Spoilage characterized by bulging as a result of gas formation in bottled ketchup was studied, Samples produced microbial growth on MRS and Rogosa selective Lactobacillus agar. Seventy randomly selected isolates typed by using restriction endonuclease (ClaI, EcoRI, HindIII) analysis were found to have identical DNA fragment patterns in gel electrophoresis. The strain was identified as Lactobacillus fructivorans using morphological, physiological and biochemical characteristics, combined with the information obtained from ribotyping. Factors affecting growth and survival of this L. fructivorans strain in ketchup production were also studied. An L. fructivorans count of 105 CFU/g resulted in spoilage of inoculated ketchup samples. Spoilage occurred only in samples incubated at 15 to 30°C. The L. fructivorans implicated in causing spoilage demonstrated heat resistance with a D value of 1.2 min at 65°C. The strain did not show resistance to alkaline active chloride-containing detergent sanitizer; alkyldimethylbenzylammonium chloride and alkyldimethylethylbenzylammonium chloride-containing sanitizer were also found to be effective antimicrobial agents.

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