Microbiological characterization of çiğ köfte sold at retail in Ankara, Turkey, and evaluation of selected antimicrobials as ingredients to control foodborne pathogens in çiğ köfte during refrigerated storage

Abstract

We monitored the occurrence and fate of Shiga toxin-producing Escherichia coli, E. coli O157, Listeria monocytogenes, and/or Salmonella spp. in çiğ köfte (translated as “raw meatball”) purchased from establishments in Turkey or prepared and inoculated in our laboratory. Of the 24 beef and 144 vegetarian samples of çiğ köfte purchased, Salmonella were recovered from the vegetarian samples (1 of 24 samples), but not from the samples containing beef (≤2.3 log CFU/g detection limit). L. monocytogenes were recovered from 2 of 24 beef (8.3%) and 2 of 144 vegetarian (1.4%) samples of çiğ köfte, whereas E. coli O157 were recovered from 5 of 24 meat (20.8%) and 21 of 144 vegetarian (14.6%) samples of çiğ köfte tested. Levels of total aerobic bacteria ranged from 3.7 to 9.0 log CFU/g, whereas levels of Enterobacteriaceae and coliforms ranged from 2.3 to 7.3 log CFU/g. In our laboratory, finely-ground beef (93:7%, lean:fat) was separately inoculated (ca. 4.0 log CFU/g) with multi-strain cocktails of STEC, Salmonella spp., or L. monocytogenes and then mixed with either bulgur wheat alone or with bulgur wheat along with tomato sauce, vegetables, and various spices. Next, aliquots of buffered vinegar (BV) or distilled white vinegar (DV; 5% acidity) were added as antimicrobials to the inoculated batter to deliver 0, 2.5, or 5.0% (vol/wt) of the antimicrobial. The resultant batter was shaped into ca. 15 g balls by hand and stored at 4° or 15 °C. When çiğ köfte was formulated with or without spices and with or without antimicrobials, pathogen numbers remained relatively unchanged after 3 days of storage at 4 °C. In contrast, when çiğ köfte was formulated without spices and without antimicrobials, pathogen levels increased by ca. 0.2 to 0.9 log CFU/g, respectively, after 3 days at 15 °C. When product was formulated with spices, in the absence of antimicrobials, STEC and L. monocytogenes levels decreased by ca. 0.3 and 0.7 log CFU/g, respectively, whereas Salmonella spp. increased by ca. 0.3 log CFU/g after 3 days at 15 °C. Thus, the formulation of çiğ köfte used in this study did not support growth (≤1.0 log CFU/g) of either STEC, Salmonella spp., or L. monocytogenes. Our data also confirm that pathogens can be recovered on occasion from çiğ köfte sold at restaurants and at retail in Turkey, as well as highlight the importance of proper formulation, handling, and storage practices to ensure its safety.