ABSTRACT
In order to determine the microbial quality of fruits and vegetables sold in YolaJimeta 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 YolaJimeta 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
vii
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.
viii
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
ix
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
x
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
1
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).
2
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)
3
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).
4
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
5
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 lowincome 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
6
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
7
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
9
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).
10
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 4 Microscopic view of E. coli (credit: cdc.gov/ecoli).
11
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 5 . Routes of transmission for E. coli O157 by year (Credit:
wwwnc.cdc.gov/eid/article/11/4/04-0739-f3).
12
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).
13
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 noncomplicated cases)
Salmonella 6-72 hrs.
(Usually 12-
36hrs.)
Poultry, eggs,
sprouts, person-toperson and personto-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.
14
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).
15
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,
17
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
DISCLAIMER: All project works, files and documents posted on this website, eProjectTopics.com are the property/copyright of their respective owners. They are for research reference/guidance purposes only and some of the works may be crowd-sourced. Please don’t submit someone’s work as your own to avoid plagiarism and its consequences. Use it as a reference/citation/guidance purpose only and not copy the work word for word (verbatim). The paper should be used as a guide or framework for your own paper. The contents of this paper should be able to help you in generating new ideas and thoughts for your own study. eProjectTopics.com is a repository of research works where works are uploaded for research guidance. Our aim of providing this work is to help you eradicate the stress of going from one school library to another in search of research materials. This is a legal service because all tertiary institutions permit their students to read previous works, projects, books, articles, journals or papers while developing their own works. This is where the need for literature review comes in. “What a good artist understands is that nothing comes from nowhere. The paid subscription on eProjectTopics.com is a means by which the website is maintained to support Open Education. If you see your work posted here by any means, and you want it to be removed/credited, please contact us with the web address link to the work. We will reply to and honour every request. Please notice it may take up to 24 – 48 hours to process your request.
