Characterization, antigenicity and detection of fish gelatine and isinglass used as processing aids in wines

Fish gelatine (FG) and isinglass (IG) are widely used in the pharmaceutical industry and as ingredients or processing aids in food production. Both products are the focus of interest since several countries, particularly the member states of the EU and Japan, USA, Australia and New Zealand, have introduced special labelling regulations for allergenic foodstuffs, such as fish and products thereof. Thus, there is a demand for a reliable and sensitive method for the detection of FG and IG in foodstuffs. In this study, the characterization of various FGs and IGs, polyclonal antibodies raised against fish collagen and the development of a sensitive indirect ELISA for the detection of FG and IG is described. The ELISA method detected < or =0.11 microg ml(-1) from all FGs and IGs tested. The indirect ELISA was applied to various experimental wines where FG and IG had been used as processing aids and to several commercial wines. No residues of FG and IG were detected in the experimental wines additionally treated with bentonite, a strong adsorbent for proteins, and successive filtration. Additionally, no residues were found in the commercial wines. However, amounts of up to 0.33 microg ml(-1) were found in some experimental wines not treated with bentonite and successive filtration. Therefore, wines may contain traces of FG and IG that were used as processing aids during wine production. However, treatment with bentonite in combination with additional filtration had a clear impact on these residues.