Creep and recovery experimental investigation of low oil content food emulsions

Creep and recovery tests have been performed to study the viscoelastic behavior of low oil content food emulsions. Formulations of salad dressings usually include modified starch (MS) due to its low cost and the special creamy texture if affords. The combination of starch with other natural gums may improve the quality of the product. A reference emulsion containing 4% MS, and four other formulations in which the starch was partially replaced by xanthan gum (XG), locust bean gum (LBG) and two synergistic blends of these gums were formulated. Gels prior to emulsification were studied for comparative purposes. The viscoelastic behavior of all the systems was characterized by means of the Burger model, based on the creep tests. Each of the parameters of the model differs considerably among the different gels and proves similar in the case of the emulsions. Based on the creep and recovery tests, a procedure is proposed for calculating the contribution of the different elements of the model to the total compliance of each system. The final percentage recovery of the system is defined, considering a theoretically infinite recovery time. It has been shown that all the emulsions present a similar final percentage recovery, which moreover is greater than that of the corresponding gels. Of note is the fact that replacing part of the starch with a small proportion of XG or LBG increases the percentage recovery of the resulting emulsion. (C) 2007 Elsevier Ltd. All rights reserved.