Functional properties and application of salted duck egg white powder as a natural foaming agent in foam-mat dried sukiyaki sauce

Salted duck egg white (SDEW), a protein-rich byproduct from salted egg processing, was evaluated for its potential as a natural foaming agent in dried food formulations. Whole duck eggs were brined in 30% w/v salt solution for 0 to 4 weeks, then the egg whites were separated, whipped, foam-mat dried at 60°C for 2 h, and milled into salted duck egg white powder (SDEWP). Powder produced at week 3 exhibited foam capacity of 36.50 ± 5.20%, foam stability of 16.86 ± 0.33% and solubility of 47.74 ± 1.04%, supporting its functionality for foam systems. Fourier-transform infrared (FTIR) spectra of SDEWP across 0–4 weeks revealed stable amide I – III peaks but decreasing intensities consistent with partial protein unfolding and aggregation, which correlated with declines in foaming. To evaluate its functionality in foam-mat drying, SDEWP was added to diluted sukiyaki sauce (SS) at 5–15% and compared to a control containing 0.25% MethocelTM (MET) and 5% maltodextrin (MAL). The 15% SDEWP formulation generated foam with an overrun of 124.45 ± 3.57%. The dried powders showed a moisture content of 8.26 ± 0.62% and a water activity of 0.285 ± 0.003, together with a solubility of 7.31 ± 0.46% and a rehydration index of 1.77 ± 0.24 g/g. The FTIR spectra of sukiyaki sauce powder showed lower amide I and II intensities in the MET/MAL control than in SDEWP samples, indicating its lower protein content. SDEWP functions as an egg-based ingredient that maintains foaming ability during foam-mat drying and provides natural saltiness from by-product of salted egg yolk production, offering a new approach for dried sauce development.