Design and characterization of bigels composed of agar, κ-carrageenan, candelilla wax, and monoglycerides

The aim of this study was to formulate and characterize plant-based hydrogels and bigels structured with agar (A), κ-carrageenan (κC), candelilla wax (CDW), and monoglycerides (MGs). First, hydrogels were formed with A (1-4 %), κC (0.5-2 %), and combinations of them. Next, bigels were created using the selected hydrogels, combined with oleogels made from CDW (15 %), MGs (15 %), or a combination of 7.5%CDW + 7.5%MGs. Specifically, the study assessed the effects of different types and concentrations of gelators, the use of different edible oils in the oleogel phase, and different hydrogel-to-oleogel ratios on the bigel characteristics. Bigels containing CDW in all studied hydrogel-to-oleogel ratios were self-standing, while those containing either MGs or CDW + MGs formed self-standing gels only in the 80/20 ratio. The hydrogels' hardness increased with higher concentrations of gelators, while the formation of mixed hydrogels was driven by hydrogen bonding and ionic interactions. For the bigels, an increase in the hydrogelators' concentration led to increased hardness, while the type of oleogel influenced their microstructure and the lipid droplet size. Differential scanning calorimetry and FTIR analyses indicated that the interactions between the two structured phases were mainly physical. Overall, the bigels demonstrated excellent stability, making them suitable for applications in various plant-based food products.