Enhancing the nutritional profile and in vitro digestion properties of dual-protein extrudates by blending surimi with soybean flour

Abstract

Plant protein-based meat analogues often suffer from imbalanced amino acid pattern and poor protein digestibility. To address these drawbacks, this study adopted a dual-protein strategy by co-extruding surimi and soybean flour at ratios from 0:10 to 4:6. Analysis of nutritional composition, fatty acid/amino acid profiling, and in vitro digestion coupled with peptide identification were used to evaluate the changes of nutritional and digestive properties of dual-protein extrudates. While basic composition changed minimally, surimi incorporation diversified the fatty acid profiles: total unsaturated fatty acids decreased gradually, but the proportion of ω-3 polyunsaturated fatty acids (EPA and DHA) reached a maximum of 10.37%. Meanwhile, the amino acid profile was improved with essential-to-total amino acid (EAA/TAA) meeting FAO/WHO recommended standards (>40%) at ratios of 3:7 and 4:6, accompanied by progressive increases in essential amino acid index (EAAI) and biological value (BV). Most notably, surimi incorporation linearly enhanced protein digestibility from 79.33% to 86.12%, along with increased free amino acids, 14.50% more identified intestinal peptides, more low-molecular-weight and potential bioactive peptides. These findings demonstrate that co-extruding surimi with soybean flour is an effective strategy to achieve nutritional complementation and enhance protein digestibility, with an optimal processing window identified as ratios ≥3:7.