Modulating process parameters to change physical properties of bigels for food applications

Abstract

The effect of the process parameters involved in the production of bigels was investigated through the study of structural, mechanical and rheological properties. Four level (24) Central Composite Rotational Design (CCRD) configuration was applied in order to study the organogelator concentration, hydrocolloid concentration, organogel:hydrogel ratio and shear of mixing. Gellan gum and high oleic sunflower oil with glycerol monostearate were used to produce hydrogels and organogels, respectively. All formulations were water-in-oil systems with gel-like behavior. FTIR and XRD results showed that bigels were formed only by physical arrangement with no chemical interactions, but gellan gum decreased the crystallinity of the systems due to its amorphous character. However, hydrogel particles acted as an active filler, reinforcing the structure in comparison to pure gels. Also, the glycerol monostearate present in the organogel could self-assemble at the interface in order to interact with the aqueous phase, improving the interaction and affinity between the phases. Moreover, depending on the composition, systems could be softer or harder and present some frequency dependence. CCRD showed that all parameters evaluated changed with organogel:hydrogel ratio and organogel concentration. Shear of mixing was also significant for some parameters; however, hydrocolloid concentration did not exert a significant effect on the range studied. From PCA analysis it was possible to distinguish different groups, which means that some conditions produced bigels with similar characteristics. Thus, it is expected that these results will allow customizing and fine-tuning properties of structured two-phase systems for diverse applications, ranging from food to pharmaceutical and cosmetic industries.