DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
FACULTY OF AGRICULTURE AND NATURAL RESOURCES MANAGEMENT (FARM)
IN PARTIAL FULFILLMENT FOR THE AWARD OF BACHELOR OF SCIENCE (B.Sc) DEGREE IN FOOD SCIENCE
TABLE OF CONTENT
1.0 Introduction 1
1.1 Objectives of the Study 3
2.0 Literature Review 4
2.1. Yam 4
2.1.1. Origin / History of yams 4
2.1.2. Agronomic characteristics of yam 4
2.1.3. Nutritional composition of yam 5
2.1.4. Utilization and processing of yam 7
2.1.5. Production process in instant poundo yam flour 9
2.1.6 Utilization of instant poundo yam flour 16
2.1.7 Nutritional aspects of yam processing 16
2.2 Millet 17
2.2.1 Origin/History of Millet 17
2.2.2 Description of Millet 18
2.2.3 Nutritional Composition of Millet 19
2.2.4 Utilization of Millet 20
2.2.5 Production process of Millet Flour 22
2.2.6Storage of Millet Flour 23
2.3 Composite Flour 23
2.3.1 Importance of composite flour 24
3.0 Materials and Methods 25
3. 1. Source of Raw Materials 25
3. 2.Equipments and Instruments used 25
3.3.Methods for Flour Production 25
3.4. Dough Making 29
3.5. Proximate Analysis 29
3.6 Functional Properties Determination 33
3.7. Sensory Evaluation 42
Yam (Dioscorea species) is an important tropical root crop. It is also an important source of carbohydrate for many people of the Sub-Sahara region, especially in the yam zone of West Africa (Akissoeet al, 2003). Babaleye (2003) reported that yam contributes more than 200 dietary calories per capita daily for more than 150 million people in West Africa and serves as an important source of income to the people.
Yam constitutes a nutritious high carbohydrate and fibre food source. Other nutrients present in yam are caloric proteins, minerals and vitamins (Onwueme and Charles, 1994). The crop is important in household food security, diet diversification, employment and income generation as well as alleviation of poverty (Akinoso and Olatoye, 2013). Yams are ranked as the fourth major root crop in the world after cassava, potatoes and sweet potatoes (Adeleke, 2010). Yams are characterized by high moisture content, which renders the tubers more susceptible to microbial attacks and brings about high perishability of the tubers with an animal production of above 28 million metric tonnes (FOS, 2011); Nigeria is the world's largest producer of edible yam with D. rotundataand D. alataas the two most cultivated yam species in the country.
According to Egbeet al. (1984), D. rotundata(white yam) is made up of 67% moisture. By dry weight, the yam is composed of 80% starch, 7% protein, 7% minerals, 3% fiber and 1.7% lipids. Industrial processing and utilization of yam includes starch, poultry and livestock feed, production of yam flour and instant-pounded yam flour production. Traditionally, the processing of pounded yam using pestle and mortar is highly valued but is gradually being replaced in the market with the instant -pounded yam flour. Instant- pounded yam flour requires short processing time and less energy (Akinoso and Olatoye, 2013).
Poundo yam which is also referred to as instant pounded yam flour (IPYP) is a processed white powdery form of yam (dehydrated yam flour) which is produced in a desiccating machine (Ayodejiet al., 2012). It is a fast means of making pounded yam which is done by pouring a measured quality of the yam flour into boiling water, which is stirred continuously until the required texture and taste is achieved (Ayodejiet al., 2012). The basic technology of yam includes peeling, washing, slicing/dicing, cooking, drying, milling and packaging.
Millets are indigenous African cereals that, unlike wheat or rice are well adapted to African semi-arid and sub-tropical agronomic conditions. They are basically use as human foods and folder (Wikipedia, 2012). The most widely grown millet is the Pearl millet, which is an important crop in India and parts of African (FAO, 1996). Indeed, in many African countries, millet is often the main component of many meals and is essentially consumed as steam –cookedproducts (couscous), thick porridges (TO) and thin porridge (Ogi), which can be used as complementary food for infants and young children and also used in brewing beer (Fasasi, 2010). Pearl Millet is nutritional better than most other cereals; it has high levels of calcium, iron, zinc, fiber, vitamin, lipids and proteins (Wikipedia, 2012). However, millet also features high fiber content and poor digestibility of nutrients, which severely limits their value in nutrition and influence their consumer acceptability (FAO, 1996).
Although Millets are nutritionally superior to other cereals, yet their utilization in the country is not widespread (Vijayakumar and Mohankumar, 2009). They are mostly used in preparation of traditional dishes. One possible way of extending their utilization could be done by blending them with other flours like yam flour as the suitable processing. On addition of millet flour to yam flour or other flours, there would be changes in nutritional and functional characteristics of the flour. This is because some of the chemical composition of the yam flour will be increased. For example, the millet flour which is high in fiber content will increase the low fiber content of the yam flour, since high fiber content of the food product increases bulk in humans and helps to reduce constipation among the consumers. Such information will be useful to food processors and nutritionists to formulate commercial product based on yam and millet flour blends.
OBJECTIVES OF THE STUDY
The objectives of this study are:
I. To produce high fibre instant poundo yam flour with millet flour blend.
II. To determine the proximate and functional properties of the high fibre instant poundo yam blended with millet flour.
III. To determine the sensory properties of the meal of the fibre instant pound yam flour blended with millet flour
2.1.1. ORIGIN / HISTORY OF YAMS
Yam (Dioscorea species) is an annual or perennial tuber-bearing and climbing plants belonging to the family of Diocoreceae. 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 (Halmet al, 1987). Today, yams are grown widely throughout the topics and they have a large biological diversity including more than 600 species worldwide (Burkill, 1960; Coursey, 1967), but only six species are widely cultivated in West and Central Africa. There cultivated species are D. alata, D. bulbifera, D. dumetorun, D. esculenta, D. cayenensis and D. rotundata. Wild types of yam also exist and may be used as food after undergoing processing during the' hunger seasons (Tettch and Saakwa, 1994). A few yam species are also grown and used as health food and for medicinal purposes (Albrecht and McCarthy, 2006). In the West Africa, which is the principal producer of yam on a global basis, D rotundata, D. cayenesisand D. alataare commonly grown.
2.1.2. AGRONOMIC CHARACTERISTICS OF YAM
Yam is a plant of the tropical climates and does not tolerate condition (Coursey, 1967). It is grown and cultivated for its energy - rich tuber. It is adapted to fairly fertile soils and is suitable for intercropping with grain legumes such as cowpeas, soybeans and a variety of leafy vegetables. A well drained rich loamy soil however is the most favourable for yam cultivation. Yam requires a warm humid climate; however the crop possesses considerable drought resistance (IITA, 2009). Light intensity is known to affect growth and tuber formation. Short days between 10 to 11 hours promote tuber formation while days longer than 12 hours 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 are propagated vegetatively from whole tubers (seed yams); large tuber pieces (sets) or from mini sets. The growth of yam starts with a sprout from the post dormant (Passam, 1977; Onwueme, 1978). Yams exhibit a sigmoidal growth pattern common to most annual plants. A period of slow growth during establishment is followed by a phase of rapid exponential growth as the canopy reaches a maximum area and finally growth rates decline as the canopy senesces (Sobulo, 1972). Maturity has not been defined in yam even though it is traditionally measured by the dryness of vines (Okoli, 1980). Osagie and Oputa (1981) also reported that the physiological status of yam tuber at harvest may be influence its storage period and food quality characteristics.
2.1.3. NUTRITIONAL COMPOSITION OF YAM
Yam tuber is the most 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 - 85% of the fresh weight. Carbohydrate on the other hand is the major component of dry weight basis and second on wet weight basis accounting for about 20 - 35% of the fresh weight (Dutta, 2003).
Most of its species contain carbohydrate which are mainly starch i.e. amylopectin branched chain starch existing in the cells in form of starch granules (Uguru, 1993). Sugar and protein are only in a quantity of about 2 -3% respectively, with protein being mainly sulphur containing amino-acid most of which are caused if the tuber is chilled (Purseglove, 1976). When cut the tuber exudes mucilage and these are mostly glycoprotein containing the enzymes that help in the defence of the yam tuber under the soil against external attack or when injured (Asiedu, 1992). Yam also has small amount of fat,vitamins and minerals like iron, phosphate, and zinc. Alkaloids and steroids, for examples dioscorine and diosgenien respectively, are also found in yam and they create a bitter taste which discourage pest from eating the tuber. This toxin could kill the consumer if taken in a large quantity in its raw state. Basically yams contain low fibre content.
Table 1: Chemical composition of yam (D. rotundatd) (White yam)
Source: Walsh, (2003)
Furthermore, most yams tend to be rich in thiamin, riboilavin, niacin, etc (Edijala, 1980). Yam products generally have a lower glycemic index than potato production which means that they will provide a more sustained form of energy and give better protection against obesity and diabetes (CCIAR, 2006).
2.1.4. UTILIZATION AND PROCESSING OF YAM
By far, the greater part of the world's yam crop is consumed fresh. Tuber utilization is mostly as boiled or pounded yam. For use in fresh form, tubers are stored between harvest periods. The use in fresh form, tubers has been in home food with little including trial involvement (Rasper and Coursey, 1967). Changes in whole wholesomeness during storage include would repair diseases and pests of stored tubers. Hence, yam tubers are lost after 4 -5 months of storage. Drying of (injured) tubers soon after harvest and converting into slices or milling into flour for fufuensures availability of yam in various forms. Traditionally processed yam products are made in most yam-growing areas, usually as a way of utilizing tubers that are not fit for storage. Usually, fresh is peeled, boiled and pounded until a sticky elastic dough is product (Coursey, 1967; Osagie, 1992). Another important product from yam processing is yam flour (instant poundo or pounded yam flour).
Traditionally yam is processed to fufu by peeling, slicing/cubing, cooking, and pounding in mortar (wooden mortar) and fufu is constituted though this process. Up till today, this procedure is still practiced in remote parts of South East Nigeria and yam pounding into fufu still accompany many ceremonial occasions in this part of the country (Bonetalet al, 1994),
Industrial processing has brought a more enhanced and efficient method of yam processing into instant fufu flour or instant poundo yam flour (yam yam). It has made the fufu making process easier and the availability of yam fufu increased, as the yam flour can be stored for a very long period of time than the fresh yam which is used for the traditional processing; as well as the stress in pounding the yam (cooked cubes) are reduced as it only needs reconstitution of the flour into fufu with hot boiled water and stirring it till the required texture is formed (Bonetaet al, 1994).
2.1.5. PRODUCTION PROCESS IN INSTANT POUNDO YAM FLOUR
The production process consisting of simple unit operation which have been mechanized the Hour chart for the production of poundo yam flour production is presented below:-
Yam Selection and Weighing
Washing and Slicing
Dicing and Sulphiting (0.1% Sodium metabisulphite)
Drying (hot air oven 50 – 700C)
INSTANT POUNDO YAMFLOUR
The Basic unit operations in yam processing are:-
220.127.116.11.YAM SELECTION AND WEIGHING
Wholesome suitable yam tubers are selected for IPYF (Instant Pound Yam Flour) production; the wholesome tubers are sorted during sorting. During sorting, yam tubers that are disfigured during harvest are rejected and it is very important to select carefully or internal deterioration due to aging may have started. If the yam tuber have been stored for a long period of time, the enzymes that are present may have brought about deterioration due to temperature of the storage area (barn, store house, underground etc). If the yam tubers have been exposed to some light, this type of condition can also lead to spoilage which may not be visible at mere looking at the yam tuber. A simple way of detecting spoilage is by scalping off the back of the yam tuber and viewing it for seconds, if there is internal spoilage, it will show brown to black discolouration in few seconds depending on the level of spoilage. The enzymes that can cause discoloration of yam and spoilage are polyphenoxidase (PPO), perioxide (POP), fenitic acid, flavanol, climanic acid, hexokinase, phosphorylase, alcohol dehydrogenase (Ugochukwuet al, 1984).
The second unit operation after the sorting of the yam tubers is weighing and it involves using a measuring balance, to know the weight of the yam tubers.
18.104.22.168. PEELING OF YAM
This is the removal of the outer corky periderm. The method of peeling varies. The general methods apply include:-
(a) Steam Peeling: This involves the exposure of the tubers to steam pressure for a period of time. The process may be batch or continuous.
During this steam exposure, the stream penetrates the cortex, often the peel and results in a slight expansion of the space between the peel and the cortex. This makes it easy for the peels to be removed when subject to minor abrasive or mechanical processing.
(b)Chemical Peeling: This involves the immersion of the yam tuber in some non-toxic chemical such as caustic soda solution of low concentration which helps to soften the peel. Usually, when this method is used, they are couplet with the use of heat. The process is controlled by varying the concentration of the lye and its temperature for effective peeling process. One major setbacks of this method is the need to use a large volume of water to remove the effect of the chemicals during the post-peeling washing.
(c) Mechanical Peeling: The basic mechanical methods includes the Abrasive peelers, rotary laid mounted rim peelers and use if belt conveyor. In the abrasive peeler, the peeler consists of a vertical cylinder with a rotating disc in the bottom and a hinge cover at the top. Abrasive grits may be applied to the inner walls of the chambers or to rotating disc or both. A measured load of the root or tuber is put into the cylinder and when the disc is rotated, the tuber spins or thimble so that the peels are rubbed off when the tubers shall against the abrasive surface.
Sulphiting serves a multifunctional role in foods. They posses antimicrobial activity and inhibit both enzymatic non-enzymatic browning reactions which during. Bisulphate exerts competitive inhibitory effect on polyhenoloxides, by binding a sulphydrl group at the active site of the enzyme. On the other hand, bisulphate inhibition is due to the reaction of sulphites with intermediate quinones, resulting in the formation of sulphoquinones which irreversibly inhibits polyhenol oxidase causing complex inactivation.
Although sulphites are very effective in controlling browning, they are subject to regulatory restrictions owing to their potentially adverse effect on health. Many reports have described allergic reactions in humans, following the ingestion of sulphite-treated foods by hyper sensitive asthmatics. The of sulphiting agents in food processing is based on sulfurdioxide equivalences. The Joint Expert Committee on Food Additives (JECFA) of the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) recommended an acceptable sulphite intake of 0.07mg sulphur dioxide per kg of body weight. Food and Drug Administration (FDA) has proposed maximum residual sulpher dioxide levels for certain foods.
22.214.171.124 BLANCHING: Steam blanching is the operation that takes care of phenoxidase and polyphenoxidase compounds and other enzymes which act on the phenol compounds present in yam tubers to bring about discolouration (Browning), when exposed to air for some time after cutting. When the yamclips turn brown, the colour of the yam flour after milling will also be brownish due to the fact that the colour of the dried yam chips must affect the colour of the flour after milling.The purpose of blanching operation is to reduce browning or discoloration of the yam clips when milled to flour and will have a brighter colour and more acceptable look or appearance to compare with unbalanced yam flour. The time of blanching also determines the levels of enzyme reduction (Negron, 1995).
The blanching temperature is the most important parameter in the unit operation, because if the temperature is not up to achieved deactivation. The purpose of blanching is not achieved but if the operation is carried out at required temperature which is not favourable to the target enzymes 20 minutes can deactivate polyphenoxidase, or either use of 100 °C in 2 minutes can still do the same (Bonetaet al., 1984).Blanching time can also affect the operation. If the time is not well kept, it can lead to over blanching or under- blanching and some of the targeted enzymes will not be favoured by this phenomenon.
Blanching time is directly proportional to the temperature used for the operation and when blanching at low temperature, longer time should be taken than when blanching at high temperatures.
Drying is defined as a process of simultaneous heat and moisture transfer in which heat is required to evaporate the moisture that flows from the product surface into an external drying medium usually air. It could also be defined as the removal of biologically active water. These stop the growth of microorganisms, reduce the rate of enzyme activity and chemical reaction.
The main objective of drying is to preserve the product during prolong storage. The drying process meets the objective by reduction the moisture content of the product to levels which are adequate to limit microbial growth or other reactions. Moisture content reduction results in preservation of quality characteristics such as flavour, nutritive value and the significant reduction in product volume. The removal of moisture to produce most dehydrated foods is accomplished by thermal dehydration, a process that utilizes heat to remove the moisture held in the product. First heat transfer is involved in removing the heat from the heating medium to the point at which evaporation occurs (Heldman, 1975).
Drying not only inhibits microbial growth in foodstuffs but also preserves colour, texture, flavour and nutritive value; so the process of drying should benecessarily controlled in order to prevent thermal degradation of the products. The level of moisture required to prevent microbial growth is usually less than 10% where as for prevention of biochemical deterioration, is much lower than 5% (Peterson and Johnson, 1974). The basic methods of drying include oven drying, sun drying and micro wave or UV radiation drying.
Milling is aimed at grounding the food materials to the required particle size of the fine flour which required. Good milling quality gives good reliable flour. There are many types of machines used in the milling of food products. The recommended milling machine like hammer mill is good for the instant poundo yam flour processing operations as it is efficient in obtaining the particle size, as well sieves of required aperture size can be used to sieve the flour after milling to get the required size of flour particle.
126.96.36.199 PACKAGING AND STORAGE CONDITIONS OF YAM FLOUR
After the production of yam flour, it is still prone to spoilage if not well packaged. The flour can re-absorb moisture from the atmosphere and microbial activity can be enhanced from this point. The packaging material should be such that there will be no interaction with the packaged product (yam flour) and the external environment which means that the natural should be permeable to moisture and gases that can cause spoilage. When yam flour is stored in a good packaging material like polyethylene bags, the shelf life is not altered (OtusanyaandJegar, 1996).
Yam after packaging can be effectively stored for a long period of time of about 12 months or more. It is stored in environments where rodents and insects are absent, because rodents and insects cause a great deal of damage to stored yam flour. Storage of yam flour should be done in correctly constructed storage silo, built very well so that rodent and insect infestation will be impossible aswell insecticide should be applied on the surrounding of the storage silo, but care should be taken so that the insecticide being toxic do not get close of diffuse into the stored yam flour. Example of insect that attack the yam flour is fasciculate D.G. (Krokida, 1998).
2.1.6 UTILIZATION OF INSTANTPOUNDO YAM FLOUR (IPYF)
IPYF is generally stirred vigorously in boiled hot water to yield fufu of good texture and consistency which can be eaten with vegetable soups or meats and fish stews. IPYF can also be combined with other flours like wheat, cocoyam, potato, cassava, maize, millet flours to form better flour for the production of confectionary foods, For example, IPYF and wheat flour can be combined in making of biscuits (Bonetaet al, 1984).
As well, IPYF can serve as stabilizers in soup making. For example, Nsala soup, this is an Ibo soup from the south eastern part of Nigeria. It is normally consumed by women that newly gave birth to babies; it can serve as household soup as well, but in cultural aspect it is regarded especially as soup for women that just put bed (Okaka and Okaka, 2001).
2.1.7 NUTRITIONAL ASPECTS OF YAM PROCESSING
On the basis of reduction in nutrients the preparation of yam flour appears to be most detrimental process dealing to heavy nutrient losses, particularly minerals and vitamins.
Fufu preparation and boiling of peeled yam (blanching) also causeexcessive losses due to the fact that yam contain water soluble vitamins and minerals which are lost during this process. Although blanching unpeeled yam tuber is a relatively lengthy process, but it has little effect on the nutritional values (Bonetaet al, 1994).
The processes that appear most advantageous are charcoal grilling and frying in palm oil. Nutrient loses thus appear to depend primarily on the amount of edible surface exposed during processing. Peeling after blanching reduces loses in the edible portion source less is removed during this operation.
Blanched yam flour when compared to un-blanched yam flour will have lower nutritional quality due to vitamins and minerals loss during the blanching operation, to reduce the rate of nutrients loss. Time of blanching should not be so long or lengthy as well as blanching of unpeeled yam can go a long way in retention of nutrients in yam (Krokida, 1998).
2.2.1 ORIGIN/HISTORY OF MILLET
Millets are a group of highly variable small-seeded grasses, widely grown around the world as cereal crops, or grains for both human food and folder. Millets are indigenous African cereals that unlike wheat or rice are well adapted to African semi- arid and sub-tropical agronomic conditions (Wikipedia, 2012). The crop is favoured due to its productivity and short growing season under dry, high temperature conditions (McDonough etal, 2000).
The most widely grown millet is Pearl millet, which is an important crop in India and parts of Africa (especially in Nigeria and Niger). Finger millet, Proso millet and Foxtail millet are also important crop species. In the developed world, millets are less important. For example, in the United States the only significant crop is Proso millet, which is mostly grown for bird seeds (McDonough et al, 2000).
While millets are indigenous to many parts of the world, millets most likely had an evoluntary origin in tropical Western African, as that is where the greatest number of both wild and cultivated forms exist (FAO, 1995). Millets have been an important food staples in human history, particularly in Asia and Africa, and they have been in cultivation in East Africa for the last 10,000 years (Luetal, 2009).
2.2.2 DESCRIPTION OF MILLET
The height of the Pearl millet plant may range from 0.5 to 4 meters. The Pearl millet grain has great variation, and can be nearly white, pale yellow, brown, grey, slate blue or purple. The kernel shape has different classification; obovate, hexagonal, lancerlate globular and elliptical (McDonough et al, 2000). Grains of Pearl millet are about 3 to 4mm long, much larger than those of other millets. The seeds usually weigh between 2.5 and 14 grams, with a typical mean of 8 grams. The size of the pearl millet kernel is about one-third of sorghum. The relative proportion of germ to endosperm is higher in pearl millet than in sorghum.
2.2.3 NUTRITIONAL COMPOSITION OF MILLET
Millets, like sorghum are predominantly starchy. The protein content is comparable to that of wheat and maize. Pearl and little millets are higher in fat, while finger millet contains the lowest fat. They are also rich in carbohydrate content and energy valve. Millets are also relatively rich in iron and phosphorous. The bran layers of millets are good sources of B-compare vitamins. However millets also feature high fiber content and poor digestibility of nutrients, which severely limit their valve in nutrition and influence their consumer acceptability (FAO, 1995).
The protein content in millet is very close to that of wheat; both provide about 11% protein by weight, on a dry water basis. Millets are rich in B vitamins (especially niacin, B6 and folic acid), calcium, iron, potassium, magnesium and zinc. Millets contain no gluten, so they are not suitable to raise bread. When combine with wheat, they can be used to raise bread. Alone, they are suited for flat bread (FAO, 1999).
Table 2: Chemical composition of Pearl millet (per l00g portion, raw grain)
Water (%) 9.2
Energy (KJ) 1582
Protein (%) 13.3
Fat (%) 6.3
Carbohydrate (%) 75
Fiber (%) 8.5
Calcium (mg/kg) 55
Phosphorous (mg/kg) 358
Source: FAO, 1995
2.2.4 UTILIZATION OF MILLET
Of the 30 million tonnes of millet produced in the world, about 90 percent in utilized in developing countries and only a tiny volume is used in the developed counties outside the former Soviet Union. Exact statistics that are unavailable for most countries, but it is estimated that a total of 20 million tonnes are consumed as food, the rest being equally divided between feed and other uses such as seed, the preparation of alcoholic beverages and waste. Six countries (China, Ethiopia, India, the Niger, Nigerian and the former Soviet Union) are estimated to account for about 80% of global millet utilization (FAO, 1996).
188.8.131.52 AsHuman Food
Consumption of millet varies greatly among countries, though it is the highest in Africa. In the Sahel, millet is estimated to account for about one-third of the total cereal food consumption in Burkina Faso, Chad and the Gambia, roughly 40 percent in Mali and Senegal and over two thirds in the Niger. Other countries in Africa where millet is significant food item includes Ethiopia, Nigeria and Uganda.
In Western India, sorghum has been commonly used with millet flour, to make local staple, hand rolled flat bread. Millet porridge is a traditional food in Russian, German and Chinese Cuisines. People with coeliac disease can replace gluten-containing cereals in their diets with millet (FAO, 1995).
184.108.40.206As Animal Feed
Utilization of millet as animal feed is negligible in absolute terms and compared with other uses and other cereals. It has be estimated that only about 10 percent of the millet used globally is fed to animals and birds (Wikipedia, 2012).
220.127.116.11 As Alcoholic Beverages
Millets are traditional important grains used in brewing millet bear in some countries, for instance by the Tao people of Orchid island and in Taiwan. Various people in East Africa brew a drink from millet known as "ajono", a traditional brew of the Teso. The fermented millet is prepared in a large pot with hot water and people share the drink by sipping it through long straws (Wikipedia, 2012)
2.2.5 PRODUCTION PROCESS OF MILLET FLOUR
Steeping (24 hours)
Steaming (20 minutes)
Drying (over at 70oC for 10hrs)
Steeping (24 hours)
Steaming (20 minutes)
Drying (over at 70oC for 10hrs)
Figure 2: Flow Diagram for the production of millet flour Storage
The millet grains are cleaned, winnowed and soaked in water for 24 hours. The soaked grains are steamed for 20 minutes, and sun-dried to moisture content of 10-12% and milled into flour.
2.2.6 STORAGE OF MILLET FLOUR
Flour is usually produced as it is needed and is not often stored for a long period of time because it tends to turn rancid. This is particularly evident with Pearl millet flour, because of its very high fat content. Millets especially Pearl millets are therefore best stored as whole grain.
2.3 COMPOSITE FLOUR
Composite flour is a mixture of different flours from cereal, legumes and roots and tubers that air created to specific function characteristics and nutrition (Akobundu, 2009). Composite flour that contains cereals and legumes has proven practical uses and are being utilized in many parts of the world to improve the nutritional and functional properties of the flour.
Basically, composite technology refers to be as the process of mixing cereal flour with legumes, root and tubers to make use of local raw to produce high quality food products in an economical way. In many cases, it implies the practical substitution of wheat flour in a staple diet with other cereals, or flour derived from legumes, root and tubers as a means of divesting and upgrading the local agricultural find products (UNECA, 1985).
For economic and pulses as social reason, the India sub-content heavily depends on pulses as sources of protein, minerals and vitamins in the daily diet of people (Singh, 1997). In selecting the components to be used in composite flour blends, the materials should be preferably be readily available, culturally acceptable and provide increase nutritional potential (Akobunduet al, 1998).
2.3.1 IMPORTANCE OF COMPOSITE FLOUR (A case study of the instant poundo yam flour and the millet flour blend).
1. Nutritional Enhancement and their Proportion: Flours produced from either cereals, legumes or tubers will have a nutritional valve inferior to those produce from the combination of cereals, legumes or tuber. For instance, yam flour is readily low in fiber content; but blending the flour with millet flour whose fiber content is richly high will make the flour blend to be richly high in fibre content.
2. The use of composite flour of water yam and millet for meal production would enhance the utilization of local crops as rawmaterials, improve the nutritive quality of meals and improve the local economy (Okpalaetal., 2010).
3. The use of composite flours finds their greater use in providing variety to diet (Iwe, 2003). Since the importance of fiber foods (instant poundo yam and millet flour blends) will help nutritionally in high blood sugar and cholesterol reduction in the body.
MATERIALS AND METHODS
3.1. SOURCE OF RAW MATERIALS
The yarn tubers (Diosocrearotundata] locally called white yam and the millet seeds will be purchased from Abakaliki Main Market, Abakaliki, Ebonyi State, Nigeria.
3.2. EQUIPMENTS AND INSTRUMENTS USED
a. Oven, b. Weighing balance, c. Hammer Mill, d. Warring Blender
3.3. METHODS FOR FLOUR PRODUCTION
3.2.1. Preparation of Instant Poundo Yam Flour
3.2.1. Preparation of Instant Poundo Yam Flour
Instant Poundo Yam Flour (IPYF) will be produced from the method as described by FIIRO (2005). The yam tubers will be selected, weighed and washed to remove sand, dirt and other adhering materials. The yam tubers will be peeled and sliced to 0.02mm thickness, after slicing the yam slices will be dipped in water containing 0,1% Sodium metabisulphate so as to arrest the browning reaction and placed in a sieve to remove excess water after which they will be blanched for 10 minutes at 100°C. The blanched yam slices will be dried in an oven at 70°C for 10 hours which will be milled and sieved, packaged in polyethene bag and stored prior to analysis.
Yam Selection and Weighing
Washing and Slicing
INSTANT POUNDO YAMFLOUR
Washing and Slicing
INSTANT POUNDO YAMFLOUR
Figure 3: Flow sheet for the production of IYPF
3.2.2. Millet Flour Production
Millet flour will be prepared by the method described by AOAC (1990). Millet grains will be sorted to remove particles, defective seeds and stones before cleaning thoroughly washed in clean tap water. The seeds will be soaked in water (steeping) for 24 hours. The seeds will be boiled in water for 20 minutes at 100°C and drained so as to deactivate the trypsin inhibitors. The seeds will be oven dried at 70°C for 10 hours. After drying, the millet seeds will be milled to fine powder and sieved through a standard sieve of 400um particle size. The flour will be packed in a polyethene bag and stored prior to analysis.
Steeping (24 hours)
Steaming (20 minutes)
Drying (over at 70oC for 10hrs)
Figure 4: Flow chart for millet flour production.
Steeping (24 hours)
Steaming (20 minutes)
Drying (over at 70oC for 10hrs)
Figure 4: Flow chart for millet flour production.
2.2.3 Blend formation
The instant poundo yam flour (!PYE) and millet flour (MF) will be blended together using a warring blender at different ratio of 90:10, 80:20, 60:40 and 70:30% of IPYE and MF, respectively. The flour blends will be labelled as follows: -
YF: (100% IPYE), YFMF1: (90% IPYE: 10% Millet Flour), YFMF2: (80% IPYF: 20% millet flour), YEMF3: (70% IPYE: 30% millet flour) and YFMF4: (60% IPYF: 40 millet flour).
Figure 5: Flow diagram of blend formation.
IYPF = Instant poundo yam flour
MF = Millet flour
YSMF 1 = 90% IPYF + 10% millet flour
YSMF 2 = 80% IPYF + 20% millet flour
YSMF 3 = 70% IPYF + 30% millet flour
YSMF 4 = 60% IPYF + 40% millet flour
3.3.4. Storage of Samples
All flour samples will be stored in polyethene bags prior to analysis.
3.4. DOUGH MAKING
The high fiber instant poundo yam flour and millet flour will be prepared in the laboratory using the manual method of processing.
3.4.1. Dough preparation
The hot water will be boiled on a pot on a gas cooker. A quality of the flour blend i.e. 90:10%, 80:20%, 60:40% and 70:30% will be poured in the boiling water and stirred continuously till it gelatinizes into a thick dough. A little quality of water will be added to allow the flour cook properly; the paste will be stirred till semi-dough will be obtained.
Mixed flour Blends (Yam and Millet Flours)
Boiling water (1000ml)
Stirring the dough
Addition of water (500ml)
Stirring the dough unitl it gelatinizes
Figure 6: Flow diagram for high fiber Instant Poundo Yam and Dough Processing
3.5. PROXIMATE ANALYSIS
Each flour sample will be analyzed for moisture content, crude protein, crude fat, Ash, crude fiber and the carbohydrate content will be calculated by difference method.
3.5.1 DETERMINATION OF MOISTURE CONTENT
The moisture content will be determined using the procedure described by AOAC (1990). The moisture content of each sample will be determined by weighing 5g of the sample into an aluminum moisture canor a crucible. The sample will be dried in the oven to a constant weight at 105±2°C .
% Moisture Content =
(weight of can + sample) - (weight of empty can) x100
Weight of sample 1
3. 5.2 DETERMINATION OF CRUDE PROTEIN
The protein content will be determined using a Foss Tescator Protein digester and KJECTEC 2200 distillation apparatus (Kjeldhal method) according to the procedure of AOAC, (1990). Concentrated H2SO4 (12ml) and 2 tablets of catalyst will be put into a kjedhal digestion flask containing Ig of the sample. The flask will be placed in the digestor in a fume cupboard and switched on and the digestion will be done for 45 minutes to obtain a clear colourless solution. The digest will be distilled with 4% boric acid, 20% sodium hydroxide solution will be automatically metered into it in the KJECTEC 22000 distillation apparatus or equipment until distillation will be completed. The distillate will then be titrated with 0.1 HCI until a purple colour formation indicating the end point. A blank will be run under the same condition as with the sample. Total nitrogen content will be calculated according to the formula below:
Crude Protein = (Titre valve (of sample) - blank) xO.Olx 14.007 x 6.25 x 100
Weight of sample 1
3.5.3 DETERMINATION OF CRUDE FAT CONTENT
Crude fat will be extracted in a soxhlet extractor with hexane and quantified gravimetrically as described by AOAC (1990). Ig of sample will be weighed into an extraction thimble and will be topped with grease-free cotton. Before extraction will commenced, the round bottom flasks will be washed, dried, cooled and weighed. The thimble will beplaced in the extraction chamber and 80ml hexane will be added to extract the fat. The extraction will be carried out at 135°C and will last for 1 hour 40 minutes after which the fat will be collected in the bottom flasks will be cooled in a dessicator.
% Crude Fat =weight of fat + 100
Weight of Sample 1
3.5.5. DETERMINATION OF CRUDE FIBER
Crude fiber will be determined using the method described by AOAC (1990). 2g of the sample will be transferred into 1 liter conical flask. 100ml of Sulphuric acid (12.5M) will be heated to boiling and then introduced into the conical flask containing the sample. The contents will be then boiled for 30 minutes and ensuring that the level of the acid will be maintained by addition of distilled water. After 30 minutes, the contents will be filtered using a muslin cloth held in funnel. The residue will be rinsed thoroughly until its washing will no longer acidic to litmus. The residue will be transferred into a conical flask containing the sample. 100ml of sodium hydroxide (12.5M) will be brought to boil and will be introduced into the conical flask containing the sample. The contents will be boiled for 30 minutes and ensuring that the level of the base was minted by the addition of distilled water. After 30 minutes, the content will then filter thoroughly until its washing will no longer be alkali. The residue will be introduced into an already dried crucible and will be ashedat 600°C ± 200°C
% Crude Fiber = Final weight of crucible - initial weight of cruciblex 100
Weight of sample 1
3.5.6 DETERMINATION OF CARBOHYDRATE CONTENT
The difference method described by AOAC (1990) will be used to calculate the % carbohydrate content.
% Carbohydrate Content = 100% - % (Protein + Moisture + Fat + Fiber
+ Ash Contents).
3.6 FUNCTIONAL PROPERTIES DETERMINATION
3.6.1 DETERMINATION OF BULK DENSITY
The method as described by Onwuka (2005) will be used to determine the bulk density of the samples. Ten milliliters capacity graduated measuring cylinder will be weighed and recorded. The cylinder will be filled with the sample and tapped gently from the bottom for 30 times until there will be no further dimunsion of the sample level after to the 10ml mark. The bulk density will be calculated as follows.
Bulk Density (g/ml) = weight of sample (g)
Volume of sample (ml)
3.6.2 DETERMINATION OF DISPENSABILITY
Dispensability will be determined using the method described by Kulkarniet al. (1991). 10 grams of the flour sample will be weighed into 100ml measuring cylinder, water will be added to each volume of 100ml. The set up will be stirred vigorously and allow to stand for 3 hours. The volume of the settled particles will be recorded and subtracted from 100. The difference will be reproved as the percentage dispensability.
% Dispensability = 100 - Volume of settled particles.
3.6.3DETERMINATION OF WATER ABSORPTION CAPACITY
The water absorption capacity shall be determined according to the method described by AOAC (1990). 1g of the sample shall be weighed into a labeled test tube; 10ml of distilled water shall be added. The tube shall be allowed to stand for 30 minutes at room temperature, they shall be centrifuged at 5000rpm for 10 minutes and the supernatant water shall be poured into graduated measuring cylinder. The volume of water decanted shall be measure and recorded as the excess water remaining after absorption. The water absorption capacity shall be calculated as:
Water Absorption Capacity = V1 – V2 x SG
V1 = Initial volume of water
V2 = Volume of water left after absorption
W = weight of sample used
SG = Specific gravity of water (1.0)
3.6.4 SWELLING CAPACITY DETERMINATION
The swelling capacity of the sample shall be determined by the method described by Lin (1973). 1g of the sample shall be weighed into a centrifuge tube and the weight of the tube plus the sample shall be taken. 10ml of distilled water shall be added and thoroughly stirred with a glass rod for about a minute. The suspension shall be left to stand for 30 minutes at room temperature. The free water shall be decanted, after which the new weight of the sample shall be recorded. The swelling capacity shall be calculate as:
Swelling Capacity (%) = W2 – W1 x 100
W1 = Weight of sample after decanting water
W2 = Weight of sample before water was added.
3.6.5.DETERMINATION OF GELATINIZATION TEMPERATURE
The method as described by Onwuka (2005) shall be used 10g of the sample will be weighted into a test tube. The aqueous suspension shall be heated in a boiling water bath with continuous stirring. Gelatinization temperature shall be determined and recorded 30 seconds after gelatinization shall be visually noticed.
3.6.6DETERMINATION OFOIL ABSORPTION CAPACITY
The method of Onwuka (2005) will be used to determine oil absorption capacity. One (1) gram of the sample will be weighted into a graduated centrifuge tube and mixed thoroughly with 10ml of oil using a warring whirl mixer, for 30 seconds. The sample will be allowed to stand for 30 minutes at room temperature and then centrifuged at 1600 rpm for 30 minutes. The volume of free oil (the supernatant) will be read directly from the graduated centrifuge tube.
Oil Absorption Capacity
= Total volume of oil – free oil x density of oil
Weight of sample
3.6.7 DETERMINATION OF EMULSION CAPACITY
The emulsion capacity will be determined according to the method by Naczket al. (1985) with slight modifications. A flour sample (3.5g), distilled water (25ml) and vegetable oil (25ml) will be blended for 30 seconds in a moulinex blender at high speed. After complete dispersion, vege table oil (25ml) will be blended for 30 seconds. After complete dispersion, the sample will be transferred into graduated centrifuge and centrifuged at 1600 rpm for 10minutes or until there is separation into two layers. The triplicate mean values of the emulsified layer will be recorded. The emulsion capacity will be evaluated as.
Emulsion Capacity = X x 100
x = height of emulsified layer
y = height of whole solution in centrifuge tube
3.6.8 DETERMINATION OF FOAMING CAPACITY
The foaming capacity will be determined by the modified method of Lin et al. (1974). Fifty milliliter of 3% (w/v) dispersion of flour sample in water will be transferred into a 100ml graduated cylinder and the foam volume in the cylinder will be recorded. The volume will be recorded before and after whipping and measured as % of volume increase due to whipping. The foaming capacity will be evaluated as:
= Volume after mixing – volume before mixing x 100
Weight of sample 1
Means of triplicate determinations will be reported.
Sensory evaluation will be carried out 24 hours after the dough production by 20 panelists that will comprise of staff and student that will be randomly selected from the department of Food Science and Technology, Ebonyi State University, Abakaliki. Sensory parameters of the dough meal that will be evaluated are taste, appearance, mouth feel, flour and general acceptability. A 9- point hedonic scale will be used with 9 = like extremely, 8 = like very much, 7 = like moderately, 6 = like slightly, 5 = neither like nor dislike, 4 = dislike slightly, 3 mdislike moderately, 2 = dislike slightly and 1 = dislike extremely.
All data will be collected in triplicate. One way Analysis of Variance (ANOVA) will be conducted on each of the parameters using SPSS version 15 .0 Statistical Package Significant means will be separated by Duncan's Multiple Tests (DMRT) at a significance level of P < 0.05 (Steel and Torrie, 1980).
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