PRODUCTION AND QUALITY EVALUATION OF SPOONABLE AND DRINKABLE YOGHURT WITH WATERMELON (Citrullus lanatus) JUICE AND PULP

ABSTRACT

Yoghurt was produced and flavoured with graded levels of watermelon pulp and juice. Watermelon (Citrullus lanatus) juice and pulp was used to substitute 0, 10, 20, 30, 40 and 50% of yoghurt. The chemical, sensory and microbiological properties of the yoghurts were determined. The results showed that the pH of the yoghurt ranged from 4.68 to 4.90. The protein, ash, and fat content decreased with increase in watermelon juice and pulp. The fiber content increased with the watermelon pulp while the moisture content increased with increase in watermelon juice. Micro-nutrient (vitamin A and C) increased with increased level watermelon juice and pulp in the yoghurt while sodium decreased with increased level watermelon juice and pulp in the yoghurt. Lactose content increased with increased watermelon juice and pulp content of the formulated yoghurt. The total viable count and lactic acid bacteria ranged from 1.15×10⁵ to 2.1 ×10⁵cfu/ml and 3.8×10³ to 1.3 x 10⁴cfu/ml, respectively. High mean values (8.35) were obtained for the plain yoghurt (control) for all sensory attributes (colour, flavour, taste, aftertaste, consistency and mouthfeel), therefore making the plain yoghurt most preferred sample with an overall acceptability of 8.35. Sample PY+ WMJ (90:10) had the highest mean for general acceptability (7.00) compared to the other flavoured yoghurt in overall preference. Samples containing 10 and 20 % of watermelon pulp and juice in yoghurt were generally acceptable while samples containing 30, 40 and 50 % of the juice were generally unacceptable. There was no significant (p<0.05) difference between the plain yoghurt and the flavoured yoghurt sample PY+WMJ (90:10) while the difference with the flavoured yoghurt containing 10 % watermelon pulp was significant (p<0.05).

TABLE OF CONTENTS

Title page

Abstract

Table of content

List of tables’

List of figures

List of appendices

CHAPTER ONE: INTRODUCTION

1.1 Statement of problem

1.2 Aims and objectives

1.3 Justification of the study

1.4 significance of the study

CHAPTER TWO: LITERATURE REVIEW

2.1.1    Yoghurt

2.1.1    Types of yoghurt

2.1.2    Special types of yoghurt

2.1.3    Varieties of yoghurt

2.1.4    Raw material for yoghurt production

2.1.5    Yoghurt production

2.16.Nutritional composition of yoghurt

2.1.7    Benefit of yoghurt

2.1.7.1 Nutraceuticals benefits of yoghurt

2.1.7.2 Therapeutic benefits of yoghurt

2.1.8    Preservation of yoghurt

2.2       Watermelon

2.2.1    History of watermelon

2.2.2    Varieties of watermelon

2.2.3    Harvesting of watermelon juice

2.2.5    Pest and diseases of watermelon

2.2.5.1 Processing of watermelon

2.2.6    Nutritional benefits of watermelon

2.2.7    Health benefits of watermelon

2.2.8    Arginine benefits of watermelon

2.2.9    Importance of watermelon

2.2.9.1 Uses of watermelon

CHAPTER THREE: MATERIALS AND METHODS

3.1       Procurement of raw materials

3.2       Processing of samples

3.2.1    Production of watermelon juice and pulp

3.2.2    Production of spoonable and drinkable yoghurt

3.2.3    Proportion for the formulation of spoonable and drinkable yoghurt

3.3       Sample analysis

3.3.1    Proximate composition of the flavoured spoonable and drinkable yoghurt

3.3.2    Determination of moisture content of the formulated flavoured yoghurt

3.3.3    Determination of crude protein content of the formulated flavoured yoghurt

3.3.4    Determination of crude fibre content of the formulated flavoured yoghurt

3.3.5    Determination of crude fat content of the formulated flavoured yoghurt

3.3.6    Determination of ash content of the formulated flavoured yoghurt

3.3.7    Determination of carbohydrate of the formulated flavoured yoghurt

3.4       Determination of pH of the flavoured spoonable and drinkable yoghurt

3.4.1    Determination of total titrable acidity (TTA) of the flavoured spoonable and drinkable yoghurt

3.4.2    Determination of total solid of the flavoured spoonable and drinkable yoghurt

3.4.3    Determination of lactose content of the flavoured spoonable and drinkable yoghurt

3.4.5    Determination of vitamin A content of the formulated spoonable and drinkable yoghurt

3.4.6    Determination of vitamin C content of the formulated spoonable and drinkable yoghurt

3.5.      Determination of potassium content of the formulated spoonable and drinkable yoghurt

3.5.1    Determination of sodium content of the formulated spoonable and drinkable yoghurt

3.6       Microbial analysis of the formulated spoonable and drinkable yoghurt

3.6.1    Determination of total viable count of the formulated spoonable and drinkable yoghurt

3.6.2    Determination of lactic acid bacteria (LAB) of the formulated spoonable and drinkable yoghurt

3.7       Sensory evaluation of the formulated spoonable and drinkable yoghurt

3.8       Data analysis and experimental design of the formulated spoonable and drinkable yoghurt

CHAPTER FOUR: RESULTS AND DISCUSSION

4.1       Proximate composition of yoghurt blended with graded levels of watermelon juice and Pulp

4.2       Micro-nutrient composition of yoghurt flavoured with graded levels of watermelon juice and pulp

4.3       Physico-chemical properties of yoghurt flavoured with graded levels of watermelon juice and pulp

4.4       Microbial count (cfu/ml) of yoghurt flavoured with graded levels of watermelon juice and pulp

4.5       Sensory scores of yoghurt flavoured with graded levels of watermelon pulp

4.6       Sensory scores of yoghurt flavoured with graded levels of watermelon juice

CHAPTER FIVE:

Conclusion and Recommendations

Contribution to knowledge

REFERENCES

APPENDICES

CHAPTER ONE

1.0                                                                    INTRODUCTION

Yoghurt is a food obtained by controlled fermentation of milk by a mixed culture consisting of Lactobacillus bulgaricus (or occasionally acidophilus) and Streptococcusthemophilus selected to produce flavor and typical aroma according to Schmidt (1992). The milk sugar (lactose) is fermented to lactic acid and it causes the characteristic curd. The lactic acid lowers the pH, makes it dart, causes the milk protein to thicken and act as a preservative since pathogenic bacteria cannot grow in an acid condition. The partial digestion of the milk when these bacteria ferment the milk makes yoghurt easily digestible (David, 2003). Under proper storage conditions, yoghurt could be kept safe for up to ten days. According to Bystron and Molenda (2004), fermentation ensures not only increased shelf-life and microbial safety but also makes food more digestible while preservation by fermentation depends on the anaerobic enzymatic conversion of organic compounds especially carbohydrates to simple end product. Generally organic acid, ethyl alcohol and carbon (IV) oxide. The formulation of yoghurt varies considerably, depending on the style that is being produced (Ramesh et al., 2006).

To modify certain properties of yoghurt, various ingredients may be added for instance, to sweeten yoghurt, sucrose may be added, and cream could also be added to provide texture. The consistency and shelf stability of the yoghurt could be improved by adding stabilizers such as food starch, gelatin, locust bean gum, guar gum and pectin. To improve taste and flavor, many kinds of fruits may be added (Tamine and Robinson, 1986). Recently, manufacturers have become so creative in the type of yoghurt they produce by using natural or artificial flavor to boost their product. Some of the exotic products in existence are: vanilla, orange, pineapple, strawberry, raspberry, milk, cinnamon among others. According to Elson and Haas (2005), yoghurt is not just a food accompaniment, desert, or mainly a diet food, it is considered as health food because of its therapeutic value. The ability of yoghurt to help in the digestion of lactose in lactose intolerant patients is only achieved with live flora Bresson (2002). In the processing of flavored yoghurt, natural fruit would be used. However, fruit may be taken in their fresh forms but because of their outstanding perishable and seasonal nature, a lot of fruits are processed traditionally where a food processing culture exist. According to Okaka (2007), processing of fruits reduces post-harvest losses and spreads its availability over the year. According to Enwere (1998), fruits may be processed into other products or used as ingredient in various foods and are processed depending on the desired end product. These fruits are prone to post harvest loses and so may be processed and incorporated into food product to extend its shelve life. Example of product in which fruits can be processed into includes: concentrated juice, canned juice etc. The pulp of the fruit is the stingy content of the fruits endocarp. It contains juice of the fruit and the nutrients. The colour of fruit pulp varies according to the specie of the fruits, ripening stage, maturity among others.

Some indigenous fruits exist which includes watermelon (Citrullus lanatus Thumb) have already been established as a flavouring agent or a special flavour that are generally liked by people who have known its benefits, function and how it will improve the colour and taste of yoghurt. Watermelon is a wine like Scrambler and Traiter flowering plant originally from Southern Africa, a creeping annual fruit which belong to the gourd (Cucurbitaceae) family. Shortly after the discovery of the new world, it was brought to China in the 10^th century and then the western hemisphere. Although they are found in the market variably throughout the year. The season for watermelon is the summer season or during the dry periods. According to Wikipedia,.(2013), watermelon fruit are classified according to different varieties which are yellow watermelon, orangeglo, the moon and stars variety....

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