Behaviour of Shiga-toxigenic/enterohemorrhagic Escherichia coli (STEC/EHEC) in minisalami.

摘要

To date, the behaviour and survival of Shiga-toxigenic/enterohemorrhagic Escherichia coli (STEC/EHEC) in minisalami-sausages have not been established. Here we describe the result of challenge studies with these food borne pathogens in five different types of minisalamis including smoked sausages (pork, pork and beef, poultry), air dried and mould ripened salamis. The German Federal Ministry of Food, Agriculture and Consumer Protection (BMELV) commissioned this study to obtain information on the occurrence and on the decline or potential survival of food borne pathogens in these raw fermented sausages, which are characterized by a small caliber and median a_w levels between 0.82-0.84 (smoked and air dried salamis) and 0.69 (mould ripened salamis) (GAREIS et al., 2010a). Background of the project was an outbreak of salmonellosis by S. Panama among children in Germany in summer 2007. Based on epidemiological data a discussion about minisalamis as risk foods and their possible role as causative food vector for these cases followed (RKI, 2008). In two publications we already reported about the occurrence of Salmonella spp., STEC/EHEC, Listeria monocytogenes and Staphylococcus aureus in minisalami products obtained from the retail (GAREIS et al., 2010a) and a challenge study with Salmonella spp. in minisalami (GAREIS et al., 2010b). Here we describe the survival STEC/EHEC in five types of artificially contaminated minisalami products. The batters were inoculated prior to further processing with low (2 log₁₀ cfu/g) and high (4 log₁₀ cfu/g) levels of a pool of three isolates of E. coli O157:H7 and one strain of E. coli O26:H11. Their survival, as affected by the particular recipe of the product and the ripening program, was monitored over 42 days. Irrespective of the different types of minisalamis, rapid decline of STEC/EHEC was observed in all products tested. The results are supported by previous studies with raw sausages demonstrating that the behaviour of gramnegative pathogens in long fermented raw sausages was characterized by significant reductions of initial germ counts. The numbers decreased to less than 1 log₁₀ cfu/g within 8 or 13 days, the end of the ripening process (smoked, air dried and mould ripened sausages, respectively) and the time when the salamis are usually packed for sale. The technology normally used for the production of minisalamis clearly prevents growth STEC/EHEC. One major reason is the rapid drying to a_w <0.86. Results also indicate that optimization of parameters during the ripening process, especially the temperatures used, enhances the inactivation of the pathogens and attributes to the microbiological stability of the product.