Novel plant-based bigels formulated with sunflower wax, monoglycerides, agar and κ-carrageenan

Abstract

The development of novel plant-based bigel systems using agar, κ-carrageenan, sunflower wax (SW) and monoglycerides (MGs) was investigated in this work. The hydrogel phase was structured with 2 % agar and 1 % κ-carrageenan, while the olive oil oleogels were structured using either SW or a 1:1 mixture of MGs and SW, with concentrations ranging from 6 % to 12 % w/w. The effects of the type and concentration of oleogel phase gelators and the hydrogel-to-oleogel ratio (80:20, 60:40, 40:60, and 20:80) on the microstructural and physicochemical attributes, as well as the oxidative stability of these systems, were examined. All bigels were self-standing except for the 40:60 ratio and the 60:40 formulations containing 10 % and 12 % SW + MGs, which displayed phase separation. The hardness of the bigels increased as the proportion of hydrogel increased. Moreover, increased hardness was observed when MGs were present, in most cases. Microscopy analysis revealed that higher structurants concentrations in the 80:20 ratio resulted in smaller oil droplets and adding MGs led to a more uniform oil droplet size distribution. Differential scanning calorimetry and FTIR analyses revealed that the two structured phases interact mostly physically, without the formation of new chemical bonds. Furthermore, all bigels exhibited low swelling capacity (0.3–3.4 %) and effectively entrapped both water and oil, resulting in low total liquid release (1.02–3.46 %). These findings offer valuable insights into the structural and functional characteristics of plant-based bigels, which are important to consider on their future application in food products.