Abstract: This study was performed to determine the effect of electron beam dose rate on myofibrillar protein structure and physicochemical properties of chilled nitrogen-packaged beef. Longissimus dorsi muscles from Chinese yellow cattle were irradiated by a high-energy electron accelerator at 2.5 kGy at dose rates of 30, 150 and 300 kGy/min and then stored at 4 ℃ for up to 25 days. Changes in the secondary structure and physicochemical properties of myofibrillar proteins and the thermal stability of muscles were examined at five-day intervals during storage. Compared with the control group, the sulfhydryl group content in the three irradiated groups declined significantly (P < 0.05) by 19.05%, 22.00% and 22.60% at day 0 of storage, respectively. The surface hydrophobicity and solubility of myofibrillar proteins decreased in irradiated samples. In addition, the contents of α-helix and β-sheet decreased along with a simultaneous increase in β-turn and random coil; the protein structure became more disordered. Myosin was oxidized and degraded after electron beam treatment, and the thermal stability declined. To conclude, the irradiation treatment could result in changes in the structure and consequently some physicochemical properties of myofibrillar proteins in beef muscles, thereby affecting beef quality. However, the structure of myofibrillar proteins and meat quality were comparatively less affected at a dose rate of 150 kGy/min.

Key words: electron beam dose rate, myofibrillar protein, secondary structure, thermal stability, physicochemical characteristics