Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands.
Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands.
Int J Food Microbiol. 2019 Jul 2;300:53-63. doi: 10.1016/j.ijfoodmicro.2019.03.020. Epub 2019 Apr 9.
Microbial survival of heating and cross-contamination are the two transmission routes during food preparation in the consumers' kitchen that are relevant for QMRA (Quantitative Microbial Risk Assessment). The aim of the present study was to extend the limited amount of data on microbial survival during real-life preparation of meat and meat products and to obtain accessory temperature data that allow for a more general (product unspecific) approach. Therefore survival data were combined with extensive measurements of time- and location dependent temperature using an infrared camera for the surface and buttons for the inside of the product, supplemented with interpolation modelling. We investigated the survival of heating of Escherichia coli O111:H2 in beefsteak, hamburgers (beef and 50% beef 50% pork (HH)), meatballs (beef and HH) and crumbs (HH). For beefsteak, survival as a whole is dominated by the sides, giving a log reduction of 1-2 (rare), 3-4 (medium) and 6-7 (done). Limited measurements indicated that done preparation gave 5-6 log reduction for crumbs and at least 8-9 log for the other products. Medium preparation gave a higher reduction in hamburgers (2-4 log) than in meatballs (1-2 log) and in beef (3-4) than in HH (2-3) hamburgers. In general, our 'done' results give larger inactivation than found in literature, whereas 'rare' and 'medium' results are similar. The experiments resulted in two types of curves of D/z-values, dependent on product, doneness and for beefsteaks sides vs. top/bottom. One type of curve agrees reasonably with literature D/z estimates from isothermal temperature experiments, which supports using these estimates for home style cooking QMRA calculations. In case of the other type of curve, which is mainly found for (near) surface contamination in close contact with the pan, these literature estimates cannot be applied. We also applied a simplified approach, assuming thermal inactivation is dominated by the highest temperatures reached. The time duration of this highest temperature gives accessory D-values which prove to fit with isothermal temperature literature data, thus suggesting application of such data for QMRA is possible by this approach also, which is less labor intensive both in terms of measurements and modelling. In real life, variability in product properties and preparation styles is large. Further studies are needed to analyze the effect on survival, preferably focusing on determining the essential variables. More variation in heating time will allow for estimating D/z point estimates rather than curves representing possible sets of D/z-values.
在消费者厨房的食品制备过程中，微生物的存活和交叉污染是两种与定量微生物风险评估（QMRA）相关的传播途径。本研究的目的是扩展在实际制备肉和肉制品过程中微生物存活的有限数据，并获得更多一般（产品非特异性）方法所需的辅助温度数据。因此，我们结合使用红外摄像机对表面和产品内部按钮进行的时间和位置相关温度的广泛测量，以及插值建模，来获得生存数据。我们研究了加热大肠杆菌 O111:H2 在牛排、汉堡（牛肉和 50%牛肉 50%猪肉（HH））、肉丸（牛肉和 HH）和面包屑（HH）中的存活情况。对于牛排，整体存活情况主要由侧面决定，给出了 1-2（罕见）、3-4（中等）和 6-7（完成）的对数减少。有限的测量表明，对于面包屑，完成制备可减少 5-6 个对数，对于其他产品，至少减少 8-9 个对数。与肉丸（1-2 个对数）相比，中等制备在 HH（2-3 个对数）汉堡中比在汉堡（2-4 个对数）中的减少更多，与牛肉（3-4 个对数）相比，在 HH（2-3 个对数）汉堡中比在牛肉（3-4 个对数）中的减少更多。一般来说，我们的“完成”结果给出的失活比文献中发现的更大，而“罕见”和“中等”结果则相似。实验结果产生了两种 D/z 值曲线类型，取决于产品、完成度以及牛排的侧面与顶部/底部。一种类型的曲线与从等温温度实验中得出的 D/z 估计值相当合理，这支持将这些估计值用于家庭烹饪 QMRA 计算。对于另一种类型的曲线，主要是在与平底锅紧密接触的（近）表面污染中发现，这些文献中的估计值不能应用。我们还应用了一种简化方法，假设热失活主要由达到的最高温度决定。这种最高温度的持续时间提供了辅助 D 值，这些 D 值证明与等温温度文献数据相符，因此通过这种方法也可以应用这些数据进行 QMRA，这在测量和建模方面都更加省力。在现实生活中，产品特性和制备方式的变化很大。需要进一步的研究来分析其对生存的影响，最好是侧重于确定基本变量。加热时间的更多变化将允许估计 D/z 点估计值，而不是代表可能的 D/z 值集的曲线。
