Process/Product Control: Analysis of Cheese by Proteomics Techniques
Antonio Trani, Pasqua Loizzo, Angela Cassone and Michele Faccia
Department of Soil, Plant and Food Sciences, University of Bari, Bari, Italy
Two definitions of proteomics are currently considered. The first is the more traditional definition, regarding the analysis and characterization of all proteins of a cell, organism, or tissue. The second and more inclusive definition combines protein studies with analyses that have a genetic readout (Graves & Haystead, 2002). The term proteomics will be used with the former meaning applied to the analysis of milk and cheese proteins. Two fundamental tools of proteomics are electrophoresis and mass spectrometry techniques. Electrophoresis has been employed since 1930 to separate proteins in complex matrices; among the electrophoretic techniques the most commonly used in cheese protein analysis are Urea Polyacrylamide Gel (Urea-PAGE), Sodium Dodecyl Sulphate Polyacrylamide Gel (SDS-PAGE), and Isoelectric Focusing electrophoresis (IEF). Since high resolution is required to achieve a high score in the protein identification by mass spectrometry, generally two of the above-mentioned techniques are used together in a double run on the same sample, performing a two-dimensional gel electrophoresis (2-DGE). Common combinations of 2-DGE are IEF-SDS PAGE or IEF-Urea-PAGE. Until 2005, the most comprehensive review of proteomics analysis applied to dairy products was provided by Manso, Leonil, Jan, and Gagnaire (2005). Today, proteomic analysis of cheese proteins primarily focuses on the control of products' authenticity or to monitor the cheese making process. Some of the following methods described are included in the official methods of analysis, Commission Regulation (EC) No. 273/2008 of March 5, 2008, laying down detailed rules for the application of Council Regulation (EC) No. 1255/1999 as regards methods for the analysis and quality evaluation of milk and milk products.