3.1 Sources of Raw Materials
The
palm fruits that were used for this work were purchased from Ikwo Local Market
in Abakaliki, Ebonyi State. You can also find it in Imo State, Anambra State, Abia State, Enugu State in Eastern Nigeria.
3.2 Method of
Preparation:
The fruit was divided into two equal
parts and was processed into palm oil using two different traditional
processing method (boiling processing method and fermentation processing
methods).
3.2.1. Boiling
Processing Method:
The first part of the palm fruit was
washed, boiled for one hour and pounded using mortal and pestle until the
tissue separated from the kernel. The pounded palm fruit was allowed to cool by
addition of cold water so that during pressing, oil will flow on top of the
water. Oil was collected by decantation to drain off water. The oil was then
heated to remove the moisture present in the oil. Other unwanted impurities
were scooped out. The resultant oil was allowed to cool, then transferred to a
plastic container and stored at ambient temperature for a specified period of
time. Samples were analyzed monthly for up to six months.
3.2.2
Fermentation Method
The second part of the palm fruits was kept
in a sack, covered with plastic cover and allowed to ferment for a period of 10
days starting from the day the fruit was purchased. The palm fruit were watered
everyday to keep them moist. After the 10days the fruits were pounded using
mortal and pestle without cleaning off any moldy growth. The pounded palm fruit
was kept till the following morning before extracting the oil. The extracted
oil was heated to remove unwanted impurities and moisture. The resultant oil
was transferred to a plastic container and stored at ambient temperature. The
oil obtained was analyzed monthly for specific gravity, Acid value/ free fatty
acid, Iodine value, saponification value, peroxide value, melting point,
freezing point.
3.3
PHYSICOCHEMICAL PROPERTIES ANALYSIS:
3.3.1 Specific
Gravity Determination
The method described by Onwuka (2005) was
employed. Pynometer bottles (50ml) thoroughly washed with detergent, water, and
petroleum ether were dried and weighed.
The
bottle was filled with distilled water and weighed. After this the bottle was
emptied, dried, then filled with oil and weighed. The specific gravity of the
oil was calculated as:
Specific
gravity = Weight of xml of oil
Weight of
xml of water
Where
x is the volume of the bottle
3.3.2 Acid Value
or Free Fatty Acid Determination
The
method described by Onwuka (2005) was used. 1g of the oil was weighed and
poured into (250ml) conical flask. 25ml of diethyl ether was poured into a 250ml conical flask. 25ml
ethanol and 1ml phenolphthalein, were added and the mixture carefully
neutralized with 0.1N NaOH, were shaken constantly till a pink colour was
obtained. The acid value was calculated as:
Acid
value = titre (ml) x 5.61
Weight of sample used
%FFA
is calculated as palmitic acid,
FFA%=
titre (ml) ×
0.0256
Weight of sample used
The
FFA figure usually calculated as palmitic(1ml 0.1M NaOH≡ 0.0256g)
3.3.3 Iodine
Value Determination:
The method described by Onwuka (2005)
was used.1g of oil sample was weighed into a 250ml conical flask and 10ml of
carbon tetrachloride added to it. The mixture was dissolved with 20ml wij’s
solution after which the stopper that has been moistened with potassium iodide
solution was inserted. This mixture was thoroughly mixed and allowed to stand
in a dark cupboard for 30mins. At the end of the time, 15ml of potassium iodide
solution and 100ml distilled water were added to the mixture and mixed
properly. This was later titrated with 0.1M sodium thiosulphate solution using 1%
starch as an indicator (aml).
A blank was carried out commencing with
10ml of carbon tetrachloride(bml).
Iodine
value = (b-a)
x 1.269
weight of
sample used
where
b = titre value of blank
a = titre value of the sample
3.3.4 Saponification Value Determination
The method described by Onwuka (2005)
was used. 2g of the oil was weighed into a conical flask and 25ml ethanolic
potassium hydroxide solution added to it. A reflux condenser was attached to
the conical flask after which the flask content was headed in boiling water for
1 hour with frequent shaking. About 1ml phenolphthalein (1%) solution was added
and solution them titrated when hot with alkali. A blank was also carried out
without addition of the extracted oil. The saponification value was expressed
as:
Saponification
value = (b-a) x
28.05
wt
(g) of sample
where
b = blank litre value
a = sample titre value
3.3.5 Determination
of Peroxide Value
The method described by Pearson (1976)
was used to determine the peroxide value of the palm oil. 1g of the oil sample
was weighed into a clean conical flask followed by 1g of powdered potassium
iodide and 10ml of the solvent mixture (2 volume glacial acetic acid and 1
volume chloroform i.e. 2:1). The conical flask was placed on a boiling water
bath so as to allow the mixture to boil vigorously for a time not exceeding 30
seconds; 20ml of potassium iodide solution (5%) was added and the mixture
titrated with 0.002N sodium thiosulphate using (1%) starch as an indicator
Peroxide value is given by
Peroxide
value = (b-a) N x 100
wt
of the oil
where b = titre value of the blank
a = titre value
of the sample
N = normality
of the acid used.
3.3.6
Melting Point
Oil was placed in a crucible and frozen
in a refrigerator. The frozen oil was brought out and a thermometer placed in
it. Beaker containing oil and thermometer was placed in hot water bath to warm.
The temperature at which the oil started
to melts and completed were recorded. The temperature at which the oil
completely melted was taken as the melting point.
3.3.7
Freezing Point
About 50ml of the oil sample was
measured and poured into crucible dish. Then crucible dish was placed in a
refrigerator and its temperature was taken and recorded as it initial
temperature. The temperature was measured using thermometer. The temperature at
which the oil sample got completely frozen was noted as the freezing point of
the oil sample.
4.0 RESULTS
AND DISCUSSION
4.1 RESULTS
Table 4.1 shows the effect of processing methods and
storage time on some characteristics of palm oil.
Table 4.1: Variation of physico-chemical properties of
palm oil with processing method and
storage time.
|
|
Processing methods
|
Storage time (Months)
|
|||
|
0
|
2
|
4
|
6
|
||
|
SG
|
Fermented
|
0.910
+ 0.014a
|
0.915
+ 0.0071a
|
0.923
+ 0.00424a
|
0.925
+ 0.0071a
|
|
Boiled
|
0.912
+ 0.028a
|
0.912
+ 0.01697a
|
0.9128
+ 0.0099a
|
0.913
+ 0.00283a
|
|
|
FFA%
|
Fermented
|
22.56
+ 0.0849a
|
28.764
+ 0.0198b
|
37.788
+ 0.0396c
|
45.00
+ 0.5657d
|
|
Boiled
|
3.384
+ 0.00849a
|
5.64
+ 0.05657b
|
8.46
+ 0.05657c
|
10.152
+ 0.01697d
|
|
|
PVmeq/kg
|
Fermented
|
3.50
+ 1.69706a
|
4.0
+ 1.11723b
|
5.0
+ 0.45255c
|
5.8
+ 0.28284d
|
|
Boiled
|
1.50
+ 1.41421a
|
2.50
+ 1.69706b
|
3.80
+ 1.10309c
|
4.05
+ 0.98995d
|
|
|
SVmeq/kg
|
Fermented
|
181.142
+ 0.0283a
|
188.51
+ 0.01414b
|
254.60
+ 0.4243c
|
350.31
+ 0.0283d
|
|
Boiled
|
175.91
+ 0.0141a
|
183.20
+ 0.28284b
|
185.49
+ 0.0283c
|
189.54
+ 0.05657d
|
|
|
IVwij’s
|
Fermented
|
26.141
+ 0.0566a
|
28.523
+ 0.0424b
|
32.994
+ 0.141c
|
37.0548
+ 0.0283d
|
|
Boiled
|
3.807
+ 0.0141a
|
17.2584
+ 0.0283b
|
28.695
+ 0.0849c
|
34.7706
+ 0.0849d
|
|
|
MP0C
|
Fermented
|
29
+ 1.1414a
|
29
+ 0.2828b
|
30+
0.5657c
|
30
+ 0.2828d
|
|
Boiled
|
29
+ 0.14142
|
32
+ 1.14421b
|
34
+ 0.42426c
|
37
+ 0.28284d
|
|
|
FP0C
|
Fermented
|
26
+ 1.14421a
|
27
+ 0.28284b
|
27+
1.14421c
|
28
+ 0.28284d
|
|
Boiled
|
23
+ 0.4101a
|
24
+ 0.1556b
|
24
+ 0.1414c
|
24
+ 0.4243d
|
|
Means
with the same alphabet = no significant at 5% probability. SG = specific
gravity, FFA= free fatty acids, PV =
Peroxide value, SV = saponification value, IV = iodine value, SP = smoke point, FP = freezing point.
Fig 4.1. Variation of
specific gravity of palm oil with processing method and storage time.
Fig 4.2. Variation of
Free Fatty Acid of palm oil with processing method and storage time.
Fig 4.3. Variation of
peroxide value of palm oil with processing method and storage time.
Fig 4.4. Variation of
iodine value of palm oil with processing method and storage time.
Fig 4.5. Variation of
saponification value of palm oil with processing method and storage time.
Fig 4.6. Variation of
Freezing point of palm oil with processing method and storage time
Fig 4.7. Variation of
melting point of palm oil with processing method and storage time.