Microbial risk assessment of mixed vegetable salads from selected canteens in the Kumasi Metropolis

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2015-04-15
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The aim of this study was to assess the microbiological quality of mixed vegetable salads and the risk associated with its consumption from food vendors on and around two university campuses in the Kumasi Metropolis. Microbiological quality of mixed vegetable salads from the vendors was determined using Aerobic plate count (APC) as well as enumeration and detection of S. aureus and Salmonella spp. using standard microbiological methods. A total of twenty seven (27) mixed vegetable salad samples were taken from nine (9) randomly selected vendors (three different times from each vendor), from 8th to 15th November, 2013. A survey was also carried out with structured questionnaire that had both observational and responsive questions to determine handling practices and consumption pattern that are critical to microbial quality and the risk of mixed vegetable salads. Monte Carlo simulation of S. aureus using the exponential model (r = 7.64x 10-8) for 10,000 iterations for quantitative microbial risk assessment of three exposure scenarios was used. APC with range of 3.1 log CFU/g to 4.83 log CFU/g was obtained which was in agreement with both the Ghana Standards Board (GSB) and the UK Public Health Laboratory Services (PHLS) standard references of < 5 log CFU/g and 6 to < 7 log CFU/g, respectively while the S. aureus count ranging from 2.97 log CFU/g to 5.13 log CFU/g obtained was above both the GSB and PHLS acceptable standards of < 4 log CFU/g in majority (66.67%) of the test canteens. Salmonella spp. was, however, not detected in any of the samples. The survey conducted revealed that, storage temperature for vegetable salads during sales and frequency of consumption had critical effects on the microbiological quality and annual risk of vegetable salad consumed. The mean annual risks of S. aureus infection for the three exposure scenarios were 10.90 x 10-1, 10.05 x 10-1 and 7.71 x 10-1 for frequent, average and occasional consumers respectively. This indicates approximately 11, 10 and 8 out of 10 frequent, average and occasional mixed vegetable salad consumers, respectively, could be infected with S. aureus. Thus, the study revealed the likelihood of a very high risk associated with the consumption of mixed vegetable salads from food vendors on and around the two university campuses in the Kumasi Metropolis.
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A thesis submitted to the Department of Food Science and Technology, College of Science in partial fulfilment of the requirement for the degree of Master of Science (Food Quality Management),
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