Peptides and proteins as markers of quality and safety in food: an approach by Mass Spectrometry

The present Ph.D. thesis concerns the development of Mass Spectrometry (MS) methods for studying proteins and peptides in food, as an innovative approach for assessing food safety and food quality. Casein traces contaminating hypoallergenic infant formulas were determined by a proteomic bottom-up approach; structures of the allergens of peach (Pru p 3) and plum (Pru d 3) were elucidated by means of a combination of bottom-up and top-down approach. MALDI Mass Spectrometry Imaging was used to detect the two allergen distribution in fruit sections. Peptides derived from simulated gastro-intestinal digestion of peach LTP have also been determined by MS techniques and their allergenic potential has been evaluated by means of dot-blotting technique. In the second part of this thesis, LC/MS based methodologies have been exploited in order to study oligopeptides in cheeses. Several peptides have been identified, many of them never previously reported, allowing new insights on the influence of ripening time and technologies of production on the proteolysis occurring in cheese. New peptide-like structures constantly increasing during ageing have been identified for the first time. An LC/MS method has also been developed in order to easily detect the undeclared presence of cows’ milk in sheep milk cheeses.