Inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium in edible bird's nest by low-energy X-ray irradiation

Abstract

Continuing polychromatic low-energy X-ray possesses a high linear energy transfer (LET) effect and correspondingly a high relative biological effect (RBE), which makes it a promising non-thermal processing method for food preservation. This study evaluated the efficacy of low-energy X-ray with cut-off energy of 150 KeV to inactivate two of the most prevalent foodborne pathogens in dry edible bird's nest (EBN). The X-ray irradiation at 350 and 400 Gy decreased E. coli O157:H7 and S. Typhimurium from 6.35 ± 0.56 and 5.84 ± 0.67 log CFU/g, respectively, to undetectable level. The low-energy X-ray irradiation yielded the tR1 value of 37.6 ± 6.9 and the D10 value of 83.3 ± 7.0 Gy for E. coli O157:H7 and S. Typhimurium, respectively, which indicates that S. Typhimurium exhibited more resistant to low-energy X-ray irradiation than E. coli O157:H7. Based on dose distribution in 10 sacked pieces of EBN, two-sided irradiation can assure the uniformity of processing. As for the quality of processed EBN, while the irradiation increased the yellowness of EBN (p < 0.05), no sulfur-containing volatile compounds were detected in the irradiated samples. These results show that low-energy X-ray can serve as an effective method to inactivate foodborne pathogens in dry EBN.