Investigating the rheological properties and structure of grass pea protein isolate- sesame oil bigels for effective fat substitution in low-fat cream formulation

In this study, bigels with optimized mechanical properties (high firmness and viscoelasticity) and long-term stability were developed to identify the most effective formula for use as a fat substitute in low-fat cream. For this purpose, bigels were prepared using different concentrations of grass pea protein isolate (GPPI) for the hydrogel and carnauba wax (CW) for the sesame oil oleogel, along with different hydrogel to oleogel mixing ratios. All bigels exhibited gel-like behavior with semicrystalline structures. The maximum hardness (1.12 N) and adhesiveness (1.61 N.s⁻¹) were observed at a hydrogel to oleogel ratio of 70:30 when 9 % CW and 12 % GPPI concentrations were used. The increase in hydrogel to oleogel ratio to 70:30, GPPI concentration to 12 %, and CW concentration to 9 % resulted in a more compact structure in the bigel, which led to an increase in G' and G" values. During 90 days of storage at refrigeration temperature, no phase separation was noticed. The thermal stability of the bigels improved with increasing oleogel content, reaching optimal properties at a hydrogel to oleogel ratio of 30:70. The fluorescence micrographs showed that the bigels were of the O/W, bicontinuous, and W/O types at hydrogel to oleogel ratios of 70:30, 50:50, and 30:70, respectively. To replace fat in the cream at varying substitution levels (0 %, 25 %, and 50 %), a bigel was formulated using 12 % GPPI and 9 % carnauba wax at a 70:30 hydrogel to oleogel ratio. The results demonstrated that replacing cream fat with bigel improved the structural strength of the bigel-cream. Moreover, up to 50 % fat replacement with bigel yielded a product that closely resembled the rheological properties of commercial cream.