Effects of cold plasma-assisted alcalase on the structure, allergenicity and epitopes of shrimp tropomyosin

Tropomyosin (TM) is the major allergen in shrimp. In this study, the effects of cold plasma (CP)-assisted alcalase treatment on the structure, digestibility and allergenicity of TM were investigated. The results showed that CP pretreatment promoted the hydrolysis of TM by unfolding the structure and reducing the spatial site resistance. Compared with native TM, CP-assisted alcalase protease-treated TM showed a significant decrease in α-helix content, along with an increase in irregular curl and free sulfhydryl content. CP-assisted alcalase significantly decreased the IgE and IgG binding capacities of TM compared to native TM (87.56 % and 47.59 %, respectively). Moreover, the reduced stability of trypsin digestion further inhibited allergic reactions induced by TM. Mass spectrometry analysis revealed that extensive enzymatic cleavage sites were identified within alcalase including M11, L46, A109, L144, and A235 substantially compromised the integrity of TM antigenic epitopes. The amount of intact antigenic epitope peptides in the TM from CP-assisted hydrolysis was reduced by 164 compared to hydrolysis alone, revealing the mechanism of reduced allergenicity of TM. It can be concluded that CP-assisted enzymatic hydrolysis presents a promising novel strategy for desensitizing aquatic products.