Xu Sa, Labuza Theodore P, Diez-Gonzalez Francisco
Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave., St. Paul, MN 55108, USA.
Appl Environ Microbiol. 2008 Jun;74(11):3336-41. doi: 10.1128/AEM.02072-07. Epub 2008 Apr 4.
The milk supply is considered a primary route for a bioterrorism attack with Bacillus anthracis spores because typical high-temperature short-time (HTST) pasteurization conditions cannot inactivate spores. In the event of intentional contamination, an effective method to inactivate the spores in milk under HTST processing conditions is needed. This study was undertaken to identify combinations and concentrations of biocides that can inactivate B. anthracis spores at temperatures in the HTST range in less than 1 min. Hydrogen peroxide (HP), sodium hypochlorite (SH), and peroxyacetic acid (PA) were evaluated for their efficacy in inactivating spores of strains 7702, ANR-1, and 9131 in milk at 72, 80, and 85 degrees C using a sealed capillary tube technique. Strains ANR-1 and 9131 were more resistant to all of the biocide treatments than strain 7702. Addition of 1,260 ppm SH to milk reduced the number of viable spores of each strain by 6 log CFU/ml in less than 90 and 60 s at 72 and 80 degrees C, respectively. After neutralization, 1,260 ppm SH reduced the time necessary to inactivate 6 log CFU/ml (TTI6-log) at 80 degrees C to less than 20 s. Treatment of milk with 7,000 ppm HP resulted in a similar level of inactivation in 60 s. Combined treatment with 1,260 ppm SH and 1,800 ppm HP inactivated spores of all strains in less than 20 s at 80 degrees C. Mixing 15 ppm PA with milk containing 1,260 ppm SH resulted in TTI6-log of 25 and 12 s at 72 and 80 degrees C, respectively. TTI6-log of less than 20 s were also achieved at 80 degrees C by using two combinations of biocides: 250 ppm SH, 700 ppm HP, and 150 ppm PA; and 420 ppm SH (pH 7), 1,100 ppm HP, and 15 ppm PA. These results indicated that different combinations of biocides could consistently result in 6-log reductions in the number of B. anthracis spores in less than 1 min at temperatures in the HTST range. This information could be useful for developing more effective thermal treatment strategies which could be used in HTST milk plants to process contaminated milk for disposal and decontamination, as well as for potential protective measures.
由于典型的高温短时间（HTST）巴氏杀菌条件无法使炭疽芽孢杆菌孢子失活，因此牛奶供应被认为是炭疽芽孢杆菌孢子生物恐怖袭击的主要途径。万一发生故意污染，就需要一种在HTST加工条件下使牛奶中的孢子失活的有效方法。本研究旨在确定在HTST温度范围内，能在不到1分钟的时间内使炭疽芽孢杆菌孢子失活的杀菌剂组合和浓度。使用密封毛细管技术，评估了过氧化氢（HP）、次氯酸钠（SH）和过氧乙酸（PA）在72、80和85摄氏度下使牛奶中7702、ANR - 1和9131菌株的孢子失活的效果。ANR - 1和9131菌株比7702菌株对所有杀菌剂处理的耐受性更强。在牛奶中添加1260 ppm的SH，在72摄氏度下不到90秒、在80摄氏度下不到60秒，就能使每个菌株的存活孢子数减少6 log CFU/ml。中和后，1260 ppm的SH将80摄氏度下使6 log CFU/ml失活所需的时间（TTI6 - log）缩短至不到20秒。用7000 ppm的HP处理牛奶，在60秒内可达到类似的失活水平。在80摄氏度下，1260 ppm的SH和1800 ppm的HP联合处理，能在不到20秒内使所有菌株的孢子失活。将15 ppm的PA与含有1260 ppm SH的牛奶混合，在72摄氏度和80摄氏度下的TTI6 - log分别为25秒和12秒。通过使用两种杀菌剂组合：250 ppm的SH、700 ppm的HP和150 ppm的PA；以及420 ppm的SH（pH 7）、1100 ppm的HP和15 ppm的PA，在80摄氏度下也能实现TTI6 - log小于20秒。这些结果表明，不同的杀菌剂组合能够在HTST温度范围内，在不到1分钟的时间内持续使炭疽芽孢杆菌孢子数量减少6个对数级。这些信息对于制定更有效的热处理策略可能有用，这些策略可用于HTST牛奶厂处理受污染的牛奶以进行处置和去污，以及用于潜在的防护措施。
