The Production of Yam Flour
Chapter One
OBJECTIVE OF THE STUDY
MOTIVATION
The growing need for the variety of food in Nigeria has become a primary concern for the urban and rural households in Nigeria. In recent times, the concern has raised much researcher’s interest to do related studies. As reported in many different studies around the world, food security is a common problem.
OBJECTIVES
The present study aims at carryout an experiment on fresh yams, optimize the drying parameters and investigate the effect of drying conditions on the quality of the yam. To result to this, the present study which will address particular issues food drying could stimulate producers, farmers, agriculturists, educational practitioners on the phenomenon of drying to enhance the quality of yams to solve past harvest losses.
CHAPTER TWO
LITREATURE REVIEW
YAM
ORIGIN AND CULTIVATION OF YAM
Yam (dioscorea spp) in an annual or perennial tuber bearing and climbing plant belonging to the family of DIOSCOREACEAE. Some species of yam originated from Africa before spreading to other parts of the world while some originated from asia and have spread to Africa (Hahn et al 1987). Today, yams are growm widely throughout the tropics and they have a large biological diversity including more than 600 species worldwide (Burkill.,1960. Coursey.1967) but only six are widely cultivated in west and central Africa. These cultivated species are D.esculenta, D.alata, D.bulbifera, D.dumetorum, D.cagenensis and D.rotundata. wild types of yams also exist and may be used as food after undergoing processing during the hunger seasons (Telteh and Saakwa, 1994). A few yam species are also grown and used as health food and medicinal purposes (Albrecht and Mc carthy,2006). In the west Africa yam zone which Is the principal producer on global basis, D.rotundata, D.cagenensis and D.alata are commonly grown.
WATER YAM
Water yam (dioscorea alata) is also referred to as Asian greater yam and ten month yam (Martin, 1976). It is more important as food in west Africa and the caribbean than in asia and the America where it originated and also has been competing with the most important native species, D.roundata. it was introduced to Africa some hundred years ago from Malaysia through agriculturists and portugnese and Spanish seafarears,(Martin 1976) it is next to D.rotundata in terms of volume of production of extent of utilization. D.alata species is the highest yielding among the yam species and can store relatively longer that the other species (5-6 months) after harvest,D.alata is also known for its nutritional content with crude protein content of 7.4%, starch content of 75-84% and vitamin C content of ranging from 13.0 to 14.7mg/100g (Osagie,1992).
D.alata tubers have variable shapes, the majority being cylindrical,its tubers vary in numbers from one to five. The flesh of the tubers ranges in colour from white to purplish (FAO, 1994). The texture of its flesh is usually not firm as that of white yam and less suitable than other species for the preparation of most popular food product from yam (fufu and pounded yam especially in the west Africa region. However, it is reported that D.alata is a major staple food in cote‘d’ ivoire where it constitute about 65% of the yam owned in the country. (Orkwor, 1998).
AGRONOMIC CHARACTERISTICS OF YAM
Yam is a plant of the tropical climate and does not tolerate frosty condition (Coursey, 1967) it is grown and cultivated for its energy-rich tubers. And it is adaptable to fairly fertile soils and is suitable for inter-cropping with grains legumes such as cowpea, soya bean and variety of leafy vegetable. A well drained rich loamy soil however is the most favoured i.e for yam cultivation; yam requires a warm humid climate. However the crop possesses considerable drought. Resistance (IITA, 2009). Light intensity in known to affect growth and tuber formation. Short days between 10-11 hours promote tuber formation, while days longer than 12hours promote vine growth. This is usually the reason why yam vines are staked to ensure maximum interception of light by the leaves to promote yield (Coursey, 1982,Okezie,1987).
Traditionally, yams propagated vegetatively from whole tubers (seed yam) large tubers pieces (sets) or from minisets. The growth of yam starts with a sprout from the post dormant tubers (Passam.,1977,Onwueme,1978). Yams exibit a sigmoiodal growth pattern common to most annual plants. A period of slow growth during establishment is followed by phase of rapid exponential growth as the canopy reaches maximum area and finally growth rates decline as the canopy senesces(Solubo,1972).maturity has not been well defined in yam even though it is traditionally measured by dryness of vines (Okoli,1980). Osagie and Oputa (1981) also reported that the physiological stature of yam tuber as harvest may influence its storage period and food quality characteristics.
COMPONENT OF YAM
Yam tuber is the economically utilized part of the yam plant. Its chemical composition varies with species. It may vary due to the environmental condition of the places of cultivation(Onwueme.,1978). Yam is essentially a starchy food. its greatest single component is water accounting for about 65%-68% of the fresh weight. Carbohydrate on the other hand is the major component of the dry weight bases and second on the wet bases accounting for 20%-35% of the fresh weight (Dutta, 2003).
Most of the species contain carbohydrate which is mainly starch i.e. amylopectic branched chain starch exist in the cells in form of starch grains (Uguru.,1993). Sugar and protein are mainly in the quality of about 2-3% respectively with protein being mainly in sulphur containing amino-acid most of which are cost If the tuber is chilled (Purseglove, 1976). When cut, the tuber exudes mucilages and they are mostly glycoprotein containing the enzymes that help in the defence of the yam tubers under the soil against external attack or when injured (Asiedu,1992). Yam has small amount of alkaloids, vitamins and minerals like iron,phosphate.zins. alkaloids and steroids for examples dioscorine and diosgenien respectively are found in yam and they create a bitter taste which discourage pest from eating the tuber. This quantity could kill if taken in a large quantity in its raw state.
CHAPTER THREE
METHODOLOGY
The experiment was carried out to study the effect of the different drying method on the quality, colour and texture of the yam samples to used to obtain the yam flour and also to know and determine the effect of the drying parameters e.g. temperature, moisture content on the white yam(dioscorea rotundata).
MATERIALS AND REAGENTS
The white yam were purchased from ogbete market in enugu town,enugu state. The electrical oven used was obtained from caritas university amorji nike, enugu state.
The reagents used were water (H20) and sodium bi-carbonate (baking powder)
CHAPTER FOUR
RESULTS AND DISCUSSION
EFFECT OF TOTAL TIME ON THE DRYING YAM SAMPLES
The drying characteristics of the various yam samples varied according to the drying conditions. The rates were analyzed as total drying time. The total drying time to reduce the moisture content of the samples from approximately 90% dry weight to 10% dry weight basis varies for the different samples depending upon the operating conditions, drying time varied from 2-3days for the samples dried using an oven and 4-10 days for the other samples dried using sun drying method due to some fluctuations in weather and electrical supply for both methods.
CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
CONCLUSION
This project work was undertaken to experiment the effect of the different drying conditions on the quality, texture and colour of the yam flour.
A fully developed yam of marketable grade variety were acquired from ogbete main market in enugu state. The yams were cut and sliced to 2mm thickness and were separated into different samples ranging from sample A-G,the samples were dried from moisture content of 90% (w.b) to the final moisture of 10% (d.b).
The project were performed with an oven drying method of which the oven was kept at constant temperature of 500C (degrees) which was also monitored to avoid alteration and also the sun drying method was used and the temperature was indeterminable.
The focus were on the effect of the drying temperature, moisture content and batch size on the quality and colour of the yam flour.the drying characteristics and the quality of the processed yam flour were analyzed, the total drying time to reduce the moisture content of the yam samples approximately from 90%(w.b) to 10% (d.b) for processing of the yam flour were also established.
From the result gotten, it was observed that the oven method of drying though not really stable gave a better result on the samples it was used for other than the sun drying method whose temperature could not be determined. Also the effect of the sodium bi-carbonate used on some of the samples was seen as it gave a better colour and result when compared to the other samples it wasn’t used for. Finally, sample B which was yam boiled with sodium bi-carbonate and dried through the oven drying method at constant temperature of 50 degrees gave a best result, quality and colour when tested with hot water more than the other samples and this was as a result of the drying condition used and the presence of bi-carbonate in it which helped in achieving a flour with a brighter colour and better and quality.
RECOMMENDATIONS
From the experiment carried out and the results gotten, it could be seen that temperature variation had a great effect on the colour and quality of processed yam flours. To achieve a better and more acceptable result, the temperature should be kept low, constant and should be monitored closely to avoid alteration which might result in a poor quality of yam flour gotten as seen in the sun drying method used.
Also further studies should be carried out on the best chemicals which can be added to the yam samples to achieve better quality and result of flour. To make the results gotten more accurate, electricity supply should constant be during the time of the experiment as a instability of the supply might affect the drying time and the colour generally of the yam flour.
Finally based on the results of the study, studies should be carried out on how to improve on the colour, quality and nutritional value of the product.
REFERENCES
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- Burkill, I.H. (1960). The Organography and Evolution of Dioscoreeaceae, the family of the yams. Journal of Linnean Society of London, Botany 56: 319-412.
- Coulson , J.M., & Richardson J. (2003). Separation of Particle Volume 6. India: Elsevier publisher.
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