Pearce L E, Truong H T, Crawford R A, Yates G F, Cavaignac S, de Lisle G W
New Zealand Dairy Research Institute, Palmerston North, New Zealand.
Appl Environ Microbiol. 2001 Sep;67(9):3964-9. doi: 10.1128/AEM.67.9.3964-3969.2001.
A pilot-scale pasteurizer operating under validated turbulent flow (Reynolds number, 11,050) was used to study the heat sensitivity of Mycobacterium avium subsp. paratuberculosis added to raw milk. The ATCC 19698 type strain, ATCC 43015 (Linda, human isolate), and three bovine isolates were heated in raw whole milk for 15 s at 63, 66, 69, and 72 degrees C in duplicate trials. No strains survived at 72 degrees C for 15 s; and only one strain survived at 69 degrees C. Means of pooled D values (decimal reduction times) at 63 and 66 degrees C were 15.0 +/- 2.8 s (95% confidence interval) and 5.9 +/- 0.7 s (95% confidence interval), respectively. The mean extrapolated D72 degrees C was <2.03 s. This was equivalent to a >7 log10 kill at 72 degrees C for 15 s (95% confidence interval). The mean Z value (degrees required for the decimal reduction time to traverse one log cycle) was 8.6 degrees C. These five strains showed similar survival whether recovery was on Herrold's egg yolk medium containing mycobactin or by a radiometric culture method (BACTEC). Milk was inoculated with fresh fecal material from a high-level fecal shedder with clinical Johne's disease. After heating at 72 degrees C for 15 s, the minimum M. avium subsp. paratuberculosis kill was >4 log10. Properly maintained and operated equipment should ensure the absence of viable M. avium subsp. paratuberculosis in retail milk and other pasteurized dairy products. An additional safeguard is the widespread commercial practice of pasteurizing 1.5 to 2 degrees above 72 degrees C.
使用一台在验证的湍流条件下运行（雷诺数为11,050）的中试规模巴氏杀菌器，研究添加到原料奶中的副结核分枝杆菌的热敏感性。将ATCC 19698标准菌株、ATCC 43015（琳达，人类分离株）以及三株牛分离株在原料全脂奶中，于63、66、69和72摄氏度下加热15秒，进行重复试验。在72摄氏度下加热15秒后没有菌株存活；在69摄氏度下只有一株菌株存活。63和66摄氏度下合并的D值（十进制减少时间）平均值分别为15.0±2.8秒（95%置信区间）和5.9±0.7秒（95%置信区间）。72摄氏度下的平均外推D值<2.03秒。这相当于在72摄氏度下加热15秒时杀灭率>7个对数10（95%置信区间）。平均Z值（十进制减少时间跨越一个对数周期所需的温度度数）为8.6摄氏度。无论在含有分枝杆菌素的赫罗尔德蛋黄培养基上恢复培养还是通过放射性培养方法（BACTEC），这五株菌株的存活情况相似。用患有临床型副结核病的高粪便排菌者的新鲜粪便材料接种牛奶。在72摄氏度下加热15秒后，副结核分枝杆菌的最小杀灭率>4个对数10。正确维护和操作的设备应确保零售牛奶和其他巴氏杀菌乳制品中不存在活的副结核分枝杆菌。另外一项保障措施是普遍的商业做法，即巴氏杀菌温度比72摄氏度高1.5至2摄氏度。
