Effect of irradiation on kinetic behavior of Salmonella Typhimurium and Staphylococcus aureus in lettuce and damage of bacterial cell envelope

详细信息	查看全文 | 推荐本文 |

• 作者：Won-Bo Shim¹ ; ^a ; Gil-Soo Je^a ; Kyeongyeol Kim^a ; Adelard B. Mtenga^a ; Won-Gyeong Lee^a ; Jeong-Un Song^a ; Duck-Hwa Chung^a ; Yohan Yoon^b ; ^{yyoon@sm.ac.kr}
• 关键词：Irradiation ; Salmonella ; Staphylococcus aureus ; Lettuce
• 刊名：Radiation Physics and Chemistry
• 出版年：2012
• 期刊代码：68_0969806x
• 类别：ph
• 出版时间：May, 2012
• 卷：81
• 期：5
• 页码：566-571
• 文件大小：559 K

摘要

This study evaluated effect of gamma irradiation on survival of Salmonella Typhimurium and Staphylococcus aureus on lettuce and damage of cell envelope. S. Typhimurium and S. aureus were inoculated on red leaf lettuce, and they were irradiated at 0, 0.5, 1, 1.5, 2, 2.5, and 3 kGy, and the samples were then stored at 7 and 25 掳C for 7 days. Survival of S. Typhimurium and S. aureus were enumerated on xylose lysine deoxycholate agar and Baird-Parker agar, respectively. D₁₀ value (dose required to reduce 1 log CFU/leaf) was calculated, and kinetic parameters (maximum specific growth rate; 渭_max and lag phase duration; LPD) were calculated by the modified Gompertz model. In addition, cell envelope damage of the pathogens was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). D₁₀ values were 0.35 and 0.33 kGy for S. Typhimurium and S. aureus, respectively. During storage at 7 掳C, S. Typhimurium and S. aureus had significant (P<0.05) growth only on non-irradiated samples up to about 2.5 and 4 log CFU/leaf at 0.42 and 1.28 log CFU/leaf/day of 渭_max, respectively. At 25 掳C, cell counts of S. Typhimurium and S. aureus on the samples irradiated at 0 and 0.5 kGy increased (P<0.05) up to 3-6 log CFU/leaf. The 渭_max of both pathogens were higher in 0 kGy (1.08-2.27 log CFU/leaf/day) and 0.5 kGy (0.58-0.92 log CFU/leaf/day), and LPDs ranged from 1.53 to 3.14 day. SEM and TEM observations showed that cells irradiated at 1.5 and 3 kGy showed disrupted cell membrane. These results indicate that gamma irradiation could be a useful decontamination technology to improve food safety of lettuce by destroying cells of S. Typhimurium and S. aureus.