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Bread Production – Comparative Study Of Yeast From Palm Wine And Bakers’ Yeast Performance

Bread Production – Comparative Study Of Yeast From Palm Wine And Bakers’ Yeast Performance

Bread Production – Comparative Study Of Yeast From Palm Wine And Bakers’ Yeast Performance
LITERATURE REVIEW
2.1 BREAD PRODUCTION
The purpose of bread making is to present cereals flour to the consumers in an attractive palatable and digestible form ( Kent 1982). The universal importance of bread as food has led to its use as a symbol of nourishment. Its appetite appealing aromas when baking have magnetic power in attracting patronage. The general acceptance of it as food makes bread a voluable medium for improving the nutrition of both the rich and the poor (Terrel 1970).
Bread is traditionally made from flour, water, salt and yeast. It has a honey comb structure and may be regarded as a solid foam with a multitude of pockects of carbon dioxide distributed uniformly through out its bulk. Sugar are naturally present in flour. The maltose is made available e by the action of anylases. This is hydrolysed to glucose and is fermented by zymase present in the yeast. Alcohol and carbon dioxide are formed and the latter aerates the dough ( Fox and Cameron 1995).
Bread making generally involves the baking of a dough which has for its main ingredients wheat flour, water, yeast and salt. Other optional ingredients include flours of other cereals, fat malt flour, soya flour, yeast foods emulsifiers mailk and milk products ( Ihekoronye and Ngoddy 1985).

When the ingredients are mixed in correct proportions with water, the protein in the flour begins to hydrate. A cohesinve material called gluten is formed. It has perculiar extensible propertion of stretching like elastic, and possession of a certain degree of recoil or spring. The action of the enzymes upon the sugars, evolves carbon dioxide gas which increase size of the dough when left for a period of one hour and at the appropriate proofing temperature of 290 c (Lundberg and Kotschevar 1980).
The risen dough is baked at the temperature of 25000 – 2600 c to form a rigid structure with an aerated, finely vesiculated crumb that is easily masticated ( Sultan 1982).
Three important requirements in bread making from wheat flour would include formation of gluten network, the aeration of the mixture by incorporation and coagulation of the material by heating in the Oden so that the structure of the materials are stabilized ( Kent 1983.
2.2 FUNCTIONS OF THE INGREDIENTS IN BREAD PRODUCTION
2.02.1 Wheat flour: This is unique in the baking of bread and other baked products. This is because it is the only crop possessing gluten in appreciable quantity to permit substantial increase in volume of baked products which is both palatable and digestible quantity to permit substantial increase in volume of baked product which is both palatable and digestible. To this, its special suitability for bread making is due ( Kirk and sawyer 1991).
The composition of the gluten present has a bearing on the strength and water-holding properties of the flour. Strong wheat flour, suitable for bread making produces strong elastic dough, which produces bold, well – risen loaves with good cruing texture and keeping properties.
GOOD BREAD MAKING IS CHARACTERIZED BY HAVING
i. Adequate quantity of protein which when hydrated, yields gluten which is satisfactory in respect of elasticity strength and stability.
ii satisfactory gassing properties and amylase activity.
iii Satisfactory moisture content ( about 14 percent) to permit safe storage
iv satisfactory colour (Kent 1983)
2.02.2 Yeast: the type of yeast used in bread making is the bakers yeast. This bakers yeast comprises cultured varieties of Saccharomyces cerevisiae selected for optimum gas production. In the production of baked goods, yeast is a key ingredient and serves three primary functions.
i. Production of Carbon dioxide: Carbon dioxide is generated by the yeast as a result of the break down of fermented sugars present in the dough. The evolution of carbon dioxide causes expansion of the dough as it is trapped within the protein matrix of the dough.
ii Maturation of dough: This is accomplished by action of the yeast enzyme present in the dough. As carbon dioxide gas is produced, the volume of the dough increases. The gluten is conditioned and mellowed, becomes elastic and springy as a result of the effect of the alcohol produced by the yeast.
iii Development of Flavour: Yeast imparts the characteristics flavour of bread and other yeast leavened products. During dough fermentation, yeast produce may secondary metabolites such as ketones, higher alcohols, organic acids aldehydes and esters. Some of these alcohols escape during baking. Others react with one another and with other compounds found in the fermenting dough to form new and more complex flavour compounds. These reactions occurs primarily in the crust and the resultant flavour diffuses into the crumb of the baked bread.
2.02.3 Salt: salt is an essential ingredient in bread. It is added to toughen the gluten and gives a less sticky dough. It also helps to control fermentation rate and improve the flavour of bread which has a flat inspid taste without it ( Kent 1983)
2.02.4 Sugar: Sugar in the form of sucrose and syrups contributes sweetness and flavour of bread. It serves as a substrate for yeast in the fermentation for leavening of bread it also helps in the formation of the brown colour of the crust (caramalisation)
2.02. 5 Fat (Shortening): Fats are used to shrten the gluten strands and improve of gives thinner crumb cell walls, resulting in a softer texture loaf with improved slicing characteristics (Kent 1983)
2.3 TYPES OF BREAD    Bread Production
i. Whole meal bread: This is made from flour obtained by milling whole wheat grains including the bran and germ and no other cereals. It may contain ascorbic acid if made by charley wood bread process. Addition of L – cysteine or any of the flour improvers is prohibited.
ii Brown bread: This must contain at lease 0.6% crude fibe calculated on the dry matter and flour other than whole-meal flour. It may contain any other permitted additional ingredients.
iii Wheat germ bread: This must contain at least 10% processed what germ calculated on the dry matter, it may contain any other permitted addition ingredients or additives.
iv White bread: this is defined by exception as bread which is not whole meal, brown or wheat germ. It may contain a wide range of additional ingredients including milk and milk products, liquid or dries eggs, wheat germ rice flour, soy bean flour oils and fats, malt extract, malt flour sugars, and may contain permitted additives.
v. Soda bread: This contains sodium hydrogen carbonate ( Sodium bicarbonate) NAHco3 and other ingredients
vi. Starch – reduced bread: This type of bred contains not less than 50 percent carbohydrate ( Fox and cmeron 1995).
2.4 PROCEDURES INVOLVED IN BREAD PRODUCTION
2.4.1 Dough Mixing: This is done to thoroughly and completely distribute the ingredients and develop the gluten to maximum extensibility and elasticity proper mixing of the dough is very important since the subsequent aerating of dough cannot be retained if gluten is poorly developed.
2.0.4.2 Fermentation: The mixed dough is left in a room (270c) to increase in size through the activity of yeast. The gluten is further developed and mellowed to become more elastic due to the action of alcohol and low acidity. The gluten develops thin walls which retain gas under pressure of fermentation gases. The dough matures until it reaches maximum spring and elastic.
2.04.3 Punching (Knock back): This is done to keep the dough at a nuiform temperature by actually turning the dough inside out to release carbon dioxide which will restrict fermentation. If allowed to stay in, introduces oxygen which produces vigorous fermentation and to mechanically develop the gluten
2.04.4 Scaling: This should be quick since it is still a port of the fermentation period. Scaling is done to measure and grade the dough to produce bread of particular sizer.
2.04.5 Moulding: The dough is moulded to its final shape before it is panned.
2.04.6 Panning: The moulded units are placed on dusted bread peels. These peels are then attached to special poles for loading into the oven.
2.04.7 Proofing: This gives the dough its final conditioning. The gluten becomes quite tender, extended and the outer surface becomes smooth and light in appearance.
2.04.8 Baking : Baking changes the dough to a cooked, appetizing, digestible and brown product (Sulten 1982).
2.5 BREAD QUALITY
Good quality bread implies that the loaf has sufficient volume, an attractive appearance as regards shaped and colour a crumb that is evenly and finally vesicullated and soft enough to mastication, yet firm enough to permit their slicing ( Kent 1983).
The attainment of good quality in bread depends partly on the inherent characteristics of ingredients particularly the flour and partly the baking process. A good quality bread should have a golden brown colour which should be crisp and brittle rather than tough ( Fox and Cameron 1995).
2.6 PALM WINE (ELAEIS GUINNEENSIS)
Palm wine, a natural alcoholic beverage widely cherished and consumed throughout the southern parts of Nigeria, is produced by the fermentation of the palm sap. The two common species of the palm tree from which palm wine can be obtained include the tree Elaeis guinneensis, which produces the popular oil palm wine and the Raphia hookeri, which produces the raffia palm wine.
When the in inflorescence of the oil palm tree is tapped by tapers, a milky juice containing initially well over 13% sucrose is collected in a calabash which is hung at the base of the incision (Ihekoronye and Ngoddy 1985) soon after leaving the tree yeast spore especially those saccharomyces cerevisiae infect the juice and soon starts to ferment the fermentable sugar.
Within hours, ethanol has been produced, with the liberation of large amount of carbon dioxde. This could cause most vessels to explode if they are corked within three days, oxidative yeasts and species of Acetobacter, Oxdise the ethanol into vinegar. Palm wine is regarded as spoled when the total acid content measured as a percentage has gone beyond 0.6% (Ikekoronye and Ngoddy 1985).
Apart from the direct consumption as alcoholic beverage, palm wine is used in leavening of dough. This was based on the report of past work that Saccharomyces cerevisiae, the yeast mainly employed in leavening of dough, and alcohol production by fermentation constitution about 70% of the total population of yeast about in the palm wine (Somiaria and Udoh 1993).
The nature of innoculam of fermenting palm wine is varied as reported by various workers. This is dure to the traditional tapping practice of using tapping implements repeatedly, especially receiving vessels and funnels for inner surfaces to get rid of microbial deposits. Such vessels contain huge deposits of micro organisms ( Palm wine flora), which are compoletely irrelevant to palm wine fermentation.
Okafor (1991) in his study, examined the yeast from commercial palm wine and hoted the consistent occurrence in abundance of saccharomyces and candida species. He suggested that these yeast is the most important in palm wine fermentation ( Uzochukwu, Balagh and Ngoddy 1991).
Inspite of these findings, researches so far conducted with palm wine have been directed towards understanding the mechanism of its fermentation, microbiology, extension of shelf life, formulation of extenders and analogue and use of standard pure culture inoculum for fermentation of palm sap into palm wine.
Since palm sap contains a variety of micro organisms, dough leavened with palm wine are seldom consistent in quality studies on the use of palm wine dregs in baking showed that good loaves can only produced with 20% substitution of bakers yeast with palm wine dregs ( Somiari and Udoh 1993).
2.7 GENERAL CHARACTERISTICS OF SACCHAROMYCES CEREVISIAE
2.0.71 MORPHOLOGICAL CHARACTERISTICS
i. The structure: Bakers yeast which is of the yeast strain saccharomyces cerevisiae belongs to the genus of saccharomyces.. they have round, ovate spherical or enlogated cells and may form a pseudomycelium.
ii. Reproduction: Reproduction occurs by mutipotar budding or by ascopore formation that ofter leads to the formation of chains of cells. The ascopores one to four per ascus are usually round or ovate.
iii. Polar budding as a process in which some of the protoplasm bulges out of the cell wall. The bulge grow in size and finally wall off as a new cell.
2.07.3 CULTURAL CHARACTERISTICS
Growth as a film on the surface of liquid media suggests on oxidative or film yeast. This is not a usually method of identifying the yeast. However, the appearance of growth is important especially when it causes cultured on agar plate with microscopic examination of the organism.. it cultural characteristics is determined . most colonies are moist and slimmy. Some are whitish some are cream coloured or pink and some changes with age.
2.7.4 YEAST CYTOLOGY
yeast cells are surrounded by a wall which is case of baker’ yeast and many other species consists of ploly-saccharides which as glucan and mannan, a small amount of chitin, protein, lipids and minerals. The filamentous yeast have a higher chiten content than the budding yeast. Some species contain as yet uncertified components. With electron microscope bud scars can be observed in the walls of yeat. Successive buds 20-40 from one bakers yeast cell, are always formed at different place on the cell surface.
A cell also contains a birth scar, which differs in appearance from a bud scar. yeast cells are generally uniuncleaste. The cytoplasm , may contain lipid globules volutin (Polyphosphate) granules, mitochondria and submicroscopic particles. Yeast cells usually stain deep brown when treated with iodine because of their high glycogen content.
2.8 CHARACTERISTICS OF BAKERS’ YEAST
Bakers’ yeast is composed of cells of one or more strains of sacchoromyces cerevisiae. Certain characteristics are required for the selection of this strains and it includes the following.
i. The yeast strains must possess the ability to give a good yield of cells in the mash or medium chosen for their cultivation.
ii. The yeast strains must possess the ability to give a good yield of cells in the mash or medium chosen for their cultivation.
iii. The strain should be of the characteristic to remain in the cake or dried form for a reasonably period.
iii. The should be stable. Mutation especially from true or ascospore forming yeast eg. Saccharomyces cerevisiae is undesirable as this will lead to the cultivation of an entirely different yeast strain, therefore stability is needed.
iv. The should be able to ferment the sugar vigorously and grow rapidly resulting in the production of carbon dioxide.
v. They should also be able to produce carbon dioxide rapidly during dough leavening. Is should be accelerated in the early phase of baking to form oven spring ( abrupt increase in volume of baked product before they are killed by the oven heat.
Vi The yeast strain should be able to import good aroma and sweetness on the dough.
2.9 PURE CULTIVATE ISOLATION AND CULTIVATION
Yeast grow over a wide range of temperature from ) to 470C. some will not grow below this whereas others will not grow below this temperature. The optimum temperature for most yeast is 200C to 300 C with 30 and 370C for pathogemic varieties.
Yeast generally grow best on media adjusted to PH 3.5 to 3.8, which inhibits most bacteria. The acid tolerance range varies with the specie from PH 2.2 to 8.0 sccharomyces cerevisiae growns at a temperature range between 20 to 300 C and an acid at Ph of 4 to 4.5 at this PH, competing bacteria are eliminated Broad spectrum antibiotics are added to the medium to inhibit bacteria.
5.0 CONCLUSION AND RECOMMENDATION
5.1 CONCLUSION
The purpose of bread making process is to present ceral flours to the consumer in an attractive palatable and digestibale form (Kent 1983). Fermented baked products such as bread is leavened by addition of baking yeast produced from saccharomyces cerevisiae. From the analysisdone, it was noticed that the crust colour, the texture, flavour taste and overall acceptability of both solate and the control at 300C temperature of proofing are relatively the same. This shows that our local palm wine is a good source of bakers’ yeast and can be efficiently used in bread production.
4.2 RECOMMENDATION
It is therefore recommended that bread should be produced at the options proofing0 temperature of 300c. because the isolated yeast and the control ( commercial bakers” yeast) at temperature of 300 C compared favourable in all the attributes tested.
Bread Production – Comparative Study Of Yeast From Palm Wine And Bakers’ Yeast Performance