Partial incorporation of salted duck egg white into fresh duck egg white-based edible films through a two-solution
1Department of Animal Science and Technology, National Taiwan University, Taipei, 106, Taiwan.
Abstract:
Salted duck egg white (SDEW), a high-salt by-product of salted egg production, poses processing challenges in alkaline-thermal film formation because salting alters protein aggregation and thermal processability. This study developed a two-solution blending strategy for partial incorporation of SDEW into fresh duck egg white (FDEW)-based edible films and evaluated their functional properties. An SDEW dispersion containing 45% (w/w) original liquid SDEW, prepared by diluting the original liquid SDEW with deionized water, remained visually flowable after heating at 65°C for 20 min, but became semi-solid at 66°C and formed an opaque gel at 70°C. Therefore, FDEW film-forming solution (FDEW-FFS) and SDEW-FFS were prepared separately and blended on a total FFS weight basis. Films prepared with 1-5% SDEW-FFS replacement showed mechanical properties comparable to those of the FDEW control (P > 0.05). At 5% replacement, tensile strength was 6.60 MPa compared with 6.77 MPa for the FDEW control (P > 0.05), whereas it decreased to 4.70 MPa at 10% replacement (P < 0.05). At 20% replacement, all measured mechanical properties were significantly lower than those of the FDEW control (P < 0.05). Water vapor permeability at 10% replacement was 11.03 × 10⁻¹⁰ g m⁻¹ s⁻¹ Pa⁻¹ compared with 8.83 × 10⁻¹⁰ g m⁻¹ s⁻¹ Pa⁻¹ for the FDEW control (P < 0.05), whereas air permeability was not significantly affected up to 10% replacement (P > 0.05). Increasing SDEW-FFS replacement decreased water contact angle and increased microstructural heterogeneity. After immersion in water at 95°C for 5 min, all films remained intact, absorbed approximately 4 to 5 times their initial weight, and formed translucent, elastic gel-like sheets. The 5% SDEW-FFS film retained handling strength during storage, delayed peroxide formation in packaged canola oil at 25 and 40°C, and gradually lost recoverable integrity under soil-burial conditions. Overall, 5% was the highest tested SDEW-FFS replacement level that maintained the mechanical performance of the FDEW-based film matrix.
