3.0 MATERIAL
AND METHODS
3.1 Source of African yam bean (AYB)
The African yam bean (Brown colour) will be purchased
from Meat market, Abakiliki, Ebonyi State. The bean will packaged in
polyethylene bags, transported to the laboratory and kept at ambient
temperature until required.
3.2 Preparation of sample
Prior to processing of milk and moi moi from African Yam Bean. First,
the beans will be sorted manually to remove extraneous materials like dirt
residue and diseased seeds to obtain healthy ones.
3.2 Production of African Yam Bean Milk and
Moi Moi
African yam bean seeds will be
divided into four portions. Two portions will be soaked for 12 hours dehulled
and dried under the sun. The dried seeds will be milled with locally fabricated
attrition mill to obtain fine flour. African Yam Bean milk will be prepared
from the flour as described by (Anminigo et al; 2007). The bean flour will be
blended with 850C hot water (1:4 seed: water) in blender for 3 mins.
The resulting slurry will be filtered through two layers of double folded
cheese cloth and coarse particles will be removed by allowing the filtrate to
settle for 10 mins. The moimoi will also be prepared from the flour by addition
other local condiments and wrapped in aluminum foil and placed in boiling water
in a pot with lid and allowed to steam for 2hours.
Another two portion
will be soaked for 12hours, dehulled and wet milled. One portion will be heated
for 5 mins at 100oC. The slurry will be filtered through two layers
of double cheese cloth and coarse particles were removed by allowing the
filtrate to settle for 10 mins. The moimoi will also be prepared form the wet bean and
other local condiments will be added and wrapped in aluminum foil and placed in
boiling water in a pot with lid and allowed to steam for 2 hours.
3.3 Proximate Analysis
The crude protein, fat, moisture,
and ash of the four processing methods were determined by AOAC (1990), while carbohydrate
was ruined by difference.
3.3.1 MOISTURE DETERMINATION
The moisture content will be determined
by AOAC method (1990) using dry oven method. Five grains of the sample were
weighted separately into crucible of a known weight (W1) the sample
in the crucible (W2) were place in an oven for 6 hours at 1050C
and were cooled in desicator and were reweighed (W3). The moisture
content will be calculated using the equation below.
% Moisture = W2-W3 x 100
W2-W1 1
Where
W1 = Weight of empty crucible
W2 = Weight of the
empty crucible +weight of the sample
before drying
W3 = Weight of
crucible + weight of sample after drying
3.3.2 Ash
Determination
The ash content of the sample will
be determined by the method described by AOAC (1990) by putting about 5g in curable
of known weight and will be dried in an Oven for about 4 hours at 1050C.
The sample in the curable will be ashes in a muttle furnace at 5500C
until white or grey ash were gotten. It will be cooled in a desolator and
reweighed (W3) the percentage ash content will be calculated using the
equation below;
%
Ash =
Where
W1 = Weight of empty
crucible
W2 = Weight of
sample + weight of crucible before ashing
W3 = Weight of
sample + weight of curable attar ashing,
3.3.3 Fat Determination
The fat will be determined by AOAC
method (1990) by weighing five grams of the sample into a labeled thimble, and
thimble weighed. The bathing flask will be filled with about 100 millimeter to
n-hexane, (Boiling pt 40-60). The extraction thimble will be assembled and
allowed to reflux for about six times hour. The thimble will be removed and then
hexane collection from the solution of fat. The fat left behind in the flask
will be placed in the oven to dry at 1050C for one hour. The round
will be cooled in the desicator and weighed. The percentage of fat in the
sample will be calculated using the formula below.
%
Fat = 
3.3.4 Protein Determination
The AOAC (1990) described method
will be used to determined the protein by Kjedahl procedure using a protein
factor of 6.25. Two grams of the sample will be weighed into a digestion tube
and (H2SO4) 98% will be added using a dispenser. The tube will be
placed in a pre-heated digester, cooled and diluted with water and will be
placed in the distillation. A conical flask contain 35ml of boric acid with
indicator will be placed under the condenser output. About 25ml of 40% sodium
hydroxide (NaoH) will be filtrated with 0.1m tetramosulphate vi acid to
purplish-greg end point.
Percentage nitrogen (% N2)
will be calculated using the formula below
%
Nitrogen
%
crude protein = % N x 6.25
3.3.5 Carbohydrate Determination
The AOAC (1990) described method will be used to
determined the carbohydrate content by difference, the percentage of moisture,
protein, fat and ash were subtracted from 100 to get the carbohydrate value.
%Carbohydrate=100
- (moisture 1% protein + % fat+% ash)
3.4 Function properties
3.4.1
Water/oil absorption capacity (WAC/OAC)
The WAC/OAC will be determined using the method
described by Onwuka (2005). One gram of the sample will be weighed into a
conical centrifuge tube where a warring whirl mixer will be used to mix the
sample thoroughly and 10ml distilled water/oil for 30 seconds. The sample will
be allowed to stand for 30 minutes at room temperature and centrifuge at
5,000xg for 30minutes. The volume of the free water/oil the supernatant will be
read directly from the graduated centrifuge tube.
Calculation
The amount of oil or water absorbed
(total minus free) in multiplied by its density for conversion to grams.
3.4.2 Determination
of Emulsification for capacity (EC)
The method of Onwuka (2005) will be adopted and use 2
gram of the sample will be blended with 25ml of distilled water at room temperature
after complete dispersion, 5ml of oil (groundnut oil) will be added and blended
continuously for another 30 second transferred into a centrifuge which will be
finally directly from the tube.
The emulsion capacity is expressed
as the amount of oil emulsified and held per gram of same.
Emulsion
capacity = x x 100
Y 1
Where
x = height of emulified layer
Y = height of whole solution in the centrifuge tube.
3.4.3 Bulk density
Bulk density will be calculated using
the method, of Okaka and Potter (1979). Fifty gram of the sample will be placed
in a graduated cylinder and the volume will be taped against a table until the
flour be tightly packed. The volume of 1the sample will be noted and the bulk
density will be calculated as weight per unit volume of the sample.
Calculation
Bulk density (g/ml)=
Weight of sample(g)
Volume
of sample (ml)
3.5 ANTI-NUTRITIONAL FACTOR
DETERMINATION
3.5.1 Tannins
The method of Onwuka (2005) will be adopted. One gram
of the sample will be dispersed in 10 ml distilled water and agitated, left to
stand for 30mins at room temperature being shaken every 5 min. At the end of
the 30 mins, it was centrifuged and the extract gotten. 2.5 ml of the
supernatant (extract) was dispersed into a 50 ml volumetric flask. Similarly 12.5ml
of standard tannic acid solution was dispersed into a separate 50ml flask. A 1.0
ml Folic-Denis reagent was measured into each flask, followed by 2.5 ml of
saturated Na2co3 solution. The mixture was diluted to
mark in the flask (50ml) and incubated for 90min at room temperature. The absorbance
was measured at 250nm a Grenway model 600 electronic spectrophotometer. Reading
was taking with the reagent blank at zero. The tannin content was given as
follows
% Tannin – An
x C x 100 x 5
As
w
Where An = Absorbance
of text sample
As = Absorbance
of standard solution
C = Concentration
of standard solution
W
= weight
of sample used
3.5.2 AIKALOIDS
The
method of Onwuka (2005) will be adopted and use. fifty gram of the sample and
dispensed into 50ml of 10% acetic acid solution in ethanol, shake the mixture
well and allowed to stand for 4hours before filtering. The filtrate will be
evaporated to one quarter (1/4) of its original volume. A drop of concentrated
NH40H to precipitate the alkaloids. The precipitate will be filtered
with a weighed filter paper and wash with 1% NH40H solution. The
filtering should do with a weighed filter paper. The precipitate in the filter
paper is dried in the oven at 60oc for 30minis and reweigh. The weight
of alkaloid is determined and expressed as a percentage of the sample weight.
%Alkaloid =
Where W = Weight
of sample
W1 = Weight
of empty filter paper
W2 = Weight
of paper plus precipitate
3.5.3 OXALATES
The
titration method will be used as describe by Onwuka (2005). It involves three
steps digestion, Oxalate precipitation and permanganate titration. 2gram of the
sample is suspended in 190ml 4 distilled water in a 250ml volumetric flask.
10ml of 6m Hcl is added and the suspension digested at 100oC for 1
hour. Cooled, and then make up to 250ml mark before titration. Duplicate
portions of 125ml of the filtrate are measured into beakers and four drops of
methyl red indicator added. Followed by the addition of conc NH4OH
solution until the test solution changes from salmon pink colour to a faint
yellow colour (pH-4-5). Each portion is then heated to 900c, cooled
and filtered to remove precipitate containing ferrous ion. The filtrate is
again heated to 900c and 10 ml of 5% of CaCl2
solution is added while being stirred constantly. After heating, it is cooled
and left overnight at 50C. The solution is then centrifuged at 2500
rpm for 5 minutes. The supernatant is decanted and the precipitate completely
dissolved in 10ml of 20% (v/v) H2So4 solution. At this
point, the total filtrate resulting from digestion of 2 gram of the sample is
made up to 300ml. Aliquots of 125ml of
the filtrate is heated until near boiling and then titrated against O.o5M
standardized KMnO4 solution to a faint pink colour which persist for
30 seconds.
The
calcium oxalate content is calculated content is calculated using the formula.
T x (Vme) (DF) x 105 (mg/100g)
(ME)
x Mf
Where
T = The titer of KMn04 (ml)
Vme =
The volume – mass equivalent
(ie1cm3 of 0.05M KMn04
solution is equivalent to 0.000225g
anhydrous oxalic acid)
DF = Is the dilution of tractor VT /A (2.4
where
ÑT is the total value of titrate (300ml) and
A
Is the aliquot used (125 ML),
ME = is the molar equivalent of KMn04
in
Oxalate (KMnO4 redox reaction).
Mf =
is the mass of the sample used.
3.6 Sensory Evaluation
Sensory evaluation of the sample will be carried out
using twenty semi-trained panelist consisting of students from Food Science and
Technology Department, Ebonyi State University, CAS Campus Abakaliki. The panel
will be instructed to evaluate appearance, taste/flavor, texture, colour and
general acceptability using 9-point hedonic scale as described by Ihekoronye
and Ngoddy (1985) with 1-dislike extremely, 5= neither like or dislike and
9=like extremely. Sample will be coded and presented in random sequence to the
panelists.
3.7 Statistical analysis
Data will be analyzed by analysis of variance (steel
and Torie,1980).The difference between mean values will be determined by Least
significant difference. Significance will be accepted at 5% probability.