ABSTRACT
This study was aimed at determining the shelf stability of zobo wine using sodium benzoate. Zobo wine was produced by fermentation of the must using brewer’s yeast, Saccharomyces cerevisiae at 280C for a total of 28 days with addition of sodium benzoate (0.5% w/v) and stored for 21 days. The sample and a red wine from grape (oster wine) were analyzed for their physicochemical, microbial and sensory qualities. The results obtained revealed that the physicochemical properties ranged from 5.50 to 6.45, 0.99 to 0.99, 114 to 487 mg/l, 67.50 to 78.50 g/100ml, 21.00 to 40.50%, 0.28 to 0.31 nm, 13.85 to 76.45 mg/l, 0.50 to 0.69 g/100 ml and 6.61 to 10.04 % for pH, specific gravity, total dissolved solids, total titratable acidity, dry matter, colour intensity, phenol content, total solids and alcohol content, and total solids. In as much as red wine from grapes was higher in the physicochemical properties pH, phenol content, total solids and alcohol content; zobo wine showed higher values in total dissolved solids, total titratable acidity, dry matter and colour intensity. From microbial analysis, no significant bacteria growth was isolated from the samples, although lower in zobo wine. Also, no fungal or coliform growth was observed. The zobo wine was of comparable microbial quality with the red wine from grapes possibly due to presence of sodium benzoate generally used as preservative in beverages. Sensory evaluation indicated higher acceptance of zobo wine than the red wine from grapes (oster wine). The sensory attributes ranged from 6.90 to 7.65, 5.80 to 7.00, 6.15 to 7.05, 5.85 to 7.05, 5.25 to 7.20 and 6.10 to 7.75 for colour, appearance, clarity, taste, flavour, mouth-feel and general acceptability respectively when evaluated on a 9 - point hedonic scale. Although zobo (Hibiscus sabdariffa) extracts are readily contaminated by spoilage microbes, it can be used in the production of shelf stable wine with addition of sodium benzoate and could favourably compete with imported wines.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables ix
List of Figures x
List of Plates xi
Abstract xii
CHAPTER 1: INTRODUCTION
1.1 Background of study 1
1.2 Statement of problems 3
1.3 Justification 4
1.4 Objectives of the study 4
CHAPTER 2: LITERATURE REVIEW
2.1 An overview of zobo calyces 6
2.1.1 Nutritional composition of zobo calyces 7
2.1.2 Medicinal benefits of zobo calyces and its use in food 7
2.1.3 Utilization of zobo calyces in food and beverage production 8
2.2 Wine production and classification 9
2.2.1 Raw materials used in wine production 11
2.2.2 Cultured yeast and inoculation 12
2.2.3 Fermentation of wine 12
2.2.4 Stages involved in zobo wine production 14
2.2.5 Maturation and bottle ageing of wine 18
2.3 Physicochemical properties of wines 20
2.3.1 Importance of phenolic compounds 20
2.3.2 Effect of organic acids and ph on wine quality and stability 21
2.3.3 Alcohol content of wines 21
2.3.4 Development of aroma compounds in wine undergoing maturation 22
2.3.5 Effect of volatile acidity /acetic acid on wine quality 23
2.3.6 Residual sugars in wines and their effect on consumer choices of wines 24
2.4 Sensory properties of wines 26
2.5 Standards for wines 27
2.6 Spoilage of wines 27
CHAPTER 3: MATERIALS AND METHODS
3.1 Sources of raw materials 29
3.2 Sample preparation 29
3.2.1 Preparation of must 29
3.3.2 Fermentation of must 29
3.2.3 Clarification and storage of young wine 30
3.3 Physicochemical analyses of the wine samples 34
3.3.1 pH 34
3.3.2 Specific gravity 34
3.3.3 Total dissolved solid 34
3.3.4 Total titratable acidity 35
3.3.5 Dry matter 35
3.3.6 Colour intensity 35
3.3.7 Determination of phenols content 36
3.3.8 Total sugar 37
3.3.9 Alcohol content 37
3.4 Microbial analysis 38
3.4.1 Total viable microbial count (TVC) 38
3.4.2 Total fungi count (TFC) 38
3.4.3 Total coliform bacteria count 38
3.5 Sensory evaluation of wine 39
3.6 Experimental design 39
3.7 Statistical analysis 40
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Production of zobo wine 41
4.2 Physicochemical properties of wine samples 42
4.3 Microbial characteristics of wine samples 46
4.4 Sensory evaluation of the test wine samples
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 52
5.3 Recommendations 52
5.2 Contribution to knowledge 53
REFERENCES 53
LIST OF TABLES
Table 2.1: Classification of wines based on residual sugars 25
Table 4.2: Physicochemical properties of wine samples 43
Table 4.3: Microbial quality of test wine samples 47
Table 4.4: Sensory properties of wine samples 49
LIST OF FIGURES
Figure 2.1: Flow diagram showing production of red wine 17
Figure 3.1: Flow chart for the production of wine from Zobo wine 31
LIST OF PLATES
Plate 1: Zobo calyces 32
Plate 2: Granulated sugar 33
Plate 3: Zobo wine 41
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Fruit wines are fermented alcoholic beverages made from a variety of base ingredients (other than grapes). They may also have additional flavours taken from fruits, flowers and herbs. Fruit wine can be made from virtually any plant matter that can be fermented. Most fruits and vegetables have the potential to produce wine. Few foods other than grapes have the balanced quantities of sugar, acid, tannin, nutritive salts for yeast feeding, and water to naturally produce a stable, drinkable wine; so most wines are adjusted in one or more respects at fermentation. However, some of these products do require the addition of sugar or honey to make them palatable and to increase the alcoholic content (sugar is converted to alcohol in the fermentation process) (Ihekoronye and Ngoddy, 2015).
In recent times, there has been an increase in the use of several locally grown tropical fruits and vegetables as raw materials for alcoholic beverages (wine) production in Nigeria. Among the assortments of such indigenous tropical fruits are the kolanut (cola acuminata), cocoa (theobroma cacao L.), African star apple (chrysophyllum albidium), pawpaw (carica papaya) and zobo calyces. The temperature restriction of grape to the temperate regions and the very high duty on imported wines has stimulated interests in producing wines from tropical fruits (Odigie et al., 2003).
Roselle, which is zobo calyces (Hibiscus sabdariffa) belongs to the family Malvaceae, and is an important annual crop grown successfully in tropical and sub-tropical climates. The plant is cultivated for its stem, fibre, edible calyces, leaves and seeds which are used in making various foods. The commercially important part of the plant is the fleshy calyx (sepals) surrounding the fruit (capsules). It is used for making wine, juice, jam, jelly, syrup, gelatin, pudding, cakes, ice cream and flavours and also dried and brewed into tea, among other things (IfieIdolo et al., 2012).
The red calyces contain antioxidants including flavonoids, gossypetine, hibiscetine and sabdaretine. Delphinidin 3-sambubioside and cyaniding 3-sambubioside are the major anthocyanins comprising 70 and 29 % of total anthocyanins respectively. Its calyx also contains 4 % citric acid, organic acids, minerals and amino acids. The seeds contain 17.8 to 21 % non-edible oil and 20 per cent protein, and are sometimes used for animal feed (Odigie et al., 2003).
A very widely-used preservative, sodium benzoate is used throughout various industries, including food and beverage, pharmaceutical, cosmetic, and industrial. As a food additive, sodium benzoate was the first preservative allowed in foods by the FDA. Today, it is classified as Generally Recognized as Safe (GRAS), meaning experts consider it safe when used as it’s intended. It is internationally approved as a food preservative and is identified by the number 211 (listed as E211 in Europe). It functions as a preservative by inhibiting the growth of harmful bacteria, mold, and other microbes, preventing product spoilage. It’s also used to preserve over-the-counter medications such as cough syrup and as a lubricant in pill manufacturing (Odigie et al., 2003).
Sodium benzoate is commonly found in soft drinks, it can also be used in winemaking both to prevent spoilage and stop the fermentation process. Like potassium sorbate, sodium benzoate is a yeast inhibitor. Rather than killing off the yeast, it hinders yeast’s ability to multiply and be active. Winemakers usually add small quantities of sodium benzoate to sweet and sparkling wines when active fermentation has ceased. For sweet wines, it can also be added at the same time as the final syrup. Sodium benzoate can also be added to wines that have difficulty maintaining clarity after fining. It can also be used post-fermentation balance the wine’s pH and pressure. When using sodium benzoate as a stabilizer, it must be used in conjunction with an aseptic dose of potassium metabisulfite (Campden tablet).
1.2 STATEMENT OF PROBLEM
Most wines consumed in Nigeria are imported and there is little or no local production. Wines are mostly produced from grapes, which are not available in the tropics hence the need for alternative use of plant materials and other fruits for wine production in the tropics. A survey conducted in Lagos and other states in the Western part of Nigeria to know their choice of wines indicated that the wines used by most respondents were all imported wines from countries like Israel, Spain, Italy, America and South Africa, with alcohol levels below 7%.
Despite the fact that the popularity of beverage from zobo calyces is increasing, one of its greatest limitation for large scale production is that it has a very short shelf life of 24 hours if not refrigerated (Omemu et al., 2006). Therefore, there is urgent need to explore various preservation methods that could be employed to extend the shelf life of this product.
Most producers depend heavily on the use of preservatives. Electricity supply in which processors depend mainly on for refrigeration is grossly inadequate and often characterized by frequent power outage. On the overall, when electricity supply is low, the drink could easily be invaded by spoilage microorganisms.
Food safety is an essential concern of both the consumers and the producers (Witkowska et al., 2013). Microorganism in food is not always detrimental, because their growth may result in pleasant taste and texture (Bukar et al., 2010). But microorganisms such as Staphylococcus aureus, Pseudomonas aeruginosa, E. coli, Vibro cholera, Salmonella, Bacillus, Clostridium species etc. could contaminate food and transfer a wide range of disease conditions in food (Bukar et al., 2010).
1.3 JUSTIFICATION
Low alcohol wine produced from extracts obtained from zobo calyces extract will provide health benefits to its consumers due to its rich source of phenolic compounds and low alcohol. The production of low alcohol wine will help in the alcohol control measures intended to curb alcohol consumption levels and drinking habits and reduce related social and health problems. This move is in line with the World Health Organization’s (WHO) public health objective on alcohol which is to reduce the health burden caused by the harmful use of alcohol and thereby, to save lives, reduce disease and prevent injuries. 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 churches that rely on imported wines for communion services. This product could be relatively cheap because of the use of locally available raw materials and will save the government some foreign exchange for development. The near absence and epileptic public electricity power supply used to power home appliances including refrigerators has made the preservation of such beverages in Nigeria difficult limiting the shelf life of many of such beverages to just few days. Research into the shelf stability of wine product without refrigeration has therefore intensified. The aim of this research was to examine the preservative effect of sodium benzoate on wine produced from zobo calyces
1.4 OBJECTIVES OF THE STUDY
The main objective of this study was to examine the preservative effect of sodium benzoate on wine produced from zobo calyces.
The specific objectives include to:
i. produce wine from zobo calyces.
ii. determine the physicochemical properties of the produced wine.
iii. determine the microbial quality of the produced wine.
iv. determine the sensory characteristics of the wine product after storage.
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