Highly proteolized novel and traditional foods

Abstract

The present Ph.D. Thesis concerns the molecular characterization of highly proteolyzed foods, with particular attention to the influence on their biological and functional properties exerted by oligopeptides and amino acids. Different kinds of foods containing low molecular weight nitrogen compounds have been considered: traditional food products derived from a natural proteolytic processes, , and in particular Parmigiano-Reggiano cheese and Culatello sausages, and novel foods obtained by a proteolytic digestion through an innovative biocatalytic processes, considering in particular proteic hydrolyzates obtained from the recovery of poultry industry leftovers. The nitrogen fractions of the proteinaceous hydrolyzates extracted from the different food matrices, both traditional and produced according to novel technologies, have been extensively studied by means of mass spectrometry coupled with liquid chromatography. This technique has been demonstrated to be a valid approach to monitor the composition of complex peptide mixtures, because of its high sensibility and selectivity. In particular a new LC/MS/MS methods to quantify free and total amino acids without any derivatization step has been developed and validated, and improved LC/MS methodologies have been set up also for the analysis of other nitrogen components Cheese is a natural product with a potential high biological value. Proteolysis occurring during ageing time leads to the release of a large number of peptides from caseins, which have been demonstrated to be biologically active by in vitro studies. The composition of the oligopeptide fraction of different Parmigiano-Reggiano cheeses at different ageing times has been extensively studied in a very detailed way by means of LC/MS methodologies. Antioxidant and antihypertensive properties of these peptide fractions have been studied. Moreover, since data on the effective bioavailability of these peptides are still quite scarce, the work of the present PhD. thesis also addressed the study of their bioaccessibility through simulated gastrointestinal digestion. Low molecular weight nitrogen compounds in Culatello sausages, one of the most famous Italian dry pork meat products, have also been studied. For the first time data on the amount of characteristic’s meat compounds, such as carnosine, anserine, creatine and creatinine, in cured meat are reported and their amount was found to be strictly related to the technological production process. Finally, free and total amino acid analysis of the biosynthetic proteinaceous hydrolyzates derived from poultry leftovers have shown that this potential novel foods posses an high nutritional value, due to the high content of bioavailable essential amino acids. These proteic hydrolyzates showed interesting antioxidant and antihypertensive properties. Amino acidic composition, and overall oligopeptide fractions, have been found to be strictly related to the proteolytic conditions used for food production, thus bioactive compound amounts may be regulated on the basis of the desired features. For example, samples with the highest hydrolysis degree may be used as functional food ingredients in virtue of their high antioxidant capacity. In conclusion, the present thesis demonstrated that proteolyzed foods can be considered high quality food and food ingredients, either if traditional food obtained by natural proteolytic processes or novel foods obtained through innovative technologies. In the latter case, it has been demonstrated that leftover of the food industry can be transformed in new food and feed not only having a high nutritional value, but also possessing biofunctional properties.