Rapid animal species identification of feta and mozzarella cheese using MALDI-TOF mass-spectrometry

Abstract

The correct labelling of foodstuffs with regard to the value-determining ingredients is decisive for the consumer. Therefore, one of the main topics of official food control for meat, seafood and milk products is the inspection of the declared animal species. The use of unlabeled cow's milk products to substitute highly-priced sheep's or buffalo's milk cheese has concerned consumer protection laboratories for many years. Recently, matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) has been demonstrated to identify the animal species of milk used for production of cheese and some other dairy products. The identification was conducted by comparison of mass spectra resulting from samples with those in a corresponding reference database. In this study, a MALDI-TOF MS database for animal species identification of dairy products was created using Bruker's MALDI Biotyper-system in combination with a simple extraction method without a tryptic digestion step. The database contains more than 150 reference spectra of milk and cheese from different dairy species. Using feta/white cheese as well as mozzarella, two of the most consumed cheeses from goat, sheep, cow's or buffalo's milk, we demonstrated MALDI-TOF MS to be an easy, fast and specific tool to identify the animal species of the milk these cheeses were made from. This method has been validated and established in the routine analysis of official food control. Exchange of reference spectra generated and used in this study is facilitated by the MALDI-user platform (https://maldi-up.ua-bw.bwl.de).