Food Gel Emulsions: Structural Characteristics and Viscoelastic Behavior

Abstract

If the continuous phase of an emulsion or foam is a semisolid system, these systems can be described as 'filled gels' or 'composite solids'. Gel emulsions are widely used in different industries like cosmetic, pharmaceutical, and food, among others. Typical examples are cheese, many desserts, sausages, low-fat may-onnaises and bakery products. The aggregation and cross-linking of protein and polysaccharides molecules into three-dimensional solid-like networks ('gels') is one of the most important mechanisms for developing microstructure with desirable textural attributes. Due to their elastic characteristics, oil droplets can be kept in suspension avoiding creaming. The structure and the rheological properties of gel emulsions are dependent on the nature of the interactions between the emulsifiers adsorbed on the surface of the droplets that fill the emulsion and the biopolymeric network formed in the aqueous phase. The present chapter deals with the viscoelas-tic behavior of o/w gel emulsions containing either polysaccharides or proteins in the aqueous phase. Two case studies are discussed, i.e., emulsions with low lipid content, stabilized with bovine gelatin of different molecular weights and heat-induced gel emulsions containing high acyl gellan gum. Small amplitude oscillatory shear tests (stress and frequency sweeps) and transient studies (creep-recovery) were performed over the different matrices and modeled to interpret the structural characteristics of the gel emulsions. The Broadened Baumgaertel-Schausberger-Winter spectrum was used to represent the linear viscoelastic behavior of the continuous phase and the emulsified system. Relaxation spectra were validated using creep experiments.