Food-grade bigels: Evaluation of hydrogel:oleogel ratio and gelator concentration on their physicochemical properties

Soft-matter formulations like bigels (i.e., hybrid systems) usually exhibit superior properties than singlestructured emulsion gels. In this study, a bigel system was developed using a carrageenan/locust bean gumbased hydrogel (1:1 ratio with concentrations of 0.5-2.5 wt%) and a glyceryl monostearate-based oleogel (5, 10 and 20 wt%), obtaining self-standing semi-solid structures. Solvent holding capabilities, micro-structural, rheological and textural properties, a X-ray diffraction and infrared spectroscopy (FTIR) were accessed. Furthermore, bigel formulations starting at 70 wt% of hydrogel fraction showed elevated structural matrix continuity, linked to self-standing ability. The most balanced properties, concerning microstructural stability were exhibited by the formulations containing 2 wt% of biopolymers. These formulations also demonstrate an increased capacity to arrest the oil phase even compared to formulations with high biopolymer concentrations. Rheology studies showed a certain level of destabilization among the sol-gel transition at higher temperatures for high polymer concentrations. The higher storage and loss modulus values were recorded at the end of the nonisothermal sweeps and positively correlated with the glyceryl monostearate (GM) concentration. Despite that, texture analysis did not evidence any increase of bigel hardness when concentrations of GM surpassed 5% (w/w), probably due to a lack of interfacial stabilization. Major differences in bigel hardness due to increased oleogel content were only seen for higher biopolymer concentrations. Also, the non-chemical arrangement was confirmed through FTIR. These results guide the development of bigel systems towards their use in novel food products.

Automated summary

In this study, a bigel system was developed using a carrageenan/locust bean gum-based hydrogel and a glyceryl monostearate-based oleogel, resulting in self-standing semi-solid structures. The bigel formulations with 70 wt% of hydrogel fraction showed good structural matrix continuity and self-standing ability, while the formulations with 2 wt% of biopolymers exhibited the most balanced microstructural stability. Rheology studies indicated a destabilization at higher temperatures for high polymer concentrations. Texture analysis did not show an increase in bigel hardness when glyceryl monostearate concentration surpassed 5% (w/w).