Challenging the Limit of Detection for Egg Allergen Detection in Red Wines by Surface Plasmon Resonance Biosensor

The improvement of a surface plasmon resonance (SPR)-based immunoassay for the detection of traces of egg-based fining agents in red wines is herein described. The latter represents an extension of a previously developed direct assay targeted to the detection of ovalbumin (OVA) as marker of the presence of egg white powder residues, a typical fining agent utilized by the winery industry. In this paper, a suitable pre-treatment procedure was optimized for the sensitive detection of OVA at sub-ppm levels in red wines fortified with egg-white powder, by using an immunoassay proved to be reliable for both white and roseé wines. A red wine from Chianti grapes selected as reference matrix was artificially contaminated with egg-white powder before undergoing different sample purification. Several purification strategies were investigated and tested in order to challenge the limit of detection (LOD) obtained with the methods currently in use for egg allergen detection. Finally, the optimized two-step pre-treatment, combining polyvinylpolypyrrolidone-based purification and size exclusion chromatography, enabled to achieve an LOD in red wine as low as 0.2 μg/mL. The optimized SPR-based method met the method performance criteria issued by the International Organization of Vine and Wine (OIV) concerning the minimum sensitivity required for the analyses of potentially allergenic fining agent proteins in wines, confirming the biosensor as promising tool to monitor the residual contamination level of fined red wines.