INTRODUCTION
African bread fruit (Treculia African Decne) is a
member of the maraca family. The seed s are highly nutrition and constitute a
source of vitamins, minerals protein,
carbohydrate and fat (Okafe and Okow 1994, make ride and Elema, 1985). Bread
fruit seeds are generally consumed in the entire South Eastern Nigeria and
beyond. They can be consumed in
various form; cooked as porridge or roasted and eaten with palm kernels (Edet
et al 1985). African bread fruit has a limited shelf life period due to
its high moisture and fat content
(Okafor 1990). Oknokwo and Ubani (2012) reported that African breadfruit seeds
can preserved by sundrying of the dehulled seeds.
Dehydration operations are important steps in the
chemical and food processing industries. The basic objective in drying food
products is the removal of water in the solids up to a certain level, at which
microbial spoilage is minimized (Krokida and Marinoskouris, 2003). Further research
has shown that on the local level, some people dry breadfruit seeds using not
only sun drying but also shade drying to extrend the shelf life of the product
(personal communication, 2013) this has resulted in products of various
qualities and there is a need to study the effect of these different drying
methods on not only the sensory quality but also the physical properties and
proximate composition of the seeds. Jokic
et al (2009) reported that the
changes in quality that can occur in any part product during drying are those
on its optical properties (colour, appearance), sensory properties (odour,
tase, flour), and structural properties (density, porosity, specific volume,
textural properties, etc).
The
knowledge of the influence of drying on the food properties can be efficiently
used to create new quality attributes and new functionalities for the final
products (Lewicki 2006). Also, the knowledge of the physical properties o the
dehydrated African breadfruit seeds like those of other seeds is essential for
the design and construction o equipment systems, handling storage and
preparation as they affect food quality and acceptability (Onwuka 2005).
1.1 OBJECTIVES
The
objectives of this work are:
1. To dry
African breadfruit seeds using three different methods namely sun drying, oven
drying and shade drying.
2. To
determine the effect of these drying methods on the physical, proximate and
sensory properties of the seeds.
CHAPTER TWO
2.0
LITERATURE REVIEW
2.1 AFRICAN
BREADFRUIT (TRECULIA AFRICANA)
African breadfruit (Treculia
Africana) is a multipurpose tree species which belongs to the family moraceae
and it grows in the forest zone. Particularly the coastal swamp zone (Agbogidi
and Onomaregbo, 2008). It is widely grown in Southern Nigeria for its seeds,
and is known by various tribal names in the country. Such names include “afon”
(Yoruba), “Barafuta” (Hausa), “Ize” (Bini), “eyo” (Igala), “ediang” (efik) and
“ukwa” (igbo). (Iruine, 1981; Onweluzo and odume, 2008). The most popular of
these tribal names is the igbo tribal name which is “ukwa” the specie is a large
tree which grows up to 30m high and it flowers between October and February
(Salami, 2002).
According to Okafor (1985), there
are three varieties of African breadfruit, these include var. Africana, var
mollis and var. inverse. These are distinguished based on the size of the fruit
heads and hairiness of the branches and leaves. Beside varieties, Africana and
inverse thrive well in a wide range of soil from sandy to clay soil and require
high rainfall and humidity as well as ample sunlight. Propagation is by see,
stem and budding which has helped production f the maturing tree fruit in about
2-4yers, opening up the flood gate for mass production of breadfruit and as a
result the need form an enhanced utilization of African breadfruit to match the
production.
In addition, African breadfruit
variety rates higher both in yield and nutrition.
2.1.1 Description
of African Breadfruit Plant
African breadfruit is a large tree
growing up to 30m high with a girth of 4.6m. It has a dense spreading crown and
fluted trunk. The bark is grey, smmoth and thick exuding capious cram latex
which later turns rusty red when cut (Agbogidi and Onomeregbor, 2008). The
leaves are simple, alternate, very large, dark green, smooth above, tough and
paler bwlow with some hours on the 10th-18th pains of
clear reins with painted tips and short stalk (WAC, 2004). African breadfruit
is a monvecious dictyledonous plant with flowers crowded into compact heads.
The flowers of the both sexes are surrounded by specialized bracts between
which stamen or stigmas project above the surface of the flower head (Ugwuoke
et al, 2003). The fruit is round in shape, big, greenish yellow in colour and
spongy in texture when ripe and contains numerous seeds, which are embedded at
various depths in the fleshy pulp (Enibe, 2007). The seeds are brown in colour
with fibrous coating (Okafor, 1990).
2.1.2 Utilization
of African Breadfruit
African breadfruit is a
traditionally important edible fruit in Nigeria (Okafor, 1985) whose importance
is due to the potential use of its seeds leaves, timber, roots and bark. It is
increasingly becoming commercially important in Southern Nigeria hence, Baiyeri
and Mbah (2006) described it as an important natural resource which contributes
significantly to income and dietary intake of the poor. African breadfruit
could be processed and utilized in variety of ways. The seeds are used for
cooking and are highly nutritious as pointed out by various authors (Okafor and
Okolo, 1974; Okafor, 1990; Onyekwelu and Fayose, 2007). The seeds are variously
cooked as pottage or roasted and eaten with palm kernel as read side snacks.
Apart form being consumed as a main dish, the seeds are also processed into
flour which has high potential usage for pastries (Keay, 1989).
The seeds are also used as
flavouring in alcoholic drinks and edible oil can be processed form the seeds
(Irvine, 1981; Ugwuoke et al; 2003). Ejiofor et al; (1988) prepared a
non-alcoholic beverage form seeds of the species which was found acceptable
when taken without milk and sugar therefore, giving the beverage obtained from
the specie an obvious advantage over cocoa-derived beverage in view of the
scarcity and expensiveness of milk and sugar in rural areas of developing
countries. The wood is suitable for firewood and charcoal production (Field
survey, 2008).
The breadfruit oil could be used for
cooking, preparation of soaps in the pharmaceuticals, production of hair
shampoo, alkyl resin used in paints and varnish industries due to the drying
nature of African breadfruit oil with its high oil yield (AJiwe et al; 1995).
The bran and pulp of Arican breadfruit have been found to be nutritious for use
in live stock feeds (Okafor, 1090). The roots are used as a malaria tonic and
worm expeller for children while the bark is used as treatment for cough neck
swelling and rheumatism (Irvine, 1981).
2.1.3 Limitation
in Breadfruit Utilization
There are various factors that limit
the use of breadfruit when it is compared to other plants like legumes since it
has same functions with breadfruit these include:
i. The long period of maturity and
fruiting which makes it seasonal fruit.
ii. The long
cooking time, which is associated with hard-to-cook phenomenon which has
contributed greatly to the low consumption in the urban dwellers whose cooking
time are limited, as such a rich and equally cheap source of dietary protein is
neglected.
iii. The
ability to produce gas in the gastro intestinal tract, which is referred to as
flatulence.
iv. The
limited shelf life period during due to high moisture and fat content (Okafor,
1990).
2.1.4 Nutritional value of African Breadfruit
The African breadfruit produced by Treculia a wild
tropical evergreen tree and has immense potential as a nutritional sources for
man (Osabord et al; 2009).
Like most grain legumes cultivated in Africa, African
breadfruit is a source of protein, fat, vitamin, mineral etc. African
breadfruit like other grain legume is rich in protein than that for cereals and
similar to most pulses and is also particularly high in aromatic amino acids
which makes it a potential source of good quality protein (Makinde et al,
1985). It is also rich in carbohydrate due to its high carbohydrate contents
and could therefore serve as a good source of energy. African breadfruit seeds
contain less fat than some other nuts and about 4-7% total lipid content
(Nwaokorie, 1983). It is therefore recommended, as part of weight reducing diet
the seeds are low in crude fibre and also not a good source of dietary fibre,
which is important for reducing cholesterol levels in the body to minimize risk
of cardiovascular disease caused by high plasma cholesterol (Umoh, 1998). It is
also a good source of vitamins like beta-carotene, vitamin C and folic acid
(folate).
African breadfruit is rich in some minerals notably
magnesium, potassium, and calcium but poor in sodium, iron and copper as
reported in literature (Oyenugo, 1968; Edet, 1982; Ejidike and Ajileye, 2007). They
therefore need to be fortified with sodium, iron and copper when used in food
formulations because of their low inherent levels. African breadfruit seeds are
also rich in flavonoids, polyphenols, cardiac glycoside saponins and
authraguinones, which are known to have antimicrobial activity (Sofowora,
1980). The presence of these secondary metabolites accounts for the usefulness
of the seed medical purposes (Ebena et al, 1995).
2.2 FOOD
PRESERVATION BY DRYING
Preservation of food by drying is a
common practice in different parts of the world and it is used to extend the
shelf life of food. Drying allows food to be preserved by removing te moisture
in the food in order to prevent the growth of microorganisms that cause
deterioration (Mukhtar, 2009). Since drying removes the water from the food,
the weight of the food items also reduces. This not only makes it lighter but
also shrinks it in size thereby making it easy to store and sorry. Dried food
requiring no refrigeration makes it ideal for domestic use as well as for use
in the rough outdoors.
Drying food is simple, safe and easy
to learn. Dried foods are good source of quick energy and whole some nutrition,
since they only thing lost during preservation is moisture (www.partselect.com,
2013). Dried foods are on easy option for busy executives, active women and
children, all of whom can benefit form the case and nutritional content of
dried foods.
There are several ways of drying
food which include: In the sun, in on oven, in the shade, in the room or in a
commercial dehydrator.
2.2.1 Sun
Drying
There are many techniques of drying
but the cheapest and most commonly used in Nigeria is sun-drying. The method
however, results in contamination with dust and microorganisms and is sometimes
too slow to accomplish the desired purpose especially in wet weather (Adom et
al; 1997). Sun drying is also a cheap process and the dried foods have more
monetary value when compared to dehydrated food due to improved quality. Sun
drying has advantages but not on the basis of time to dry and quality
(Desrosier; 1970).
2.2.2 Oven
Drying
An oven can easily and effectively
be used to dry food ovens have all the three elements needed for food
drying-had, low humidly, and air flow. Drying food in the oven is a slow and
time consuming process. Most ovens do not have an in-built fan and therefore
they end up taking more time and energy to dry relatively small quantity of
food (www.partslect.com 2013).
2.2.3 Shade
Drying
Shade drying is a drying technique
which requires full air circulation. It should not be undertaken inside
convectional buildings but in on open-sided shed purposely built for shade
drying. Shade drying takes a little longer than sun-drying but it prevents the
loss of a foods natural colour and better preserves its vitamins and minerals (www.partselect.com
2013)
2.2.4 Room
Drying
Drying food in the room is different form sun drying.
Here, the food that has to be dried is placed in a well ventilated room or
covered space (www.Portselect.com. 2013).
2.2.5
Effects of Different Drying methods on Food
Properties
Loss of nutrients has been reported
for various food processing techniques (Brar et al, 2006; Uhling, 1998;
Svanberg and Nyman, 1997). Sun oven and solar drying methods utilize heat to
remove water from food by evaporation. The removal of water by heat has been
reported to effect the nutrient contents of food in various ways. It can either
increase the concentration of some nutrients 1g making them more available or decrease
the concentration of some nutrients (Hassan et al, 2007); Morris et al, 2004;
Ladan et al, 1997). Application of
heat can be both beneficial and detrimental to nutrients. Heat improves
digestibility of food, promotes palatability and also improves the keeping
quality of food, making them safe to eat. Heating process also result in
nutritional losses by inducing biochemical and nutritional variation in food
composition.
According to Rozis et al (1997),
vitamin losses are often greater during peeling than during drying. Loss of far
soluble vitamins can also be reduced by shade drying and loss of eater soluble
vitamins by careful slicing using sharp knives. Ascorbic acid and carotene are
subject to damage by oxidative processes. Riboflavin is light sensitive whereby
Thiamin is heat sensitive and destroyed by sulfuring (Desiosier, 1970). Sun
drying causes large loses in carotene content. The retention of vitamins in
dehydrated foods is generally superior in all counts than in sun-dried foods.
In drying, a food loses its moisture
content which results in increasing the concentration of nutrients in the
remaining mass. Proteins, fats and carbohydrates are present in large amounts
per unit weight in dried foods than in their fresh counter part. The biological
value of dried protein is dependent on the method of drying. Prolonged
exposures to high temperatures can render the protein less useful in the
dietary. Low temperature treatments of protein may increase the digestibility
of protein. Over native material (Desrosier, 1970).
Rancidity is an important problem in
dried foods. The oxidation of fats in food is greater at higher temperatures
than at low temperatures of dehydration. Fruits are generally rich sources of
carbohydrates, poor sources of protein and fats the principal determination in
fruits is in carbohydrates. Discoloration may be due to enzymatic browning or
to carmelization types of reaction. Slow sun drying permits extensive
deterioration unless the tissues are protected with sulfites or other suitable
agents. Animal tissues do not contain large amount of carbohydrate and
therefore their carbohydrate deteriorations are of minor importance.
2.3 PHYSICAL
PROPERTIES OF FOOD MATERIALS
Physical properties of food are
those properties which are used in process design, product and process
optimization, product development, food quality control and food process
modeling, (Salin and Gulum summnu, 2006). Physical properties of agricultural
materials affect how they are to be processed, handled, stored and consumed and
so are required in the design of planting, harvesting and post-harvest
operations such as cleaning, conveying and storage (Mosoumi and Tabill, 2003:
Kotwaliwale et al, 2004; Wilheim et al; 2004). Processing techniques and
handling of legumes require accurate knowledge of the physical properties such
as shape, size, porosity, surface area, bulk density (Alobadan, 1996).
2.3.1 Porosity
The porosity is the fraction of the
space in the bulk seeds which is not occupied by the seeds (Coskiner and
Karababa, 2007). Porosity also depends on geometry and surface properties of
the material. The percent void of an unconsolidated mass of material such as
grain, hay and other porous materials
are often needed in air flow and heat studies (Mohsenis, 1986). This property
allows fluid to pass through the bulk, it is useful in the calculation of rate
of aeration and cooling, drying and heating and the design of heat exchangers
and other similar equipment (Asoegwu et al., 2006).
2.3.2 Density
Bulk density is the mass of a
material per unit volume. It is the property that makes it possible to separate
them form materials that are less dense than water (Sirisomboon et al., 2007);
Pliestic et al, 2006; and Cevat & Ozcan, 2002). Decrease is bulk density is
an indication reduced overall quality of grain. Factors which commonly affect bulk
density are insect infestation, excessive foreign matter and high percentage
moisture content (WFP, 2006).
True density is also a property that
makes it possible to separate them materials that are less dense that water.
True density is a characteristic that can be used to design separation or
cleaning process. According to Eke et al.; 2007, the three density indicates
that African breadfruit seeds float water, whereas bambara seeds do not.
Bulk density and porosity affect the
structural loads and are important parameters in designing of drying and
storing systems.
2.3.3 Sphericity
Sphericity of the seeds indicate the
ability of the seeds to roll. Bambara seed are more spherical and will roll
rather than slide unlike African breadfruit seeds (Mporokwene et al., 2008).
This property is useful in the design of hopper, chutes, storage facilities and
dehilling equipments for seeds (Mporokeane et al., 2006).
2.3.4 Surface
Area
The surface area affects the
velocity of air stream that can be used in order to separate seed from unwanted
material in pneumatic separator no to sepank
seed in pneumatic conveying specific surface area is considered during mass and energy transfer through the
surface of seeds (Asoiro et al, 2011).
2.3.5 Size
and Shape of Seeds
These properties are always considered when designing
hoppers and dehulling equipment for seeds.
CHAPTER THREE
3.0 MATERIALS AND METHOD
3.1 SOURCE OF MATERIAL
About 2kg of fresh seeds of African bread fruit
(Treculia Africana) to be used for this work will be purchased from meat market
in Abakaliki, Ebonyi State, Nigeria.
3.2 SAMPLE
PREPARATION
The sample will be prepared by
sorting of the African breadfruit to separate them form stones ano other
unwanted seeds. This will be done by spreading the African breadfruit on a wide
flat and clean surface screen.
3.2.1 Srying
Treatment
The African breadfruit will
be divided into four parts of 500g each. The first part will be dried in a hot
air oven at a temperature of 50oc till dried. The second part will
be dried under the sun. the third part will be dried indoors while the fourth
part will not be dried and will sere as the control. The dried samples will be
stored in labeled air tight polythene bags until needed for analysis.
3.3 PROXIMATE
COMPOSITION ANALYSIS
The following analysis will be
carried out to determine the proximate composition of the fresh and dried
samples respectively.
3.2.1 Determination
of Moisture Content
Moisture content of the sample will
be determined according to the method described by AOAC (1990). Empty Petridis
will be washed, dried in an oven and cooked in a dessicator. The dry clean dish
will be weighed and recorded as w1, after which 5g of the sample
will be introduced into the dish, weighed and recovered as w2. The
dish + sample will be transferred into an oven at 1050c to dry for 2
hrs. A pair of tongs will used to transfer the dish into a dessicator, allowed
to cool and weighed. The dish will be returned to the oven for 3o mins and
again cooled in a desiccators and weighed. The procedure will be repeated until
a constant weight is obtained and recorded as w3
(%)
moisture = w2
– w3 x 100
w2
– w1 1
where
w1 = weight (g) of Petri dish
w2 = Weight (g) of
Petri dish + sample before drying
w3 = Weight (g) of
Petri dish + sample after drying
3.3.2 Determination
of Ash Content
The ash content will be determined
as described by AOAC (1990). The empty crucible will be washed, dried and
cooked in a dessicator. About two grammes of the sample will be weighed into a
tared silica dish and the sample will be heated inside a fume cupboard until
the smoke disappears. The sample will be transferred into a muffle furnaces at
the temperature of 55ooc for 2 hrs until a white or light grey ash
result when the residual is black in colour, it will be moistened with a small
amount of water to dissolve salts. It will be cooled in a dessicator and
re-weighed.
%
Ash = w3 – w1 x 100
w2 – w1 1
where
w1 = weight (g) of crucible
w2 = weight (g) of crucible + sample before
ashing
w3 = weight (g) of crucible + sample after
ashing
3.3.3 Determination
of Crude Protein
Crude protein content will be
determined by micro kjeidahl method (AOAC, 1990). A quantity of sample (0.5g)
will be weighed into a 500ml kjeldahl flaks. Ten grammes (10g) of sodium
sulphate (Na2so4) and lg of copper sulphate, followed by
20ml of H2so4 will be weighed into the flask too. The
mixture will be digested under a fume cupboard until a clear solution is
obtained. The digest will be cooled and 20oml of distilled water will be added
followed by 6oml of 40% sodium hydroxide solution. The ammonia in the boric
acid solution containing 0.5ml of indicator (screen methyl read. The distillate
will be collected and titrated with 0.1 NHCL. The nitrogen content will be
multiplied by 6.25 to obtain the protein content of African breadfruit and
expressed as percentage on the weight basis.
%
protein = Tv x 0.1N x 0.014 x 6.25 x 100
weight of sample 1
where
TV = Titre
value
N = Normality of HCL used
6.25 = Conversion factor of protein
3.3.4 Determination
of Cruds Fat Content
The crude fat will be determined
using soxhlet apparatus with petroleum ether as solvent described by Onwuka
92005). Two hundred and fifty milliliters capacity boiling flask will be
washed, dried in an oven and transferred into a dessicator and allowed to cool.
Two grammes of the sample will be accurately weighed into a labeled thimble.
Cooked boiling flask will be filled with 300ml of petroleum ether. The
extraction thimble will plugged light with cotton wool. The soxhlet apparatus
will be assembled and allowed to reflux for about 6 hours. The thimble will be
removed with care and petroleum ether will be collected in the tap container of
the set up and drained into a container for reuse. When the flask is almost
free of petroleum ether, it will be removed and dried. It will be transferred
form the oven into a dessicator and allowed to cool then weighed.
%
fat = weight of fat x 100
weight of
sample 1
3.3.5 Crude
Fibre Determination
The crude fibre will be determined
using the method described by Joslyn (1970). Two grammes of sample will be
weighed into a thimble together with petroleum ether into the soxhlet extraction
Apparatus. The operation will be corried out until fat is extracted. The dried
residue will be boiled under reflux for 30 mins with 200ml of 1.25% H2so4,
it will then be filtered. The residue will be boiled with 200ml of 1.25% HaoH
in a round bottom flaks for another 3o mins. It will then be filtered with a
filter paper in a butcher funnel. The crucible will be weighed and dried in the
oven, cooled in the dessicator and weighed. It will then be incinerated in the
muffle furnace at 600oc for 21/2 hours, cooled in a dessicartor and
weighed. The loss in the weight will then be recorded as the crude fibre.
Percentage crude fibre will be calculated as
Crude
fibre(%) = weight of crude fibre x
100
Weight
of sample used 1
3.3.6 Carbohydrate
content Determination
The carbohydrate content will be
calculated by difference, 100-(% moisture + % fat + % protein + % crude fibre).
3.3.7 Determination
of physical Properties
the method stated by mpotokwone et al., (2008) will be adopted to
measure the linear dimensions of the African Breadfruit. Hundred (100) whole
seeds will be selected form each sample. The length (L), width (w), and the
thickness (T) will be measured using a vernier caliper. The geometric mean
diameter (Dg) and sphericity (CP) will be calculated using the following
formula reported Mohcenin (1986).
Dg = (LWT)1/3
a = (LWT)1/3
L
Seed
volume (c) and seed surface area (S) will be calculated using the formula
reported by Jain and Bal (1997).
V = BeLe
6(2L-B)
S = BeLe
2L-B
where
B = (WT)0.5
Aspect
ratio (AR) will be calculated using (Mohsenin, 1986; ciro: 1997).
AR = W
L
Thousand
unit mass of seeds will be calculated using the formular reported by Asoiro et al (2011). The mass of one hundred
seeds of each sample will be recoded using an electronic balance. 1000-unit
mass will be calculated by multiplying the 100 units of the seeds by 10.
Bulk and seed Density
The bulk density of the seeds will
be calculated using the method of Asoewgu et al (2006) cited by Mpotokwae et al
(2008). A 500ml cylinder will be filled to the 500ml mark with breadfruit seeds
and weighed on an electric balance. The bulk density will be calculated as the
ratio of bulk weight and volume of the cylinder (g/ml).
The true density will be calculated
using the liquid displacement method of Asoegwu et al. (2006). All weights will
measured using a top loading balance. A 500ml beaker will be filled to the
350ml mark with water. Appproximately 100g of seed will be immersed in the
water. The mass of the water displaced will be balance reading with the seed
submerged minus the mass of the beaker will water. The seed volume will be estimated
by dividing the mass of displaced water (g) by the density of water (glcm8).
Seed density will be determined by dividing the seed mass by the measured seed
volume. This was repeated thrice for each sample.
Seed Porosity
Seed porosity is the property of the
grain that depends on its bulk and kernel densities. The formula stated by
Mpotokwane et al 92008) will be used to calculate the porosity.
P =
1 –
Pb x 100
Pt
Where
Po = bulk density (kg/m3) and Pt = seed density (kg/m3).