Bigel system based on whey protein hydrogel and rice bran wax-peanut oil oleogel: Fabrication and physico-functional characteristics

This study reports the development of a novel bigel system composed of a whey protein isolate (WPI) hydrogel and a rice bran wax-peanut oil oleogel as a potential fat replacer for food applications. Bigels were prepared using different WPI concentrations (10% and 15% w/v) and hydrogel-to-oleogel ratios (70:30, 50:50, and 30:70). All formulations produced homogeneous, self-standing systems with solid-like behavior. Increasing WPI concentration and oleogel proportion enhanced viscoelasticity, hardness, viscosity, and oil-binding capacity, while FTIR analysis confirmed that bigel formation was governed primarily by physical interactions. Increasing the hydrogel-to-oleogel ratio from 30:70 to 70:30 raised the melting enthalpy from 113.2 to 187.8 J/g. The most oil leakage occurred in the W-10-H70:O30 sample, which had an oil binding capacity of 84.08%. All samples exhibited low peroxide values during storage, indicating acceptable oxidative stability. Overall, the results highlight the tunability of this protein-lipid bigel system and demonstrate its practical potential as a structurally stable and functional fat substitute in food formulations. • Oleogel was fabricated from rice bran wax and peanut oil. • The bigels system was developed from whey protein hydrogel and oleogel. • Protein concentrations and hydrogel/oleogel ratio showed significant effects on the bigel characteristics. • FTIR spectra of the bigels revealed the physical interactions without new bands. • Storage modulus (Gʹ) of the bigels was higher than loss modulus (Gʺ), confirming the gel network.