Multi-allergen quantification of fining-related egg and milk proteins in white wines by high-resolution mass spectrometry.
BACKGROUND
A method based on High-Resolution Mass Spectrometry was developed for the simultaneous determination of fining agents containing potentially allergenic milk (casein) and egg-white (lysozyme and ovalbumin) proteins, added to commercial white wines at sub-ppm levels. Selected tryptic peptides were used as quantitative markers. An evaluation of protein digestion yields was also performed by implementing the (15)N-valine-labelled analogues of the best peptide markers identified for αS1 -casein and ovalbumin.


METHODS
The method was based on the combination of ultrafiltration (UF) of protein-containing wines, tryptic digestion of the dialyzed wine extracts and liquid chromatography/high resolution mass spectrometry (LC/HRMS) analysis of tryptic digests. Peptides providing the most intense electrospray ionization (ESI)-MS response were chosen as quantitative markers of the proteins under investigation.


RESULTS
Six-point calibrations were performed by adding caseinate and egg-white powder in the concentration range between 0.25 and 10 µg/mL, to an allergen-free white wine. The following three peptide markers, LTEWTSSNVMEER, GGLEPINFQTAADQAR and ELINSWVESQTNGIIR, were highlighted as best markers for ovalbumin, while GTDVQAWIR and NTDGSTDYGILQINSR for lysozyme and YLGYLEQLLR, GPFPIIV and FFVAPFPEVFGK for caseinate. Limits of detection (LODs) ranged from 0.4 to 1.1 µg/mL.


CONCLUSIONS
The developed method is suited for assessing the contemporary presence of allergenic milk and egg proteins characterizing egg white and caseinate, fining agents typically employed for wine clarification. The LODs of the method enable the detection of sub-ppm concentrations of residual fining agents, that could represent a potential risk for allergic consumers.
Institute of Sciences of Food Production, National Research Council of Italy, Via Amendola 122/O, 70126 Bari, Italy. linda.monaci@ispa.cnr.it
Linda
L
Monaci
Ilario
I
Losito
Elisabetta
E
De Angelis
Rosa
R
Pilolli
Angelo
A
Visconti
D000485:Allergens / Q000032:analysis*; D002364:Caseins / Q000032:analysis; D004527:Egg Proteins / Q000032:analysis*; D005506:Food Contamination / Q000032:analysis*; D057230:Limit of Detection; D013058:Mass Spectrometry / Q000379:methods*; D008894:Milk Proteins / Q000032:analysis*; D009113:Muramidase / Q000032:analysis; D010047:Ovalbumin / Q000032:analysis; D014920:Wine / Q000032:analysis*
D000485:Allergens; D002364:Caseins; D004527:Egg Proteins; D008894:Milk Proteins; D010047:Ovalbumin; D009113:Muramidase