Studies on the Texture of Salad Dressings Containing Xanthan Gum

Abstract

Characteristics of xanthan gum as a stabilizer, emulsifier and bodying agent when it was formulated in salad dressings were investigated. Flow curves of xanthan gum aqueous solutions were obtained with a concentric cylinder viscometer for the shear rate range from 101;to 10 2sec–1. The power law model S=KD y was applied to the solutions. K increased with concentration, but y were constant between 0.5% and 1.0% concentration. Both K and y were constant with temperature change. Salad dressings containing xanthan gum showed the highest thixotropy index, apparent viscosity, dynamic elasticity and dynamic viscosity compared to those formulated with other stabilizers such as corn starch, guar, tragacanth, pectin and tamarindo seed extracts. Proteins such as egg white and soy protein interacted with xanthan gum resulting in increased apparent viscosity of the salad dressings. Scanning Electron Microscope photographs of frozen salad dressings showed that xanthan gum prevented the oil globules from growing even after 6 months storage at 5°C. Emulsifying activity and the pseudo plastic property of xanthan gum prevented the oil globules from growing and was assumed to stabilize the salad dressings.