CHAPTER FOUR
RESULT ON DISCUSSION
Table
4.1 Effect of Pre-processing Condition
on Saponification Value of Palm Kernel Oil
Sample
Storage time Saponification Value
(meq/kg)
months Boiled Fermented
0 25.25 29.45
2 42.08 57.50
4 119.21 131.88
6 197.75 221.59
Total =12 384.29 440.42
X =3 96.07 110.105
R2 0.969 0.977
ᵪ2 195.74 201.39
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The result on the effect of
pre-processing condition on the characteristics of palm kernel oil revealed
that the saponification value of the palm kernel oil sample increased with
increase in storage time. Saponification value (SV) obtained for the palm
kernel oil samples ranged from 29.45 to 221.59 MgKOH/g and from
25.24 to 197.75 MgKOH/g for palm kernel oil gotten from fermented
and boiled palm fruits processing methods respectively, presented in table 4.1.
The increase in saponification value with storage time indicated that the
amount of soap obtainable from a unit mass of the product palm kernel oil (PKO)
increased with time. This suggest that the overall reaction in the stored palm
kernel oil resulted in the breakdown of the lipids and fatty acid into smaller
molecules leading to lower average molecular weight of the palm kernel oil.
(Table 4.1) the sponification value obtained in this study are less than the
expected range of 318 to 319MgKOH/g of oil for edible palm kernel
oils as specified by NIS (1997), as from 0 month upto 6 months storage. The
saponification values of oil for both fermented and boiled process were less
than 318MgKOH/g oil, hence not recommended for use in edible purpose within 6
month storage. Low saponification value of the palm kernel oil from both
fermented and boiled process is an indication that the oils will be most
suitable for biodiesel as an alternative to traditional oil.
The results were of statistical
significant (P<0.05) on the storage time of the palm kernel oil sample, and
were not significant (P>0.05) on processing method, while the interaction
between storage time and processing method were not significant P>0.05)..
Table 4.2 Effect of the Processing Condition on Free Fatty Acid of Palm Kernel Oil Sample
Storagetime Free Fatty
Acid Value (MgKOH/g)
months Boiled Fermented
|
0 6.564 1.907
2 8.308 2.917
4 9.088 3.983
6 11.108 6.900 Total=12 35.068 15.707
X = 3 8.767 3.927
R2 0.988 0.961
ᵪ2 1.215 3.546
The
effect of processing condition on the characteristics of free fatty acid (FFA)
of palm kernel oil obtained show different methods is presented in (Table 4.2).
The result indicate that there was a remarkable increase in FFA of palm kernel
oil from the boiled processing method of palm fruits than the one from
fermentation processing method throughout the storage period. From the result
obtained in table 4.2, it can be seen that the acid value increased from 6.564
MgKOH/g to 11.108MgKOH/g within the palm kernel oil storage time of 6 months.
The increment in the value with storage time could be due to hydrolysis or
splitting of some fats and oil (lipids) to give more fats acids, diglycerides
and monoglycerides. The value obtained were not within the range reported by
AOCS, (1996) and Swerm et al, (1964). Storage time and processing method are
significant effect (P>0.05) on the FFA while
the interaction between the
storage time and processing method are not significant (P>0.05) on free
fatty acid of the palm kernel oil
sample.
Table 4.3 Effect of Pre-processing
Condition on Peroxide Value of Palm
Kernel oil Sample
Toragetime Peroxide Value (Meq/Kg) months Boiled Fermented
0 28.60 26.60
2 39.00 32.60
4 41.60 38.20
6 46.40 45.60
Total=12 155.6 143
X =3 38.9 35.75
R2 0.965 0.998
ᵪ2 4.361 5.501
The peroxide value determine the
extent to which the oil has under gone rancidity, thus it could be used as an
indication of the quality and stability of fats and oils (Ekwu and Nwagu, 2004)
the peroxide value (Meq/Kg) of the palm kernel oil
extracted from fermented and boiled palm fruits increased with increase in
storage time respectively (Table 4.3), with the palm kernel oil from boiled
palm fruits process had the higher peroxide values from 28.60 Meq/Kg
to 46.40 Meg/Kg during the 6 month of storage period,
than palm kernel oil from fermentation process ranging from 26.60 Meq/Kg
to 45.60 Meq/Kg during the 6 months storage period. The
statistical analysis shows that there is significant variation on the storage
time, no significance difference (P>0.05) on processing method. while the
interaction between the storage time and processing method are not significant
(P>0.05) on the peroxide value of palm kernel oil sample. Steady increase in
the peroxide value of palm kernel oil with storage time could be due to
increase in the extent of oxidation resulting in increase in the formation of
hydro peroxides during fats oxidation. The observation that the peroxide values
of palm kernel oil from boiled palm fruits process were higher than those from
fermented process could be due to the fact that initial extent of hydrolysis
was higher in the product of the boiled process. Although peroxides are
possibly not directly responsible for the taste and odour of rancid fats, their
concentration is often useful in
accessing the extent to which the rancidity has advanced.
As presented in (Table 4.3) the
peroxide value range from 28.60 to 46.40 Meq/Kg and 26.60
to 45.60 Meq/Kg for boiled and fermented process are
highly than the standard minimum value of 10 Meq/Kg
specified by SON (2000) and NIS (1992). Within the 6 months storage period, the
peroxide value of palm kernel oil gotten
from both fermented and boiled process were great than 10 Meq/Kg
oil, hence not recommended for used in
edible purpose within the 6 months storage time without refining. The increase
in peroxide value with increase in storage time could indicate the onset of
primary oxidation due to lipid degrading enzymes like peroxidase and
lipoxygenase Onyeka et al (2005) which
progressed with time.
Table 4.4 Effect of Pre-processing Condition on Iodine
Value of Palm Kernel Oil Sample
Storagetime Iodine
Value (Wij/s) Mouths Boiled
Fermented
0 5.329 0.508
2 6.599 0.761
4 8.122 1.269
6 10.659 2.30
Total=12 30.569 4.568
X =3 7.677 1.142
R2 0.986 0.976
ᵪ2 2.054 1.184
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Iodine value is an index of the
degree of unsaturation, which is one of the most important analytical
characteristics of oil. The on changes in the iodine value of the palm kernel
oil is presented in (Table 4.4) it was observed from the figure that iodine
value increased during storage time of the palm kernel oil from the two
processes studied. Minimum iodine value
was 5.329 Wij’s initially in palm kernel oil from boiled palm fruits
process and 0.508 Wij’s in palm kernel oil from fermented palm
fruits process. The values increased to 10.659 and 2.030 Wij’s for
palm kernel oil from boiled and fermented palm fruits respectively at the end
of 6 months storage period (Table 4.4). The changes in iodine value of palm
kernel oil samples may be attributed to propagation of auto oxidation process
where hydro peroxides are formed from free radicals in fatty acids generated by
initiation stage of the auto oxidation reaction. The iodine value obtained were
within the limits of standard range of 45 to 53 Wij’s, recommended
by SON (2000) NIS (1992). However, the value obtained indicate the increase in
iodine value with storage time of palm kernel oil could be due to the
detachment of fatty acids which can lead to increase in degree of unsaturation
of the lipid (oil) and therefore, susceptible to oxidation.
The addition of antioxidants may be
necessary to prolong the storage stability of this type of palm kernel oil. The
storage time, processing method and the interaction between the storage time
and processing method on the iodine value of the palm kernel oil sample had
significant effect (P>0.05) on the iodine value.
Table 4.5 Effect of Pre-processing Condition on Moisture Content of Palm
kernel Oil Sample
Storagetime Moisture Content (%) 
Months Boiled Fermented
0 9 6
2 12.5 11
4 15.5 14
6 18 16.5
Total=12 55 47.5
X =3 13.75 11.88
R2 0.997 0.986
ᵪ2 3.291 5.150
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Moisture content is the quantity of
water contained in a material such as oil, it is used in a likely range of
scientific and technical areas and its expressed as ratio can range from 0
(completely dry) to the value of the materials porosity at saturation. The
moisture content is one of the most important indicator of oil determination.
The changes in moisture content during 6 months of storage period are given in
(Table 4.5). The moisture increase from 0 month of storage period 9% to 18% for
the palm kernel oil from boiled palm fruits and 6% to 16.5% for the palm kernel
oil from fermented palm fruits. The increases of moisture content of the palm
kernel oil both the one extracted from boiled and fermented palm fruits during
the storage period could be due to the storage environment of the palm kernel
oil. The value obtained are higher than value (6.5%) reported by Alasie et al
(2009). The result in the moisture content shows that the storage time of the
palm kernel oil sample are significant effect (P<0.05) on the moisture
content while the processing method were not significant (P>0.05) and the
interaction between storage time and processing method were not significant on
moisture content.
Table 4.6 Effect of Pre-processing Condition on Melting Point of Palm
kernel Oil Sample
Storagetime Melting Point (oC)
Months Boiled Fermented
0 26 27
2 24 26
4 23 25
6 21 24
Total=12 94 102
X =3 23.5 25.5
R2 0.992 1
ᵪ2 0.553 0.196
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The experimental results showed
decrease in the melting point of palm kernel oil from both the one extracted
from boiled and fermented palm fruits. The decrease in melting point of palm
kernel oil from boiling process was only from 26oC to 21oC
for the 6 months storage period while for fermentation process decreased from
270C to 24oC (Table 4.6). The high melting point observed
for palm kernel oil from fermentation process of palm fruits could be due to
the presences of some high melting saturated components in the palm kernel oil
sample. By boiling the palm fruits, the portion of the unsaturated fatty acids
increased but these fatty acids do not take part in any chemical change in the
oil, do not interact with
triacylglycerol as they are of similar chemical composition of the molecular
species of triacylglycerol would have changed the other physical properties of
the palm kernel oil as the physical and chemical properties of palm kernel oils
are function of fatty acids in triglycerides (Tan and Man 2002; Fogila et al,
1993).
The melting behavior of the palm
kernel oil from both boiled and fermented varies due to the different
characteristics and composition of fatty acids in terms of triglycerides in
both processed palm fruits (Fassina et al, 2008). The melting point were of statistical significant (P<0.05)
on the storage time, processing method and interaction between storage time and
processing method on the melting point of the palm kernel oil sample.
Table 4.7 Effect of
Pre-processing Condition on Freezing Point of Palm kernel Oil Sample
Storagetime
Freezing Point (oC) Months Boiled Fermented
0 0 0
2 2.0 2.2
4 2.1 2.3
6 2.4 2.5
Total 12 6.5 7 X 3 1.63 1.75
R2 0.946 0.935
ᵪ2 2.213 2.361
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The result presented in (Table 4.7 ), shows that the
freezing point slightly increased with storage time for both procedures. These
show that the component with the lowest freezing point did not significantly
change with storage time. However, the products from fermentation process had
higher freezing point from (0oC to 2.5oC) than those from
boiled process of palm fruits (00C to 2.40C). This could
be due to the fact that fermented process had the capability of extracting
higher broad spectrum of component which resulted during n-hexane extraction of
palm kernel oil including the poly unsaturated which had lower freezing points.
The result were statistical not significant (P>0.05) for both storage time,
processing method and interaction between the storage time and processing
method on the freezing point of palm kernel oil sample
Effect of Pre-processing Condition
on the stability of Palm kernel Oil
Sample
The stability of palm kernel oil
(PKO) were measured by the rate change of key properties such as the free fatty
acid and peroxide value as presented in (table AI), it should be noted that
process of oxidation and hydrolysis normally go through induction, propagation
and termination steps and antioxidants can help in early onset of termination.
The sample from fermentation process of palm kernel oil gotten from palm fruit
displayed higher hydrolytic stability having lower rate of change of free fatty
acid with storage time. ( FFA/ t) this could be due to the fact that the
product from palm kernel oil gotten from boiling process of palm fruits
experience hydrolysis during the boiling period and this hydrolysis had already
gotten through the initiation and propagation stages prior to the oil
production where as the fermentation process experience less hydrolysis which
may still be in the induction prior to oil production. From the result it can
also be seen that for both processes, the stability decreased with storage time
up to 4 months after which it increased. The decrease in stability up to 4
months was as a result of the propagation step of free fatty acid liberation
been higher than the termination may have become predominant leading to the
reduction in FFA liberation and observed increase in hydrolytic stability. The
oxidative stability of palm kernel oil extracted from boiling process of palm
fruits were higher than those of palm kernel oil extracted from fermentation
process of palm fruits as shown in Appendix A1. The reason for this is probably
due to the fact that the fermentation operation retard some hit labile
antioxidants which could have aided in the oxidation reaction where as the
boiling process did not.
On the effect of pre-processing
condition, the oxidation stability decreased with storage time up to 6 months
after which it increased with time. This is similar to the observation on the
variation of hydrolytic stability with storage time. Similar reason can be
deduced. In order words, the propagation step control the oxidation reaction up
to 6 months while the termination step took over after 6 months. Furthermore,
the reaction of the peroxides to other products such as aldehydes and ketones
may have set in after 6 months storage result in decrease in observed rate of
increase in peroxide value.