Dalzini Elena, Cosciani-Cunico Elena, Monastero Paola, Bernini Valentina, Neviani Erasmo, Bellio Alberto, Decastelli Lucia, Losio Marina-Nadia, Daminelli Paolo, Varisco Giorgio
National Reference Centre for Emerging Risks in Food Safety, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna "B. Ubertini", Milan, Italy; Department of Food Microbiology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna "B. Ubertini", Brescia, Italy.
National Reference Centre for Emerging Risks in Food Safety, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna "B. Ubertini", Milan, Italy; Department of Food Microbiology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna "B. Ubertini", Brescia, Italy.
Int J Food Microbiol. 2017 Dec 4;262:71-79. doi: 10.1016/j.ijfoodmicro.2017.09.018. Epub 2017 Sep 27.
As reported on RASFF's portal, in the first 9months of 2016, a total of 13 "alerts/information for attention" were issued concerning the presence of Listeria monocytogenes in mould cheeses throughout Europe. This study analyzes the behaviour of L. monocytogenes in Gorgonzola cheese, a typical Italian soft blue-veined cheese, when contaminated at different time points. In the first challenge test, the pasteurized milk was contaminated and the complete cheese manufacture (cheesemaking, ripening) and shelf life was simulated. After a decrease during the first days of the cheesemaking, the pH remained constant for 35days (5weeks) and then it increased rapidly reaching the final values of 6.8±0.02 in the core and 5.8±0.4 on the rind. At the same time, the pathogen concentration decreased (about 2logCFU/g), although during the last week a rapid pathogen growth was observed after the rise in pH values. When the cheese was stored at thermal abuse condition (8-12°C), the pathogen concentration on the rind was 4.8±0.3 log CFU/g and after 66days (about 9weeks) no significant difference (p>0.05) was observed; whereas, a growth from 5.4±0.4 to 7.1±0.5logCFU/g was observed in the core. A second challenge test was performed using three batches of commercial slices of Gorgonzola cheese inoculated by L. monocytogenes and stored at 8°C. The maximum specific growth rates (μ, 1/h) of L. monocytogenes estimated ranged from 0.007 to 0.061. The square root model was used to predict the μ at others temperature and to establish the time necessary to reach the European critical legal limit of 2logCFU/g, in different storage scenarios. The predictions obtained in this study can be applied to any time-temperature profile, and in particular to the conditions to which the product is most likely to be subject in normal use, up to its final consumption. This study can be considered a valuable contribution also aimed at supporting the monitoring surveys carried out by officers of the Regional Veterinary Authority.
据RASFF门户网站报道，2016年前9个月，欧洲各地共发布了13条关于霉菌奶酪中存在单核细胞增生李斯特菌的“警报/需关注信息”。本研究分析了典型的意大利软质蓝纹奶酪戈尔贡佐拉奶酪在不同时间点被污染时，单核细胞增生李斯特菌的行为。在首次挑战试验中，对巴氏杀菌牛奶进行污染，并模拟整个奶酪生产过程（奶酪制作、成熟）和保质期。在奶酪制作的头几天pH值下降后，pH值在35天（5周）内保持恒定，然后迅速上升，核心部位最终值达到6.8±0.02，外皮部位达到5.8±0.4。与此同时，病原体浓度下降（约2logCFU/g），尽管在最后一周，pH值上升后观察到病原体快速生长。当奶酪在热滥用条件（8 - 12°C）下储存时，外皮上的病原体浓度为4.8±0.3 log CFU/g，66天（约9周）后未观察到显著差异（p>0.05）；而在核心部位，观察到病原体从5.4±0.4 logCFU/g增长到7.1±0.5logCFU/g。使用三批接种了单核细胞增生李斯特菌的商业戈尔贡佐拉奶酪切片进行第二次挑战试验，并在8°C下储存。估计的单核细胞增生李斯特菌最大比生长速率（μ，1/h）范围为0.007至0.061。使用平方根模型预测其他温度下的μ，并确定在不同储存场景下达到欧洲法定临界限量2logCFU/g所需的时间。本研究获得的预测结果可应用于任何时间 - 温度曲线，特别是产品在正常使用直至最终消费时最可能遇到的条件。本研究也可被视为一项有价值的贡献，旨在支持地区兽医当局官员进行的监测调查。
