DEVELOPMENT OF LACTIC ACID BACTERIA STARTER CULTURE FOR USE IN YOGHURT PRODUCTION

ABSTRACT

Lactic Acid Bacteria (Lactobacillus acidophilus, Lactobacillus plantarium, and Bifidobacterium) isolated from fermented Ogi and Breast milk using MRS agar medium and a commercially acquired lactic acid bacteria (LAB) were used to produce yoghurt samples. Fermented Ogi and breast-milk samples was appropriately diluted and plated out on the MRS Agar using pour plate method. The plates were incubated under 35oC-37oC and at different pH for 48 hours under Micro aerophilic condition using excello anaerobic jar. The effect of varied temperature and pH on the growth of the isolates was investigated to determine the optimum temperature and pH for the growth of the organism. The isolates and the commercially acquired Lactic acid bacteria were used to produce Yoghurt samples A-D from DANO powdered milk in an 8 hours fermentation process. The fermented product was used to compare favourably against the commercial product in terms of both nutritional and sensory attributes. The three LAB isolates were used singly as starter culture. The optimum pH for the Yoghurt production was 5.5 while the optimum temperature is 40oC. The Yoghurt sample C had the highest pH (6.60 ± 0.00; p<0.05) and highest moisture content (88.10 ± 0.04; p<0.05), the highest protein content was from sample A and D (control). Sample A has the highest crude fat (0.85 ± 0.00; p<0.05) ash content was highest in sample D (control) (3.29 ± 0.05; p<0.05) and the fibre content of the Yoghurt was: 0.14 ± 0.02; p<0.05. It was therefore concluded that L. acidophilus, L. plantarium and Bifidobacterium can be used in Yoghurt production as a starter culture which are sourced from breast-milk and fermented Ogi. However, Bifidobacterium are more suitable for use as starter culture than the others.

TABLE OF CONTENTS

Title page                                                                                                                                i

Certification                                                                                                                           ii

Dedication                                                                                                                              iii

Acknowledgements                                                                                                                iv

Table of Contents                                                                                                                   v

List of Tables                                                                                                                          viii

List of Figures                                                                                                                         ix

Abstract                                                                                                                                  x

CHAPTER ONE

1.0       Introduction                                                                                                                1

1.1       Aims and Objectives                                                                                                  2

CHAPTER TWO: LITERATURE REVIEW

2.1       Lactic Acid Bacteria                                                                                                   3

2.1.1    Sources of Lactic Acid Bacteria                                                                                 4

2.1.2    Conditions that favour the growth of Lactic Acid Bacteria (LAB)                                    5

2.1.3    Classification and Uses of Lactic Acid Bacteria                                                        7

2.1.4    Uses of Lactic Acid Bacteria                                                                                      8

2.2       Yoghurt and Its Components                                                                                      9

2.2.1    Other Components of Yoghurt                                                                                   11

2.3       Milk and Its Constituents                                                                                            11

2.3.1    Water in Milk                                                                                                             12

2.3.2    Fat of Milk                                                                                                                  12

2.3.3    Protein                                                                                                                         12

2.3.4    Lactose                                                                                                                        13

2.3.5    Ash or Mineral Matter (Salts of Milk)                                                                       13

2.3.6    Vitamins in Milk                                                                                                        14

2.3.7    Microorganisms in Milk                                                                                             14

2.3.7.1 Lactic Acid Bacteria                                                                                                   14

2.3.7.2 Coliforms                                                                                                                    15

2.3.7.3 Spoilage Microorganisms in Milk                                                                              15

2.3.7.4 Pathogenic Microorganisms in Milk                                                                          15

2.4       Significance of Microorganisms in Milk                                                                    16

2.5       Yoghurt Starter Cultures                                                                                            16

2.5.1    Selection of Pure Culture                                                                                           17

2.6       Classification of Yoghurt                                                                                           17

2.7       Health Benefits Effect of Yoghurt                                                                              19

2.8       Uses of Yoghurt                                                                                                          21

CHAPTER THREE: MATERIALS AND METHODS

3.1       Sample Collection                                                                                                      22

3.2       Sample Preparation                                                                                                    22

3.3       Bacterial Strains and Growth Conditions                                                                   22

3.4       Isolation of Lactic Acid Bacteria (LAB)                                                                    23

3.5       Determination of Bacterial load at Different Temperature and Pressure Using

            Direct Plate Count                                                                                                      23

3.6       Identification and Characterization of Bacterial Isolates                                           23

3.6.1    Macroscopic Examination                                                                                          24

3.6.2    Gram Staining Reaction (Microscopic Examination)                                                24

3.6.3    Biochemical Reaction Test                                                                                         24

3.7       Measurement of pH                                                                                                    28

3.8       Determination of Titratable Acidity                                                                           28

3.9       Proximate Analysis                                                                                                     28

3.9.1    Determination of Moisture Content                                                                           28

3.9.2    Ash Determination                                                                                                     29

3.9.3    Determination of Protein                                                                                            30

3.9.4    Determination of Carbohydrate Content                                                                    31

3.9.5    Determination of Fat Content                                                                                     31

3.10     Sensory Properties of Yoghurt Samples                                                                     32

CHAPTER FOUR

4.0       Results                                                                                                                        33

CHAPTER FIVE: DISCUSSION, CONCLUSION AND RECOMMENDATION

5.1       Discussion                                                                                                                   42

5.2       Conclusion                                                                                                                  45

5.3       Recommendation                                                                                                       46

References                                                                                                                             47                                                                                           

LIST OF TABLES

Table 4.1: Characterisation of Lactic Acid Bacteria isolated from both Ogi and Breast Milk                                33

Table 4.2: (%) Occurrence of LAB isolates in ogi and bread milk as sources for starter culture development        34

Table 4.3: Quality Characteristics of Yoghurt Produced with LAB starter cultures                       36

Table 4.4: Proximate composition of 2 Yoghurt produced with LAB starter cultures (%)     38

Table 4.5: Mean Sensory scores of acceptability of yoghurts produced with LAB starter cultures                        40

LIST OF FIGURES

Figure 3.1: Flow chart of Yoghurt Production                                                                      27

CHAPTER ONE

1.0       INTRODUCTION

Many Lactic bacteria strains, characterized as probiotics, have been proven to beneficially affect humans or animals by improving the properties of their indigenous gut flora (Fuller 2011; Havenaar and Huis int Verd, 2012). The incorporation of potentially probiotic lactic acid bacteria of human origin in traditional fermented foods has been established in the dairy industry, leading to the production of different types of fermented milks and yoghurts (Gomes and Malcata, 2014). Strains of the lactobacillus genus, such as Lactobacillus acidophilus, Lactobacillus caseiand Lactobacillus paracasei, Lactobacillus bulgaricus constitute significant proportion of the lactic acid bacteria used in commercial probiotic-based milk products (Shorrt, 2014). New applications of probiotic microorganisms in foods have been introduced into the market or are still in the developmental phase such as frozen yoghurt, soy yoghurt, ice cream bread and chocolate (De Vuyst, 2010).

Probiotic products are usually standardized, based on the presumption that culture viability is a reasonable measure of probiotic activity, thus the ability the strain to attain high cell population is of primary importance. A concentration of approximately 10⁷ ml^-1at the time of consumption is considered functional (Gomes and Macata, 2014; Shortt, 2014). High cell growth and acidification would also result in the reduction of fermentation time and enhance the viability of the specific strain by preventing of undesirable microorganism present in the raw material (Mark Linder and Lonner, 2012). A starter culture are those microorganism that are used in the production of cultured products such as yoghurt and cheese. The natural microflora of the natural substrate is either inefficient, uncontrollable and unpredictable or is destroyed altogether by the heat treatments given to the substrate. Traditional methods are still used in producing some products but advances in starter technology, especially in selection, maintenance, freezing and lyophilisation of commercial starter, have brought starter availability, flexibility and reliability to product manufacturers (Cogan and Accolas, 2016). Lactobacilli are very fastidious microorganisms that require fermentable carbohydrates, vitamins and nucleic acids and minerals to grow regardless of the specific nutrient requirements of the strain (Gomes and Macata, 2014). Thus the substrate composition and nutritional requirements of the strain considerably affect the overall performance of the fermentation. A number of studies on the development of food fermentation process based on the use of cereal and vegetable substrates have been reported (Caralampopoulos et al., 2014; Yoon et al., 2016; Demir et al., 2017). Microbial growth on these substrates depends on the environmental factors such as pH, temperature and accumulation of metabolic end products. However, as natural fermentation rely on microbial populations present in the raw material, these products exhibits substantial variations in flavor and quality (Giraud et al., 2011). The good adaptation of lactic acid bacteria in cereals and vegetables suggests that utilization of a potentially probiotics strains as starter culture in these substrate other than milk would produce a fermented food with defined and consistent characteristics and possibly health promoting properties.

1.1       AIMS AND OBJECTIVES

The objectives are:

1.         To isolate, identify and characterize different genera of lactic acid bacteria from fermenting milk capable of being used as probiotic strains.

2.         To study the key factors influencing the growth and embolic activity of the strains.

3.         To use the isolated organism as starter culture to produce yoghurt as probiotic food

Buyers has the right to create dispute within seven (7) days of purchase for 100% refund request when you experience issue with the file received. 

Dispute can only be created when you receive a corrupt file, a wrong file or irregularities in the table of contents and content of the file you received. 

ProjectShelve.com shall either provide the appropriate file within 48hrs or send refund excluding your bank transaction charges. Term and Conditions are applied.

Buyers are expected to confirm that the material you are paying for is available on our website ProjectShelve.com and you have selected the right material, you have also gone through the preliminary pages and it interests you before payment. DO NOT MAKE BANK PAYMENT IF YOUR TOPIC IS NOT ON THE WEBSITE.

In case of payment for a material not available on ProjectShelve.com, the management of ProjectShelve.com has the right to keep your money until you send a topic that is available on our website within 48 hours.

You cannot change topic after receiving material of the topic you ordered and paid for.