Simultaneous quantification of glutathione, glutathione disulfide and glutathione-S-sulfonate in grape and wine using LC-MS/MS.

A fast, sensitive and reproducible method using LC-MS/MS for simultaneous quantification of glutathione (GSH), glutathione disulfide (GSSG) and glutathione-S-sulfonate (GSSO3H) was developed, optimised and applied in analysis of grape juice and wine samples. The results show that only GSH (10-60 mg·L-1) and GSSG (2-11 mg·L-1) are found in grape juice when SO2 is not added. GSSO3H was detected in must samples treated with SO2 but only at a low concentration (<1 mg L-1). In the wine samples, the dominant form of glutathione was GSSO3H (5-11 mg L-1), followed by GSH (0-5 mg L-1) and GSSG (0-6 mg L-1), underscoring the importance of GSSO3H quantification. GSSO3H formation in wine was correlated with the total SO2 level in the wine. We believe this is the first report on GSSO3H quantification in wine.

Implementation of an Enzyme Linked Immunosorbent Assay for the Quantification of Allergenic Egg Residues in Red Wines Using Commercially Available Antibodies.

Since the early 2000s, labeling of potentially allergenic food components to protect people who suffer from food allergies is compulsory in numerous industrialized countries. In Europe, milk and egg components used during the winemaking process must be indicated on the label since July 1, 2012. Several ELISA procedures have been developed to detect allergenic residues in wines. However, the complexity of the wine matrix can inhibit the immunoenzymatic reaction. The aim of this study was to implement an ELISA assay for the detection of ovalbumin in red wines using commercially available antibodies. The specificity of the acquired antibodies and the absence of cross reactivity were assessed by immunoblotting and ELISA. An ELISA assay with a LOD of 14.2 µg/L and a LOQ of 56.4 µg/L of ovalbumin in aqueous solution was obtained. Differences in ELISA signals were observed when analyzing various fining agents, although reproducible conformation of the antigen could be reached for the comparison of ovalbumin and Ovicolle. The differences between samples in terms of pH could be leveled but the inhibition of the ELISA signal, positively correlated to the tannin content of the wines, could not be suppressed. Thus, standard curves of ovalbumin in several wines were obtained by relative quantification. The control steps and the difficulties encountered presented in this study should be considered by anybody working toward the development of ELISA assays for the detection of allergenic residues in complex food matrices.