title: Development of a method for the quantification of caseinate traces in Italian commercial white wines based on liquid chromatography-electrospray ionization-ion trap-mass spectrometry.
abstract: A method using the combination of size exclusion-solid phase extraction and ultrafiltration, followed by tryptic digestion and analysis of the protein digest by liquid chromatography-electrospray ionization-3D ion trap-mass spectrometry (LC-ESI-3D IT-MS), was developed for the detection and quantification of caseinate traces potentially resulting from fining processes in white wines. In particular, several tryptic peptides generated from the main proteins constituting caseinate (β-, αS1-, and αS2-caseins) were used as markers of its presence in the wine matrices; among them, the β-casein peptide GPFPIIV was found to be the best marker for quantification purposes. Method linearity and sensitivity were assessed on a series of Italian commercial white wines, first checked for the absence of any peptide signal attributable to caseins introduced during their production and subsequently spiked with increasing concentrations of caseinate, to provide samples for matrix-matched calibrations. Limits of detection ranging between 0.09 and 0.29 mg/L (S/N = 3), according to the wine, were achieved using a 10 mL sample volume and the MS signal of GPFPIIV as the response related to the caseinate concentration. Such levels are comparable or even lower than the one (0.25 mg/L) recently adopted as a threshold by European Union legislation concerning the indication of milk- and egg-derived fining agents on wine labels, that is, the most restrictive one among those currently proposed in the world.
authors.affiliation: Department of Chemistry, University of Bari "Aldo Moro" , Via Orabona 4, 70126 Bari, Italy.
authors.forename: Ilario
authors.initials: I
authors.lastname: Losito
authors.forename: Barbara
authors.initials: B
authors.lastname: Introna
authors.forename: Linda
authors.initials: L
authors.lastname: Monaci
authors.forename: Silvana
authors.initials: S
authors.lastname: Minella
authors.forename: Francesco
authors.initials: F
authors.lastname: Palmisano
mesh_terms: D002364:Caseins / Q000032:analysis* / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D007558:Italy; D052616:Solid Phase Extraction; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014920:Wine / Q000032:analysis* / Q000191:economics
chemical_list: D002364:Caseins