Rheology, structure, and printability of surimi-based hybrid inks containing Bambara groundnut, pea, and soy protein isolates for the development of salmon fillet analogs

This study explored the incorporation of Bambara groundnut (BGPI), pea (PPI), and soy (SPI) protein isolates (30 or 50 g/100 g surimi) into threadfin bream surimi to develop 3D-printed salmon analogs. The effects on printability, rheology, texture, microstructure, and nutritional properties were assessed. Printability tests showed that hybrid inks added with protein isolates at lower amount (30 g) exhibited the highest shape retention and stability than those added with higher amount (50 g) at appropriate water level, suggesting the major role of moisture content in food inks. Rheological analysis confirmed shear-thinning behavior across all formulations, required for 3D printed foods. SPI30 printed salmon exhibited the highest hardness, followed by PPI30, while BGPI added samples showed the lowest value. Microstructural analysis revealed that protein isolate at a higher level yielded the printed fillets with more aggregated and brittle network, particularly for surimi-BGPI-based fillets, which could lead to the formation of weaker gels. FTIR analysis confirmed increased β-sheet content (61.74–65.90 %) in hybrid inks due to secondary structural rearrangement. Nutritionally, all the printed salmon fillets showed the highest amino acid content than that of real salmon (RS). Similarly, printed fillets exhibited higher PUFA than RS, attributed to shrimp oil as colorant. Sensory evaluation showed the highest acceptability for SPI30 and PPI50. Pearson correlation analysis revealed that higher α-helix content and moderate β-sheet formation were associated with increased gel hardness and texture-liking. Overall, PPI50 and SPI30 could mimic RS in texture, appearance, and sensory properties, with potential improvements in flakiness and shape stability.