Collaborative Tests of ELISA Methods for the Determination of Egg White Protein and Caseins Used as Fining Agents in Red and White Wines

Methods are needed for detecting allergenic proteins in wine after fining processes, both for legal requirements and to estimate any risk for allergic individuals. Two of the critical allergens in this case are the protein fraction from egg white and caseins. Requirements for methods were set up both by the International Organisation of Vine and Wine (OIV) and the European Commission and included collaborative tests to determine repeatability, reproducibility, limit of detection (LOD), and recovery. Two collaborative tests with 18 participants from all over the world were conducted using commercial enzyme-linked immunosorbent assay kits to quantify egg white protein and casein. For each analyte, nine red and white wines (RW and WW, respectively) with different analyte concentrations were prepared and sent to the participants. Resulting sets of data were analyzed according to the AOAC by eliminating outliers and calculating the performance statistics for each assay. For wines with no or very low analyte concentrations, the values were extrapolated from the calibration curve and the resulting LODs are in accordance with the performance criteria set by the OIV method OIV-MA-AS315-23: R2012. For casein in WW and egg white protein in RW, all Horwitz ratio values for samples with concentrations above the required limit of quantification (0.5 mg/L) were below 2. While the recovery of egg white protein from RW is 90 % or more, the recovery of casein from WW is between 73 and 76 %, which is attributable to the instability/solubility of casein in wine.