ABSTRACT
Foodborne illnesses have been associated with the
consumption of fresh produce, specifically leafy vegetables due to their soft
texture and method of cultivation. As a safety precaution, these vegetables are
usually cleaned with chemical sanitizers before consumption, hence the efficacy
of various chemical sanitizers was tested on leafy vegetables to ascertain
their potency. Lettuce, cabbage and spinach were collected aseptically in
plastic bags from Kumasi central market to the laboratory. Samples were taken
through pretreatment by washing with distilled water, sanitizing with 70%
alcohol under Ultra Violet light to ensure complete sterility. Test organisms E.
coli, Salmonella and L. monocytogenes inoculum were obtained from
the microbiology laboratory of the Centre for Scientific Research into Plant
Medicine (CSRPM), Akuapem Mampong and inoculated on samples using the dip
method. Samples dried for an hour at 37oC and were sanitized with
varying concentrations of peracetic acid, acetic acid, hydrogen peroxide,
sodium hypochlorite and sodium chloride within varying exposure times.
Microbial analysis were carried out at a temperature of 37oC for 48
hours on all samples using spread plate technique on plate count agar (PCA) for
enumerating colonies that will grow on plates. Results showed that there was a
significant difference (P˂0.05) between the loads on various test organisms.
However, E. coli was chosen as a model organism. After inoculating
cabbage, lettuce and Spinach, the results showed no significant difference (P>0.05)
in the loads, thus cabbage leaves were selected for the assay. Inoculum sample
of pretreated leaves showed 0 CFU/g and served as a control. Plate count before
and after sanitizer treatment were also obtained and used to determine the
potency of chemicals on microorganisms through the reduction in microbial
population. All the sanitizers were found to have an efficacy of 99.99% except
for sodium chloride which was 99.90%.
CHAPTER ONE
INTRODUCTION
1.0 BACKGROUND
Food safety is a science that is concerned with handling,
preparation, and storage of food in ways that forestall food borne
unhealthiness. This entails the elimination of physical, chemical and
biological hazards from food to make it safe for consumption ( o un a gi et
al., 2011).
The objective of food safety is to eliminate food-borne
disease outbreak and enhance consumer confidence in food by making food safe
for human consumption (Jay et al., 1999). The application of pre-requisite
programs such as good agricultural and sanitation practices from farm to fork
through the implementation of Hazard Analysis for critical Control Point
(HACCP) goes a long way to realize this objective.
Consumer food choices are made based on many factors such as
satiety, taste, availability, convenience, age, health awareness, environmental
influence, cost etc. One of such choices is the consumption of fruits and
vegetables which form a vital aspect of peop e’ diet a round the world because
of the health awareness created and increased urbanization (Cisse ,1997;
Olayemi, 1997; Armar Klemesu et al.,1998 ; Niang 1999; Faruqui et al. 2004;
Amoah et al.,2005). Vegetables form the basis for a healthy and balanced diet
due to the nutritional components they possess such as vitamins, minerals,
proteins, calcium, chlorophyll, carotene, potassium, dietary fiber and folate
(Koffi-Nevry et al., 2012).
Vegetables also have a beneficial impact on general wellbeing
and prevention of diseases (Remesy et al., 1998) by decreasing the risk of
acquiring illnesses such as cancer, coronary heart disease, etc.
In Ghana and other developing countries, general sanitation
and proper waste management remains a challenge and cropping practices of foods
like vegetables cannot be assured to be pathogens free. Numerous studies in
West Africa has revealed high levels of microorganism infection in irrigation
water; on farms and market vegetables (Cisse ,1997) which surpasses the
International Commission on Microbiological Specification for Food standards by
far (ICMSF 19742 ).Other common sources of microorganisms are soil, air, farm
pests, food handlers and irrigation containers used (Taura and Habibu, 2009).
According to markets and street food surveys conducted in
Accra Ghana, about 200,000 urban residents consume foods containing raw
vegetables treated by sewer water in urban and peri-urban agriculture (Obuobie et
al. 2006; Amoah et al., 2007). These foods have been quoted as a serious
explanation for the increasing diarrheic diseases (Tjoa et al. 1977; Mensah et
al. 1999; King et al. 2003).
In a report given by the World Health Organization in 2015,
the burden of food borne illness has been identified to be caused by 31 hazards
which include bacteria, virus, toxins, chemicals and parasites. These cause an
estimated number of 22 diseases with the most common agents being Escherichia
coli, Salmonella, Norovirus and Campylobacter. These organisms cause 70% of the
wor d’ food borne i ne with Africa and Southea tern A ian recording highest
number of incidence and death followed by eastern Mediterranean region.
Due to the exposure levels of vegetables to bacteria,
effective wastewater treatment using high-technology treatments and
decontamination structures can be used. These processes are however difficu t
and expensive to carry out as they need high energy, infrastructure and
maintenance necessities, as well as skilled labor, which makes it less feasible
in countries with low income (Carr & Strauss, 2001).
Another way of removing pathogenic microorganisms from fruits
and vegetables apart from waste water treatment is the use of effective
sanitization treatments to eliminate food borne diseases in connection with
fresh vegetable consumption (Xu, 2005). This is more feasible and less
expensive to practice.
An accepted and widely used sanitizer for fresh vegetables is
hypochlorite at 50-200mg/L. Chlorine also produces 1-2 log reduction in
microbial content at common concentrations although it raises safety concerns
of its ability to form trihalomethanes which is a carcinogen (Delaquis et al.,2004).
The utilization of acetic acid as a substitute to chlorine for sanitizing
vegetables has also been explored especially as vinegar, an inexpensive acetic
acid source and also used in household applications (Sengun and Karapinar,
2004; Chang and Fang, 2007).
The presence of pathogenic and spoilage bacteria in vegetables
has already been established, hence this study seeks to determine the efficacy
of common sanitizing agents in reducing these pathogenic organisms to tolerable
levels before consumption to enhance food safety hence, consumer protection.
1.2 Problem Statement
In recent times, there has been an increasing demand for
vegetable salads because of the assertion that vegetables are healthier.
However leafy vegetables have been associated to food‐borne illness because of pathogens like Escherichia coli
O157:H7. In 2001, Salmonella spp, faecal coliforms, Shigella spp and E. coli were
found in unacceptable levels in tomatoes and lettuce from farms and markets in
Accra Metropolis (Mensah et al., 2001).
The incessant occurrences of food borne illnesses through the
ingestion of fresh produce is caused by rise in alteration in production
processes; science, harvesting; storage, distribution and ingestion routines
and practices (Hedberg et al.,1999).As a safety precaution, consumers wash
leafy vegetables in water together with sanitizers such as chlorine dioxide,
salt, peroxyacetic, hypochlorite, hydrogen peroxide etc. before consumption.
However re idua concentration
in thi food (vegetab e ) may
fluctuate becau e of ac of
now edge regarding the anitizer di
infection efficiency and the microbia
contaminant that remains on
vegetables surface. This presents a task for researchers and food processors to
identify and ensure the microbiological quality and safety of vegetables
(Garcia et al. 2003).
1.3 Need for the Study
Vegetables are known to harbor pathogenic microorganisms due
to their soft texture and mode of cultivation which causes food borne illnesses
when consumed untreated. Vegetables are however of increasing demand due to the
health benefits associated with them.
There is therefore the need to properly sanitize vegetables
and rid them of these pathogens to acceptable levels in order to curb food
borne illnesses and promote food safety.
1.4 Objectives
Main Objective:
To assess the efficacy of common sanitizing agents in
reducing microbial load in leafy vegetables at different concentrations and
contact times.
Specific objectives:
To determine the microbiological load of pathogens inoculated
on leafy vegetables.
To determine the concentration of the sanitizing agent
capable of reducing the microbial load to acceptable levels.
1.5 Organization of Study
The thesis was organized in five chapters. Chapter one being
the introduction entails the background, problem statement, need for the study
and objectives.
Chapter two, the literature review discusses vegetables and
their importance to man, microbial contaminations they are exposed to, common
illnesses they cause, through to sanitizers that are used for treatment and
factors that enhance their efficacy.
Chapter three outlines the protocol used to inoculate
microorganisms of known concentration onto vegetables and the sanitizing
treatment they undergo while chapter four highlights the figures and graphical
representation of results obtained from the experiment conducted. Chapter five
discusses into detail the results and recommendations to support and sustain
the proper practice of chemical treatment of vegetables.
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