ABSTRACT
Zobo wine was produced by fermentation of the must using brewer’s yeast, Saccharomyces cerevisiae at 28 0C for a total of 18 days with addition of citric acid (0.5% w/v) and stored for 4 weeks. The sample and a red wine from grape (oster wine) were analyzed for the physicochemical, microbial and sensory qualities. The results obtained revealed that the physicochemical properties ranged from 0.993 to 0.986, 4.600 to 5.800, 4.660 to 10.035 %, 37.500 to 75.000 g/100 ml, 0.485 to 0.685 g/l, 4.400 to 12.450 % and 111.000 to 860.000 for specific gravity, pH, alcohol content, total titratable acidity, total sugar, dry matter and total dissolved solids respectively. There was significant difference (p<0.05) in the alcoholic content of the samples and could be due to the composition or production process. The microbial analysis indicated the total viable count (TVC) of 0.4 x 101 CFU/ml showing insignificant growth of Staphylococcus aureus which was observed for zobo wine with no growth detected for red wine from grapes. No fungal or coliform growth was observed in the samples. In terms of sensory attributes, the wine samples were evaluated using the 9 - point hedonic scale. Thus, the sensory score obtained for colour ranged from 6 to 8, 7 to 8 for clarity, 5 to 7 for taste, 6 to 7 for aroma, 6 to 8 for mouth-feel and 6 to 8 for general acceptability. Generally, consumers accepted the zobo wine more than the red wine from grapes. Therefore, the results revealed that alternative raw materials to grapes like zobo (Hibiscus sabdariffa) calyces could be used in the production of acceptable wine which can compete with imported wines in the market and beneficial to the consumers while providing a cheaper alternative to imported wines.
TABLE OF CONTENTS
Title i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of Contents vi
List of Tables ix
List of Figures xi
List of Plates xii
Abstract xiii
CHAPTER 1: INTRODUCTION
1.1 Background of the study 1
1.2 Statement of problem 3
1.3 Justification of the study 4
1.4 Objectives of the study 4
CHAPTER 2: LITERATURE REVIEW
2.1 An overview of roselle 5
2.1.1 Nutritional composition of roselle 5
2.2 Zobo drink 8
2.2.1 Nutritional composition of zobo drink 8
2.2.2 Microbial quality of zobo drink 10
2.3 Wine 13
2.3.1 Classification of wine 13
2.3.2 Raw materials used in wine production 15
2.3.3 Production of wine 16
2.3.3.1 Red wine grapes 17
2.3.3.2 Crushing and destemming of berries 17
2.3.3.3 Pressing 17
2.3.3.4 Fermenting the must 17
2.3.3.5 Fining 18
2.3.3.6 Cooling and settling 18
2.3.3.7 Bottling 19
2.3.4 Fermentation of wine 19
2.3.5 Standards for wines 20
2.3.6 Spoilage of wines 21
2.4 Preservative 23
2.4.1 Classification of Preservatives 23
2.5 Important constituents of wine 26
2.5.1 pH 26
2.5.2 Yeast 26
2.5.3 Nitrogen 27
2.5.4 Water 27
2.5.5 Sugar 27
CHAPTER 3: MATERIALS AND METHODS
3.1 Source of materials 30
3.2 Sample preparation 30
3.2.1 Preparation of must 30
3.2.2 Fermentation of must 30
3.2.3 Clarification and storage of young wine 31
3.3 Physicochemical properties of the wine 36
3.3.1 pH measurement 36
3.3.2 Determination of specific gravity 36
3.3.3 Determination of total titrable acidity 36
3.3.4 Determination of total dissolved solids 37
2.3.5 Determination of total sugars 37
2.3.6 Determination of dry matter content 38
3.3.7 Alcohol content 38
3.4 Microbiological analysis of the wine 38
3.4.1 Total viable count of bacteria (TVC) 38
3.4.2 Total coliform bacteria 39
3.4.3 Yeast and mould enumeration 39
3.5 Sensory evaluation of the wine 39
3.6 Experimental design 40
3.7 Statistical analysis 40
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Production of zobo wine 41
4.2 Physicochemical properties of test wine samples 42
4.3 Microbial characteristics of the test wine samples 46
4.4 Sensory evaluation of the test wine samples 48
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 52
5.2 Recommendations 52
5.3 Contribution to knowledge 52
References 54
LIST OF TABLES
Table 2.1: Proximate analysis of roselle calyces (g/100 g) dry matter 6
Table 2.2: Mineral composition of roselle calyces (mg/100 g) 7
Table 2.3: Details regarding use of preservatives 25
Table 4.1: Physicochemical properties of test wine samples 43
Table 4.2: Microbial quality of test wine samples 47
Table 4.3: Sensory properties of test wine samples 49
LIST OF FIGURES
Figure 2.1: Flow diagram showing production of red wine (Belitz et al., 1999) 21
Figure 3.1: Flow chart for the production of wine from Hibiscus sabdariffa extract using modification to method described by Akuba (2013) 32
LIST OF PLATES
Plate 1 Zobo calyces 32
Plate 2 Granulated sugar 33
Plate 3 Citric acid 34
Plate 4: Zobo wine 40
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Wine is a complex mixture, consisting of both organic and inorganic compounds, including esters, high alcohols, fixed acidity (malic, tartaric and citric acid), sugars, aldehydes, tannins, pectins, vitamins and minerals (Odibo et al., 2002; Amerine et al., 2012). It can be defined as an alcoholic beverage made from grape juice or other fruits through fermentation of “must” by wine yeasts (Archer and Castor, 2006). Most wines have a total acidity content ranging from 0.3 to 0.55% (as tartaric acid and acetic acid). The European Economic Community recommends that the alcoholic content for table wines should range from 8.5 to 19.5% (Austin, 2008).
Wine can be classified as table wine, sparkling wine, fruit wine, fortified wine, dry wine or sweet wine (Umeh et al., 2015). They may also be classified on the basis of the countries of origin or fruit type from which they were obtained. For example red table wines are made from black grapes while white wines are made from black or white grapes. It is now known that it can be produced from other fruits such as oranges, bananas, mangos, pineapples, lemons, etc. and the wine so produced bears the name of the fruit used in its production (Robinson, 2006; Amerine et al., 2012).
Most wines consumed in Nigeria are completely fermented, aged, bottled and imported ones. The temperature restriction of most grapes to temperate regions predisposes this trend (Okoro, 2007). Imported products are costly now due to high duties paid on them. This had made imported wines too expensive to local consumers and for these reasons, there arose the need for more wine from other plants species. The use of home grown fruits and vegetables for wine production would enhance efficient utilization of these abundant natural resources and would invariably increase the Nation’s Gross Domestic Product (GDP).
Hibiscus sabdariffa popularly called ‘Zobo’ in the Northern part of Nigeria and Roselle in English is a plant belonging to the family Malvaceae (Omemu et al., 2006). The hot water extract of the plant’s leaves is used to produce non-alcoholic beverage which is usually sweetened with sugar and flavoured with ginger (Idolo et al., 2012). According to Mohamed et al. (2007), zobo drink is a good source of vitamin C, calcium, iron and phosphorus. Economically, it is cheaper when compared with other available soft drinks. In spite of the nutritional, medical and economic benefits of this beverage, the greatest limitation of zobo products such as zobo drink or wine is that it deteriorates rapidly. It has a very short life of 24 hours if not refrigerated, as it contains microorganisms which can cause food spoilage (Omemu et al., 2006). Zobo drink is often contaminated with enteropathogenic microorganisms with as much as 2.49 x 104 CFU/ml, which could be harmful to persons who consume large quantities of the drink (Bukar et al., 2009). This short shelf-life of the drink is associated with degradation of the nutrient component which erodes its health benefits and antioxidant property (Umeh et al., 2015). This has generated an interest in the possible fermentation and preservation of this drink to produce red wine that can impart additional nutrient and extend viability.
According to Idise and Odoyo (2011), wine could be preserved by chemical or physical means. Chemicals used include simple organic acids (such as propionic acid, sorbic acid, benzoic acid) p-hydroxyl benzoate alkylester (parabens), ethylene/propylene oxides, sulfides, ethylene oxide (as a gas sterilant), ethyl formate and sodium nitrates (Doughari et al., 2007) while the physical means include pasteurization and sterile filtration (Okafor, 2007). However, most of the aforementioned preservatives may be detrimental to human health, and as such may cause health related problems (Svans, 2008). This Therefore, necessitate further search into other chemical preservative such as citric acids which may have less or no effects on the health of the consumers and as well prolong the shelf life of the carrier product.
1.2 STATEMENT OF PROBLEMS
Among the major challenge facing production and marketing of beverages such as zobo drink and its related products is the rapid quality deterioration and reduced shelf life. Zobo drink has not been successfully produced at commercial scale. This is associated with its short shelf life attributable to microbial activity. This short shelf-life of the drink is associated with degradation of the nutrient component which erodes its health benefits and antioxidant property (Omole and Oranusi, 2019). This has generated an interest in the possible fermentation of this drink to produce red wine that can impart additional nutrient and extend viability.
Also, quality deteriorations of beverages lead to undesirable changes which are characterized by changes in colour, texture, flavour, and nutritive value (Doughari et al., 2007). Overall, the management of these quality challenges may result in reductions in availability, edibility, quality as well as wholesomeness, contributing to the incidence of spoilage and subsequent financial losses.
However, there is little information on the scope and effectiveness of citric acid in food preservations. Therefore, there is a need to investigate and compare the effectiveness of citric acid in preservation of wine developed from zobo calyces. The information obtained from this study will be useful to the small scales food processors as well as the consumers.
1.3 JUSTIFICATION
One way by which these challenges can be averted is through the use of chemical preservatives. These chemicals are substance of no nutritional significance. They are added to foods as antimicrobial agents to preserve them from deterioration and extend shelf life (Jay, 2005).
The use of chemical preservatives at low allowable concentrations to control the growth of microorganisms in beverages is desirable and gaining research interest worldwide. Also, the successful storage of zobo wine with citric acid may be helpful in prolonging the shelf stability of the wine developed.
Low alcohol zobo wine produced from extracts of Hibiscus sabdariffa calyces extract seems to provide health benefits to its consumers due to its rich source of phenolic compounds and low alcohol. The product will be a potential red wine which can compete with imported wines on the market and the product would be beneficial to the local consumers that rely on imported wines. Therefore, this study is aimed at evaluating the preservative effects on the shelf stability of zobo wine using citric acid.
1.4 OBJECTIVES OF THE STUDY
The main objective of this study was to determine the quality of wine produced from zobo calyces extract.
The specific objectives were to:
i. produce zobo wine from zobo calyces extract.
ii. determine the physicochemical properties of the zobo wine.
iii. determine the microbial quality of the zobo wine.
iv. evaluate the sensory properties of the zobo wine.
Click “DOWNLOAD NOW” below to get the complete Projects
FOR QUICK HELP CHAT WITH US NOW!
+(234) 0814 780 1594
Login To Comment