Cristian De Gobba

Chemical derivatization can improve the detectability of analytically challenging compounds, but untargeted feature identification and annotation for chemically derivatized samples are limited by the availability of reference spectra. With the workflow presented in this manuscript, challenges associated with library‑dependent identification of derivatized species are mitigated by in silico derivatization and -MS/MS prediction, which reduce the need for dedicated experimental reference libraries. Furthermore, an improved CCS-value prediction algorithm provides an orthogonal dimension that increases confidence in feature annotation for both native and derivatized compounds. The annotated feature lists can be used for automated generation of target lists for quantitation. Additionally, they can be used for semi‑untargeted stable-isotope labeling analyses, which can be performed, from raw data to results, within the same software environment. Finally, natural isotope abundance correction can be applied on the resulting isotopologue distributions, which allows for a full analysis of stable-isotope labeling data. Consolidation of all processing steps in a single environment minimizes operator intervention, reduces error risk, and makes stable-isotope labeling more widely attainable in metabolomics research. This workflow is exemplified with a nutrient contribution experiment in murine brown adipocytes, presenting substrate integration into metabolic intermediates.

Reduced physiological capability of the human gastrointestinal tract with increasing age has recently attracted considerable attention to the potential of novel technologies to modify food digestion. Thus, the aim of this study was to investigate gastric digestion of milk proteins after application of high-pressure processing (HPP) at 400 MPa 15 min, 600 MPa 5 min and 600 MPa 15 min using two static in vitro models of adults (INFOGEST) and the elderly in comparison to a fresh untreated raw milk. Peptides distribution classified based on the number of amino acids (AA) (30 AA) were investigated after 0, 5, 10 and 30 min of digestion using LC–MS and multivariate data analysis. Our results show significantly less efficient protein digestion of all investigated milks in the elderly model indicated by higher percentages of longer peptides during digestion, except for the HPP milk 400 MPa 15 min, which indicated an improved and comparable digestion in the elderly as in the adult model. Furthermore, increasing the pressurization time at 600 MPa did not have a significant effect on the peptides profile during the digestion. More efficient digestion of whey proteins in HPP milks, with the majority of peptides in the 16–20 AA range, compared to fresh milk was also noticed. According to the findings of this study, HPP at 400 MPa 15 min showed the most efficient digestion of major milk proteins and thus may be considered a suitable process to improve bioaccessibility of milk proteins, especially in products intended for the elderly.

Heat treatment is a widely used method for food processing, and the compounds formed by heat processes may serve as biomarkers of heated food intake in nutrition studies. Therefore, we aimed to characterize the differential metabolic signatures resulting from intake of different potato products and identify potential intake biomarkers. In a randomized, controlled, crossover meal study, healthy volunteers consumed boiled rice, boiled potatoes, and two deep-fried potato products, potato chips and French fries. The urine metabolome was acquired by LC–MS-based untargeted metabolomics. Twenty-two selected metabolites were found for deep-fried potatoes, two for potato intake in general, and one for boiled rice. Fourteen of the 22 selected metabolites were tentatively identified as furan-, pyrrole- and pyrazine-derived compounds indicative of Maillard reactions. With further validation, these candidate biomarkers will be important tools to investigate the influence of heated foods on human health.

Bovine colostrum (BC) contains bioactive proteins, such as immunoglobulin G (IgG), lactoferrin (LF) and lactoperoxidase (LP). BC was subjected to low-temperature, long-time pasteurization (LTLT, 63 °C, 30 min) or high-temperature, short-time pasteurization (HTST, 72 °C, 15 s) and spray-drying (SD), with or without γ-irradiation (GI, ∼14 kGy) to remove microbial contamination. Relative to unpasteurized liquid BC, SD plus GI increased protein denaturation by 6 and 11%, respectively, increasing to 19 and 27% after LTLT and to 48% after HTST, with no further effects after GI (all P < 0.05). LTLT, without or with GI, resulted in 15 or 29% denaturation of IgG, compared with non-pasteurized BC, and 34 or 58% for HTST treatment (all P < 0.05, except LTLT without GI). For IgG, only GI, not SD or LTLT, increased denaturation (30–38%, P < 0.05) but HTST increased denaturation to 40%, with further increases after GI (60%, P < 0.05). LTLT and HTST reduced LP levels (56 and 81% respectively) and LTLT reduced LF levels (21%), especially together with GI (47%, P < 0.05). Denaturation of BSA, β-LgA, β-LgB and α-La were similar to IgG. Methionine, a protective amino acid against free oxygen radicals, was oxidised by LTLT + GI (P < 0.05) while LTLT and HTST had no effect. Many anti-inflammatory proteins, including serpin anti-proteinases were highly sensitive to HTST and GI but preserved after LTLT pasteurization. LTLT, followed by SD is an optimal processing technique preserving bioactive proteins when powdered BC is used as a diet supplement for sensitive patients.

Thiol groups of cysteine (Cys) residues in proteins react with quinones, oxidation products of polyphenols, to form protein-polyphenol adducts. The aim of the present work was to quantify the amount of adduct formed between Cys residues and 4-methylcatechol (4MC) in minced beef. A Cys-4MC adduct standard was electrochemically synthesized and characterized by LC-MS/MS as well as NMR spectroscopy. Cys-4MC adducts were quantified after acidic hydrolysis of myofibrillar protein isolates (MPI) and LC-MS/MS analysis of meat added either 500 ppm or 1500 ppm 4MC and stored at 4 C for 7 days under nitrogen or oxygen atmospheres. The concentration of Cys-4MC was found to be 2.2 ± 0.3 nmol/mg MPI and 8.1 ± 0.9 nmol/mg MPI in meat added 500 ppm or 1500 ppm 4MC, respectively, and stored for 7 days under oxygen. The formation of Cys-4MC adduct resulted in protein thiol loss, and ca. 62% of the thiol loss was estimated to account for the formation of Cys-4MC adduct for meat containing 1500 ppm 4MC. Furthermore, protein polymerization increased in samples containing 4MC as evaluation by SDS-PAGE, and the polymerization was found to originate from protein-polyphenol interactions as evaluated by a blotting assay with staining by nitroblue tetrazolium.