The Use of Bitterleaf (Vernonia Amygdalina) Extract as a Means of Extending the Shelf-life of Locally Brewed Sorghum Beer
AIMS AND OBJECTIVES
The aim of the project is itemized into the following objectives;
- To determine the shelf-life of locally brewed sorghum beer.
- To check the effect of bitterleaf (Vernonia amygdalina) extract on the locally brewed sorghum beer.
- To compare the results from the chemical analyses of locally brewed sorghum beer with bitterleaf extract and sorghum beer brewed without bitterleaf.
GENERAL DESCRIPTION OF CEREALS
The word cereal derives from Ceres, the name of the Roman goddess of harvest and agriculture (Kneen, 1944). According to Ihekoronye (1995), Cereals, grains or cereal grains, are grasses (members of the monocot families Poaceae or Gramineae), Cultivated for the edible components of their fruit seeds (botanically, a type of fruit called a caryopsis) – the endocarp, germ and bran. The cereal grains are the staple food of the peoples of the tropics, providing them with about 75% of their total caloric intake and 67% of their total protein intake (Ihekoronye, 1995). Cereal grains are grown in greater quantities and provide more food energy worldwide than any other type of crop; they are therefore staple crops. In their natural form (as in whole grain), they are a rich source of vitamins, minerals, carbohydrates, fats, oils, and protein (Redmond,W.A, 2007) . However, when refined by the removal of the bran and germ, the remaining endocarp is mostly carbohydrate and lacks the majority of the other nutrients (kent, 1983).
GENERAL CHARACTERISTICS OF CEREALS
- They are all plant seeds and as such contain a large centrally located starchy endosperm which also is rich in protein.
- A protective outer coat consisting of two or three layers of fibrous tissue, and an embryo or germ usually located near the bottom of the seed.
- Except for two amino acids, lysine and tryptophan, most cereals contain the essential amino acids required by man as well as vitamins and minerals (Ihekoronye, 1995).
Example of Major Cereals Grown In Africa;
Rice; Oryza sativa
Wheat; Triticum aestivum
Barley; Hordeum vulgara
Oat; Avena sterilis
Great millet; Sorghum vulgare
Pearl millet; Pennisetum typhoideum ( Dutta, A.C, 2005).
MATERIALS AND METHODS.
The starting materials used were 2kg of sorghum, 500g of bitter leaf (Vernonia amygdalina), bakers yeast which was purchased from Ogbete main market, Enugu.
CHEMICALS AND REAGENTS
- 1% phenolphthalein
- 0.1M NaOH
- Distilled water
- Sterilizing tablet
- Mac Konkey Agar
- Zinc chloride
- Bakers yeast
- Blood agar
- Chocolate agar
RESULTS FOR TOTAL ACIDITY, FIXED ACIDITY, VOLATILE ACIDITY AND PH VALUE FOR SORGHUM BEER.
Table 3: Shows total acidity, fixed acidity and volatile acidity and pH values of sorghum beer with and without hop substitute for three days.
- Values are means values of triplicate determinations + standard deviations
Table 3; The total acidity value for sorghum beer without hops was 0.650g/100ml which did not correspond to the total acidity value given by Okafor, (2007) for sorghum (kaffir beer). This could be as a result of higher acid production in the beer as a result of the bakers yeast used for the fermentation, initiating the development of lactic acid bacteria during fermentation; this is stimulated by the yeast, which provides soluble nitrogen compounds and other growth factors (Nout, 1991). Total acidity measures the organic acids in the sample and the quantity of the acid that would react. The total acidity value for sorghum beer with hops 0.564g/100ml is lower than that without hops. This indicates that sorghum with hops has a lower acid level than sorghum brewed without hops. The Ω- acids in bitter-leaf extract (Vernonia amygdalina) was able to stabilize the acidity of the hopped beer relative to the unhopped one. There was a significant decrease (p≤0.05) between the total acidity for day 1 (0.564g/100ml) and day 5(0.560g/100ml) in sorghum beer brewed with hops, showing that the drink will keep for a period of time. There was an increase between the total acidity for day 1(0.650g/100ml) and day 5(0.654g/100ml) in sorghum beer without hops, showing that the drink is deteriorating.
The fixed acidity values for day 1(0.204g/100ml) and day 5(0.202g/100ml) for sorghum beer with hops, when compared, has a significant increase (p≤0.05). Also, the fixed acidity of sorghum beer with hops is higher than the value of sorghum beer without hops. This could be as a result of high alcohol content of the sorghum beer with hops.
Sorghum beer without hops has a higher volatile acidity value (0.475g/100ml) than sorghum beer with hop (0.360g/100ml). This could be as a result of a high lactic acid production in the drink without hop by lactobacillus, indicating that the sorghum beer with hops will keep for a while that without hops will deteriorate.
The PH of sorghum beer with hops was 3.93, which is not in line with that given by Okafor (2007) for sorghum beer. This could have been as a result of high concentration of organic acid production in the beer (Akinrele, 1970). The pH of sorghum beer without hops (3.50) was lowered than that with hops and when both were compared, gave a significant difference (p≤0.05). This indicates that sorghum beer with hops has a lower acidity level than sorghum beer without hops. This could also be as a result of pH and temperature that determines the amount of lactic acid production by the lactobacilli specie. The higher the pH, the lower the acidity.
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