title: Determination of hidden hazelnut oil proteins in extra virgin olive oil by cold acetone precipitation followed by in-solution tryptic digestion and MALDI-TOF-MS analysis.
abstract: Adulteration of extra-virgin olive oil (EVOO) with hazelnut oil (HO) is an illegal practice that could have severe health consequences for consumers due to the possible exposure to hidden hazelnut allergens. Here, matrix-assisted laser-desorption/ionization (MALDI) mass spectrometry (MS) was used as a rapid and sensitive technique for the detection of a low concentration of hazelnut proteins in oil samples. Different protocols were tested for protein extraction, and the most efficient (cold acetone) was applied to HO and EVOO adulterated with HO. The subsequent in-solution tryptic digestion of protein extracts and MALDI-MS analysis, using α-cyano-4-chlorocinnamic acid as matrix, allowed the detection of stable hazelnut peptide markers (i.e., the m/z ions 1002.52, 1356.71, 1394.70, 1440.81, 1453.85, 1555.76, 1629.83, 1363.73, and 1528.67) attributable to the main hazelnut proteins Cor a 9, Cor a 11, and Cor a 1. Thus, the approach might allow the direct detection of specific hazelnut allergens in EVOO at low concentration without time-consuming pretreatments.
authors.affiliation: Dipartimento di Chimica and ‡Centro Interdipartimentale di Ricerca S.M.A.R.T., Università degli Studi di Bari , Aldo Moro Via Orabona, 4, 70126 Bari, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: De Ceglie
authors.forename: Cosima Damiana
authors.initials: CD
authors.lastname: Calvano
authors.forename: Carlo Giorgio
authors.initials: CG
authors.lastname: Zambonin
mesh_terms: D011232:Chemical Precipitation; D031211:Corylus / Q000737:chemistry*; D005506:Food Contamination / Q000032:analysis*; D000069463:Olive Oil; D010938:Plant Oils / Q000737:chemistry*; D059748:Proteolysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014357:Trypsin / Q000737:chemistry
chemical_list: D000069463:Olive Oil; D010938:Plant Oils; D014357:Trypsin
keywords: MALDI; allergens; cold acetone; hazelnut; olive oil; protein digestion