Hazards and critical control points of food vending operations in a city in Zambia

Hazard analyses were conducted at several cooked food vending operations in a large city in Zambia, near a downtown bus park and at a large market. Samples of raw, processed, and cooked foods sold on streets or by small food shops were collected and tested for common foodborne pathogens and indicator organisms. Results showed that some raw foods (ground meat, chicken, chicken intestine) or processed foods (dried minnows; kapenta) were contaminated by salmonellae or contained high populations of Staphylococcus aureus (pasteurized milk) or Bacillus cereus (caterpillars). Cooking usually gave time-temperature exposures that would have been lethal for vegetative forms of foodborne pathogens. Holding of foods other than nshima often provided time-temperature exposures conducive to microbial growth, particularly in foods held overnight. Large populations of aerobic mesophilic organisms, thermotolerant coliform bacteria, and sometimes Escherichia coli were recovered from these foods. Ten million Clostridium perfringens per gram were isolated from a sample of leftover beef stew. Large populations (> 10(5)) of S. aureus were recovered from a sample of leftover chicken, and large populations of B. cereus (> 10(7)) were isolated from leftover rice. Time-temperature exposures during reheating had variable effects in terms of killing the microorganisms that germinated from surviving spores or that reached the foods after cooking, but heat-stable toxins would not have been inactivated.