Effects of food grade organics acids on inoculated Listeria monocytogenes in meat stored at refrigeration temperature

EFFECTS OF FOOD GRADE ORGANIC ACIDS ON INOCULATED Listeriamonocytogenes IN MEAT STORED AT REFRIGERATION TEMPERATURE(M.Sc. Thesis)Elif YILDIZGAZ UNIVERSITYINSTITUTE OF SCIENCE AND TECHNOLOGYDecember 2005ABSTRACTIn this research, chicken breast meat, chicken liver and beef samples weredecontaminated with hot water treatment and inoculated with Listeriamonocytogenes. Samples were spray washed and dipped with 2 % lactic acidand 1,5 % acetic acid + 1,5 % propionic acid combinations. Inoculated L.monocytogenes was found to be highly sensitive to acid combination treatmentas compared to lactic acid alone. L. monocytogenes count of the spray washedchicken breast meat, chicken liver and beef samples was reduced by about 2,73-2,93 log units, 1,83-2,58 log units, 3,80-3,73 log units, respectively. L.monocytogenes count of the dipped chicken breast meat, chicken liver, beef andcalf mince meat samples was reduced by 2,54-2,78 log units, 1,26-2,03 log units,3,92-3,91 log units, 3,81-3,81 log units respectively. Shelf-life of acid and acidcombinations treated samples was increased 4 and 7 days. Furthermore,resistance of inoculated and organic acids treated L. monocytogenes isolated tothe antibiotics such as Eritromycin, Ampicillin, Cyprofloxacin, Vancomycin,Streptomycin, Cephalothin, Nalidixic acid, Tobramycin was tested. Nodifference was found between the antibiotic resistance of inoculated and treatedL. monocytogenes. All L. monocytogenes isolates were resistant to nalidixic acidand susceptible to Eritromycin, Ampicillin, Cyprofloxacin, Vancomycin,Streptomycin, Cephalothin, Tobramycin. Meat spray washing or dipping withacid alone or acid combination were found to be suitable for extension of shelf-life and improvement in the sensory and microbiological quality of meat.Science Code : 401.01.04Key Words : Lactic acid, acetic acid, propionic acid, organic acid, meat,L.monocytogenes.Number of Page : 69Director of Thesis : Assist. Prof. Dr. Neslihan GÜNDOĞAN