USE OF COLIFORM ORGANISMS AS INDICATORS OF QUALITY OF YOGHURT PRODUCTS SOLD IN MICHAEL OKPARA UNIVERSITY OF AGRICULTURE, UMUDIKE

ABSTRACT

This study examined the quality of yoghurts sold in Michael Okpara University of Agriculture, Umudike using coliform as indicator of quality. Five different brands of yoghurt were bought from different outlets in Michael Okpara University of Agriculture Umudike. Pour plate method was used for the isolation of bacteria from the yoghurts. The isolates were identified using some standard microbiological techniques. 0nly two (2) bacterial sp were isolated namely; Klebsiella sp and Lactobacillus sp. Escherichia coli was not isolated from any of the samples examined while  Lactobacillus sp was isolated from all the samples. The highest bacteria count          (1.6x104 cfu/ml) was recorded against sample C (Pastures yoghurt). This study shows that the yoghurt samples’ quality conformed to the standard quality specifications by food regulators.  

TABLE OF CONTENTS

Certification i

Dedication ii

Acknowledgement iii

Table of Contents iv

List of Tables vi

Abstract vii

CHAPTER ONE -     INTRODUCTION

1.1 Aims and Objectives of Study 2

1.2   Main Objective of Study 2

1.3 Significance of Study 3

CHAPTER TWO -      LITERATURE REVIEW

2.1 Definition of Terms 4

2.1.1 Fermented Foods 4

2.1.2 Starter cultures 4

2.1.3   Protective Cultures 4

2.1.4 Probiotics 5

2.2 Significance of Enterobacteriaceae to Food industry 5

2.3 Coliforms as Indicator and Index Organisms 6

2.4 Coliforms as Food Borne Pathogens 11

2.5 The Lactic Acid Bacteria (LAB) 12

2.6. Lactobacillus acidophilus 14

CHAPTER THREE     -     MATERIALS AND METHODS

3.1   Sample Collection and Preparation 16

3.2   Preparation of Media 16

3.3    Inoculation of Samples 17

3.3.1 Total plate count 17

3.3.2 Coliform count 17

3.3.3 Isolation of Escherichia coli 18

3.3.4 Lactobacillus sp count 18

3.4   Characterisation and identification of bacteria isolates 18

3.4.1 Indole test 18

3.4.2   Methyl-red test 19

3.4.3   Voges proskauer test 19

3.4.4    Citrate utilization test 19

3.4.5 Gram Staining 20

CHAPTER FOUR   -   RESULTS 21

CHAPTER FIVE     -    DISCUSSIONS, CONCLUSION AND RECOMMENDATIONS

5.1 Discussions 24

5.2    Conclusion 25

5.3 Recommendations 25

References 26

Appendix

LIST OF TABLES

Table Title Page

2.1: Indicator functions associated with Enterobacteriaceae and

Escherichia coli 9

2.2: Examples of Enterobacteriaceae limits stated in the process hygiene

criteria of commission regulation 2073/2005 on microbiological

criteria for food stuffs and subsequent amendments

(No. 1441/2007 and 365/2010) 10

4.1: Results of viable bacteria count of yoghurt samples   22

4.2: Biochemical characterization of the bacteria isolates 23

CHAPTER ONE

INTRODUCTION

Yoghurt is a popular fermented milk product consumed in many parts of the world. It is produced in different forms such as whole milk yoghurt, skim milk yoghurt, cream yoghurt, fruit yoghurt and liquid yoghurt (Balasu and Kulkarni, 1991). The bacteria used to make yoghurt are known as yoghurt cultures. The yoghurt culture is a system of two or more microbial populations with mutually complementing metabolisms (Beshkova 2002). Starter cultures used in dairy industries are mixtures of carefully selected lactic acid bacteria which are added to the milk to fulfill the desired fermentation. Dairy starter cultures must reach high densities in milk in order to produce lactic acid at the required rates for manufacturing. Under these conditions, amino acid supply becomes limited due to their scarce concentrations in milk and to the auxotrophies shown by many starter bacteria (Mayo, 1993). Yoghurts as other dairy products are frequently contaminated by bacteria and this often led to food intoxication/poisoning. Health complications associated with consumption of inadequately pasteurized milk products includes serious infections that are hard to treat with antibiotics. This becomes clinically significant if organisms isolated from an assessed sample is resistant to conventional antibiotics, thus can confer antibiotic resistance to the infected host while providing no alternative drug (Agu et al 2014). Yoghurt is a product of the lactic acid fermentation of milk, so to ensure the proper quality of yoghurt, there should be a complete check on the method yoghurt is produced and sold in local markets and major streets. Some of the yoghurts sold by mobile vendors was linked to poor personal and handling hygiene and were reported to be substandard (Kawo et al. 2006). A practical approach towards the quality of yoghurts is to evaluate the different samples of yoghurt sold in local markets. Research in the field of quality evaluation of market yoghurt is the basic need to create awareness among common people about the existing situation and protect the consumers’ health and rights. The bacteriological quality of milk and dairy product is influenced by initial flora of raw milk, the processing conditions, post-heat treatment and contamination. Undesirable bacteria that can cause spoilage of dairy products include gram - negative psychrotrophs, coliforms and lactic acid bacteria. In addition, various bacteria of public health concern such as Salmonella sp, Listeria monocytogenes, Campylobacter jejuni,  Yersina enterocolitica, pathogenic strains of Escherichia coli (E.coli) and enterotoxigenic strains of Staphylococcus aureus (S. aureus) may also be found in milk and dairy products. For these reasons, increased emphasis should be placed on the bacteriological examination of milk and dairy foods.

1.1 Aims and Objectives of Study

· To know the quality of yoghurt products

· To estimate the shelf life of yoghurt products

· To evaluate the possible presence of pathogenic microorganism in the products.

Hence it is highly essential to evaluate the coliform status of the various yoghurt products in our markets to determine their level of compliance with quality specifications (especially bacteriological qualities) of such products.

1.2   Main Objective of Study

To determine the degree wholesomeness of yoghurt products sold in Michael Okpara University of Agriculture Umudike (MOUAU)

1.3 Significance of Study

This project work termed use of coliform organisms as indicator of quality of yoghurt products is to help in educating the general public and food vendors on the relevance and importance of maintaining a safe environment and proper handling hygiene to prevent contamination of yoghurts and other ready-to-eat foods. 

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