Nofima-Norwegian Institute of Food, Fisheries and Aquaculture Research, P.O. Box 8034, N-4068 Stavanger, Norway.
Int J Food Microbiol. 2012 Apr 16;155(3):227-33. doi: 10.1016/j.ijfoodmicro.2012.02.011. Epub 2012 Feb 23.
Dry-fermented sausages (DFS) are considered possible risk products regarding Shiga toxigenic Escherichia coli (STEC). We have compared the reduction of 11 E. coli isolates of various serogroups in salami during the sausage production process and during post-process measures including storage, heating and freezing. The 11 E. coli isolates, mainly STEC, included enterohaemorrhagic E. coli (EHEC) outbreak strains linked to DFS along with apathogenic E. coli. During sausage production, there was a statistically significant difference in reduction between the E. coli strains ranging from 1.3 to 2.4 log₁₀ (p<0.001). When sausages were subjected to post-process heat treatment of 43 °C for 24 h, a total reduction of more than 5 log₁₀ was obtained for all E. coli isolates. Freezing and thawing of DFS with subsequent storage for 1 month at 16 or 20 °C generally contributed to large E. coli reductions with the latter conditions giving an average additional 3.9 log₁₀ reduction, with a range from 3.4 to 4.4 log₁₀. The combination of freezing and 1 month of storage gave higher reductions compared with storage for 2 months for all examined temperatures. No systematic differences in survival of E. coli of different serogroups were detected for the different post-process measures. The reductions were also similar to those of apathogenic control isolates. Isolates showing higher survival during the ripening process did not have a lower reduction when exposed to post-process stress like storage, heating and freezing. The ability of the isolates to survive in salami was also compared with their survival at equivalent conditions in a tryptic soy broth (TSB) model. There was a low and not significant correlation (p>0.1) between the reductions of E. coli in salami and in the TSB broth model. Results based on broth models and/or single or surrogate strains must therefore be interpreted with caution. The EHEC reducing post-processing measures tested can easily be implemented in DFS production with marginal influence on the quality of the sausages.
干发酵香肠（DFS）被认为是与产志贺毒素大肠杆菌（STEC）有关的潜在风险产品。我们比较了 11 株不同血清群的大肠杆菌在香肠生产过程中和储存、加热和冷冻等后处理措施中的减少情况。这 11 株大肠杆菌分离株主要为 STEC，包括与 DFS 相关的肠出血性大肠杆菌（EHEC）暴发株以及非致病性大肠杆菌。在香肠生产过程中，大肠杆菌菌株的减少量存在统计学上的显著差异，范围为 1.3 至 2.4 log₁₀（p<0.001）。当香肠经过 43°C 24 小时的后处理热处理时，所有大肠杆菌分离株的总减少量超过 5 log₁₀。DFS 的冷冻和解冻以及随后在 16 或 20°C 下储存 1 个月通常会导致大肠杆菌大量减少，后一种条件下平均额外减少 3.9 log₁₀，范围为 3.4 至 4.4 log₁₀。与所有检查温度下储存 2 个月相比，冷冻和 1 个月储存的组合可带来更高的减少量。对于不同的后处理措施，不同血清群的大肠杆菌的存活没有系统差异。减少量也与非致病性对照分离株相似。在成熟过程中存活能力较高的分离株在暴露于储存、加热和冷冻等后处理应激时，减少量并没有降低。还比较了分离株在萨拉米香肠中的存活能力与其在胰蛋白酶大豆肉汤（TSB）模型中的存活能力。在萨拉米香肠和 TSB 肉汤模型中，大肠杆菌的减少量之间存在低且无显著相关性（p>0.1）。因此，基于肉汤模型和/或单一或替代菌株的结果必须谨慎解释。测试的减少 EHEC 的后处理措施可以很容易地在 DFS 生产中实施，对香肠的质量影响很小。
