Molecular Insights into Soy Protein-Lupin Flour Meat Analogues through FTIR Spectrochemical Analysis

Fourier transform infrared (FTIR) spectroscopy and spectrochemical imaging were used to investigate the structural and compositional changes in extruded high-moisture meat analogues (HMMAs) produced from soy protein isolate and lupin flour (LF) blends. Extrusion induced shifts in the amide I band (∼1637 cm^-1 in raw blends to ∼1650 cm^-1 in HMMAs), indicating protein denaturation and structural rearrangement associated with fibrous structure formation. Changes in carbohydrate- and lipid-associated bands further reflected extrusion-driven molecular reorganization. FTIR spectrochemical analysis revealed distinct HMMA regions, including aligned protein-rich domains and lipid-starch-rich domains appearing as polygonal grids. Increasing the LF content from 15 to 45% progressively increased lipid- and carbohydrate-associated spectral features (i.e., areas of the fatty acid ester peak at 1744 cm^-1 and the carbohydrate peak around 1060 cm^-1) relative to proteins. These insights advance the understanding of structure-function relationships in HMMAs and highlight the value of FTIR spectrochemical imaging for optimizing texture and the effective design of meat analogues.