ABSTRACT
Studies were carried out on species of fungi associated with deteriorated loaves of bread. Ten (10) loaves of bread each weighing 10kg each were purchased from different shops in local market within Umuahia metropolis in the morning and evening. A total of thirty seven (37) fungi species were isolated using the pour plate technique. The fungal isolates included; Aspergillus niger, Fusarium oxysporum, Aspergillus flavus, Rhizopus stolonifer, Mucor alternaria and Rhodotorula spp, which were responsible for the bread spoilage. The results in this study revealed that after incubation period, the total fungal count of each bread samples over a storage period of fifteen (15) days ranged from 0.20x1011 to 6.95x1011. There was no fungal count on the first two days of study for the ten (10) bread samples used. The percentage of occurrence of the fungi in the bread samples showed that Rhodotorula spp 9(24.32%) had the highest percentage followed by Rhizopus stolonfer 7(18.92%) and Mucor alternaria 7(18.92%) while Aspergillius spp 4(10.8%) had the lowest frequency of occurrence. The percentage moisture content of the spoilt bread samples ranged from 43.2 to 43.7 while the pH values were between 4.90 and 4.98. Sample (C) had the highest percentage moisture content and least pH values of 43.7 and 4.90 respectively while Sample (B) and I had the lowest percentage moisture content at 43.2 each. The low pH of the samples may be due to the use of acidic chemical preservatives such as propionates, palmitates or sorbates in bread. High moisture content and low pH make bread susceptible to fungal spoilage. The knowledge of the fungal spoilage of bread will educate the consumers on the public health implications of the growth of the organisms and their toxins in bread and proffer the possible solutions to such spoilage. This study concluded that various fungi, especially Mucor spp and Rhodotorula spp are associated with spoilage of bread.
TABLE OF CONTENTS
Title Page
Title Page i
Certification ii
Dedication iii
Acknowledgement iv
Table of Contents v
List of Tables vii
Abstract ix
CHAPTER ONE
1.0 Introduction 1
1.1 Aim and Objectives 4
CHAPTER TWO
2.0 Literature Review 5
2.1 Bread Production 5
2.2.1 Flour 5
2.3 Microorganisms Associated With Bread Spoilage 6
2.3.1 Penicillium spp 6
2.3.2 Mucor spp 6
2.4 Economical Importance of Bakery Products (Bread) 7
2.5 Microbial Spoilage of Bakery Products (Bread) 8
2.5.1 Bacterial spoilage 9
2.5.2 Yeast spoilage 10
2.5.3 Mold spoilage 11
2.6 Physical Factors Influence the Microbial Growth 12
2.6.1 Effect of Temperature, Ph and Water Activity 12
2.7 Control of Microbial Growth in Bakery Products (Bread) 14
2.7.1 Freezing 15
2.7.2 Preservatives 15
2.8 Effect of Chemical Preservatives 15
2.8.1 Sorbic Acid and Sorbates 17
2.8.2 Propionic Acids and Its Salts 17
2.8.3 Effect of Bio-preservatives 18
CHAPTER THREE
3.0 Materials and Methods 20
3.1 Source/Collection of Samples 20
3.1.1 Materials and Media Used 20
3.1.1 Sterilization of Materials 20
3.2 Isolation of Fungi Associated With Bread Spoilage 20
3.2.1 Processing of Samples 20
3.2.2 Preparation of sample and inoculation of samples 21
3.2.3 Isolation of Spoilage Fungi 21
3.2.4 Sub-culturing/Purification and Identification of Test Fungi Pathogens 21
3.2.5 Identification of Fungal Isolates 22
3.2.5.1 Wet Preparation 22
3.2.5.2 Colonial Morphology 22
3.3 Determination of Parameters at Which Bread Spoilage Occur 22
3.3.1 Determination of the Moisture Content of the Bread Samples 22
3.3.2 Determination of the pH of the Bread Samples 23
3.3.3 Determination of Percentage Occurrence of the Bread Samples 23
CHAPTER FOUR
4.0 Results 24
4.1 The Mean Fungal Counts in cfu/g of Bread Spoilage Samples 24
4.2 The Cultural Morphology and Microscopic Characteristics of Fungal
Isolates from the Spoilt Bread Samples 24
4.3 The Percentage Moisture Content and pH of the Spoilt Bread Sample 24
4.4 The Percentage Occurrence of Various Fungi Isolates from Spoilt Bread Samples 24
CHAPTER FIVE
5.0 Discussion and Conclusion 29
5.1 Discussion 29
5.2 Conclusion 31
References
