Differentiation of protein types extracted from tilapia byproducts by FTIR spectroscopy combined with chemometric analysis and their antioxidant protein hydrolysates

[Display omitted] •FTIR fingerprints revealed different secondary structures of protein extracts.•Performing chemometric analysis with FTIR data can differentiate protein types.•α-helices were employed to separate sarcoplasmic protein from myofibrillar protein.•Alkali-extracted protein was classified from muscle protein by β-sheet structure.•Hydrolysates from various proteins exhibited different antioxidant activities. This research aimed to characterize protein types including sarcoplasmic protein (SP), myofibrillar protein (MP), and alkali-aided protein extract (AP) prepared from tilapia byproducts using water, 0.6 M NaCl, and alkaline solution (pH 11), respectively compared to freeze-dried minced tilapia muscle (CONTROL). Principal component analysis was performed from a secondary derivative FTIR spectra to differentiate protein type. The AP mostly contained β-sheet structure and had low total sulfhydryl content, and surface hydrophobicity. SP can be distinguished from MP by the loading plots of the FTIR bands representing α-helical structure. While the bands for lipids and β-sheet of protein were noted for differentiating AP from CONTROL. After being hydrolyzed by Protease G6, the AP hydrolysate disclosed the highest ABTS radical scavenging activity, while the SP hydrolysate revealed the strongest metal chelating ability. Thus, an understanding of how fish processing waste can be utilized in the production of antioxidant protein hydrolysates has been achieved.