UV-C-irradiated Gallic Acid Solution (UVC-GA) Inhibited the Growth of E. coli O157:H7 on the Surface of Oyster Flesh
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Abstract:
A novel ultraviolet-irradiated gallic acid antibacterial solution (UVC-GA) was developed using a new method of light-induced enhancement of GA antibacterial activity through exposing gallic acid (GA) to UV-C for 12 h. The GA solution obtained after UVC-GA for 12 h could reduce E. coli O157: H7 by 3.57 log cfu/mL (which was 22.33 times higher than that of GA. The antibacterial activity of UVC-GA solution was affected by the irradiation duration, wavelength and pH. After 60 min of irradiation, UVC-GA reduced E. coli O157: H7 by 4.42 log cfu/mL, which was significantly higher than UVB-GA and UVA-GA by 64.25% and 223.47%; The reduction of E. coli O157: H7 by UVC-GA at pH 3 was 94.23 and 87.62 times, respectively, higher than those at pH 7 and pH 11. The addition of benzenesulfinic acid (BSA) to UVC-GA lowered E. coli O157: H7 to 0.63 log cfu/mL (p<0.05), indicating that quinone compounds in UVC-GA enhanced its antibacterial activity. The addition of reactive oxygen species (ROS) quencher to UVC-GA significantly (p<0.05) reduced the antibacterial effect by 4.56% and 8.15%, respectively, compared with those of the DMSO-treated group and the mannitol-treated group (p<0.05). The generation of hydrogen peroxide and the increase of E. coli O157: H7-induced oxidative stress indicated the contribution of ROS to the antibacterial effect of UVC-GA. The results showed that UVC-GA could effectively inhibit E. coli O157:H7 on the surface of oyster flesh, and correctly treated UV-C irradiated GA can be used as a novel antimicrobial solution for sterilization of oyster products and other foods.
