Investigation on life resistance of Escherichia coli O157: h7 and listeria monocytogenes with acid and salt adapted in the recombinant chimneys produced in different salt concentrations

According to the legal changes, the amount of salt is control between 3-7.5% in Turkish cheeses. To determine the effect of salt reduction on pathogen bacteria which are common in cheese and order to fill the gap regarding risk safety in dairy products in the literature. In this study, the survival ability of acid and salt adapted or not adapted Escherichia coli O157:H7 and Listeria monocytogenes in recombine cheese samples produced with different salt concentrations during 56 days of storage were analyzed. One night cultured of E. coli O157:H7 and L. monocytogenes were cultivated in TSB broth (pH 5.4 adjusted with 1 M lactic acid ) and TSB broth (3.5% NaCI) for 2 hours. The adapted pathogenic bacteria (1×103 CFU/g) were inoculated to the recombine cheese samples with different salt concentrations (4, 6, 8, or 10%). Microbiological analysis was conducted on the certain days (1, 3, 7, 14, 21, 28, 35, 42, 56) during the storage at 4° C. In the texture analysis of the cheese samples, 50% tensile strength was measured at one time by uniaxial compression method at 2 mm/s using TA. XTPlus textile analyzer. According to the results of the analysis, with the increase of salt concentration in the samples, the bacterial counts of both pathogen bakteria decreased during the storage, while no significant difference was found. Additionally, the number of acid and salt adapted E. coli O157:H7 was observed as higher than the number of the control group in all samples (P<0.01). Although acid adapted L. monocytogenes could survive one more week (28 days) than the control group, the salt adapted group showed the same survival pattern as the control group. In the texture analysis, the hardness of cheese increased significantly with the increase of salt concentration (p <0.05). The hardness of cheese started to decrease again after 4 weeks of storage. At the end of the experiments, the salt in different concentrations did not have a significant effect on the survival of the pathogenic bacteria. Salt and acid adapted cells showed more resistancy and live longer than unadapted grup. Addition of salt had a significant effect on the hardness of the cheese samples. Keywords: Recombine cheese, Escherichia coli O157:H7, Listeria monocytogenes, salt and acid adaptation