Estimating Consumption Risk of Street Vended Fufu and Fried Rice
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Date
NOVEMBER 2017
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Abstract
Street food vending has for a long time been perceived as an unsafe source of food for the wider consumer population. The prevailing conditions of food preparation and handling is likely to introduce food safety hazards which can be detrimental to the health of the consuming population. Therefore, this study sought to contribute to improving upon the safety of the street vended foods under the prevailing conditions of food preparation and handling. The study also sought to determine vendor practices and challenges that introduce food safety hazards – chemical and microbiological, into the components of two ready-to-eat street vended foods: fried rice and fufu. The hazards were identified through participant observation and informant (vendor and staff) interviews where interview guides and observation check list were used. Samples of the different components of the two street vended fufu and fried rice were bought separately from the vendors and analyzed for the presence and levels of the food safety hazards identified. Consumption characteristics of the street vended foods were also taken from regular consumers of the street vended foods of the vendors used in the study. Microbiological (Bacillus cereus, Staphylococcus aureus, Escherichia coli and the total plate counts) and chemical (metals - (Aluminum, Lead and Iron); polycyclic aromatic hydrocarbon (PAH) (22 USEPA priority PAH) and Bisphenol A) hazards were evaluated using standard methods. The findings from the interviews and observations indicated high staff turnover, access to ‘good’ location for vendors as major challenge to business with implications for food safety. Staff had very little knowledge on good food handling practices thus affecting safety since they are the main handlers of the vended foods. The microbiological analysis indicated high levels of bacterial contaminants in all the food samples. Levels of E. coli (5.49 – 2.53 log CFU/g), S. aureus (6.44 – 4.36 log CFU/g) and B. cereus (5.44–3.49 log CFU/g) were higher than the World Health Organization (WHO) limit of 3 log CFU/g for the rice, salad, chicken and macaroni ingredients of the fried rice meal sample. Fufu recorded very high levels of all the bacterial contaminants, E. coli, above 3 log CFU/g limit set by WHO. The total plate counts for all the sample meal ingredients were also above 6 log CFU/g. However, levels of bacterial contaminants in the soup were all below the limits set by the WHO. Assessing the level of risk associated with the consumption of these street vended foods using the quantitative microbial risk assessment approach, indicated high consumption levels of bacteria. It also showed that at all levels of consumption, consumers are at risk of microbial food borne illness. Sensitivity analysis showed that interventions must be focused on preventing or drastically reducing the levels of E. coli in the salad, macaroni and fufu ingredients and S. aureus and B. cereus in fried rice, salad and fufu. The levels of Iron (Fe) in the cooked samples, rice (2.33 mg.kg-1), chicken (3.08 mg.kg-1) macaroni (2.06 mg.kg-1), fufu (3.05 mg.kg-1) and soup (3.60 mg.kg-1) were relatively higher than in the corresponding raw samples which suggested possible leaching from the utensils used in processing. Lead (Pb) levels (7.43 mg.kg-1 to 11.25 mg.kg-1) were highest in shito samples followed by mayonnaise with an average value of 7.08 mg.kg-1. Leaching from the utensil best explains the levels of Pb in the shito samples as locally manufactured utensil is used for its preparation. Rice, shito, ketchup and macaroni also had very high levels of aluminum (Al), (above 5 mg.kg-1) relative to the uncooked samples also implying possible leaching from utensils. The evaluated PAH of interest were BaP and DahA. These are the most potent carcinogens among the USEPA priority PAH. These PAH were detected in the chicken, shito and soup samples. Pyrene (Pyr), a precursor of BaP was detected in all the cooked food samples except fufu in levels between 4.8E-07 mg.kg-1 and 2.0E-02 mg.kg-1. Naphthalene, was detected in all the food samples in concentrations between 9.1E-06 mg.kg-1 and 1.2E-02 mg.kg-1. Chemical risk assessment revealed that the Hazard Index (HI) due to metals in the fried rice meal was 3.0 at 50th percentile of consumption and 23.8 at the 95th percentile, all above 1. Meaning the normal to heavy consumers of fried rice may be suffering the adverse health effects of the metals. The HI of fried rice due to PAH at the 95th percentile and fufu meal at the 50th percentile were also above 1. Sensitivity analysis indicates naphthalene having an impact on the risk levels with correlation coefficients ranging between 0.11 and 0.26 in all the food samples. Health risks due to BaP levels in the foods were above 10-4 from the 50th percentile, which was unacceptable. The Bisphenol A (BPA) concentrations in the fufu and cooked rice samples were below 40 µg.kg-1 lower the 4 µg.kg-1 of bw.day-1 limit set by EFSA in 2015. Risk assessment indicated that the consumers were not likely to suffer the adverse health effects of BPA in foods even at the 95th percentile exposure level. Sensitivity analysis show that levels of BPA be reduced to the barest minimum. As a way forward towards the enhancement of the safety of street vended foods, training of vendors on personal hygiene and good food handling practices should be tied with food preparation skill to improve the taste/value of the vended foods. Emphasis on practices such as covering of boiling food with plastic must be replaced with that of cotton material such as gray baft, The use of stainless steel cooking pots and efficient personal hygiene practices be encouraged to improve the safety of the street vended meals used in the study. Storage of cooked foods and cut up vegetables for long hours at ambient conditions should be discouraged. These practices if strongly adhered to would greatly improve safety of the vended foods.
Description
A thesis submitted to the Department of Food Science and Technology,
Faculty of Biosciences,
College of science in partial fulfilment of the requirements for the award of Doctor of Philosophy in Food Science and Technology,