MICROBIAL SPECIES ASSOCIATED WITH OPENLY HAWKED BAKED PRODUCTS IN UMUAHIA METROPOLIS

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

LIST OF TABLES

CHAPTER ONE

1.0       INTRODUCTION

Bakery products are the important staple foods in most country and cultures. Bakery products and cereals are a valuable source of nutrients in our diet providing us with most of our food calories and approximately half of our protein requirements. Cereals have been a basic food of man since prehistoric times and were consumed long before bread making was developed. Variety breads and other bakery products have increased in sales volume within the past decades. The nutrients in bakery products are carbohydrates, proteins, lipids, vitamins and minerals. Bakery industry in India is the largest of the food industries with an annual turnover of about B 3000 crores. India is the second largest producer of biscuits after USA. The biscuit industry in India comprises of organized and unorganized sectors (Guynot et al., 2004). Breads and biscuits form the major baked foods accounting for over 80 per cent of total bakery products produced in the country. The quantities of bread and biscuits produced are more or less the same.

Commercially produced and properly handled bread generally lacks sufficient amounts of moisture to slow growth of any microorganisms except moulds (Guynot et al., 2004). As normal cooking temperature destroy fungal spores, post-process contamination from airborne spores and contact with contamination surfaces must be prevented.

Filamentous fungi involved in spoilage of bread include Rhizopus sp., and Mucor sp., Penicillium sp., Eurotium sp., Aspergillus sp. and Monilia sitophilia (Adams, and Moss, 2000). One of the most common is Rhizopus stolonifer, often referred to as the ‘bread mould’. Storage of bread under conditions of low humidity retards mould growth. In addition to the economic losses associated with bakery products, another concern is the possibility of mycotoxins production. Eurotium species are usually the first fungi to colonize improperly water allowing other species, Aspergillus and Penicillium which can produce toxins to thrive. Losses of bakery products due to mould spoilage vary between 1-5 per cent depending on seasons, type of products and methods of processing.

Members of the genus Bacillus bring about bacterial spoilage of bread known as rope. This is of major economic to the baking industry. Ropiness which is the most important spoilage of bread after moldiness occurs particularly in summer when the climatic conditions favour growth of bacteria. It is mainly caused by Bacillus subtilis but Bacillus licheniformis, Bacillus magaterium and Bacillus cereus have also been associated with ropy bread (Adams, and Moss, 2000). The incidence of wheat bread spoilage caused by Bacillus has increased during the last few years presumably because more bread is produced without preservatives and often raw materials such as bran and seeds are added. Spoilage of bread by rope formation may constitute a health risk, high numbers of Bacillus subtilis and Bacillus licheniformis in foods may cause a mild form of food illness. Consumption of ropy bread has been association with food-borne illness in reports from Canada and the United Kingdom.

The stability of bakery products against the attack by fungi is mainly due to preservatives. Preservatives help to reduce or prevent wastage of food through spoilage caused by microorganisms. Longer shelf life enables a greater variety of products to be kept in store and in the home. Sofos and Busta, (1991) reported that chemical preservatives can control the growth of molds by preventing the metabolism, by denaturing the protein of the cell, or by causing physical damage to the cell membrane. Among these preservatives are propionic and sorbic acid or their salts which have been show to increase the shelf life of bakery products. Propionic acid and calcium propionate are usually employed at concentrations of 0.1 and 0.2 per cent respectively. At these levels, moulds can be inhibited for 2 days or more and the formation of rope can be prevented (Seiler, 1994).

Problems due to spoilage yeasts in bread usually result from post-baking contamination, slicing machines, bread coolers, conveyor belts and racks have been identified as sources. Yeast spoilage is characterized by visible growth on the surface of products. The most frequent and troublesome yeast is Pichia butonii, which is known as “chalk mould”. This yeast can multiply rapidly on bread, with visible growth often apparent some time before mould occurs. Filamentous fungi are more common than yeast on British breads. Since, filamentous fungi are more easily recognized than yeast, because they generate the majority of complaints (Seiler, 1994). The stability of bakery products against the attack by fungi is mainly due to preservatives. Preservatives help to reduce or prevent wastage of food through spoilage caused by microorganisms. Longer shelf life enables a greater variety of products to be kept in store and in the home.

1.1       AIM OF STUDY

The aim of this research work is to evaluate and identify the microorganisms that are associated with baked products such as bread, meat pie and egg roll.

1.2       SPECIFIC OBJECTIVES

·       To isolate and identify microorganisms associated with baked products

·       To determine the contamination rate of the various microorganisms on the baked products

·       To determine the percentage occurrence of the various isolates from the baked products

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