ABSTRACT
Fresh healthy carrot promote good health but harbour a wide range of contaminants. To assess the microbial quality of carrots sold in Ibadan, a total of fifteen samples were purchased from five vendors. Samples were analyzed to study the density of microorganisms by standard plate count.
Bacteria belonging to eight genera were identified. Escherichia coli (65%) was the most frequently isolated followed by Staphylococcus aureus, (57%) Klebsiella spp, (23%) were the least frequently isolated. Fungi such as Aspergillus niger, (38%) Rhizopus spp, (29%) and Fusarium spp,(16%) were also found associated with the samples and were identified based on their colonial and morphological characteristics. The effect of acetic acid concentration of 5% and exposure time of two minutes on the microbial load of the carrot samples were also assessed. However health education of the vendors and implementation of standard hygienic practices may reduce contamination of carrots for human consumption.
TABLE OF CONTENTS
Title i
Title page ii
Certification iii
Dedication iv
Acknowledgement v
Abstract vi
Table of contents v
Chapter One 1-3
1.0 Introduction 1-2
1.1 Objectives of study 3
Chapter Two
2.0 Literature review 4-15
2.1 Origin of carrot 4-5
2.2 Botanical classification of carrot 6
2.4 Nutritional value of carrot 7
2.5 Importance of carrot 8
2.6 Microbial contamination of carrot 9-10
2.7 Pathogens of most concern 11-12
2.7.1 Salmonella 11
2.7.2 Shigella 12
2.7.3 Escherichia coli 12
2.7.4 Staphylococcus aureus 12
2.8 Sources of microbial contamination in carrot 13
2.8.1 Source of contamination in carrot during production and harvest 13
2.8.2 Source of contamination of carrots during storage 14
2.8.3 Source of contamination in carrots during handling 14
2.9 Justification of study 15
Chapter three 16-23
3.0 Materials and methods 16
3.1 Equipment 16
3.2 Glass ware 16
3.3 Reagents and chemicals 16
3.4 Media 16
3.6 Materials 16
3.7 Collection of samples 16-17
3.8 Sterilization of materials 17
3.9 Preparation of media 17
3.9.1 Preparation of Potato Dextrose Agar 17
3.9.2 Preparation of Nutrient Agar 17
3.9.3 Preparation of Eosin Methylene Blue agar 18
3.9.4 Preparation of Salmonella Shigella agar 18
3.9.5 Preparation of Mac-Conkey Agar 18-19
3.10 Serial dilution 19
3.11 Membrane filter technique 19
3.12 Preparation of slant culture 19
3.13 Methods of isolation 19-20
3.14 Methods of identification 20
3.15 Lacto phenol cotton blue stain 20
3.16 Gram stain 20-21
3.17 Biochemical tests 21-23
3.17.1 Indole test 21
3.17.2 Citrate Test 21
3.17.3 Coagulase test 21
3.17.4 Urease test 22
3.17.5 Catalase test 22
3.17.6 Methyl Red and Voges-Proskauer (MR-VP) 22
3.17.7 Starch hydrolysis test 22-23
3.18 Control experiment 23
Chapter four
4.0 Results 24-37
Chapter five 38-50
5.0 Discussion and conclusion 38-40
5.1 Discussion 38-39
5.2 Conclusion and recommendations 40
References 41-50
LIST OF TABLES
PAGES
Table 4.1 Frequency and percentage occurrence of fungi isolated from
the carrot samples in November 2013. 29
Table 4.2 Frequency and percentage occurrence of fungi isolated from
the carrot samples in March 2014 30
Table 4.3 Frequency and percentage occurrence of fungi isolated from
the carrot samples in May 2014. 31
Table 4.4. Microbial load (Cfu/ml) 32
Table 4.5 Frequency and percentage occurrence of fungi isolated from
the carrot samples in Nov.2013 33
Table 4.6 Frequency and percentage occurrence of fungi isolated from
the carrot samples in March 2014 34
Table 4.7 Shows the frequency and the percentage occurrence of the
bacteria isolate in May 2014 35
Table 4.8 This table shows the microbial load in (CFU/ml) of the carrot
samples obtained from different vendors, before 36
treatment with 5% acetic acid (vinegar) concentration.
Table 4.9 This table shows the effect of acetic acid treatment (vinegar)
5% concentration on the microbial load of carrot samples 37
