Effect of the incorporation of galactomannans and solid lipid particles stabilized with different surfactants in the properties and stability of cold-set gels

Emulsion-filled gels (EFG) are complex systems that present properties highly dependent on the characteristics of the interactions among the dispersed lipid droplets/particles and the gelled network. This network is usually produced with protein ingredients, such as soy protein isolate (SPI), capable of forming cold-set gels. Although studies regarding cold-set gelation of SPI are already found in the literature, they commercial isolates are rarely used. Such ingredients present challenging characteristics, which can be mitigated by the incorporation of polysaccharides to the gels. In this context, and considering the interest of the food industry in the development of gels with different properties, the present PhD thesis aimed to investigate of the effects of incorporating galactomannans (locust bean gum - LBG and gum guar - GG) and solid lipid particles (SLP) stabilized with different surfactants (whey protein isolate - WPI - and tween 80/span 80), in the rheological and microstructural properties of cold-set SPI gels, produced using different salts (CaCl2 and NaCl), as well as assessing their stability . For this purpose, gels with different concentrations of SPI were produced, by incorporating different concentrations of CaCl2 and NaCl, and they were evaluated regarding visual aspects, water holding capacities (WHC) and rheological properties. It was found the type of salt affected the properties of the gels, possibly due to the different actions of the ions in the gelation process. From the obtained results, the formulations GCaCl2 (14% SPI, 100 mM CaCl2) and GNaCl (14% SPI, 300 mM NaCl) were selected to produce mixed gels, as they presented better rheological properties and WHC. Therefore, different concentrations (0.1 0.3%, w/v) of LBG and GG were incorporated to the gels, which were also characterized. The incorporations of polysaccharides had distinct effects on the gels properties, depending on the type of salt and the characteristics of the galactomannans, which influenced on the degree of demixing. Such degree had a significant effect over the protein-protein interactions and, therefore, over the rheological properties of the gels. From the obtained results, two formulations were selected for the production of EFG: GNaCl LBG (14% SPI, 300 mM NaCl, 0.1% LBG) and GCaCl2 LBG (14% SPI, 100 mM CaCl2, 0.1% LBG). SLP stabilized with WPI were active within the systems, which presented aspecto of self-supported gels before salt addition. EFG produced with SLP stabilized by Tween 80/Span 80, on the other hand, were only formed after salt incorporation. Such SLP decreased the gels strength, however, increased the stability of the systems, that could be adequately characterized during 20 days for CaCl2-induced EFG and 30 days for NaCl-induced ones. NaCl-induced EFGs were, then, satisfactorily used for encapsulating beta-carotene. In comparison to SLP dispersions, EFG presented a superior ability to protect the carotenoid and it is, therefore, an interesting alternative for the development of new functional plant-based foods, with a unique texture and stability. (AU)