PRODUCTION AND PROXIMATE ANALYSES OF YOGHURTS FROM TIGER NUTS AND SOYBEAN USING LACTIC ACID BACTERIA AS STARTER CULTURES

ABSTRACT

The aim of this study was to produce tiger nut and soybean yoghurt and determine it’s proximate values. The yoghurt was produced by inoculation of isolates of lactic acid bacteria (Lactobacillus acidiophilus, Lactobacillus Bulgaricus and Streptococcus thermophilus) into milk extract of tiger nut and soybean. pH, temperature, optical density, titratable acidity, sensory characteristics and proximate composition of produced samples were analyzed. After fermentation, tiger nut yoghurt had the lowest pH (3.6) while the commercial milk yoghurt had initial pH of 6.0. The tiger nut yoghurt and soybean yoghurt had optimum fermentation temperature of 31.50C while the dairy milk yoghurt had a maximum fermentation temperature of 290C. The tiger nut yoghurt had a maximum optical density of 1.39 while the lowest optical density (1.13) was recorded in dairy milk yoghurt. Tiger nut had a maximum titratable acidity of 1.38 while the dairy milk yoghurt had the lowest titratable acidity of 0.52.The proximate result showed that the soy milk yoghurt had the highest protein and fiber content (3.69 ±0.10 and 0.39±0.03) respectively. The commercial dairy milk had the highest fat (3.87 ±0.03), ash (2.96 ±0.16) and moisture (87.54±0.07) content while tiger nut yoghurt had the highest carbohydrate content (4.90±0.31). Yoghurts from tiger nut and soybean were considered generally accepted based on the sensory evaluation by 11 man panel. The results obtained from this study shows that it is possible to produce yoghurts using tiger nut and soybean which are beneficial to human health compared to yoghurt produced from dairy milk.

TABLE OF CONTENTS

Title Page                                                                                                                    i

Certification                                                                                                               ii

Dedication                                                                                                                  iii

Acknowledgements                                                                                                    iv

Table of contents                                                                                                        v

List of tables                                                                                                               ix

Abstract                                                                                                                      x

CHAPTER ONE

1.0       Introduction                                                                                                    1

1.1       Scope of study                                                                                                2

1.2       Statement of Problem                                                                                     3

1.3       Significance of the Study                                                                               3

1.4       Aims and Objectives                                                                                      4

CHAPTER TWO

2.0       Literature Review                                                                                           5

2.1       Chemical Structure of Yoghurt                                                                      5

2.2       Starter Culture                                                                                                5

2.3       Important Metabolic Activities of Yoghurt Technology                               6

2.3.1    Acid Production                                                                                              7

2.3.2    Flavour Compounds of Yoghurt                                                                     7

2.3.3    Production of Polysaccharides                                                                       8

2.3.4    Proteolytiç Activity                                                                                        8

2.3.5    Urease Activity                                                                                               9

2.4       Interaction between Yoghurt Bacteria                                                           10

2.5       Health Concerns/ Challenges about Dairy Milk                                             10

2.5.1    Fat Content and Cardiovascular Diseases                                                      10

2.5.2    Dairy and Cancer                                                                                            11

2.5.3    Lactose Intolerance                                                                                        11

2.5.4    Dairy Contaminants                                                                                       12

2.5.5    Dairy Protein and Diabetes                                                                            13

2.6       Tiger Nut                                                                                                        13

2.6.1    Uses and Product                                                                                            14

2.6.2    Economic and Nutritional Benefits of Tiger Nut                                           16

2.7       Soybean                                                                                                          17

2.7.1    Physical Characteristics                                                                                 17

2.7.2    Chemical Composition of Soybean                                                                18

2.7.3    Soybean and Health                                                                                        18

2.7.3.1 Effects on Hypercholesterolemia and Cardiovascular Diseases                        19

2.7.3.2 Effects on Osteoporosis and Menopause                                                        20

2.7.3.3 Hypertension Activity                                                                                    20

2.7.3.4 Effects on Insulin Secretion and Energy Metabolism                                                20

CHAPTER THREE

3.0       Materials and Methods                                                                                   21

3.1       Source of Materials                                                                                        21

3.2       Isolation of Lactic Acid Bacteria                                                                   21

3.3       Gram Staining                                                                                                22

3.4       Motility Test                                                                                                   22

3.5       Biochemical Tests                                                                                          23

3.6       Milk Extraction                                                                                              25

3.7       Production of Yoghurt                                                                                    25

3.8       Proximate Analysis                                                                                         26

3.8.1    Determination of Total Solids/ Moisture Content                                          26

3.8.2    Determination of Ash Content                                                                       26

3.8.3    Determination of Fat Content                                                                         27

3.8.4    Determination of Protein Content                                                                  27

3.8.5    Determination of Crude Fibre                                                                        28

3.8.6    Determination of Carbohydrate                                                                      29

3.9       Sensory Evaluation                                                                                         29

3.10     Statistical Analysis                                                                                         29

CHAPTER FOUR

4.0       Results                                                                                                            30

CHAPTER FIVE

5.0       Discussion                                                                                                       36

5.1       Conclusion                                                                                                      39

5.2       Recommendation                                                                                           40

REFERENCES                                                                                                         41

LIST OF TABLES

Table 1            Microbiological Result of Isolates                                                     32

Table 2            Proximate Analysis of Yoghurt Samples                                           33

Table 3            Fermentation Parameters of Yoghurt Samples                                   34

Table 4            Sensory Analysis of Samples                                                             35

CHAPTER ONE

1.0       INTRODUCTION

Yoghurt and similar fermented milk products have been very popular for a long time in Mediterranean countries North Africa), (the Balkans, in central and southwest Asia (Mongolia, Turkey, Iraq, Iran, Syria) and in central Europe. In many of these countries, yoghurt is still manufactured using traditional procedures. Since the last world war, yoghurt consumption has been steadily increasing not only in European countries, but also in the United States, enhancing its industrial-scale production. At present, new types of fermented milk are available, prepared by adding fruits or flavouring, enriched with vitamins or containing selected intestinal bacteria such as Lactobacillus acidophilus Bifidobacterium and several species (Kurmann, 1984; Puhan, 1988).

ln France, the term "yoghurt" can be used legally only to designate the product resulting from milk fermentation brought about exclusively with 2 thermophilic lactic acid bacteria, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, which must be found alive in the final product.

Traditionally yoghurt is a fermented whole milk and is believed to possess nutritional and therapeutic properties (Reed, 1982; Hughes and Hoover, 1991). Attempt has been made to produce substitute for milk and milk products from legume. (Herrick, 1969; Steinkaus, 1976; Rao et al., 1988; Terna and musa, 1998). In the developing countries and indeed in the sub-saharan Africa (except east Africa), the production of milk and milk products is limited, scarce and expensive (Fashaken and Unokiwedi, 1992).These shortages have in no small measure adversely affected the protein intake of both the old and the young.

Several legume-based milk and milk products have been developed in attempts to extend the supply of milk-like products, especially in areas where milk is in short supply. Since legumes are important sources of relatively inexpensive protein, introduction of imitation milk products from legumes may contribute to the alleviation of protein malnutrition (Rao et al., 1988).

Lactic acid fermentation of legume based milks has been user as one of the approaches to prolong the shelf life of the product, create variety, improve the nutritional value and as well enhance the acceptability of the product. yoghurt-like product have been prepared by some workers from soybeans (Terna and Musa, 1988). Cowpeas and mung beans (Rao et al., 1988). Fashakin and Unokiwedi (1992) reported the production of waragusi (a soft unripe cheese-like product from water melon milk) an analogue of warankasi (unripe cheese product from cow milk). Since tigernut (family: Liliaceae) and coconut (cocosnucifers, family: palmae) grows extensively in Nigeria and are eaten as snacks usually for the pleasure of it, they may be excellent sources of raw material for the development of dairy-like products.

1.1       SCOPE OF STUDY

This research work is limited to use of lactic acid bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus) for the production of yoghurt using tigernut milk and soybean milk and proximate analysis of the sample.

1.2       STATEMENT OF PROBLEMS

Animal milk (cow, water Buffalos, goats, ewes, camels) is commonly available worldwide and as such is the milk most commonly used to make yoghurt. Dairy product (milk) are been consumed in substantial amounts despite scientific evidence that questions their health benefits and indicates their potential health risks. Consumption of dairy products has also been linked to higher risk for various cancers, especially to cancers of the reproductive system. Most significantly, dairy product consumption has been linked to increased risk for prostate and breast cancers. Lactose intolerance is common among many populations. The symptoms include gastrointestinal distress, diarrhea, and flatulence. Dairy products also contribute significantly to the amounts of cholesterol and saturated fat which can increase the risk of heart disease and can cause other serious health problems. Dairy products contains contaminants that range from pesticides,  Pesticides, polychlorinated biphenyls (PCBs), and dioxins and do not readily leave the body and can eventually build to harmful levels that may affect the immune, reproductive, and the central nervous systems.

1.3       SIGNIFICANCE OF THE STUDY

The study of this research topic will provide more constructive frame work to formations of creating a way of eradicating the health challenges and risk factors associated with dairy milk in yoghurt production.

The tigernut and as soybean apart from minimizing the risk factors associated with dairy milk it is necessary for bones, tissue repairs, muscles, growth and development of the body and rich in vitamin E and C. It is also recommended for those who suffer from indigestion, flatulence and diarrhea because it provides digestive enzymes like catalase, lipase and amylase. The high content of oleic acid effect on cholesterol thereby preventing heart attacks, thrombosis and activates blood content of soluble glucose. The plant milk also supplies the body with enough quantity of vitamin E essential for fertility in both men and women. The milk has a relatively high antioxidant capacity which is capable of protecting the body against malnourishment.

1.4       AIMS AND OBJECTIVES

1.         To isolate, characterize and inoculate lactic acid bacteria in milk sample, isolated from procured fermented milk product.

2.         To produce yoghurt from tiger nut and soybean using lactic acid bacteria.

3.         To evaluate the proximate attributes of soymilk and tiger nut yoghurts.

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