ABSTRACT
This study evaluated the physico-chemical, ambient storage stability and sensory properties of zobo as affected by processing methods. Fresh Hibiscus sabdariffa was washed properly and divided into four parts. The first part was boiled, the second part was milled and then boiled, and the third part was steeped for 5h and then boiled, while the last was milled and steeped for 5h and then boiled. The proximate composition of the drinks ranged from total solid (8.77 – 8.90g/100g); ash (0.32 – 0.39g/100g); fats (0.58-0.67g/100g); protein (0.35 – 0.45g/100g) and carbohydrate; (7.35 – 7.51g/100g). The pH ranged from 5.49 – 5.62(Day 0), 4.38 – 4.43(Day 3) and 3.48 – 3.63 (Day 5). The total titratable acidity ranged from 0.029 – 0.034 (Day 0), 0.051 – 0.059 (Day 3) and 0.082 – 0.099 (Day 5). The total soluble solid (0brix) ranged from 8.95 – 11.20 (Day 0), 7.50 – 9.50 (Day 3) and 5.60 – 6.50 (Day 5) specific gravity of the drinks decreased while the total titratable acidity of the drinks increased during storage with sample before steeped boiling retaining the quality of the drink better than the others. The result of the sensory evaluation showed that mill-boil enhanced the general acceptability of the zobo drink, while steeping before boiling enhanced the appearance of the drink.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of contents vi
List of Tables x
List of Figures xi
List of Plates xii
Abstract xiii
CHAPTER 1: INTRODUCTION
1.1 Background of the Study 1
1.2 Statement of the Problem 3
1.3 Justification of the Study 3
1.4 Objectives of the Study 4
CHAPTER 2: LITERATURE REVIEW
2.1 Overview of Zobo Drink 5
2.1.1 Preparation of zobo drink 6
2.1.2 Preservatives used in the preparation of zobo drink 8
2.1.3 Nutritional composition and health benefits of zobo drink 11
2.1.4 Microbiological quality of zobo drink 12
2.1.4.1 Sources of microbial contamination of zobo drink 15
2.1.4.1.1 The Roselle calyces used 16
2.1.4.1.2 Contamination during preparation 16
2.1.4.1.3 Contamination during packaging 17
2.1.4.1.4 Contamination during storage 17
2.1.4.2 Public health implications of microbial food safety and foodborne Diseases 17
2.2 Consumer Acceptability of Food 20
2.2.1 Impact of sensory attributes on food product's acceptability 21
2.2.1.1 Aroma 22
2.2.1.2 Taste 23
2.2.1.3 Texture 25
2.2.1.4 Appearance 26
CHAPTER 3: MATERIALS AND METHODS
3.1 Source of Materials 28
3.2 Sample Preparation 28
3.2.1 Production of zobo drinks 28
3.3 Methods of Analyses 32
3.3.1 Physiochemical Analysis on Zobo 32
3.3.1.1 Determination of pH 32
3.3.1.2 Determination of titratable acidity 32
3.3.1.3 Determination of total sugars (0brix) 32
3.3.1.4 Determination of specific gravity 33
3.3.1.5 Determination of total solid 33
3.4 Proximate Analysis 34
3.4.1 Determination of crude protein content 34
3.4.2 Determination of ash 34
3.4.3 Determination of fat content 35
3.4.4 Determination of carbohydrate content 35
3.5 Microbiological Analysis on Zobo 36
3.5.1 Media preparation 36
3.5.2 Microbial load enumeration 36
3.6 Sensory Evaluation 36
3.7 Experimental Design 37
3.8 Statistical Analysis 37
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Proximate Composition of the Zobo Drinks 38
4.2 pH and Total Titratable Acidity of the Zobo Drink 41
4.3 Total Titratable Acidity of the Zobo Drink 43
4.4 Total Soluble Solid (brixo) and Specific Gravity of the
Zobo Drinks 45
4.5 Microbial load count of the Zobo Drinks 48
4.6 Sensory evaluation of the Zobo Drinks 50
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 53
5.2 Recommendations 53
REFERENCES 54
APPENDIX 59
LIST OF TABLES
Table 3.1: Recipe for production of Zobo Drinks 30
Table 4.1: Proximate composition of Zobo Drinks (g/100g) 39
Table 4.2: pH of the Zobo drink samples 42
Table 4.3: Total titratable acidity of the Zobo Drinks 44
Table 4.4: Total Soluble Solid (brix) of the Zobo Drinks 46
Table 4.5: Specific Gravity of the Zobo Drinks 47
Table 4.6: Microbial Load Count of the Zobo Drinks Samples (cfu/ml) 49
Table 4.7: Sensory Evaluation of the Zobo Drink Samples 52
LIST OF FIGURES
Figure 3.1: Flow chart for processing of zobo 31
LIST OF PLATES
Plate 1: Zobo Leaves (Hibiscus sabdariffa) 60
Plate 2: Sugar 60
Plate 3: Ginger (Zinigiber officinale) 61
Plate 4: Clove (Syzygium aromaticum) 61
Plate 5: Tamarind (Tamarindus indica) 62
Plate 6a: Produced and Packaged Zobo 62
Plate 6b: Project student with Produced and Packaged Zobo 63
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
The increasing awareness in health and wellbeing has led to corresponding increase in the demand for healthy beverages worldwide (Chukwu et al., 2017). Zobo is a refreshing and nutritious non-alcoholic beverage produced and sold in Nigeria (Ezeigbo et al., 2015). Zobo drinks consists of 2.5 % protein, 8.5 % carbohydrate, 6.5 % fat, 3.0 mg/100g calcium, 1.8 mg/100g phosphorus, 2.4 mg/100g potassium, 0.2 mg/100g copper, 1.5 mg/100g manganese and 1.0 mg/100g vitamin C (Adeniji, 2017). More so, it contains vitamin E, polyphenol acids and flavonoids, mainly anthocyanins (Akujobi1 et al., 2018; Mohammed et al., 2017). Zobo drink possesses antibacterial, anti-oxidant, nephroprotective and antihepatotoxicity, diuretic effect, effects on lipid metabolism (anti-cholesterol), (Ekenam, 2018; Mohammed et al., 2017), anti-diabetic and anti-hypertensive effects, among others (Chukwu and Akaninwor, 2017; Ezekiel, 2016). The consumption of zobo drink is popular because of its claimed health benefits (Chukwu et al., 2017; Ezekiel, 2016). It is consumed by different classes of people irrespective of socio economic status (Ekenam, 2018; Ezekiel, 2016), sex and age in Nigeria especially in the Northern region and other neighboring African countries (Ekenam, 2018).
Zobo is still locally prepared through indigenous technology and has become accepted in most social gatherings because of its affordability, nutritional value and attractiveness to many people as compared to carbonated drinks (Chukwu et al., 2017; Ezekiel, 2016). It is prepared in several ways using different ingredients, the dried calyces being the major ingredient for preparing the drink (Mohammed et al., 2017). All the methods result into the drink but with a little different taste, depending on the sweeteners and spices used (Mohammed et al., 2017). There are two main techniques of preparing zobo drinks: the steeping and boiling techniques (Salami and Afolayan, 2020). Generally, the steeping technique is carried out by pouring boiled water into clean calyces inside a bowl and set aside for two to four hours. The juice is then separated from the calyces using sieve; fruit juice and sweeteners are then added based on preference whereas the boiling method is carried out by putting clean calyces with sliced fruits pineapple, oranges, and lime (with peel) (based on individuals) into a clean pot, covered with water, and boiled for five minutes, and then the desired spices such as cinnamon, garlic, and ginger are added. More water is added to the content and then left to boil for 30 minutes (Salami and Afolayan, 2020). The juice is then collected from the content using sieve and sweeteners added if desired.
Techniques of storing food products varies with the nature of the food. For centuries, various storage method were adopted with the purpose of storing food product with minimum costs and optimal, retention of quality (Hu and Jacobsen, 2016). Understanding the best storage condition suitable for a particular food product is of immense significance (Hu and Jacobsen, 2016), as it influences its acceptability and market value, as well as enhancing storage stability (Almeida et al., 2017).
The acceptance of food products entirely depends on whether it corresponds to consumer expectations and needs (Ekenam, 2018; Chukwu and Akaninwor, 2017). The process through which an individual accepts or rejects food is considered to be of a multi-dimensional nature (Ekenam, 2018). The structure of food acceptability is both variable and dynamic among individuals in different groups and the same individuals I n different time periods and contexts (Maina, 2018). Food acceptability directly relates to the interaction it has with the consumer at a given moment in time. The key factors that determine food acceptability are the sensory characteristics of food since consumers seek foods with specific sensory attributes (Maina, 2018).
1.2 STATEMENT OF PROBLEM
Despite the obvious advantages of zobo drinks, their producers are battling with the proper processing technique and best storage method that will enhance its shelf-life considering that it deteriorates quickly after preparation, a condition which may be attributed many factors such as contamination from the sorrel calyces, ingredients and poor quality water used for production, lack of personal hygiene of the producers resulting to microbial activities and growth, and gross inadequate electricity supply in Nigeria. Zobo drinks are commonly hawked in market places, schools, churches, hospitals, motor parks and other public places by low income earners who are not acquainted in food safety measures. The hawkers mostly produce this drink in environment with poor sanitary condition and also package the drink in already used plastic bottles which are inadequately sterilized and could predispose zobo consumers to pathogens of public health importance and as well adversely affect its storage stability. Besides, there is still limited data on the effect of processing techniques and storage on quality acceptability of zobo.
1.3 JUSTIFICATION OF THE STUDY
Zobo is a popular indigenous drink consumed by different classes of people irrespective of socio economic status. Evaluating the effect of processing techniques and storage on its quality properties and consumer’s acceptability is a cost-effective means of revealing the appropriate processing technique that is more stable to storage, retained more of the quality attributes of zobo, and as well more acceptable to consumers. Such method will be of immense importance to small scale and industrial zobo processing companies, as well as zobo consumers. Outcome of this research will be of great benefit to researchers.
1.4 OBJECTIVES OF THE STUDY
The main objective of the study was to evaluate the sensory, physico-chemical and ambient storage stability of zobo as affected by processing methods.
The specific objectives were to:
i. Produce zobo drink using different techniques
ii. Evaluate the proximate of the zobo
iii. Determine the physicochemical properties of the zobo at 0, 3 and 5 days
iv. Assess the microbial quality of the zobo at 0, 3 and 5 days.
v. Assess the sensory properties of the zobo.
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