Estimation of soybean softening based on Raman spectral analysis of solubilized components in cooking water

Dynamic and nondestructive monitoring of soybean softening during thermal processing is essential for ensuring consistent texture and quality in processed foods. However, achieving accurate and nondestructive assessment remains challenging, particularly in sealed high-temperature cooking conditions. Therefore, this study investigated the molecular changes in the proteins and pectin released into water during soybean boiling and their relationship with textural softening. Raman spectroscopy, both with and without the use of ethanol as an internal standard, was utilized to capture spectral variations. This was supported by chemical quantification of protein and pectin concentrations and texture analysis. Principal component analysis identified key Raman peaks at 682 cm -1 (C–S), 558 cm -1 (S–S), and 936 cm -1 (glycosidic linkages), reflecting the accumulation of solubilized components and correlating strongly with textural softening (R 2 = 0.69–0.73). The addition of ethanol improved spectral stability across replicates without interfering with key molecular signals, enabling more consistent detection. These findings demonstrate that Raman spectroscopy, when standardized with an internal reference, offers a reliable, nondestructive method to assess soybean softening in real time. This approach provides a foundation for future applications in legume quality monitoring and industrial thermal processing control. • Raman spectroscopy tracks soybean softening during thermal processing. • An internal standard improves spectral reproducibility and quantification accuracy. • Raman bands at 682 and 936 cm -1 strongly correlate with texture changes. • Spectral intensity shifts reflect protein and pectin solubilization.