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

The focus of this research was to develop a novel bi-phasic system using whey protein isolate (WPI) as a hydrogel phase and rice bran wax-peanut oil as an oleogel phase. The bigels were fabricated at various protein concentrations (10%, 15% w/v) and hydrogel-to-oleogel ratios (70:30, 50:50, 30:70). All the bigels were homogeneous and self-standing. Increasing the WPI concentration and altering the phase ratios increased the Gʹ and Gʺ moduli. The highest viscosity (7896.31 Pa.s) was observed in the W-10-H30:O70 sample at a shear rate of 10 s⁻¹. All samples exhibited shear-thinning behavior. The highest hardness values were recorded for the oleogel (109.81 g) and the W-15-H30:O70 bigel (104.51 g). FTIR spectra confirmed that physical interactions were the primary mechanism driving bigel formation. 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%. The highest peroxide value (2.34 meq/kg) was found in the W-15-H30:O70 bigel after 30 days of storage. These findings provide profound structural insights into the bigels as influenced by protein concentration and phase ratios, suggesting their potential use as fat replacers in functional foods.