Allergenicity of crustacean extractives and its reduction by protease digestion

This study was undertaken to evaluate and reduce the allergenicity of crustacean extractives that are added to a variety of processed foods as seasonings. Tropomyosin, the major crustacean allergen, was detected in only one of the six kinds of crustacean extractives by SDS–PAGE and immunoblotting. However, all the extractives were shown to be considerably allergenic by inhibition ELISA using sera from crustacean-allergic patients. Analyses by gel filtration HPLC suggested that tropomyosin is mostly degraded to peptide fragments during manufacturing of the extractives but at least some of the fragments are still IgE-reactive. On digestion with proteases, the allergenicity of the extractives was almost completely lost. The effectiveness of protease digestion to reduce the allergenicity of tropomyosin was also confirmed in model experiments using the heated extracts from four species of crustaceans.