Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, National Reference Centre for Paratuberculosis, Strada Faggiola 1, loc. Gariga - Podenzano (PC), 29027, Italy.
Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, National Reference Centre for Paratuberculosis, Strada Faggiola 1, loc. Gariga - Podenzano (PC), 29027, Italy.
Int J Food Microbiol. 2019 Sep 16;305:108247. doi: 10.1016/j.ijfoodmicro.2019.108247. Epub 2019 Jun 8.
Mycobacterium avium subsp. paratuberculosis (MAP), the agent of paratuberculosis in ruminants, is suspected to be involved in the aetiology of some human diseases. Notably, the consumption of milk and dairy products is considered to be the main route of human exposure to MAP because of its ability to survive during pasteurization and manufacturing processes. The aim of this study was to investigate, through a microbiological challenge test, the survival of MAP during the manufacturing and ripening period of two Italian hard cheeses, Parmigiano Reggiano and Grana Padano, made from raw bovine milk. The challenge test was performed in two different phases: the creaming phase and the manufacturing phase. The creaming phase, which is the first step of cheese production, was reproduced in the laboratory employing raw cow's milk spiked with a MAP reference strain at a final concentration of 5.58 log CFU/mL. After the creaming at 18 °C and 27 °C for 12 h, a decrease of 0.80 log and 0.77 log was observed in partially skimmed milk, respectively. In the second phase, two batches of raw cow's milk (1000 L each) were inoculated with MAP reference and wild strains, respectively. Then, the entire manufacturing process for Parmigiano Reggiano and Grana Padano, both of Protective Designation of Origin (PDO), was reproduced in an experimental cheese factory, starting from a concentration in milk of 5.19 ± 0.01 and 5.28 ± 0.08 log CFU/mL of MAP reference and wild strains, respectively. Heating the curd at 53 °C for 20 min did not affect MAP survival, however a significant decrease (p < 0.05) in MAP viability was observed during the moulding phase and after salting in brine, regarding the wild strains and the reference strain, respectively. In addition, a significant decrease was observed during the ripening period, at which time the MAP concentration dropped below the limit of detection from the second and the third month of ripening, for the wild and reference strains, respectively. Taking into account the poor data availability about MAP survival in hard cheeses, this study may improve the knowledge regarding the effect of the cheese manufacturing process on the MAP dynamics, supporting also the safety of traditional raw milk hard cheeses.
分支杆菌 avium subsp。paratuberculosis（MAP），反刍动物中副结核病的病原体，被怀疑与一些人类疾病的病因有关。值得注意的是，由于其在巴氏消毒和制造过程中能够存活，因此食用牛奶和奶制品被认为是人类接触 MAP 的主要途径。本研究通过微生物挑战试验，研究了 MAP 在两种意大利硬质奶酪 Parmigiano Reggiano 和 Grana Padano 的制造和成熟过程中的存活情况，这两种奶酪均由生牛乳制成。挑战试验分两个阶段进行：制乳阶段和制造阶段。制乳阶段是奶酪生产的第一步，在实验室中使用生牛乳进行模拟，生牛乳中添加 MAP 参考株，最终浓度为 5.58 log CFU/mL。在 18°C 和 27°C 条件下分别进行 12 h 的凝乳后，部分脱脂乳中的 MAP 数量分别减少了 0.80 log 和 0.77 log。在第二阶段，分别用 MAP 参考株和野生株对两批生牛乳（各 1000 L）进行接种。然后，在一个实验奶酪工厂中复制 Parmigiano Reggiano 和 Grana Padano 的整个制造过程，这两种奶酪均为受保护原产地名称（PDO）。从 MAP 参考株和野生株在牛奶中的初始浓度分别为 5.19±0.01 和 5.28±0.08 log CFU/mL 开始。将凝乳加热至 53°C 20 min 不会影响 MAP 的存活，但在成型阶段和盐渍过程中，野生株和参考株的 MAP 活力均显著下降（p<0.05）。此外，在成熟阶段也观察到了显著的下降，此时，野生株和参考株的 MAP 浓度分别从成熟后第 2 个月和第 3 个月开始下降到检测限以下。考虑到有关硬质奶酪中 MAP 存活数据的缺乏，本研究可能会提高对奶酪制造过程对 MAP 动态影响的认识，同时也支持传统生牛乳硬质奶酪的安全性。
