Behaviour of Escherichia coli O157:H7 during the fermentation of Datta and Awaze, traditional Ethiopian fermented condiments, and during product storage at ambient and refrigeration temperatures

• Published in: Food microbiology 2004-12, Vol.21 (6), p.743-751
• Main Authors: Tsegaye, Mekonnen, Ephraim, Eden, Ashenafi, Mogessie
• Format: Article
• Language: English
• Subjects: ambient temperature; antibacterial properties; bacterial contamination; bacterial proteins; Biological and medical sciences; Condiments; cultured product starters; E. coli O157:H7; Escherichia coli; Escherichia coli O157:H7; Fermentation; food contamination; Food engineering; Food industries; Food microbiology; food pathogens; food storage; Fundamental and applied biological sciences. Psychology; fungal proteins; General aspects; inoculum density; lactic acid bacteria; pathogen survival; plate count; refrigeration; secondary metabolites; slurries; storage temperature; storage time; traditional foods; yeasts
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2004.02.003

The survival of E. coli O157:H7 in fermenting foods and its prolonged survival in refrigerated fermented foods is documented. This prompted the study to evaluate survival of E. coli O157:H7 during the fermentation of Datta and Awaze, traditional Ethiopian condiments. Datta was prepared by wet milling a variety of spices along with green or red chilli and fermenting it by lactic acid bacteria. Awaze is a slurry made of red pepper, garlic and ginger to which various other spices were added and fermented by lactic acid bacteria (LAB) and yeasts. The Datta or Awaze slurry was separately inoculated with three strains of E. coli O157:H7 and the fermentation was allowed to proceed at ambient (20–25°C) temperatures for 7 days. When fermenting Datta or Awaze was initially inoculated at low inoculum level (3 log cfu/g), the test strains were not recovered after 24 h of fermentation. At higher initial inoculum level (6 log cfu/g), however, counts of the test strains in Datta at day 7 were less by about 1.5 log unit than the initial inoculum level. In fermenting Awaze, all test strains were completely eliminated in 7 days. The pH of the fermenting green and red Datta was reduced from 5.2 to 4.4 and that of Awaze dropped from 4.9 to 3.8 during this time. In another experiment, the fermented products were separately inoculated with the E. coli O157:H7 test strains at levels of 6 log cfu/g and incubated at ambient and refrigeration (4°C) temperatures for 7 days. In fermented Datta, two of the three strains were not recovered by enrichment after 6 days of storage at ambient temperatures. In fermented Awaze, all strains were below countable levels at day 5, but could still be recovered by enrichment at day 7. At refrigeration storage, counts of the test strains in Datta and Awaze products were