ABSTRACT

This study evaluated and identified various microorganisms associated with baked products in Umuahia metropolis of which five (5) different baked products comprising of Biscuits, Bread, Cakes, Pie and Eggroll were randomly selected for the purpose of the work. From this study a total of fourteen (14) bacteria strains were isolated and identified using morphological characteristics, pigmentation on media, microscopy, biochemical and sugar fermentation methods. This reveals the major bacterial isolates to belong to Salmonella species, Escherichia coli, Staphylococcus aurues, Proteus species and Pseudomonas aeruginosa respectively, while the microscopic and cultural characteristics revealed three (3) fungal strains to belong to Aspergillus niger, and Aspergilus flavus. The total viable microbial counts evaluated in this study varied from one sample to the other. Amongst the five (5) different baked products investigated however within Umuahia metropolis, Pie had the highest viable bacteria count at 9.1x106, followed by Bread (8.4x106), Eggroll (6.9x106), Cakes (5.7x106), while the least viable bacteria count was recorded on Biscuit (3.3x106) in that order. The total viable fungal plate count investigated on the different baked products, reveals Bread as having the highest viable fungi count at (1.7 x106) and Biscuit having the least viable fungi count at (1.2 x106). The contamination rate and percentage distribution accessed on different baked products revealed that Salmonella species and Staphylococcus aureus are the most frequently occurring isolates with a high percentage occurrence of 4(30%) each, followed by Escherichia coli (17.6%), Proreus spp 2(11.8%) and Pseudomonas aeruginosa 1(5.9%) at respectively. However, there were slight variations in the fungi population, with Aspergillus niger 2(11.8%) being most predominant and occurring isolates, followed by Aspergillus flavus 1(5.8%). Therefore, microorganisms are the common genera of molds generally isolated from the fresh baked products during the present investigation. These molds have been known to produce toxins, which are both acutely and chronically toxic in animal and humans.

TABLE OF CONTENTS

Title Page   i

Certification iii

Dedication iv

Acknowledgement v

Table of Contents vi

List of Tables vii

Abstract ix

CHAPTER ONE

1.0 Introduction 1

1.1 Aim and Objective 3

CHAPTER TWO

2.0 Literature Review 4

2.1 Economical Importance of Bakery Products 4

2.2 Microbial Spoilage of Bakery Products 6

2.2.1 Bacterial spoilage 7

2.2.2 Yeast spoilage 8

2.2.3 Mold spoilage 8

2.3 Physical Factors Influence the Microbial Growth 9

2.3.1 Effect of temperature, pH and water activity 9

2.3.2 Effect of salt tolerance 12

2.4 Control of Microbial Growth in Bakery Products 12

2.4.1 Reformulation to reduce product aw 13

2.4.2 Freezing 13

2.4.3 Preservatives 14

2.5 Effect of Chemical Preservatives 14

2.5.1 Sorbic acid and sorbates 15

2.5.2 Propionic acids and its salts 16

2.6 Effect of Bio-preservatives 18

CHAPTER THREE

3.0 Materials and Methods 21

3.1 Collection of Samples 21

3.2 Sterilization of Materials 21

3.3 Preparation of Culture Media 21

3.4 Inoculation and Isolation 21

3.4.1 Method 21

3.5 Purification of Isolates 22

3.6 Identification of Bacterial Isolates 22

3.7 Gram Staining 22

3.8 Biochemical Test 23

3.8.1 Catalase Test 23

3.8.2 Indole Test 23

3.8.3 Citrate Utilization Test 23

3.8.4 Hydrogen Sulphide (H2S) Production Test 23

3.8.5 Starch Hydrolysis 24

3.8.6 Motility, Indole, Urease (MIU) 24

3.8.7 Coagulase Test 25

3.8.8 Oxidase Test 25

3.9 Identification of Fungi Isolates 25

3.9.1 Microscopic Features 25

CHAPTER FOUR

4.0 Results 26

CHAPTER FIVE

5.0 Discussion, Conclusion and Recommendation 33

5.1 Discussion 33

5.2 Conclusion 37

5.3 Recommendation 37

References