MICROBIOLOGICAL ANALYSIS OF AFRICAN SALAD

ABSTRACT

Food safety is a major issue of concern in the world. This is because unsafe foods pose global health challenges/threats. Foodborne diseases have been reported to cause about 48 million illnesses each year. These illnesses usually result from uncooked food of animal origin, fruits and vegetables contaminated with feces, raw shellfish and industrial pollution. Ready-to-eat foods do not require further preparation before consumption therefore they could contain pathogens that form part of their microflora thereby posing a public health challenge. They include foods such as salads that are eaten raw or fresh as they are gotten. Fresh vegetables can become contaminated by pathogens such as Salmonella at any point during the food production process either through contact with contaminated irrigation water, soil, manure and fecal matter of wild animals, polluted water used in its preparation, asymptomatic human carriers or the environment where the production process takes place. African salad is a staple food which is processed from cassava (Manihot esculenta Crantz) that contains lots of fresh and raw vegetables and some other ingredients consumed without further cooking. African salad is susceptible to microbial contamination during production, storage and sale which can lead to its spoilage and the secretion of some toxic substances such as aflatoxins by microorganisms that are of public health importance. The aim of this research is to determine the microbiological quality of African salad sold within Umuahia metropolis by roadside hawkers. To this end, samples were collected from five (5) different locations within Umuahia and isolation, enumeration and identification of the microbial isolates were done. Bacterial isolates identified in the African salad samples include Bacillus spp, Staphylococcus aureus, Escherichia coli, Klebsiella spp, Samonella spp, Shigella spp and Serratia spp, while the fungal isolates were Aspergillus niger, Rhodotorula spp, Aspergillus flavus and Fusarium oxysporum. The mean Total Aerobic Plate Count ranged from 2.4 x 108 to 8.8 x 108, while the Total Coliform Plate Count ranged from 0.9 x 108 to 9.3 x 108 and Total Fungal Plate Count ranged from 3.7 x 108 to 7.9 x 108. Based on the specifications by International Commission for Microbiological Specification for Foods (ICMSF), the level of contaminations was unacceptable and could pose health challenges. From the results of this research, we can conclude that African salad cannot be stored beyond twenty-four (24) hours after preparation as was shown by the increase in microbial load during storage. The delicacy therefore, has to be eaten fresh and care has to be taken during its production in order to reduce the amount of contaminants introduced into the food.

TABLE OF CONTENTS

Certification page                                                                                             i

Dedication                                                                                   ii

Acknowledgements                                                                    iii

Table of Contents                                                                                     iv

List of tables                                                                                         vi

Abstract                                                                                     vii

CHAPTER ONE

1.0       INTRODUCTION                                                           1

1.1       Aim                                                                                 4

1.2       Objectives                                                                       4

CHAPTER TWO

2.0  LITERATURE REVIEW                      5

2.1       Food safety and food borne illnesses                                                                          5

2.2       Ready-to-eat foods and vegetables                                                                       6

2.3       Cassava                                                                           8

2.4       African salad    11

CHAPTER THREE

3.0       MATERIALS AND METHODS                                                                   15

3.1       Sample collection                                                                                   15

3.2       Preparation of media   15

3.3       Materials                                                                       15

3.4       Microbiological analysis 15

3.5       Identification of microbial isolates                                                                                        16

3.6       Coliform test                                                                                21

3.7       Identification of fungi                                                                             21

3.8       Statistical analysis                                                                                                                  22

CHAPTER FOUR

4.0       RESULTS                                                                     23

4.1       Mean total microbial counts (cfu/g) of African salad    23

4.2       Occurrence of presumptive coliform in tubes of the MPN of African salad samples (coliform test)                                                                               25

4.3       Identification and characterization of bacterial isolates from African salad    27

4.4       Identification and characterization of fungal isolates from African salad    29

4.5       Distribution of microorganisms isolated from Africa salad samples 31

4.6       Percentage occurrence of bacterial and fungal isolates from African salad samples                                                                         34

CHAPTER FIVE

5.0       DISCUSSION, CONCLUSION AND RECOMMENDATIONS                                                            37

5.1       Discussion                                                                     37

5.1       Conclusion                                                                    40

5.2       Recommendations                                                          40

REFERENCES

APPENDICES

LIST OF TABLES

4.1       Total average bacterial counts (Cfu/g) of African salad sold within Umuahia                                                                                  24

4.2       Occurrence of presumptive coliform in tubes of the MPN African Salad Samples                                                                                     26

4.3       Identification and characterization of Bacterial Isolates 28

4.4       Identification and characterization of Fungal Isolates from Africa salad    30

4.5A     Distribution of bacterial isolates from Africa salad    32

4.5B     Distribution of fungal isolates from African salad    33

4.6A     Percentage occurrence of bacterial isolates from Africa salad samples 35

4.6B     Percentage occurrence of fungal isolates from Africa salad samples 36

CHAPTER 1

INTRODUCTION

As the standard of living improves, concerns over food safety and potential contaminants will continue to be an important health issue. Consumers demand quality and safety of products they consume because food as energy and nutrient is necessary to sustain life. In general, consumers rely on government to ensure all food products not only are safe but are sold as what they claim to contain. Challenges and tragedies in food safety include chemical, biological, personal hygiene and environmentally related incidents. Historically, incidents of food products contaminated with industrial pollutants have been well documented (Fung et al., 2018). Japan, Iraq, United States and other nations experienced incidents where hundreds and thousands of people fell ill or died. Unsafe food poses global health threats. The young, the elderly and the sick are particularly vulnerable. If food supplies are unsecured, population shifts to less healthy diets and consume more “unsafe foods”-in which chemical, microbiological and other hazards pose health risks, that in turn costs higher healthcare expenditure and drains national wealth (Fung et al., 2018). In light of recurrent food contamination incidents, food safety in the 21st century should expand beyond improving nutritional profile, transparency of ingredients and regulations of unhealthy foods to include regular monitoring, surveillance and enforcement of food products in furtherance of the general public well-being and prevention of foodborne illnesses (Fung et al., 2018).

According to US Centers for Disease Control, foodborne diseases cause an estimated 48 million illnesses each year in the United States, including 9.4 million caused by known pathogens. The pathogen-commodity pairs most commonly responsible for outbreaks were scombroid toxin/histamine and fish (317 outbreaks), ciguatoxin and fish (172 outbreaks), Salmonella and poultry (145 outbreaks), and norovirus and leafy vegetables (141 outbreaks). The pathogen-commodity pairs most commonly responsible for outbreak-related illnesses were norovirus and leafy vegetables (4011 illnesses), Clostridium perfringens and poultry (3452 illnesses), Salmonella and vine-stalk vegetables (3216 illnesses), and C. perfringens and beef (2963 illnesses) (Fung et al., 2018). Examples of unsafe food that commonly contain these hazards include uncooked foods of animal origin, fruits and vegetables contaminated with faeces, raw shellfish and industrial pollution. In a comprehensive estimation, the 2015 WHO report not only provides numbers of foodborne illnesses in terms of incidence but also number of deaths and Disability Adjusted Life Years (DALYs) as a measure of burden due to foodborne related morbidity and mortality. With substantial global burden of foodborne diseases and deaths, the impact is most significant among young children living in low income regions where food hygiene and water sanitation are below optimal standards. Therefore, improving microbial, personal, chemical and environmental health will improve overall health of children and adults alike.

According to the definition given by the FAO and the WHO (Cerna-Cortes et al., 2015), ready-to-eat (RTE) foods include any food material that is normally consumed in its raw state. Demand for RTE food has led to an increase in the amount and selection of different products available for the consumers (Cerna-Cortes et al., 2015). RTE-salads and RTE-sprouts constitute a suitable and convenient meal for today’s lifestyles because they need no cooking or further preparation. As well as being considered low-calorie food, they are rich in fiber and provide a great variety of vitamins, minerals and other phytochemicals (Cerna-Cortes et al., 2015). Their consumption is encouraged in many countries by government health agencies to protect people against a range of illnesses such as cancer and cardiovascular diseases (Cerna-Cortes et al., 2015).Therefore, continued increase in the consumption of fresh meals has occurred as a result of efforts to promote better nutrition in the population (Cerna-Cortes et al., 2015). As RTE-salads and RTE-sprouts do not need further preparation before consumption, they could potentially contain pathogens that form part of their microflora, posing a public health problem. Fresh vegetables can become contaminated by pathogens such as Salmonella at any point during the food production process. During preharvest, contact with contaminated irrigation water, soil, manure, or feacal matter of wild animals may occur. These pathogens can both bind to plant leaves and/or be internalized via the leaves or the endophytic root system (Cerna-Cortes et al., 2015). During harvest, asymptomatic human carriers might contaminate the products and at the postharvest level, products become contaminated by contact with polluted water, other asymptomatic human carriers or the production process environment. Moreover, the number of gastroenteritis outbreaks caused by foodborne pathogens after consumption of raw vegetables salads and sprouts has increased worldwide (Cerna-Cortes et al., 2015). Even though Salmonella is the most common cause of disease outbreaks associated with lettuce and sprouts, there are other pathogens (such as Shiga toxin producing E. coli O157, Norovirus) that have been described as relevant microbial hazards (Cerna-Cortes et al., 2015). Nontuberculous mycobacteria (NTM) have been isolated from various kinds of food and many studies support the hypothesis that food, especially raw or partially cooked products, plays a role as a source of NTM for humans, primarily in countries with similar processing food routes and climates (Cerna-Cortes et al., 2015).

African salad is popularly called “Abacha, Abacha Ncha, Abacha and Ugba” by the Igbo tribe of Nigeria. It is an exotic delicacy and a special salad recipe native to Nigeria. African salad is a staple food which is processed from cassava (Manihot esculenta Crantz) as a snack or main meal in the Eastern part of Nigeria. The name African salad is thought to have originated from the Igbo’s ideology that salad contains lots of fresh and raw vegetables and some other ingredients consumed without further cooking. African salad is widely accessed for its composition of food ingredients known to be rich in protein, carbohydrate, vitamins, and minerals (Oranusi et al., 2013). Though it can be as filling as any other main course meal, African salad is usually eaten as an in-between meal or as a side dish to the various Nigerian rice recipes (Oranusi et al., 2013). African salad is also regarded as a special delicacy during traditional festivals.

Despite the nutritional values of African salad, however, it is still susceptible to microbial contamination during production, storage and sale which can lead to its spoilage and the secretion of some toxic substances such as aflatoxins by microorganisms that are of public health importance.

Though several works abound on some of the component ingredients, there is little information on the chemical and microbiological compositions of African salad and the notion that African salad is nutritionally rich is only but speculative based on its component ingredients. The objective of this work is to carry out microbiological analysis of African salad as prepared by food vendors in Umuahia, Abia State, Nigeria with a view to stirring and stimulating further research on this all important African dish.

1.1   AIM

To determine the microbiological quality of African salad sold within Umuahia metropolis by roadside hawkers.

1.2   OBJECTIVES

1.     To isolate and identify microorganisms found in African salad.

2.     To determine the colony forming units.

3.     To determine and identify the presence of pathogens.

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