Laboratorio Integral de Investigación de Alimentos, Tecnológico Nacional de México/Instituto Tecnológico de Tepic, Av. Tecnológico 2595, Col. Lagos del Country, C.P. 63175, Tepic, Nayarit, Mexico.
Departamento de Ciencia y Tecnología de los Alimentos, Facultad de Química, Universidad de la República, Avda. Gral. Flores 2124, 11800, Montevideo, Uruguay.
J Dairy Res. 2020 Feb;87(1):94-102. doi: 10.1017/S0022029919001043. Epub 2020 Feb 5.
The objectives of this study were: to assess the efficiency of high hydrostatic pressure or ultra-high pressure homogenization against Mycobacterium smegmatis in milk and to discuss whether M. smegmatis can be considered a suitable surrogate for other Mycobacterium spp. in high pressure inactivation trials using milk. Three strains of this specie (CECT 3017, 3020 and 3032) were independently inoculated into both skimmed (0.2% fat) and whole milk (3.4% fat) at an approximate load of 6.5 Log CFU/ml and submitted to HHP treatments at 300, 400 or 500 MPa for 10 m at 6°C and 20°C. Evolution of the surviving cells of the inoculated strains was evaluated analysing milk immediately after the treatments and after 5 and 8 d of storage at 6°C. HHP treatments at 300 MPa were seldom efficient at inactivating M. smegmatis strains, but lethality increased with pressure applied in all cases. Generation of sub-lethal injured cells was observed only after 400 MPa treatments since inactivation at 500 MPa was shown to be complete. Significant differences were not observed due to either temperature of treatment or fat content of milk, except for strain CECT3032, which was shown to be the most sensitive to HHP treatments. Milk inoculated with strain CECT3017 was submitted to ultra-high pressure homogenization (UHPH) treatments at 200, 300 and 400 MPa. Maximum reductions were obtained after 300 and 400 MPa treatments, although less than 3.50 Log CFU/ml were inactivated. UHPH did not cause significant number of injured cells. The usefulness of this species as a marker for pressure-based processing seems limited since it showed greater sensitivity than some pathogenic species including other Mycobacteria reported in previous studies.
评估高压或超高压均质处理对牛奶中耻垢分枝杆菌的效率，并讨论在使用牛奶进行高压失活动力学试验时，耻垢分枝杆菌是否可以被视为其他分枝杆菌属的合适替代品。将该物种的三个菌株（CECT 3017、3020 和 3032）分别以大约 6.5 Log CFU/ml 的负荷独立接种到脱脂（0.2%脂肪）和全脂（3.4%脂肪）牛奶中，并在 6°C 和 20°C 下以 300、400 或 500 MPa 的压力处理 10 m。接种菌株存活细胞的变化通过分析处理后立即和在 6°C 下储存 5 和 8 d 后的牛奶来评估。300 MPa 的高压处理很少能有效灭活耻垢分枝杆菌菌株，但在所有情况下，随着压力的增加，致死率都有所增加。只有在 400 MPa 处理后才观察到亚致死损伤细胞的生成，因为在 500 MPa 下的失活被证明是完全的。由于处理温度或牛奶脂肪含量的原因，没有观察到显著差异，除了 CECT3032 菌株，该菌株对 HHP 处理表现出最高的敏感性。接种 CECT3017 菌株的牛奶进行超高压均质（UHPH）处理，压力为 200、300 和 400 MPa。在 300 和 400 MPa 处理后获得了最大的减少，但失活量不到 3.50 Log CFU/ml。UHPH 不会导致大量损伤细胞。该物种作为基于压力处理的标志物的有用性似乎有限，因为它比以前研究中报道的一些包括其他分枝杆菌在内的致病性物种表现出更高的敏感性。
