ABSTRACT
In order to determine the microbial quality of fruits and vegetables sold in Yola-Jimeta markets and the efficacy of vinegar in decontaminant, the microbial contaminations of 16 samples of cabbage, carrot, lettuce, and tomato obtained from Yola-Jimeta market was determined before washing, after washing with water, after washing with vinegar and rinsing with water, and after soaking in vinegar for 5 minutes and rinsing with water. A significant reduction in the microbial loads of the samples was observed after washing with vinegar and rinsing with water, while no microbial growth was observed after soaking in vinegar water for 5 minutes and rinsing with water. Further tests revealed harmful microbes among the microbial growth observed. These results indicated that fruits and vegetables sold in Yola-Jimeta markets are contaminated with harmful microbes and that washing with water does not reduce the microbial load of the samples tested while a decrease in the
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microbial loads was observed only after washing with vinegar and rinsing with water. These results suggest that the use of vinegar is an effective decontamination method for fruits and vegetables.
Keywords
Bacterial contamination, disinfection, fruits, Jimeta, microbial contamination, vegetables, vinegar, Yola.
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TABLE OF CONTENTS
DEDICATION …………………………………………………………………………………………….. iv
ACKNOWLEDGMENTS …………………………………………………………………………….. v
ABSTRACT ………………………………………………………………………………………………… vi
TABLE OF CONTENTS ……………………………………………………………………………. viii
LIST OF TABLES ………………………………………………………………………………………. ix
LIST OF FIGURES ……………………………………………………………………………………… x
CHAPTER 1 ………………………………………………………………………………………………… 1
INTRODUCTION ………………………………………………………………………………………… 1
Fresh fruits and vegetables ………………………………………………………………………….. 2
Pathogenic microbes of concern and their pathways ………………………………………. 7
Survivability of pathogens ………………………………………………………………………….. 12
Commonly used methods of decontamination ……………………………………………….. 15
Food Safety Regulation in Nigeria ………………………………………………………………. 18
HYPOTHESIS, AIMS, & OBJECTIVES …………………………………………………….. 20
CHAPTER 2 ………………………………………………………………………………………………. 21
METHODS ………………………………………………………………………………………………… 21
Study area and sampling ……………………………………………………………………………. 21
Materials …………………………………………………………………………………………………. 22
Lab methods ……………………………………………………………………………………………. 23
CHAPTER 3 ………………………………………………………………………………………………. 26
RESULTS ………………………………………………………………………………………………….. 26
CHAPTER 4 ………………………………………………………………………………………………. 30
DISCUSSION …………………………………………………………………………………………….. 30
CHAPTER 5 ………………………………………………………………………………………………. 38
CONCLUSION …………………………………………………………………………………………… 38
REFERENCES …………………………………………………………………………………………… 39
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LIST OF TABLES
Table 1. Survivability, sources, and symptoms of some pathogens…………………13
Table 2. Different selective and differential media used for the identification of microbes and their respective color indication ………………………………………………….. 25
Table 3.Number of microbial counts found in the samples after each treatment …… 26
Table 4. IMViC test results for some selected samples of carrot ………………………… 27
Table 5. IMViC and phenylalanine deaminase (PDA) tests results …………………….. 28
Table 6. Means, Standard deviations, and Ranges of microbial loads for all treatments ……………………………………………………………………………………………………. 29
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LIST OF FIGURES
Figure 1. A typical African fruit and vegetable market in Kenya …………………………. 2
Figure 2. Global production of fruits and vegetables from 1982 to 2004. ……………… 3
Figure 3. A microscopic view of salmonella image ……………………………………………. 8
Figure 4. Microscopic view of E. coli. ……………………………………………………………. 10
Figure 5. Routes of transmission for E. coli O157 by year . ………………………………. 11
Figure 6. The map of Nigeria showing Adamawa state …………………………………….. 22
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CHAPTER 1
INTRODUCTION
The importance of fresh fruits and vegetables as the primary natural source of vitamin and fiber for humans cannot be overemphasized. However, fruits and vegetables are produced, marketed, and consumed with little or no sanitary measures (Fig. 1) in developing nations (Eni, Oluwawemitan, & Solomon, 2010). The use of manure that has not been composted and sewage water that has not been treated as fertilizers further increases the possibility of microbial contamination (Eni et al., 2010) and this practice has led to several outbreaks resulting from the consumption of fresh produce in Europe and the United States (Soon, Manning, Davies, & Baines, 2012). Nonetheless, fresh fruits and vegetables cannot be replaced by any other food source; hence there is a need to make sure that they are safe before consumption. To this end, many decontamination techniques have been devised to counter the effect of harmful microbes. However, the efficacy of many decontamination methods in commercial settings are still doubted (Fonseca & Ravishankar, 2007).
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Fresh fruits and vegetables
Being recognized as one of the most important source of vitamins, nutrients, and
fiber for humans has made fresh produce popular in the world. The world has seen a
large increase in the production of fruits and vegetables by 94% between 1980 and
2004 (Fig. 2) (Olaimat & Holley, 2012). The United States’ importation of fresh
produce doubled to 12.7 billion dollars from 1994 to 2004 (Aruscavage, Lee, Miller,
& LeJeune, 2006), and the daily sales of fresh produce reached 6 million packages in
2005 (Jongen, 2005) as cited in Olaimat & Holley, 2012.
This increase in the level of consumption of fruits and vegetables and the surge of
various locally produced and imported fruits and vegetables in all seasons might be
attributed to peoples’ growing attention to staying healthy and eating right as well as
the convenience provided from prepared products (Warriner, Huber, Namvar, Fan, &
Figure 1 A typical African fruit and vegetable market in Kenya (credit: alamy)
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Dunfield, 2009). The world’s fruits and vegetable consumption has increased at an
annual average of 4.5% from 1990 to 2004, and in the United States alone, the
annual consumption of fruits and vegetables between 1997-1999 increased by 25%
relative to the years 1977-1979 (Olaimat & Holley, 2012).
People became more interested in the consumption of fresh fruits and vegetables
after the release of information highlighting the health benefits of the consumption of
fruits and vegetable (DuPont, 2007). For example, in a report by the World Health
Organization (WHO), it’s recommends at least 400 grams of fruits and vegetables are
eaten in a day for protection against the risk of non-communicable diseases and
improvement of overall health (Soon et al., 2012). Additionally, Healthy People, a
U.S. government program, aims at increasing the intake of fruits and vegetables for
people aged 2 years and above to two daily servings of fruits and three daily servings
of vegetables to 75% and 50%, respectively (DuPont, 2007).
Figure 2 Global production of fruits and vegetables from 1982 to 2004 (sourced from EU,
2007).
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However, this increase in consumption of fruits and vegetables has been followed by an increase in outbreaks of foodborne illnesses linked to the consumption of fresh fruits and vegetables (Warriner et al., 2009). This increase in the consumption of fruits and vegetables was associated with change of personal dietary habits increased availability of fresh produce with some coming from sources having uncertain sanitary practices (Beuchat, 2002). The use of manure that has not been composted, untreated sewage, irrigation water contaminated by pathogens, increased contact between livestock and fresh produce due to their proximity to areas of high produce production, and also increased number of immunocompromised consumers further worsens the situation (Beuchat, 2002). The most reported pathogens associated with foodborne illnesses related to the consumption of fresh produce are Salmonella sp. and Escherichia coli O157:H7 (Warriner et al., 2009).
Fresh fruits and vegetables that receive little or no processing and thus do not undergo effective microbial decontamination and elimination steps usually carry microbes, some of which could be harmful to human health (Harris et al., 2003). Contamination can occur at any stage from the farm to the consumer due to environmental, human, or animal contact during production, storage harvesting, and transportation (FDA, 2014).
In less developed countries such as Nigeria, contamination is mostly due to the use of manure and untreated water as fertilizers in the production of fruits and vegetables (Eni et al., 2010). A high microbial contamination was observed in fruits and vegetables in a study conducted in Sango Ota, Ogun state, Nigeria. The high contamination was suggested to be due to cross-contamination during the storage
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time of the fruits and vegetables, during washing in markets where many fruits and vegetables are washed using the same water that was earlier used, and during transportation or handling by vendors (Eni et al., 2010).
In another study in Sokoto State, northwestern Nigeria, eight pathogenic microbes were found in tomatoes sold in markets. The microbes isolated were Aspergillus niger, A. ochraceous, A. flavus, A. fumigatus, Penicillium citrinum, Helminthosporim fulvum, Curvularia lunata, and Sclerotium rolfsii (Muhammad, Shehu, & Amusa, 2004). The reality that a significant portion of the Nigerian population are low-income earners and frequently consume rotten tomatoes further aggravates the situation (Muhammad et al., 2004).
In Ghana, urban farmers with a limited choice of irrigation water have no choice but to use polluted water for irrigation and thus, increasing the contamination risk even more for fruits and vegetables that are eaten raw (Amoah, Drechsel, Henseler, & Abaidoo, 2007). The detection of a foodborne pathogen in irrigation water is an indicator of possible contamination risk, although the ability of such pathogen to cause risks might depend on its excreted load, duration of latency period, ability to multiply outside mammal hosts, persistence in the environment, persistence on food, infectious dose, and human response (Steele & Odumeru, 2004).
However, fruit and vegetable contamination is not peculiar to the less developed countries; even in developed countries like the United States, this problem is common. In response to this contamination threat, the U.S. Food and Drug Administration (FDA) published a note titled Guide to Minimize Microbial Food
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Safety Hazards for Fresh Fruits and Vegetables that identifies the main sources of pathogen contamination and ways to address these sources (FDA, 2014). Similarly, in 2011, the United States developed the Food Safety Modernization Act (FSMA), which provides both reactive and preventive approaches to food safety in the US (Collart, 2016).
History of outbreaks in the US
Outbreaks associated with fresh fruits and vegetables were first reported in the United States in 1982 (Rangel, Sparling, Crowe, Griffin, & Swerdlow, 2005). Outbreaks related to fresh produce has been on the rise since then (Fonseca & Ravishankar, 2007). In the United States, such outbreaks have accounted for 38 (21%) of 183 outbreaks related to foodborne illnesses and 34% of 5,269 cases are food related. These outbreaks usually reach their peak in the summer and fall such that 74% of reported cases occurred between July and October (Rangel et al., 2005). Lettuce was the cause of 13 (34%) of fresh fruits and vegetable associated outbreaks, while apple juice contributed to 7 (18%), salad 6 (16%), coleslaw 4 (11%), melons 4 (11%), sprouts 3 (8%), and grapes 1 (3%) in the United States between 1982 and 2002 (Rangel et al., 2005). The main fruits and vegetables affected in outbreaks between 1990 and 2003 were sprouts, tomatoes, and melons (Fonseca & Ravishankar, 2007). Foodborne illnesses related to the consumption of fresh fruits and vegetables have increased rapidly with the increase in their consumption (Warriner et al., 2009)).
The U.S. Center for Disease Control (CDC) has estimated that contaminated produce has contributed to more than 47.8 million illnesses; 127,839 hospitalizations; and
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over 3,000 deaths between 2000 and 2006 (Scallan, Griffin, Angulo, Tauxe, & Hoekstra, 2011). In 1995, 40 confirmed cases of E. coli O157:H7 infection associated with lettuce consumption were reported in the US State of Montana (Ackers et al., 1998). This increase in outbreaks has been attributed to an increase in the demand for minimally processed and ready-to-eat fruits and vegetables and to the increased presence of out-of-season fruits and vegetables in the United States (Heaton & Jones, 2008).
Pathogenic microbes of concern and their pathways
Organic manure has been identified as a possible route of microbial contamination in fruits and vegetable, with slurries and animal manure as the leading source. Irrigation water that has been contaminated with fecal material and sewage overflow is a direct way of introducing pathogens to farm produce. Soil, which is a natural habitat for most pathogens, can introduce the pathogens directly to the surface of fruits and vegetables during heavy rain or when mixed up in organic manure (Heaton & Jones, 2008). It is common today to find coliform bacteria, which is normally found in human feces, in the fresh waters with little or no human contact (Higgins & Gbakima, 2008).
The bacterium Salmonella typhi (Fig. 3) is one of the most prevalent pathogens associated with outbreaks in fresh fruits and vegetables around the world between 2006 and 2008 (Lynch, Tauxe, & Hedberg, 2009). It causes salmonellosis, also called salmonella infection (Fonseca & Ravishankar, 2007), which has symptoms such as vomiting, nausea, fever, and abdominal cramps. S. Typhi caused one out of five fresh produce-related outbreaks between 1990 and 2003 in the United States
8
(Fonseca & Ravishankar, 2007). Some fresh fruits and vegetables, such as melon, tomatoes, sprouted seeds, and lettuce, have been identified as major vehicles for salmonella infections (Heaton & Jones, 2008). For example, uncooked tomatoes caused several outbreaks of salmonellosis in the US States of Illinois, Michigan, Minnesota, and Wisconsin of the United States in 1990 (Hedberg et al., 1999). Several other outbreaks associated with serotype Thompson of this pathogen were associated with the consumption of fresh cilantro in California in 1999 (Campbell et al., 2001).
Another pathogen commonly isolated from fresh fruits and vegetables is E. coli O157:H7 (Fig. 4). It is categorized into a group of bacteria called coliforms, which are bacteria known for causing gastrointestinal diseases such as diarrhea (Nkere, Ibe, & Iroegbu, 2011) and have an incubation period of 3-5 days (Holton, 2002).
Figure 3. A microscopic view of salmonella image
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Although most strains are not harmful and are found in the digestive tracts of humans and animals where they perform vital functions in our body, such as inhibiting the growth of harmful bacteria and synthesis of vitamins (Holton, 2002), the O157:H7 strain can cause serious health problems such as urinary tract infections, severe anemia, diarrhea and kidney failure and death in some cases (Özpınar et al., 2013). The harmful strain was confirmed to be the causative organism for enteric diseases by the CDC in 1982 (Holton, 2002). E. coli O157:H7 was isolated from both fresh spinach (CDC, 2006) and packaged spinach (Wendel et al., 2009) in Wisconsin and Oregon in 2006. It was also reported to have caused widespread of outbreaks in Atlanta, Georgia, in the United States, due to spinach consumption (Cunningham, 2006).
According to Rangel and colleagues (2005), E. coli has accounted for twenty-four multi-state outbreaks of foodborne illnesses in the United States since 1992; all were due to foodborne transmission, and 25% of the total outbreaks were associated with fresh fruits and vegetables (Fig. 5).
Fresh fruits and vegetable associated with outbreaks in the United States mostly originated from restaurants, with 15 (39%) of the reported cases occurring across
restaurants, and cross-contamination during food preparation contributed to 7 (47%) of the cases reported in the United States between 1982 and 2002 (Rangel et al., 2005). The average number of cases of outbreaks due to E. coli related to fresh fruits and vegetable (20) is much larger than the average number of outbreaks related to ground beef (8). Animal contact has also been reported to have been a source of contamination in the United States (Rangel et al., 2005).
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In less developed countries such as Nigeria, studies have shown that E. coli, Salmonella sp., and Enterobacter sp. are the most prevalent foodborne microbes in the country (Nkere et al., 2011). E. coli is known to be the causative agent of traveler’s diarrhea, an illness experienced by people visiting developing countries; the consumption of contaminated raw vegetables is the main cause of this illness (Harris et al., 2003).
Another pathogen, Campylobacter jejuni, which affects mostly raw peas, caused several illnesses in Alaska, United States, in 2005. This pathogen causes Campylobacteriosis, which is associated with most diarrheal illnesses in the United States (Gardner et al., 2011). Campylobacter pathogens are known to be the leading cause of bacterial enteritis in the world. Although they are mainly zoonoses, C. jejuni has also been known to contaminate lettuce and salads. While C. jejuni contaminates
Figure
Figure 44 Microscopic view of E. coli (credit: cdc.gov/ecoli).Microscopic view of E. coli (credit: cdc.gov/ecoli).
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fruits mainly by cross-contamination, they can survive on fresh-cut melon and papaya for a time long enough to harm consumers (Harris et al., 2003).
Listeria species is also another group of pathogens associated with fresh fruits and vegetables, notably raw tomatoes and lettuce (Harris et al., 2003). It is known to cause mild gastroenteritis in adults, but their symptoms are more severe in immunocompromised individuals, neonates, and pregnant women (Harris et al., 2003). Because they are very ubiquitous in the environment, Listeria spp. can be isolated from vegetables that have been irrigated with contaminated water, feces of livestock, water, and soil samples; therefore, they can contaminate fresh fruits and vegetable (Heaton & Jones, 2008). Listeria spp. are also known to cause hemolytic uremic syndrome (HUS), a group of blood-related ailments such as renal injury,
Figure
Figure 55 . Routes of transmission for . Routes of transmission for E. coliE. coli O157 by year (Credit: O157 by year (Credit: wwwnc.cdc.gov/eid/article/11/4/04wwwnc.cdc.gov/eid/article/11/4/04–07390739–f3).f3).
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hemolytic anemia, thrombocytopenia, and other related blood diseases (Rangel et al., 2005).
Shigella sp. is another pathogen that contaminates fruits and vegetables. There are four species, all of which are pathogenic: Shigella flexneri, S. bodii, S. sonnei, and S. dysenteriae. They lead to shigellosis which is known to cause severe dysentery and are pathogenic to humans even at low doses. Although transmission is mainly through interpersonal contact, contaminated fruits and vegetables that received little or no heat treatment are known to cause diseases. Shigella spp. have been known to cause outbreaks due to consumption of shredded salad and onions (Harris et al., 2003).
Staphylococcus aureus is another pathogen detected in fruits and vegetables, it is known to be carried by food handlers, and may grow on peeled oranges (Harris et al., 2003). Yersinia pseudotuberculosis O:3 outbreaks were also reportedly associated with the consumption of iceberg lettuce in many countries (Nuorti et al., 2004).
Survivability of pathogens
The ability of some pathogens associated with fresh fruits and vegetable to survive in multiple environments is another important factor to be considered when assessing the relationship between microbes and food (table. 1). For example, L. monocytogene is known to survive at refrigeration temperatures and can reproduce on stored fruits and vegetables (Heaton & Jones, 2008). S. aureus can survive for up to 14 days if stored at 40C to 80C (Harris et al., 2003).
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Table 1. Survivability, sources, and symptoms of some pathogens (credit: Food Industry Counsel LLC).
Common Pathogens
Incubation Period
Common Sources
Common Symptoms
Bacillus sphaericus
1-6 hrs. (vomiting)
6-24 hrs. (diarrhea)
Soil Organisms typically found in raw dry and processed foods
Nausea and diarrhea. Typically resolves within 24-48 hours
Botulism
(C. botulinum)
12-72 hrs. (Usually 18-36 hrs.)
Improperly canned home and commercial foods (including cans with dents and punctures), meats, sausage, fish, potatoes, leftover stews, and water.
Nausea, vomiting, diarrhea, fatigue, headache, dry mouth, double vision, muscle paralysis, respiratory failure. Duration is variable (day to months)
Campylobacter
(c. Jejuni)
2-7 days (usually 3-5 days)
Raw milk and eggs, raw or undercooked beef, poultry and shellfish, and water
Diarrhea (often bloody), abdominal cramps, nausea and headaches, typically resolves within 1-10 days
E. coli O157:H7
24+ hrs. to 10 days (usually 3-4 days)
Ground beef, raw milk, and raw produce and vegetables, and person-to-person and person-to-food transmission.
Diarrhea (often bloody), abdominal cramps and vomiting; usually no fever. HUS may develop in rare cases. Typically resolves within 1-8 days (in non-complicated cases)
Salmonella
6-72 hrs. (Usually 12-36hrs.)
Poultry, eggs, sprouts, person-to-person and person-to-food transmission.
Diarrhea, abdominal cramps, nausea vomiting, and fever. Typically resolves within 4 to 7 days
Listeria
9-48 hrs. (for GI symptoms) 2-6 weeks (for invasive disease)
Fresh soft cheeses, unpasteurized or inadequately pasteurized milk, ready-to-eat deli meats and hot dogs
Fever, muscle aches, nausea, diarrhea; pregnant women may suffer flu-like symptoms and stillbirth; elderly, immunocompromised and infants can develop sepsis and meningitis. Duration is variable.
Shigella
24-73 hrs. (Usually 12-36 hrs.)
person-to-person and person-to-food transmission; contaminated foods, raw vegetables, egg salads and water/ice
Watery diarrhea, nausea, vomiting, abdominal cramps. Chills and fever, stool may contain blood and mucus. Typically resolves within 4-7 days.
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In general, pathogens associated with fruits and vegetables survive best in the soil, irrigation water, and fertilizer (Alam, Feroz, Rahman, Das, & Noor, 2015). In some microorganisms such as S. aureus produce heat resistant toxins, and, therefore, pose a serious threat of infection even at high temperatures (Harris et al., 2003). Cut fruits and sliced vegetables also provide an environment that encourages the survival of pathogens because once cut or sliced, fruits or vegetables provide nutrients for pathogens to multiply (Lynch et al., 2009).
Shigella sonnei, another pathogen associated with fruits and vegetable, has been known to survive at 50C on lettuce for as long as three days without any decrease in number and can increase by more than 1,000-fold should the temperature be increased to 220C. This suggests that S. sonnei can survive even at refrigerated temperatures. S. sonnei can also grow on shredded cabbage and parsley stored at 240C. A combined population of S. flexneri, S. dysenteriae, and S. sonnei was observed to be able to grow on cut papaya (pH 5.69) and watermelon (pH 6.81) within just 4-6 hours at 22-270C (Harris et al., 2003).
Some laboratory studies have shown that Salmonella sp. can grow on sliced or chopped tomatoes with a pH of 4.5 stored at 200C to 300C (Harris et al., 2003). E. coli O157:H7 can grow rapidly on raw fruits and vegetables, especially at 120C. Packaging under pressure does not inhibit the survival and growth of E. coli. It is known to have very low infectious dose and can develop resistance to acid (Harris et al., 2003).
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Moisture content is also another factor that facilitates the survival and growth of microbes on fresh fruits. For example, fresh fruits and vegetables have an approximate moisture content of 0.97-1.0aw, which favors the growth of microbes (Wadamori, Gooneratne, & Hussain, 2017). Humidity and heat, which are common in tropical regions might also favor microbial growth.
Commonly used methods of decontamination
Different physical and chemical methods are used to decontaminate fruits and vegetables. Preventing contamination in the first place is the best way to eliminate pathogens from fruits and vegetables. Nonetheless, this is almost impossible to achieve, also washing and sanitizing fruits and vegetables may even not totally eliminate all pathogens (FDA, 2014).
Washing fresh fruits and vegetable with chlorine after harvest is a reliable way of reducing pathogen contamination (Warriner et al., 2009). However, Fonseca and Ravishankar (2007) have argued that many factors limit the efficacy of chlorine as a decontaminant, including the ability of pathogens to get into plant tissues, the ability of some bacteria to form a biofilm, and the hydrophobic nature of plant surfaces. Other alternative methods of decontaminating fruits and vegetables from pathogens include the use of ozonated water (Hassenberg, Fröhling, Geyer, Schlüter, & Herppich, 2008), washing under pressure (Segner & Scholthof, 2007), ultraviolet light C (UVC), calcinated calcium, electrolyzed oxidizing water, gamma irradiation, and detergent with water (Fonseca & Ravishankar, 2007). The use of antagonistic bacteria and the use of bacteriophages, or a combination of both, has also been identified as good decontamination alternatives (Olaimat & Holley, 2012). Although
16
most of these methods may have flaws, studies have indicated that most of them are effective. For example, Segner & Scholthof, found that because apples are washed with clean water under pressure, they had a relatively little amount of microbes (Segner & Scholthof, 2007).
The FDA has further reported that hot water is also used as a decontaminating agent, but pointed out that the method has some adverse effects on color and texture of fruits, and thus decreases the freshness of fruits. The effectiveness of any treatment against microbes depends on the type of the treatment, characteristics of the produces’ surface (hydrophobicity, cracks, and texture), exposure time, temperature, and pH. The ability of some microbes to get to the inside fruit tissues renders many techniques ineffective (FDA, 2014).
In developing nations, inadequacy or nonexistence of sewage treatment facilities, coupled with overpopulated urban areas, make it easy for microbes to get deposited into habitats that support their survival and growth (Higgins & Gbakima, 2008). For example, a study conducted in Ghana showed that all samples of irrigation water contain fecal coliform levels that exceeded the WHO recommended a level of 1 x 103 100ml-1 (Amoah et al., 2007).
However, it is difficult to say with certainty that disease outbreaks in these countries occur due to waterborne or foodborne or fecal-oral contamination. This is because most water-borne diseases can also be spread through fecal, person-to-person, and via contaminated foods (Issa-Zacharia, Kamitani, Muhimbula, & Ndabikunze, 2010). Because some rural areas lack proper sanitation facilities, it is easy for a pathogen,
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once introduced into a community, to spread via the fecal-oral route. This makes it likely for developing nations to experience less foodborne contamination and more of fecal-oral contamination (Issa-Zacharia et al., 2010). Some of the ways through which microbes can contaminate fruits and vegetables in developing countries such as Nigeria can be through dust in markets and bacterial soft rot.
Many other decontamination methods, such as the use of electrolyzed water (Fonseca & Ravishankar, 2007) (Issa-Zacharia et al., 2010), free chlorine, pasteurization (Cunningham, 2006), hypochlorite, bromine, iodine, quaternary ammonium compounds, acidic compounds with and without fatty acids, alkaline compounds, peracetic acid with and without fatty acids, hydrogen peroxide (Goodburn & Wallace, 2013), ozone (Hassenberg et al., 2008), and irradiation (Cunningham, 2006), are currently in use by various food companies. Biocontrol, such as the use of antagonistic bacteria and bacteriophages, is also an available decontamination method (Wadamori et al., 2017). Other non-thermal technologies, such as the application of pulsed electric light, high pressure, pulsed electric field, oscillating magnetic field, and ultrasound and UV treatments, have also been reported to reduce or, in some cases, eliminate microbes from fruits and vegetables (Goodburn & Wallace, 2013).
However, there are few published studies on the effect of these technologies on fresh fruits and vegetables (FDA, 2014). Furthermore, these methods do have something in common, which is complexity and difficulty to perform. They also require trained and educated personnel and, therefore, may not be used on a wide scale and hence,
18
the need for a verified low-tech decontamination technique that can be practiced at small scale and household levels.
Addition of detergent to water, which seems relatively easy, has been faulted because it causes infiltration of surface microbes into the inner parts of damaged fruits and vegetables by reducing the surface tension of the water (Beuchat, 2002).
Food Safety Regulation in Nigeria
In Nigeria, the National Food and Drug Administration and Control (NAFDAC), established in 1993, is responsible for food safety, and its roles are equivalent to those of the United States’ FDA. Not many studies have been conducted on the effects of harmful microbes on Nigerians. However, some independent research has been done on microbial contamination in Nigeria. For example, microbes have been found on tomatoes sold in markets in Sokoto State (Muhammad et al., 2004), and on fruits and vegetables in Ogun State (Steele & Odumeru, 2004), and in foods across restaurants in Nsukka, Enugu State (Nkere et al., 2011).
No research has been conducted to determine the microbial quality of fruits and vegetables sold in Yola-Jimeta markets. Therefore, I tested fresh fruits and vegetables available in public markets in a small urban center in northeastern Nigeria. My aim was to determine microbial contamination and evaluate the efficacy of two simple and affordable washing techniques that can be used by the general public. I intended to focus on fruits and vegetables eaten raw because they tend to pose more risk of microbe ingestion than the ones that are cooked before eaten. This research is intended to be the foundation upon which subsequent studies will be built.
19
I will share my finding with the stakeholders so as to give them an insight into the matter
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HYPOTHESIS, AIMS, & OBJECTIVES
NULL HYPOTHESIS (H0): Washing fruits and vegetables available in the local markets in Yola-Jimeta has no effect on microbial decontamination.
RESEARCH HYPOTHESIS (H1): Washing fruits and vegetables available in the local markets in Yola-Jimeta reduces microbial decontamination.
NULL HYPOTHESIS 2 (H0): There will not be harmful microbes on fruits and vegetables available in Yola-Jimeta markets.
RESEARCH HYPOTHESIS 2 (H2): There will be harmful microbes on fruits and vegetables available in Yola-Jimeta markets.
AIMS
• To determine if micro-organisms found on fruits and vegetables sold in Yola-Jimeta markets, northeastern Nigeria, are potentially harmful to people
• To compare the efficacy of simple washing practices in microbial decontamination of fruits and vegetables sold in Yola-Jimeta markets, northeastern Nigeria
OBJECTIVES
• To isolate microbes found on fresh fruits and vegetables
• To identify these microbes to the species level
• To wash the fruits and vegetables with water to determine the impact on microbial decontamination
• To wash the fruits and vegetables with water and vinegar to determine the impact on microbial decontamination
• To determine how microbial loads found on fruits and vegetables compared to World Health Organization standards
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