Differentiating the processing degree of animal material by mass spectrometry: A feasibility study on porcine and bovine blood-derived feed ingredients.

Processing food and feed sets off a variety of reactions (Maillard, (lipid) oxidation), which may be traced by covalent changes to e.g. proteins. Whereas these have been previously exploited to differentiate raw from processed milk, this proof-of-principle study aims to distinguish between differently processed blood (fractions). According to European legislation, these may enter the feed chain as typically spray-dried 'blood product' (BP) or as 'blood meal' (BM) when pressure-sterilized prior to drying. Therefore, porcine (BM: 9, BP: 19) and bovine materials (BM: 2, BP: 16) were analyzed in detail by MS-based bottom-up proteomics with dedicated workflows to (i) detect 53 processing-associated post-translational modifications and (ii) combining label-free quantitation with multi-step filtering and several protein normalization approaches. Hence analyzing the porcine (bovine) dataset encompassing more than 19,500 (21,000) peptides revealed 5 (4) markers that were identity-proven by synthetic standards and further 4 (2) candidates non-accessible to standard peptide synthesis.