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
Titlei
Title pageii
Certificationiii
Dedicationiv
Acknowledgement v
Abstractvi
Table of contentsv
Chapter One 1-3
1.0Introduction1-2
1.1Objectives of study3
Chapter Two
2.0 Literature review4-15
2.1 Origin of carrot4-5
2.2Botanical classification of carrot6
2.4Nutritional value of carrot7
2.5 Importance of carrot8
2.6 Microbial contamination of carrot9-10
2.7Pathogens of most concern11-12
2.7.1 Salmonella 11
2.7.2 Shigella12
2.7.3 Escherichia coli12
2.7.4 Staphylococcus aureus12
2.8Sources of microbial contamination in carrot 13
2.8.1Source of contamination in carrot during production and harvest13
2.8.2Source of contamination of carrots during storage14
2.8.3Source of contamination in carrots during handling14
2.9Justification of study15
Chapter three 16-23
3.0Materials and methods16
3.1 Equipment16
3.2 Glass ware16
3.3Reagents and chemicals16
3.4 Media16
3.6 Materials16
3.7 Collection of samples16-17
3.8 Sterilization of materials17
3.9 Preparation of media17
3.9.1 Preparation of Potato Dextrose Agar17
3.9.2 Preparation of Nutrient Agar17
3.9.3 Preparation of Eosin Methylene Blue agar18
3.9.4 Preparation of Salmonella Shigella agar18
3.9.5 Preparation of Mac-Conkey Agar18-19
3.10 Serial dilution19
3.11 Membrane filter technique19
3.12Preparation of slant culture19
3.13 Methods of isolation19-20
3.14Methods of identification20
3.15Lacto phenol cotton blue stain20
3.16Gram stain20-21
3.17Biochemical tests21-23
3.17.1 Indole test 21
3.17.2 Citrate Test 21
3.17.3 Coagulase test21
3.17.4 Urease test22
3.17.5 Catalase test22
3.17.6 Methyl Red and Voges-Proskauer (MR-VP) 22
3.17.7 Starch hydrolysis test22-23
3.18Control experiment 23
Chapter four
4.0Results24-37
Chapter five 38-50
5.0Discussion and conclusion38-40
5.1 Discussion38-39
5.2 Conclusion and recommendations40
References41-50
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 201430
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.201333
Table 4.6 Frequency and percentage occurrence of fungi isolated from
the carrot samples in March 201434
Table 4.7 Shows the frequency and the percentage occurrence of the
bacteria isolate in May 201435
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