Effects of Gamma-Ray and Heat Treatment on Sterilization of Escherichia coli O157:H7

Escherichia coli O157:H7의 살균을 위한 감마선과 가열처리의 효과

Treatments of irradiation alone and/or in combination with heat were investigated for the sterilization of Escherichia coli O157: H7. D values of the strain were 129.2 min at $50^{\circ}C$, 27.1 min at $55^{\circ}C$, and 2.4 min at $60^{\circ}C$. The survival effect of E. coli O157:H7 during heating at various media was investigated. On heating at temperature of $60^{\circ}C$ for 10 min, the strain was generally more resistant in the media containg such chemical substrates such as 0.03 M cysteine, 1% sodium citrate or 5% sucrose, whereas this strain was appeared weaker in the chemical substrates added group such as 1% meat extract, 1% casein or 1% casamino acid. In the case of irradiation alone, $D_{10}$ value of E. coli O157:H7 was 0.116 kGy, and inactivation factors were $17{\sim}25$ at doses of 2 to 3 kGy. Pre-and post-irradiation heating showed the same $D_{10}$ value about 0.07 kGy. And Inactivation factors were $25{\sim}41$ at doses of 2 to 3 kGy. Therefore, combination treatment with heat and irradiation significantly increased in inactivation rate by increasing radiation sensitivity of E. coli O157:H7.

본 연구는 Escherichia coli O157:H7 균주를 살균하고자 감마선 단독 및 가열과의 병용처리 효과를 조사하였다. E. coli O157:H7 균주의 가열 단독처리시 D값은 $50^{\circ}C$에서 129.2분, $55^{\circ}C$에서 27.1분, $60^{\circ}C$에서 2.4분으로 나타났다. E. coli O157:H7 균주는 0.03 M cysteine, 1% sodium citrate 및 5% sucrose가 첨가된 배지에서는 열에 대한 저항성이 증가하였고 1%, meat extract, 1% casein 및 1% casamino acid가 첨가된 배지에서는 감소하였다. 감마선 단독처리시는 $D_{10}$ 값과 불활성화 계수가 0.116 kGy와 $17{\sim}25$ 이였으나 가열과의 병용처리시는 약 0.07 kGy와 $25{\sim}41$로 나타났다. 이로서 가열과 방사선의 병용처리는 E. coli O157:H7 균주의 방사선 감수성을 현저하게 상승시켜 본 균주의 살균에 효과적이었다.