Investigation of different sample pre-treatment routes for liquid chromatography-tandem mass spectrometry detection of caseins and ovalbumin in fortified red wine

Different sample treatment protocols for the liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS) analysis of potential residuals of ovalbumin and caseins added to red wines were developed. In particular, attention was paid to the simultaneous detection and quantitation of fining agent residues, i.e. ovalbumin, α- and β-casein, in wine samples. The different sample treatment methods were compared in terms of protein recovery. The use of denaturing agents combined with size exclusion concentration and purification allowed to obtain a reproducible (RDS < 20%) analytical protocol with good recoveries (73(±2) - 109(±4) % range) for digested proteins from 12.5 mL of wine sample. Matrix-matched calibration from LC-ESI-MS/MS analysis indicated that the devised method allowed detection of target peptides in the 0.01-0.8 μg/mL range. Finally, method applicability and selectivity was demonstrated by using fining agents commonly exploited in winery industry and by analyzing 20 commercial red wine samples.