Effect of Combined Ultrasound and High Pressure CO₂ Treatment on the Structure and Allergenicity of Shrimp Tropomyosin

The combined effect of ultrasound and high pressure carbon dioxide (HPCD) on the structure and allergenicity of the tropomyosin (TM) of Litopenaeus vannamei was studied. After sequential treatment with ultrasonic at powers up to 2000 W for up to 60 min followed by HPCD at 30 MPa for 15 min, the allergenicity of TM was detected by indirect enzyme-linked immunosorbent assay (iELISA) and Western blot (WB), and the molecular mass was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The spatial structure of TM was characterized by circular dichroism (CD) spectroscopy, fluorescence spectroscopy, ultraviolet (UV) spectroscopy, free amino group and total sulfhydryl group analysis. The results showed that ultrasound at 1500 W for 30 min combined with HPCD decreased the immunobinding activity of immunoglobulin G (IgG) and IgE in TM by 55.3% and 48.7%, respectively, the α-helix relative content decreased to 42.7%, and the secondary structure was changed from an ordered state to a disordered state. The fluorescence spectra showed a blue shift with weakened fluorescence intensity, and the UV spectra exhibited a red shift with enhanced absorption intensity. The free amino group content was reduced by 21.82%, and the total sulfhydryl group content was also reduced. Therefore, ultrasound combined with HPCD treatment changed the spatial conformation of TM, being more effective in reducing the allergenicity than either single treatment.