Thermal induced the structural alterations, increased IgG/IgE binding capacity and reduced immunodetection recovery of tropomyosin from shrimp (Litopenaeus vannamei)

Shrimps were first subjected to various thermal processing, then tropomyosin (TM) was purified and their structure, IgG/IgE-binding ability and detectability were evaluated for elucidating the mechanisms responsible for thermal-induced TM immunodetection recovery alterations. According to CD and FT-IR analysis, heat-treated shrimp TM had significantly reduced α-helix and β-sheet contents with elevated random coil contents, contributing to an increase of 24.42%-62.22% in IgG/IgE reactivity as compared with raw shrimp TM. The exposure of hydrophobic residues and glycosylation occurred in various heated shrimps TM were confirmed by UV, intrinsic/extrinsic fluorescence spectrum and free amino group analysis, which caused some epitopes masking or modification, thereby inducing considerable TM recovery reduction (48.48%-90.44%). These results demonstrated that thermal-treated TMs with higher structural flexibility facilitated IgG/IgE recognition, however the lower number of epitopes within the thermal-treated TMs might cause considerable underestimation of recovery. The number of antigen binding sites might play a critical role in sandwich immunodetection.