ZARITZKY Noemi Elisabet
capítulos de libros
Biopolymers in food emulsions - a viscoelastic approach
Viscoelasticity: Theories, Types and Models. Editors: Jennifer N. Perkins y Tyler M. Lach.
Nova Science Publishers Inc
Lugar: New York; Año: 2011; p. 35 - 58
Biopolymers in food emulsions  a viscoelastic approach. Lorenzo, G.; Zaritzky, N. , Califano, A.  En el libro Viscoelasticity: Theories, Types and Models (pp 35-58). Jennifer N. Perkins y Tyler M. Lach,( Editors) New York, USA. NOVA Science Publishers Inc. ( 2011) .  ISBN: 978-1-61324-203-2.Food emulsions exhibit a great diversity of rheological characteristics, ranging from low-viscosity Newtonian liquids (e.g. milk, fruit beverages), to viscoelastic materials (e.g. salad dressings) and to plastic materials (e.g. butter). This diversity is the result of the different sorts of ingredients and processing conditions used to create each unique type of product. Biopolymeric macromolecules are usually key components in food emulsions to deal with creaming instability. Interactions between raw materials and the selected processing conditions will define each particular final product.There has been a growing emphasis on understanding the colloidal basis of the rheology of food emulsions, rather than just treating them as a ?black box?. Researchers are attempting to relate quantitatively the rheological properties of food emulsions to the characteristics, interactions and spatial distribution of each constituent in the dispersed system.Rheological measurements are appropriate tools for obtaining information about the organization of macromolecules in the medium, thus the correlation of microstructure information with rheological data is useful to understand the macroscopic behavior in terms of the microstructure organization. The relaxation of polymeric materials reveals the existence of a broad distribution of relaxation times and an effective way of examining this experimentally, is to determine the dynamic moduli G´ (storage modulus) and G" (loss modulus). Focusing on the continuous phase behavior of an emulsified system, this chapter is oriented to interpret and model the viscoelastic characteristics of different oil-in-water food emulsions based on the molecular organization of hydrocolloids included in the aqueous phase. Biopolymeric systems containing xanthan-guar mixtures and gellan gum were selected as case studies. The analysis of these systems leads to a wide variety of food emulsions, ranging from fluid dressings to highly structured systems stabilized by a three-dimensional gel structure, caused by physical entanglements among polymeric chains.The effect of hydrocolloids concentration was studied using oscillatory measurements within the linear viscoelastic range. Time-Concentration Superposition principle was applied to find the master curves that describe the mechanical spectra of the viscoelastic materials. Viscoelastic behavior of the systems was satisfactorily modeled using Baumgaertel- Schausberger-Winter equation. This empirical model was used to predict the mechanical relaxation spectrum for both emulsions and continuous aqueous phases. Validation of the predicted spectra was carried out through creep compliance data for emulsion-filled gels and steady-state flow curves for emulsions containing xanthan -guar mixtures. With a precise knowledge of the viscoelastic behavior of food emulsions it is possible to control the desired rheological properties in a particular final product and its stability.