Bigel formation through surfactant-free co-gelation-in-emulsion without thermal activation of the hydrogel: Expanding the toolbox for customizable, and food-grade fat replacers
Santamaría E. Adilbekova A. Miras J. González C. Maestro A.
March 2026Elsevier Ltd
Journal of Food Engineering
2026#407
Replacing saturated and trans fats with healthier alternatives remains a major challenge for the food industry. This study presents a simple method to fabricate food-grade bigels with improved structural and functional properties. A surfactant-free co-gelation-in-emulsion approach was applied, in which basic pullulan, sodium trimetaphosphate (STMP) solutions were emulsified with molten candelilla wax/extra virgin olive oil solutions under mild agitation. Hydro- and oleo-gelation ocurred simultaneously once emulsion was prepared, withput thermal activation of the hidrogel, directly forming the bigel. Bigels with hydrogel-to-oleogel ratios of 25:75, 50:50, and 75:25 were produced and compared with systems obtained by conventional high-shear mixing of the separately prepared hydro- and oleo-gels. Co-gelated bigels exhibited homogeneous phase distribution, solid-like rheology, and high oil-binding capacity (>80 % at 25 % hydrogel; no oil leakage at ≥50 %). When the hydrogel acted as the continuous phase (≥50 %), the systems displayed marked increases in elasticity (G′ > 6000 Pa), hardness (≈450–500 g), and swelling (up to 55 %), closely resembling pure hydrogels. In contrast, mixed bigels prepared by high shear mixing of single gels presented fragmented, heterogeneous structures with lower stability and weaker texture. FT-IR, WAXS, and confocal microscopy confirmed improved hydrogen bonding, maintenance of oleogel crystallinity, and more continuous networks in co-gelated samples. This thermally independent route of the hydriphilic domain enables the use of biopolymers with slow chemical cross-linking kinetics (such as pullulan-STMP) and yields bigels that are more homogeneous, mechanically stronger, and oil-retentive. Overall, the method broadens the possibilities of food-grade bigels as customizable fat replacers.
Bigels , Candelilla wax , Co-gelation in emulsion , Extra virgin olive oil , Pullulan , Rheology
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Chemical Engineering and Analytical Chemistry Department, Faculty of Chemistry, Universitat de Barcelona, Marti i Franques, 1, Barcelona, 08028, Spain
INSA-UB, Nutrition and Food Safety Research Institute, University of Barcelona, Santa Coloma de Gramenet, 08921, Spain
Al-Farabi Kazakh National University, Department of Analytical, Colloid Chemistry and TRE, Faculty of Chemistry and Chemical Technology, Almaty, Kazakhstan
Institute of Advanced Chemistry of Catalonia, Consejo Superior de Investigaciones Científicas (IQAC-CSIC) and Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Jordi Girona, 18-26, Barcelona, 08034, Spain
Chemical Engineering and Analytical Chemistry Department
INSA-UB
Al-Farabi Kazakh National University
Institute of Advanced Chemistry of Catalonia
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