title: Absolute quantitation of beta-lactoglobulin by protein liquid chromatography-mass spectrometry and its application to different milk products.
abstract: The absolute quantitation of proteins in biological matrixes is of great interest in many fields and can be accomplished by different methodologies. Here, a method for the absolute quantitation of the whey protein beta-lactoglobulin using protein liquid chromatography coupled to mass spectrometry is reported. The developed approach was characterized in detail and applied to the determination of beta-lactoglobulin contents in various milk products. A special focus was placed on the recovery rates of the isolation procedure and on robust quantitation by LC-MS. For these purposes protein internal standards were employed. The observed recovery rates of beta-lactoglobulin from various samples ranged from 100% for whole milk to just over 50% for a strongly processed yogurt-based baby food product. The influence of processing was investigated in greater detail, showing that an increasing intensity of the applied heat treatment resulted in an increasing loss of beta-lactoglobulin. LC-MS quantitation at the protein level proved to be highly suitable, avoiding a potentially problematic digestion step. The use of an appropriate internal standard to compensate for sample losses during sample workup was shown to be essential for obtaining accurate results.
authors.affiliation: Institute of Analytical Chemistry and Food Chemistry, University of Vienna, Währinger Strasse 38, 1090 Wien, Austria. christoph.czerwenka@univie.ac.at
authors.forename: Christoph
authors.initials: C
authors.lastname: Czerwenka
authors.forename: Irene
authors.initials: I
authors.lastname: Maier
authors.forename: Natascha
authors.initials: N
authors.lastname: Potocnik
authors.forename: Fritz
authors.initials: F
authors.lastname: Pittner
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lindner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods*; D003611:Dairy Products; D007782:Lactoglobulins / Q000032:analysis* / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D008892:Milk / Q000737:chemistry*; D008969:Molecular Sequence Data
chemical_list: D007782:Lactoglobulins