A Proteomic Approach to the Safeguard of a Typical Agri-Food Product: Fiore Sardo PDO

Background: Fiore Sardo PDO is one of the oldest Mediterranean hard cheeses, exclusively produced in Sardinia (Italy) from raw whole ewe’s milk. Some manufacturers, improperly, submit raw milk to heat-treatment. Aim of this study was to evaluate the proteomic profile of Fiore Sardo PDO and to investigate possible differences between cheese made from raw milk and from heat-treated milk. Materials and methods: Starting from the same ovine bulk milk, eight cheese wheels of Fiore Sardo PDO were produced, four from raw milk and four from heat-treated milk. The subsequent production steps were the same for both types of cheese as was sampling at different ripening times. Samples were analyzed by Urea-PAGE electrophoresis. Afterwards, blind analysis of 32 cheese samples, produced by 17 different cheesemakers was performed to evaluate the method’s analytical performance. Results: Urea-PAGE analysis showed the presence of a protein band only in cheese made from raw milk, regardless of cheese ripening time. Protein identification analysis by liquid chromatography mass spectrometry identified two different proteins in the band, alpha-S1 and alpha-S2 casein. Blind analyses conducted to verify the analytical performance of the method showed that it could be a useful tool for the protection of this typical agri-food product. Conclusion: We developed a simple, robust, and economic method for discriminating between Fiore Sardo PDO cheese made from raw milk with up to 24 months of maturation and Sardinian sheep milk cheese made from heattreated milk.