Development and characterization of bigel systems as carriers for thyme essential oil utilizing hydrogel from chicken processing by-products for food applications

A chicken protein hydrogel (HG) was enzymatically prepared and blended with a carnauba wax-based oleogel (OG) to form bigels (BG) in ratios of 50:50 to 90:10. These systems were infused with thyme essential oil (TEO) at 0.5 %, 1 %, and 2 % v/v to harness its antioxidant properties. Polarized light microscopy revealed that carnauba wax crystals were tightly arranged in thin, plate-like structures, while the HG exhibited a completely amorphous form. FT-IR analysis indicated that O[sbnd]H bonds in the HG and C[sbnd]H bonds in cycloalkanes from the OG contributed to the stability and strength of the gels. Unlike the biphasic gels, both the OG and HG samples experienced structural disintegration when the applied strain reached approximately 30 %. HG samples, with an onset melting temperature of 59.18 °C, were particularly susceptible to thermal deformation, leading to coalescence and destabilization of the BG due to the HG phase in the composite matrix. Regardless of the TEO concentrations, the BG (50:50) demonstrated the highest water-holding capacity (60.83 %), and oil-binding capacity (99.23 %) compared to the single biopolymer gels. The lightness of the BG increased as the HG ratio increased. Additionally, the antioxidant capacity increased with higher TEO concentrations, demonstrating the gels' potential for food applications.