In order to solve the problem of quality deterioration in Ningxia Tan sheep meat caused by microbial growth during long-distance transportation, an antibacterial film, GEL/KT-OEO, was prepared by the solution casting method with oregano essential oil (OEO) as the antibacterial agent and keratin (KT) and gelatin (GEL) as the film-forming matrices. Its microstructure, chemical groups, crystal structure and thermal properties were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The effect of GEL/KT-OEO on the quality preservation of Ningxia Tan sheep meat was evaluated during storage at 4 ℃. The results showed that the film with 10% OEO exhibited optimal physical and bacteriostatic properties, with light transmittance, tensile strength, elongation at break, moisture content (MC), water solubility (WS), inhibition rates against Escherichia coli and Staphylococcus aureus of (36.20 ± 0.31)%, (0.58 ± 0.06) MPa, (82.53 ± 2.73)%, (14.31 ± 0.49)%, (48.98 ± 0.69)%, (97.28 ± 1.34)% and (99.67 ± 0.33)%, respectively. The addition of OEO did not change the molecular structure or functional groups of the antibacterial film, but reduced its crystallinity and improved its thermal stability. The antibacterial film with 10% OEO resulted in superior sensory characteristics, pH, total volatile basic nitrogen (TVB-N) value and thiobarbituric acid reactive substance (TBARS) value of lamb meat stored at 4 ℃ when compared with the blank group and polyethylene (PE) film (P < 0.05), prolonging the shelf life from 5 to 7 days relative to the PE film group. The GEL/KT-OEO antibacterial film shows significant potential and value for application in meat preservation, which provides a new and effective solution for maintaining meat quality during long-distance transportation.

In this study, three enzymatic hydrolysis methods, alkaline protease (E1), pepsin + trypsin (E2), and alkaline protease + pepsin + trypsin (E3), were used to prepare hemoglobin hydrolysates from Ningxia beef cattle, which were screened for their antioxidant activity. Amino acid analysis and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to identify the amino acid compositions and sequences of the hydrolysates with molecular mass < 3 kDa. The potential antioxidant peptides were selected by computerized analysis and their activities were verified. Their action mechanism was studied by molecular simulation. The results showed that E3 exhibited the highest hydrolysis efficiency, and the < 3 kDa fraction obtained from the ultrafiltration of the resulting hydrolysate showed better antioxidant activity with half maximal inhibitory concentration (IC₅₀) of (18.382 ± 0.023) mg/mL and (0.246 ± 0.012) mg/mL against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cationic radical, respectively. The < 3 kDa fraction was rich in hydrophobic and aromatic amino acids, and four peptides with the best antioxidant activity were selected and identified, whose amino acid sequences were DWGHSW, VFYPW, GTGW and TYFPHF, respectively. Among them, VFYPW showed the highest DPPH radical and ABTS cationic radical scavenging capacity with IC₅₀ of (0.350 ± 0.013) mg/mL and (9.482 ± 0.122) µg/mL, followed by DWGHSW. DWGHSW and VFYPW were found to form stable complexes with Keap1 protein (PDB ID: 2FLU) through hydrogen bonds and hydrophobic interactions. In summary, this study provides a theoretical basis for the application of hemoglobin peptides from Ningxia beef cattle as natural antioxidant supplements and contributes to the high-value utilization of blood resources from Ningxia beef cattle.