ABSTRACT
Street vended foods are readily available sources of meals for many people across the world, the microbial quality and safety of such food is always uncertain. In developing countries, the major sources of food-borne illnesses are street vended foods because they provide a source of affordable nutrients to the majority of the low income groups. The aim of this study was thus to assess the microbiological quality and safety of street vended meat sauce in Bahir Dar Town. A total of 60 samples (30 each inn morning and afternoon) were assessed to reveal indicator bacteria and pathogens from December, 2010 to June, 2011 using standard bacteriological techniques. Mean aerobic mesophilic count of 4.16x104 and 4.71x104 cfu/g were recorded in the morning and afternoon, whereas mean total coliform count and S. aureus were 4.00x104 and 4.53x104 and 3.52x104 and 4.39x104 cfu/g in the morning and afternoon, respectively. Only the count of aerobic mesophilic bacteria was below the recommended limit. The mean microbial loads were significantly different in the morning and afternoon (p < 0.005). Salmonella was detected in all the samples of meat sauce analyzed in the morning and afternoon. The bacteriological analysis of water samples indicate the contamination of water within mean microbial load of 2.67 MPN/100 ml of water, which is beyond the acceptable limit of 2.2 MPN/100 ml of water. The observational checklist of vendors’ appearance and the environment indicates lack of personal and environmental sanitation and gives warning signal for the possible occurrence of foodborne contamination. The study publicized that contamination of street vended meat sauce is a possible health problem to consumers. Proper cooking and storage of processed foods and education of vendors on the environmental sanitation and food handling practices should be recommended.
Key words: Meat sauce, microbial quality, sanitation practice, street vended.
Street foods are defined as ready to eat foods and beverages prepared and/or sold by vendors, especially on streets and other public places for immediate consumption (WHO, 1996). These foods are well appreciated by consumers, mostly by urban workers because of their taste, low cost, nutrient value, different varieties and availability for immediate consumption (Abdalla et al., 2009). They can be found whereever there is a heavy flow of people, since their marketing success depends exclusively on location and word-of-mouth promotion (Winarno and Allain, 1991). This is not surprising when one considers that bacteria and fungi are ubiquitous and are plentiful in soil and around us and easily contaminate foods (Bukar et al., 2010). Economic situation, social difficulties and urbanization, among other factors, promote the growth of informal sector of the economy including street food vending (Hanashiro et al., 2005). These foods may be consumed without heat treatment and cause foodborne illness, a health problem in developing countries (WHO, 1996).
Meat is an important food that contains a large amount of proteins and its cut surfaces support the growth of large numbers of microorganisms. Food safety is one of the most important issues in marketing any kind of food, particularly meat and its products (Okonko et al., 2010). The most serious safety issues resulting in immediate consumers health problems is associated with bacterial pathogens (Sousa, 2008). The most common bacterial agents are Campylobacter, Salmonella, Escherichia coli, Shigella, Staphylococcus and Clostridia (Agbodaze et al., 2005). Street foods displayed on open work area can easily be contaminated by dust, exhaust smoke, insects and hands of the buyers. Thus, food vendor services is on the increase and responsibility for good manufacturing practices of food such as good sanitary measures and proper food handling practices (Clarence et al., 2009). On top of this, availability of tap water is limited to washing of hands, utensils in the vending site, hence, they are forced to be used repeatedly. There is no waste disposal facilities thus garbage is discarded close to the vending site and this attract insects and rodents to double the problem through cross contamination (Tamebaker et al., 2008). In Ethiopia, the wide spread habit of raw beef consumption is a potential cause for foodborne illness (Haimanot et al., 2010). Therefore, meat sauce is widely consumed by people at home, on the streets and in the groceries. However, there is no information on microbiological quality and safety of street vended meat sauce in Bahir Dar Town. The aim of this study was thus to assess the bacteriological safety of meat sauce and water in Bahir Dar Town, Ethiopia.
Study design and location
A cross-sectional study was conducted to assess the microbiological quality and safety of ready-to-eat meat sauce and water in Bahir Dar Town from December 2010 and June 2011. The town is located at 11° 36’ 0” North and 37° 23’ 0’’East on the southern side of Lake Tana. The town has a total population of 256,999 (CSA, 2010) and one of the leading tourist destinations with a variety of attractions in the nearby Lake Tana and Blue Nile River.
Sampling techniques
The study site was selected purposively and a total of 60 food samples (30 each in the morning and afternoon) were collected for microbiological analysis. Two hundred grams of meat sauce was collected using sterile glass containers and immediately transported to the post graduate microbiology laboratory of Bahir Dar University. Samples were stored in refrigerator until microbiological analysis was carried out. Microbiological analysis was carried out as described by the methods of Fawole and Oso (2001). Twenty five grams of the homogenized meat sauce was mixed with 225 ml of sterilize peptone water (Oxoid LTD., Basingstoke, and Hampshire, England) for 5 min in a flask. The samples prepared were used for enumeration of aerobic mesophilic bacteria, total coliforms and S. aureus. For isolation of Salmonella, the flasks were incubated at 37°C for 24 h for primary enrichment. Thirty water samples were also collected in the morning for bacteriological analysis. Standard methods were used for the enumeration, isolation and identification of bacteria. Observational checklist was used to collect data on, personal hygiene of the vendors and assessment of the vending environment.
Enumeration of bacteria from food samples
Aerobic mesophilic count
The aerobic mesophilic counts were enumerated on standard plate count agar (Donwhitley Scientific Eqp. Pvt.Ltd. India) and incubated at 37°C for a maximum of 48 h. The total aerobic mesophilic count of bacteria was determined using the procedure described by Azanza (2005). The numbers of colonies were counted with colony counter (Stuart Scientific Colony Counter made in the UK). The result was reported as means of cfu/g of food sample analyzed.
Total coliform count
The total coliform counts were enumerated on sterile MacConkey agar (Blulux Laboratorie (p) Ltd, India) and incubated at 37°C for a maximum of 48 h. The total coliform counts were determined using the procedure described by Chaiba et al. (2007). The numbers of colonies were counted with colony counter (Stuart Scientific Colony Counter made in the UK). The result was reported as means of cfu/g of food sample analyzed.
Staphylococcus aureus count
Twenty five grams of meat sauce were then homogenized into 225 ml sterile peptone water solution (Oxoid LTD., Basingstoke, and Hampshire, England) for 5 minutes. This was used as enrichment after 24 h of incubation at 37°C. The number of colonies were counted on sterile mannitol salt agar (Blulux Laboratorie (p) Ltd, India) and incubated at 37°C for a maximum of 48 h. The numbers of colonies were counted with colony counter (Stuart Scientific Colony Counter made in the UK). The result was reported as means of cfu/g of food sample analyzed. Typical colonies of S. aureus as (golden yellow colonies) were picked, purified and preserved at -4°C on nutrient agar slants and further characterized through a series of biochemical tests.
Detection of Salmonella
Twenty five grams of street vended meat sauce samples were enriched on Selenite cysteine broth (Oxoid LTD., Basingstoke, and Hampshire, England) for 5 min prior to inoculation on sterile Bismuth sulfite agar (Oxoid LTD., Basingstoke, and Hampshire, England). The plates were incubated at 37°C for 24 – 48 h under aerobic conditions. Colonies considered as Salmonella on bismuth sulfite agar were purified and preserved at -4°C on nutrient agar slants (Merck KGaA 64271 Darmstadt. Germany) and further confirmed by biochemical characterization.
Bacteriological analysis of water
The total coliform counts of water were determined using multiple test tubes with the MPN method and Lauryl tryptose broth with inverted Durham tubes (Blulux Laboratorie (p) Ltd, India) were used for the presumptive tests (Addo et al., 2009). The number of positive and negative tubes were used for calculation of the most probable number (MPN/l) using the MPN tables as provided in the standardized procedure.
Observation of vendors’ hygienic practice and vending environment
An observational check list was used for the assessment of food safety and sanitary practices of vendors with workability of the vending environment as depicted in Tables 1 to 3.
Data analysis
The data was compiled and analyzed with Statistical Package for Social Science software, version 16 for windows (SPSS inc., Chicago, IL, USA). One-way analysis of variance (ANOVA) was used to determine if significant differences exist between mean counts in morning and afternoon and level of significant was set at p<0.05. Descriptive statistics was used to state the data obtained through observational check list.
Aerobic mesophilic count
The mean aerobic mesophilic count (AMC) detected in the morning and afternoon was 4.16×104 and 4.71×104 cfu/g, respectively and the range were between 2.96×104-5.32×104 and 3.92×104-5.80×104 cfu/g (Table 4).
Coliform count
The coliform count ranged from 2.57x104 to 5.18x104 and 3.34x104-5.86x104 cfu/g (Table 5) and the mean counts between 4.00x104 and 4.53x104cfu/g in the morning and afternoon, respectively.
Staphylococcus aureus
The mean microbial count of S. aureus was 3.52x104 to 4.39x104cfu/g (Table 6) and ranged between 2.33x104-4.40x104 and 3.48x104-5.22x104 cfu/g in morning and afternoon, respectively.
Detection of Salmonella
Salmonella was detected in all meat sauce samples collected from Bahir Dar town in the morning and afternoon.
Bacteriological examination of water
The presence of coliform bacteria in the water was between 31 and >16000MPN/100 ml and had mean microbial load of 2.67 MPN/100 ml of coliforms (Table 7).
The total colony counts of AMC obtained in this study is illustrated in Table 4. There was a significant differences (p=0.00) in aerobic mesophilic count detected in the morning and afternoon. The AMC of meat sauce analyzed did not exceed the typical guide line of AMC value set at <105 cfu/g for ready to eat food products. According to Food and Agricultural Organization (Bukar et al., 2010), standard limit for AMC should be less than 105 cfu/g. In this study, the results was less than standard limit in the morning and afternoon. Similarly, microbiological qualities of processed food (ready to eat beef products) showed the count of 3.3×104 for total aerobic plate count (Ologhobo et al., 2010). This is agrees with the result of Okonko et al. (2010) that ranged between 2.62×104 and 4.48×104 cfu/g. In comparing the bacterial contamination in morning and afternoon, one-way analysis of variance indicates significant difference (p=0.00). This difference is most importantly due to improper storage time. Similarly, Tambekar et al. (2008) reported that foods that were prepared long before consumption were more contaminated than food prepared just before consumption. The presence of Coliform bacteria in ready-to-eat foods indicates unhygienic conditions during processing, handling and distribution or post processing contamination. The total counts of coliforms from the meat sauce and the probable presence in the water are presented in Tables 5 and 7. The result shows a significant differences in the means of coliform count in the morning and afternoon (p=0.00). This variation could exist as a result of the street food vendors that bought the meat and prepared it early in the morning. It was cooked and stored at ambient temperature that leads to the exposure of the food to dust, flies and other vectors from the surrounding environment.
The presence of coliform could be attributed to the use of contaminated water at different stages of processing (Hamdan et al., 2008). A similar report was recorded in Accra with the highest mean coliform count (5.12log10 cfu/g) (Agbodaze et al., 2005). Correspondingly, the mean total coliform count on fresh meat (Okonko et al., 2010) ranged between 2.24x104 and 5.0x104 cfu/g. These values exceeded the acceptable limit of 103 cfu/g for coliform count. Microbiological count for meat sauce from street food vendors is higher for meat which seems raw inside (van Kampen et al., 1998). Agbodaze et al. (2005) reported mean coliform count of 3.70log10 cfu/g in khebab sample analyzed. High level of coliform contamination indicated that the ingredient or the product had bad personal hygiene. Microbial contamination, unhygienic practices and lack of basic facilities including potable water are some of the many associated problem with street food vending as discussed (WHO, 1996).
The result of water analysis for coliforms is indicated in Table 7 and the mean of indicator organisms in water (colifoms) exceed the standard limit which is 2.67MPN/ 100 ml of water. WHO standard for drinking water shows water sample should have an MPN value of 2.2 MPN/100 ml of water (Addo et al., 2009). Similar result was reported by Lues et al. (2006) having various means of obtaining water and water collected in the morning was used until the end of the day. The initial contaminated water used for washing the raw meat is also used for hands and utensils used in production. Water is a major means by which coliforms and E.coli are spread. This is the reason why the water sample was examined for coliforms. Ethiopia is the worst of all with regards to water quality problems. It has the lowest water supply and sanitation coverage in sub-Saharan countries with only 42 and 28% for water supply and sanitation, respectively (Milkiyas et al., 2011).
The mean microbial count of S. aureus on the meat sauce is shown in Table 6. There was a significant differences (p=0.00) in the mean counts of S. aureus in the morning and afternoon. This disparity is as a result of improper storage time, handling and exposure to environmental contaminants at ambient temperature for long period before serving. S. aureus is frequently isolated from the meat sauce analyzed. This is due to the high mean count of the organism beyond the acceptable limit for S. aureus which is less than 102 cfu/g. Similar result is shown by Clarence et al. (2009) on S. aureus count of 2.5x104to4.0x104 cf u/g of meatpie. According to Ologhobo et al. (2010), S. aureus from ready to eat beef suya before and after roasting contained 102 and 104 cfu/g, respectively. This indicates that subsequent contamination might be due to improper handling by vendors. Especially, hands can be source of contamination if infected cuts are present (Podpecan et al., 2007).
Salmonella was detected in all the meat sauce samples collected from Bahir Dar town in the morning and afternoon. Foods of animal origin are considered to be the major sources of foodborne salmonellosis (Bayleyegn et al., 2003). The presence of Salmonella spp. in cooked foods is often attributed to inadequate refrigeration, sanitation and poor personal hygiene. Proliferation of this organism in foods may therefore, result from handling cooked foods by workers who are carriers of Salmonella (Lues et al., 2006). The improper handling of the meat sauce and utensils by food handlers during preparation and serving alarms the presence of the organism. This agrees with the result of Molla and Mesfin (2003) which states that cross-contamination of the hands of workers, working equipment and utensils. Karaboz and Dincer (2002) report the same result from frozen meat products. The cross contamination of the hands of workers, working equipment and utensils could also serve as a means of spread of Salmonella to uncontaminated carcasses and giblets. Mohammed et al. (2009) highlight that Salmonella pet poses threat to human, and public practitioners should consider potential means of Salmonella transmission. Spread of Salmonella in meat during slaughtering and preparation is more common. Okonko et al. (2010) agreed with this result. Contaminations of ready to eat foods and might eventually affect the health of consumers. This was illustrated by the presence of indicator organisms. The disease caused by Salmonella is a major health problem in developing countries (Asia and Africa); especially in Ethiopia due to poor sanitary conditions and lack of inadequate potable water and food (Okonko et al., 2010; Molla and Mesfin, 2003). In addition, outbreaks of infections somehow related with poor hygiene and consumption of contaminated food were reported in Ethiopia and somewhere to be caused by Salmonella and Shigella (Haimanot et al., 2010). Food handlers are an important vehicle for microorganisms and improper handling practices may cause food contamination and consequently foodborne diseases to the consumers. Causes of improper food handling practices could be related to either lack of facilities or lack of knowledge on habits concerning hygiene. This study assessed the food handling practices of the vendors as shown in Table 8.
Only 35% of the vendors wash the food before cooking. It was noted that foods were prepared on the same surface more than once by 85% of them. Of the vendors, 95% handled food with bare hands, whereas 100% handled money while serving food. Cooked street food should not be handled with bare hands.
According to revised guidelines for the design of control measures for street-vended foods in Africa (FAO, 1997), clean tongs, forks, spoons or disposable gloves should be used when handling, serving or selling food. Handling with bare hands may result in cross contamination, hence introduction of microbes on safe food. The person handling money should not handle food. This is because money is dirty and can contaminate safe food (FAO, 1997). Contamination of equipment, utensils and hands of workers can spread pathogens to uncontaminated carcass and parts with subsequent handling processing transport, storage, distribution and preparation for consumption (Ejeta et al., 2004). Based on the observational check list, the vendors did not appear clean during serving (30%) and they were not appropriately dressed and did not wear aprons (10%) and head restraints (15%) (Table 9). Because hair is known to harbor S. aureus, it is essential to prevent loose hair in the food or food preparation areas. About 50% of the vendors given that the vending site was dirty and waste were conspicuously close to the stalls, still 70% of the vendors threw waste water just beside the stalls making the environment surrounding the eateries quite filthy (Table 10).
Water for street food preparation was not enough. A similar result was recorded in Accra, Ghana on the safety of street vended food as the running water is limited (Mensah et al., 2002). This resulted in vendors using little water for washing utensils hence hygiene was compromised. The vendors provided open bins for the disposal of garbage. There was no drainage system for channeling the waste water from the vending area of the food. It was noted that the food was prepared on the ame surface more than twice without replacement.
Based on the present study, it can be concluded that, street vended meat sauce in Bahir Dar is unsafe for consumption particularly, if stored for long periods. High level of coliform and S. aureus contamination indicated that the ingredient or the product had bad sanitation and personal hygiene. The counts and more importantly types of microorganisms on the meat sauce sampled in this study was indicative of a degree of ignorance regarding proper hygiene practices on the part of food handlers. Therefore, there is a need to reduce the problems of street food contamination, growth of microorganisms and intoxication through education of street food sellers and the public on the importance of environmental sanitation and safe practices in the handling of cooked foods.
The authors have not declared any conflict of interest
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