Parvalbumin in fish skin-derived gelatin: is there a risk for fish allergic consumers?

The major allergen parvalbumin was purified from cod muscle tissues, and polyclonal antibodies were raised towards it. The antibodies were tested for specificity and an enzyme-linked immunosorbent assay (ELISA) was developed using these antibodies. The ELISA was applied to measure parvalbumin in cod skin, the starting material for fish gelatin made from deep sea, wild fish. The ELISA was sufficiently sensitive (LLOQ = 0.8 ng ml(-1) in extracts, corresponding to 0.02 µg of parvalbumin per g of tissue), and did not cross-react with common food constituents. Fish gelatin, wine and beer, matrices for the potential use of this ELISA, did not cause disturbance of the assay performance. The data show that the parvalbumin content in cod muscle tissue is 6.25 mg g(-1), while the skins contained considerably less, 0.4 mg g(-1). Washing of the skins, a common industrial procedure during the manufacturing of fish gelatin, reduced the level of parvalbumin about 1000-fold to 0.5 µg g(-1), or 0.5 ppm. From 95 commercial lots of fish gelatin it is shown that 73 are below 0.02 µg g(-1) parvalbumin. From the other 22 lots, the one with the highest concentration contained 0.15 µg g(-1) of parvalbumin. These levels are generally assumed to be safe for fish-allergic individuals.