Food Research International (2013), 52, 2, 526--534 DOI: 10.1016/j.foodres.2013.02.039
Ovalbumin is one of the principal proteins responsible for IgE-mediated egg allergy. In this study, the effect of thermal processing on the antigenicity of ovalbumin in control ovalbumin, egg white and whole egg powders and incurred pasta preparations were evaluated. Solutions (4% w/v) of control ovalbumin, egg white and whole egg were separately boiled for 0, 5, 10, 15 min and then freeze-dried. Accurately weighed portions of semolina used in the pasta were separately incurred with the egg white and whole egg powders, to give concentrations of 10, 100 and 1000 ppm. Dried pastas were boiled for 15 min. After tryptic digestion, samples were analyzed for the presence of ovalbumin using liquid chromatography–electrospray ionization-mass spectrometry (LC–ESI-MS). Enzyme linked immunosorbent assay (ELISA) kits were also used to detect the presence of egg in the raw and cooked pastas. MS coverage of ovalbumin peptides was higher in non-heated samples compared to heated samples (P < 0.05). The lowest peptide coverage was observed in the pasta samples. The allergenic epitope peptide fragment ISQAVHAAHAEINEAGR was detected in all egg white incurred samples, whereas it was not detected in the whole egg incurred samples heated for either 10 min or 15 min. EDTQAMPFRV allergenic epitope was present in all samples containing egg white and whole egg. Of all the ovalbumin epitopes detected by MS, only the allergenic epitope EDTQAMPFRV was detected in the raw pasta samples. Four other non-epitope peptide fragments identified which could be used for the detection of egg were GGLEPINFQTAADQAR, LTEWTSSNVMEER, VTEQESKPVQMMYQIGLFR and EVVGSAEAGVDAASVSEEFR. Both LC–MS and ELISA results were negative for all incurred cooked pasta samples. The results clearly show that egg allergen detection in pasta is affected by matrix and processing.