Oil-phase modulated molecular assembly in rice bran protein fibril-chitin nanofiber emulsion gels: Structural design strategy for synchronized fat replacement and sodium release optimization.

The role of oil-phase in synchronously regulating texture and saltiness perception in emulsion gels (EGs) remains unclear, limiting the design of dual-functional fat-salt replacement systems. This study investigated four vegetable oils (rice bran oil/RBO, soybean oil/SBO, rapeseed oil/RSO, coconut oil/CCO) at 0-50 % concentrations in rice bran protein fibril (RBPF)-chitin nanofiber (CNF) EGs for dual fat-salt substitution. As fat content increased, both fat-mimicking ability and saltiness perception first improved and then declined. The 30 % RBO formulation demonstrated optimal performance, achieving 90 % water holding capacity and closely mimicking margarine in key physical properties: hardness (60.91 gf), cohesiveness (0.92 mm), apparent viscosity (84,022.53 Pa·s), storage/loss modulus (7384.69/2529.80 Pa), and friction coefficients (peak transition point: 0.158 and 0.163). Saltiness perception first improved then decreased with increasing fat content, peaking at 30 % for RBO (2.80-fold) and SBO (2.23-fold), and 40 % for RSO (2.08-fold) and CCO (1.77-fold), as confirmed by electronic tongue, sodium release/diffusion/distribution, and sensory analyses. Structural analysis revealed that 30 % RBO promoted hydrogen bonding and hydrophobic interactions within the RBPF-CNF network, forming a stable three-dimensional matrix that enhanced both texture mimicry and Na+ release/diffusion/ mucin penetration. Overall, 30 % RBO-based EG synchronously achieved better fat-texture simulation and saltiness-enhancement. This study revealed the structural and molecular basis for the fat-replacement and saltiness-enhancement, advancing food matrix design for reduced-fat/low-sodium products.