ABSTRACT
In this study, yoghurt was produced using a combination of Streptococcus thermophillus, Lactobaccillus bulgaricus and Lactobaccillus acidophillus as starter culture. Citrullus lanatus (watermelon) and Citrus aurantifolia (lime), blended at a ratio 98:2, 95:5, 90:10, 85:15, 80:20 and 75:25 respectively were used to produce wine using Saccharomyces cerevisiae. The six wine samples were mixed with the yoghurt at a ratio of 50:50 and evaluated for nutritional, sensory and microbial properties using the whole yoghurt sample as control. The percentage fat, crude protein, carbohydrate, moisture and ash content of all the samples ranged from 0.151 to 3.15 %, 0.612 to 8.50 %, 4.10 to 8.31 %, 83.42 to 91.04 % and 0.42 to 0.73 % respectively, sodium, calcium, magnesium, phosphorus and potassium content of all the samples ranged from 1.00 to 37.00 mg/100g, 0.07 to 13.70 mg/100g, 9.03 to 12.00 mg/100g, 11.20 to 140.00 mg/100g, and 119.00 to 145.00 mg/100g respectively. Vitamin C and vitamin A contents of the samples ranged from 0.51 to 13.38 mg/100g and 102.30 to 560.62 IU respectively, the TTA, pH and Total solids content of the samples ranged from 1.31 to 1.71 %, 3.35 to 4.25 and 1.52 to 16.50 % respectively, sensory scores for appearance, taste, aroma and general acceptability ranged from 8.37 to 7.39, 8.70 to 7.10, 8.35 to 7.40 and 8.71 to 6.98 respectively, Total fungal count and Total coliform count of all the samples were <101 CFU/ml while the Total lactic acid bacteria count for all the samples ranged from <101 to 1.30×109 CFU/ml respectively. During assessment for 21 days, the pH of all the samples ranged from 3.61 to 4.25. There was no coliform detected. The total lactic acid bacteria count ranged from 8.05×107 CFU/ml to 1.30×109 CFU/ml while changes noticed for total fungal count during storage ranged from 4.0×101 CFU/ml to 2.5× 103 CFU/ml. Lactobaccillus acidophillus was detected from all the samples throughout storage and Esters were suspected to have been formed from the interaction between alcohol and lactic acids.The result of the evaluation showed a significant decrease (p< 0.05) in fat content, crude protein, ash content, sodium, magnesium, phosphorus, potassium, pH, total solids, sensorial taste and total viable count of lactic acid bacteria, while a significant increase (p< 0.05) in carbohydrate content, moisture, calcium, vitamin C, vitamin A, TTA, sensorial appearance, aroma and general acceptability.
TABLE OF CONTENTS
DECLARATION
i
DEDICATION
ii
CERTIFICATION
iii
ACKNOWLEDGEMENT
iv
TABLE OF CONTENTS
v
LIST OF TABLES
vii
LIST OF FIGURES
viii
LIST OF PLATES
ix
ABSTRACT
x
CHAPTER 1: INTRODUCTION 1
1.1: Background Information
1
1.2: Statement of Problem 2
1.3: Justification 3
1.4: Objective of the Study
3
1.5: Specific Objectives
4
CHAPTER 2: LITERATURE REVIEW 5
2.1: Fermented Foods
5
2.2:Overview of Yoghurt
6
2.3: Nutritional Composition of
Yoghurt 8
2.4:
Yoghurt Production 8
2.5:
Biochemical Reactions During Yoghurt Production 9
2.6: Sensory Attributes of Yoghurt
11
2.7: Volatiles Found In Yoghurt
12
2.8: Health Benefits of Yoghurt Consumption
15
2.9:
Spoilage of Yoghurt 16
2.10:
Overview of Watermelon 18
2.11:
Nutritional Composition of Watermelon.
20
2.12: Health Benefits of Watermelon
Consumption 21
2.13:
Chemical/Nutritional Composition of Citrus Lime 22
2.14: Health Benefits of Lime 23
2.15: Nutritional Value of Wines 24
2.16:
Side Effect of Wine Consumption
25
2.17: Health
Benefits of Wines 25
CHAPTER 3: MATERIALS AND METHODS 27
3.1.0: MATERALS 27
3.2.0: METHODS 27
3.2.1:
Starter preparation
27
3.2.2:
Must preparation
27
3.2.3:
Innoculation of the yeast strain
29
3.2.4:
Yoghurt preparation
29
3.3:
Determination of Physico-chemical Qualities
32
3.4: Determination of Minerals
38
3.5:
Sensory Evaluation
39
3.6:
Microbiological Analysis
39
3.7: Isolation and Identification of
Microbial Organisms
40
3.8:
Statistical Analysis
40
CHAPTER 4: RESULTS
AND DISCUSSION 42
CHAPTER 5:
CONCLUSION AND RECOMMENDATION 75
REFERENCE 78
APPENDIX 10
LIST
OF TABLES
4.1: Alcohol
by volume and specific gravity of wine samples.
4.2: Proximate composition of all
the samples.
4.3: Mineral
composition of the yoghurt and yoghurt incorporated Watermelon and Lime wine
blends in (mg/100g).
4.4:
Vitamin composition of the Yoghurt and Yoghurt incorporated Watermelon and Lime
wine blends.
4.5: Total titratable acidity, Hydrogen
ion concentration and Total solids content of the samples.
4.6: Sensory characteristics of the
samples.
4.7:
The microbial population of Samples in Colony forming units (CFU/ml).
4.8:
Sensory characteristics of the Yoghurt and Yoghurt incorporated Watermelon and
Lime wine blends on Day 0
4.9:
Sensory characteristics of the Yoghurt and Yoghurt incorporated Watermelon and
Lime wine blends on Day 7.
4.10:
Sensory characteristics of the Yoghurt and yoghurt incorporated Watermelon and
Lime wine blends on Day 14.
4.11:
Sensory characteristics of the Yoghurt and Yoghurt incorporated Watermelon and
Lime wine blends on Day 21.
4.12:
Showing the Changes in hydrogen ion concentration (pH) of the Yoghurt and
Yoghurt incorporated Watermelon and Lime wine blends.
4.13:
Total fungal count of the Yoghurt and Yoghurt incorporated Watermelon and Lime
wine blends in (CFU/ml).
4.14:
Total coliform count of the Yoghurt and Yoghurt incorporated Watermelon and
Lime wine blends in (CFU/ml).
4.15:
Total lactic acid bacteria count of the Yoghurt and Yoghurt incorporated
Watermelon and Lime wine blends in (CFU/ml)
LIST
OF FIGURES
3.1:
Flowchart for production of samples
4.1:
Sample codes
LIST OF
PLATES
3.1: Citrus
aurantifolia must.
3.2: Citrullus
lanatus must.
3.3: Blends of citrullus
lanatus and citrullus aurantifolia
must blends at varying ratios .
3.4: The produced yoghurt
3.5: The wine products
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND
INFORMATION
Yogurt is a fermented dairy food product made
by bacterial fermentation of liquid milk.(Chandan and Kilara., 2011). According
to(Chandan et al., (2008), It is a
semi solid fermented product made from heat-treated and standardized milk mixed
by the activity of a symbiotic blend of Lactobacillus delbruckii Bulgaricus
and Streptococcus thermophilus. Yoghurt
is widely consumed as a highly nutritious food as well as for its sensory
properties. It contains a reasonable level of animal protein, carbohydrate and
certain vitamins and minerals. Apart from the conversion of milk sugar
(lactose) to lactic acid, the addition of probiotic
bacteria (Lactobacillus acidophillus)
to yoghurt during its production also improves its functionality and health
benefits.
Watermelon (Citrullus
lanatus), is botanically considered as a fruit. It belongs to the Cucurbitaceae family (Edwards et
al., 2003). The fruit is
said to contain about 93 % water, hence, the name “water” melon. Watermelon is
said to be an economically important/indispensable fruit crop and valuable
alternative source of drinking water in the desert areas. Its nutritional profile includes sugar, carbohydrate,
soluble and insoluble fiber, sodium, vitamins, fatty acids, amino acids and
more. (Charoensiri et al.,2009). According to (Altas
et al., 2011), over 50 % of the
constituent of watermelon are readily fermentable liquid. It is a valued source
of natural antioxidants with special reference to lycopene, ascorbic acid, phytoene,
lutein, beta-carotene, citrulline, phytofluene and neurospnene. However, the
acidity of the juice of watermelon is low.
Lime (Citrus aurantifolia), usually referred to as
key lime belongs to a
genus known as flowering plants, in the family Rutaceae ( Lucker et al.,2002).
Its juice has acidic vesicles and has higher sugar and acid content than do
lemons (Encyclopaedia Britannica Inc, 2016). Its juice also has food and medicinal values. It contains nutrients such as vitamin
C, folic acid, carotenoids, dietary fibres, potassium, selenium and a wider
range of phytochemicals.
(Silalahi., 2002).
It is usually used to accent to the
flavour of foods, beverages as well as in the manufacture of food supplements.
Wine is a beverage which has alcoholic
tendencies and is usually produced by fermenting fruit juices. Foods can be
nutritionally enriched by adapting nutrients from other food sources. This may
be done by blending food products with the desired nutrient composition with
the food desiring nutrient improvement or enrichment. However foods to be
blended must be compatible with each other.
1.2 STATEMENT OF PROBLEM
Probiotic
yoghurts are known to be nutritionally rich in some animal nutrients but are
very deficient in other essential nutrients such as vitamin C, Calcium etc. As
such, they are only best suited for lactose intolerant patients and for
replenishment of the intestinal flora of the gut. Watermelon juice, famed for
its low acidity having high moisture content and a hydrogen ion concentration
near neutrality- responsible for its ease of deterioration on standing contains
a reasonable amount of plant nutrients including vitamin C, calcium,
carotenoids such as lycopene and citrulline. Citrus lime juice, famed for its high acidity, contains natural
acids such as ascorbic acid, flavonoids and phyto-chemicals such as coumarin
and psolaren.
This work tries to
improve probiotic yoghurt nutritionally by addition of wine produced from
blends of watermelon and lime fruit juices. Watermelon fruit juice is a low
acid food with high amount of water. It deteriorates easily on standing which
is why packaged watermelon drinks are rarely seen in the open market. The
choice of citrus lime in the blends was for its reasonable content of vitamin C
and also to guard against easy deterioration of the blends. The blends were
fermented so as to further acidify the blend all in a bid to reduce the
vulnerability of the final product from spoilage. A mix of watermelon and lime
juices blended into yoghurt should normally improve it nutritionally.
Physical,
chemical, biological reactions that may occur due to yoghurt-watermelon and
lime wine interaction are unknown. The effect of wine produced from watermelon
juice and citrus lime fruit juice on the nutritional, microbial and sensory
characteristics of yoghurt containing a probiotic bacteria may be desirable or un-desirable
and needs to be studied to detail.
1.3 JUSTIFICATION
Some
beverages sold in the open market were produced by blending high alcoholic
drinks produced from fruit juices with diary based food products. Armed with
the many health benefits of probiotic yoghurt, Water-melon and Citrus lime
juices, the success of this work will not only be a dream-come true for the
health sector but also to local and international food processors and consumers
as well. At least it will help bring to
bare the merits and demerits of blending wine from fruit juices with yoghurt
samples containing live microbial cultures for all to see. It will also reduce
the high post harvest losses/waste incurred from spoilage of watermelon and
lime in several open markets due to low patronage. It will also aid at
presenting final consumers with a high nutritionally valued and thirst
quenching beverage if the research results become positive.
1.4 OBJECTIVE OF THE STUDY
The
major aim of this work was to adapt/introduce the nutritional constituents of wine
produced from blends of water melon (Citrus
lanatus) and lime (Citrus
aurantifolia) fruit juices into probiotic yoghurt and evaluate the nutritional,
microbial and sensory qualities of the products.
1.5 SPECIFIC OBJECTIVES:
The specific objectives of this study
were
i. To introduce wine produced from
watermelon and citrus lime juices into yoghurt.
ii.
To carry out nutritional and sensory quality of the probiotic yoghurt, water
melon-citrus lime wine and probiotic yoghurt incorporated water melon-citrus
lime wine.
iii.
To determine microbial quality of the probiotic yoghurt, water melon-citrus
lime wine and probiotic yoghurt incorporated water melon-citrus lime wine.
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