ABSTRACT

The present study was conducted to assess the microbial quality of powdered soymilk samples sold in Aba, Abia state. A total of 10 samples were randomly purchased from local markets within the metropolis. The study samples were differentiated into two categories, branded and unbranded powdered soymilk samples. The branded soymilk samples were labeled TE, BC, and UCD to reflect their brand names while the unbranded samples were labeled N1 to N4 .The total viable count of the soymilk samples ranged from 2.0×105-8.7×105 (cfu/g) with a branded powdered soymilk sample (TE2) giving the lowest count, while the highest count was recorded in an unbranded sample (N2). The Total coliform count ranged from 4.5×104-9.0×104 (cfu/g), with a branded sample (UCD2) giving the lowest count while the highest count was recorded in an unbranded powdered soymilk (N2). The total fungal count ranged from 1.1×104 in a branded sample (TE1) to 3.3×104 (cfu/g) in an unbranded sample (N1). The isolates were four (4) bacteria (Staphylococcus aureus, Bacillus spp., Streptococcus spp., and E. coli) and two moulds (Aspergillus spp. and Penicillium spp.). Bacillus spp. recorded the highest incidence (8) and percentage occurrence (80%) while Aspergillus spp. and E. coli recorded the least incidence (4) and percentage occurrence (40%). Comparing the general counts, the study suggested the need for implementing regulatory measures like good manufacturing and management practices, hygienic distribution and retail storage practices for ensuring microbiological safety of powdered soymilk offered for public consumption in Aba, since both the branded and unbranded powdered soy milk samples gave results above the acceptable limits.

TABLE OF CONTENTS

Title page i

Certification ii

Dedication iii

Acknowledgement iv

Table of Contents v

List of Tables x

List of Figures xi

Abstract xii

CHAPTER ONE

INTRODUCTION

1.1 INTRODUCTION 1

1.2 AIMS AND OBJECTIVES 3

CHAPTER TWO

LITERATURE REVIEW  

2.1 SOYBEAN 4

2.1.1 ORIGIN OF SOYMILK 4

2.1.2 AGRONOMIC CHARACTERISTICS 4

2.1.3 COMPOSITION OF SOYBEAN 5

2.2 SOYMILK 7

2.2.1 DEFINITION OF SOYMILK 7

2.2.2 HISTORY OF SOYMILK 8

2.2.3 COMPOSITION OF SOY MILK 8

2.2.3.1 CHEMICAL COMPOSITION OF SOY MILK 8

2.2.3.2 PHYTOCHEMICALS IN SOY MILK 10

2.2.4 CLASSIFICATION OF SOY MILK 12

2.2.5 SOYMILK PREPARATION METHODS 12

2.2.6 NUTRIONAL VALUES OF SOY MILK 18

2.2.6.1 SOYMILK INTAKE AND HEART DISEASE 18

2.2.6.2 SOYMILK AND MENOPAUSE 19

2.2.6.3 SOYMILK INTAKE AND BONE HEALTH 20

2.2.6.4 SOYMILK INTAKE AND BREAST HEALTH 21

2.2.7 MAJOR CONCERNS ABOUT SOY SUPPLEMENTS AND HEALTH PRODUCTS

2.2.8 MICROORGANISMS ASSOCIATED WITH SPOILAGE OF MILK AND MILK PRODUCTS

2.2.8.1 PSYCHROTROPHS   22

2.2.8.2 COLIFORMS   23

2.2.8.3 LACTIC ACID BACTERIA    23

2.2.8.4 FUNGI     24

2.2.8.5 SPORE-FORMING BACTERIA     25

2.2.8.6  OTHER MICROOGANISMS     26

2.2.9 PRESERVATION AND STORAGE OF MILK AND PRODUCTS     26

CHAPTER THREE

MATERIALS AND METHODS

3.1 SOYMILK SAMPLES    28

3.2 STERILIZATION OF MATERIALS     28

3.3 MEDIA USED AND THEIR PREPARATION     28

3.4 MICROBIOLOGICALANALYSIS OF SAMPLES     29

3.4.1 SERIAL DILUTION      29

3.4.2 ISOLATION AND ENUMERATION       29 

3.5 CHARACTERIZATION AND IDENTIFICATION OF THE BACTERIAL ISOLATES 30

3.5.1 PURIFICATION AND STORAGE OF THE ISOLATES 30

3.5.2 COLONIAL MORPHOLOGY 30

3.5.3 GRAM STAINING   30

3.5.4 BIOCHEMICAL TESTS   31

3.5.4.1 CATALASE TEST    31

3.5.4.2 COAGULASE TEST    32

3.5.4.3 INDOLE TEST     32

3.5.4.4 METHYL RED TEST      32

3.5.4.5 VOGES PROSKAUER TEST       33

3.5.4.6 CITRATE UTILIZATION TEST       33

3.5.4.7 OXIDASE TEST        34

3.5.4.8 SUGAR FERMENTATION TEST       34

3.6 IDENTIFICATION AND CHARACTERIZATION OF THE FUNGAL ISOLATES

CHAPTER FOUR

RESULTS        36

4.1 RESULTS 36

CHAPTER FIVE

DISCUSSION, CONCLUSION AND RECOMMENDATIONS

5.1 DISCUSSION 42

5.2 CONCLUSION   45

5.3 RECOMMENDATIONS 45

REFERENCE   47