hy 200°C (449 m2/g, método de BET); la superficie específica de la sepiolita natural es de 321 m2/g.