FT-IR and Raman spectroscopies determine structural changes of tilapia fish protein isolate and surimi under different comminution conditions

- The FT-IR spectra showed fewer bands in FPI samples than surimi samples.
- The degree of unfolding in protein structure of FPI and surimi paste changed by comminution conditions.
- FPI and surimi gels chopped at 25 °C for 18 min showed higher chemical bonds than those at 5 °C for 6 min.

Tilapia proteins refined by pH shift and water washing were chopped under various comminution conditions and their structural changes were investigated using Fourier transform infrared (FT-IR) and Raman spectroscopies. Both techniques revealed the degree of unfolding in protein structure increased when fish protein isolate (FPI) and surimi were chopped at 25 °C for 18 min compared to samples chopped at 5 °C for 6 min. Results indicated both hydrophobic interactions and disulfide bonds were significantly enhanced during gelation. FPI and surimi gels prepared at 25 °C for 18 min exhibited higher β-sheet contents and more chemical bonds such as hydrophobic interactions and disulfide bonds than those at 5 °C for 6 min. Results suggested that controlling comminution is important to improve gel qualities in FPI and surimi from tropical fish like tilapia. Moreover, FT-IR and Raman spectroscopies are useful complementary tools for elucidating the change in the structure of protein during comminution and gelation.