Mass spectrometry based metabolomics approaches for food safety, quality and nutrition

In the last years, the research in food science and nutrition has grown parallel to the consumers’ concern about the quality and safety of the food they eat. As a result, ensuring food safety, food quality and investigating on nutrition has never been more necessary than today. More powerful analytical procedures are now required to detect and identify undesired and toxic compounds. Moreover, consumers demand is now moving toward the valorization of food with potential health benefits. The identification of bioactive compounds is crucial to provide customers a healthy diet. Finally, one of the main challenges is to improve our limited understanding of the roles of nutritional compounds at molecular level. Food scientists have to face a large number of challenges to adequately answer the new emerging questions of food science. In this context, mass spectrometry showed to be a powerful tool for the investigation on food quality, safety and nutrition. The technical developments of chromatography coupled to mass spectrometry allowed several progresses for the detection of both endogenous compounds and contaminants in food. However, the main progress was due to high resolution mass spectrometry, a promising technique that has opened new horizons in screening and identification of a wide range of unknowns compounds. Mass spectrometry-based metabolomics is a key tool that has been involved, nowadays, in the study of the food and nutrition domains. As per definition, metabolomics includes the exhaustive study of the whole small metabolite composition of a particular system, the food metabolome is not an exception, being rich of endogenous and exogenous compounds with different properties and abundances. Nowadays, three main approaches for the screening of substances can be pointed out: targeted screening (analysis of few known compounds), suspected screening (analysis of a class of expected compounds) and untargeted screening (analysis of a wide range of unknown and unexpected compounds). In this thesis, the three approaches have been studied in details to understand their difficulties, advantages and disadvantages for the analysis of food metabolome. Several steps have been proved to be necessary for the development of a reliable analysis such as sample preparation, chromatographic and mass spectrometric method, data analysis and identification. The thesis is then divided in three main sections: targeted approach for food safety, suspected approach for food quality, untargeted approach for nutrition. In each section, one of the three main approaches used in food metabolomics has been studied for its application on one of the three different food analysis fields. Moreover, each topic has been treated focusing the attention on a specific step of the method development. The topic of metabolomics for food safety has been studied in a targeted approach by developing a method for the analysis of secondary metabolites of fungi, namely mycotoxins, in food (Paper I and II). A particular material for the clean-up of mycotoxins for their quantification in milk and cereals was presented. The topic of metabolomics for food quality has been treated in a suspected approach by developing a method for the analysis of several classes of secondary metabolites of plants such as phenolic acids, flavonoids, and glucosinolates in food (Paper III, IV and V). The development of a chromatographic and mass spectrometric method for the metabolic profiling of strawberry and cauliflower was presented. The topic of metabolomics for nutrition has been treated in an untargeted approach by developing a method for the analysis of the human urinary metabolome after the consumption of meat and dairy products. Several data analysis approaches have been shown for the investigation of the whole urinary metabolome. Ultimately, it has been shown how several aspects should be taken into account when analyzing complex matrices like food through different approaches. Sample preparation, chromatographic and mass spectrometric methods and data analysis have to be treated in different ways based on the used approach. In each case, the advantages of each technique can be exploited based on the purpose of the study. However, aside from the challenges that have to be faced, mass spectrometry-based metabolomics can definitely represent a powerful tool for food safety, quality and nutrition.