The antibacterial effect of light emitting diodes (LEDs) in the visible region (461, 521 and 642 nm) of the electromagnetic spectrum was investigated on Escherichia coli O157:H7, Salmonella typhimurium, Listeria monocytogenes and Staphylococcus aureus. The irradiances of the 461, 521 and 642 nm LEDs were 22.1, 16 and 25.4 mW/cm², respectively. Bacterial cultures suspended in tryptic soy broth were illuminated by 10-watt LEDs at a distance of 4.5 cm for 7.5h at 20, 15 and 10 °C. Regardless of the bacterial strains, bacterial inactivation was observed with the range of 4.6-5.2 logCFU/ml at 10 and 15 °C after illumination with the 461 nm LED, while illumination with the 521 nm LED resulted in only 1.0-2.0 log reductions after 7.5h. On the other hand, no antibacterial effect was observed using the 642 nm LED treatment. The photodynamic inactivation by 461 and 521 nm LEDs was found to be greater at the set temperatures of 10 and 15 °C than at 20 °C. The D-values for the four bacterial strains at 10 and 15 °C after the illumination of 461 nm LED ranged from 1.29 to 1.74 h, indicating that there was no significant difference in the susceptibility of the bacterial strains to the LED illumination between 10 and 15 °C, except for L. monocytogenes. Regardless of the illumination temperature, sublethal injury was observed in all bacterial strains during illumination with the 461 and the 521 nm LED and the percentage of injured cells increased as the treatment time increased. Thus, the results show that the antibacterial effect of the LEDs was highly dependent on the wavelength and the illumination temperature. This study suggests the potential of 461 and 521 nm LEDs in combination with chilling to be used as a novel food preservation technology.

译文

在大肠杆菌O157:H7,鼠伤寒沙门氏菌,单核细胞增生李斯特菌和金黄色葡萄球菌上研究了电磁光谱的可见区域 (461,521和642 nm) 中发光二极管 (led) 的抗菌作用。461、521和642 nm led的辐照度分别为22.1、16和25.4 mW/cm ²。悬浮在胰蛋白酶大豆肉汤中的细菌培养物在20、15和10 °C下以4.5厘米的距离用10瓦led照射7.5小时。无论细菌菌株如何,在用461 nm LED照明后,在10和15 °C下观察到4.6-5.2 logCFU/ml范围内的细菌失活,而用521 nm LED照明在7.5小时后仅导致1.0-2.0 log减少。另一方面,使用642 nm LED处理未观察到抗菌效果。发现461和521 nm led的光动力失活在10和15 °C的设定温度下比在20 °C下更大。在461 nm LED照射后,4个细菌菌株在10和15 °C的d值范围为1.29至1.74小时,表明除了单核细胞增生李氏菌以外,在10和15 °C之间细菌菌株对LED照射的敏感性没有显著差异。不管照射温度如何,在用461和521 nm LED照射期间,在所有细菌菌株中观察到亚致死损伤,并且损伤细胞的百分比随着处理时间的增加而增加。因此,结果表明,led的抗菌效果高度依赖于波长和照明温度。这项研究表明,461和521 nm led与冷却相结合的潜力可用作新型食品保存技术。

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