A gas chromatography-mass spectrometry untargeted metabolomics approach to discriminate Fiore Sardo cheese produced from raw or thermized ovine milk

摘要

Thermization is a sub-pasteurization heat treatmentof cheese milk (at 57-68°C for 15-30 s) aimed to reducethe number of undesirable microbial contaminants withreduced heat damage to the indigenous milk enzymes.In this work, the effects of milk thermization on thecompositional parameters, proteolysis indices, freefatty acid levels, and low molecular weight metaboliteprofiles of ovine cheese were studied. Cheese samplesat different ripening stages and produced in 2 differentperiods of the year were analyzed. While the effectsof milk thermization on cheese macro-compositionalparameters and free fatty acid levels were not evidentdue to the predominant effects of milk seasonality andcheese ripening stage, the gas chromatography-massspectrometry based metabolomics approach of ovinecheese produced from raw and thermized milk highlightedstrong differences at the metabolite level. Discriminantanalysis applied to gas chromatography-massspectrometry data provided an excellent classificationmodel where cheese samples were correctly classified asproduced from raw or thermized milk. The metabolitesthat mostly changed due to the thermization processbelonged to the classes of free amino acids and saccharides.Gas chromatography-mass spectrometry-basedmetabolomics has proven to be a valid tool to study theeffect of mild heat treatments on the polar metaboliteprofile in ovine cheese.