CHAPTER FOUR
4.0 RESULTS AND DISCUSSION
A preliminary study was carried out
to identify the maximum concentration of adulterant (red dye) which when mixed
with fresh palm oil will yield unnoticeable adulterated red palm oil. This
maximum concentration was determined to be 0.250% [i.e. 0.25% red dye in 100ml
dissolved water]. Effort was also made to determine the maximum amount of dye
solution (adulterant /oil ratio) that will yield unnoticeable adulterated red
palm oil. It was observed that up to the equal amount of the fresh oil can be
an adulterant i.e. a maximum oil/adulterant ratio of 1:1 was possible
consequently, fresh red palm oil adulterated with 0.25% dye solution at a ratio
of 1:1 was used for further studies. The samples were stored on the shelves of
the laboratory for one week with daily visual inspection.
The table below (Table 1) shows the
changes observed in the samples.
Time
|
Sample 1
|
Sample 2
|
Sample 3
|
(days)
|
0.25%
|
0.5%
|
1%
|
0
|
It is lighter but has the same
orange-red color of palm oil.
|
This almost had the same colour
but there was noticeable differences and particles found in the mixture.
|
Turned red instantly instead of
the normal color of crude palm oil
|
0.5
|
Same
|
Same
|
Same
|
1
|
Same
|
Same
|
Same
|
2
|
Difference in consistency of
the oil, it became more viscous sample1 being the least.
|
Difference in consistency of
the oil it became more viscous.
|
Difference inconsistency of the
oil, it become more viscous, sample 3 being the most.
|
3
|
Same
|
Same
|
Same
|
4
|
Same
|
Same
|
same
|
5
|
Same
|
Same
|
Same
|
6
|
There was a separation of layer
|
Separation into two layers
|
Separation into two layers
|
7
|
There was a separation of layer
|
Separation into two layers
|
Separation into two layers
|
Table
2 shows some quality characteristics of the fresh (unadulterated) and
adulterated red palm oil. The red palm oil used in this study was processed by
self in order to ascertain that samples are free from adulteration.
Table
2
Quality
parameters of red palm oil (fresh and adulterated).
s/n
|
Parameters
|
Control
samples
|
Adulterated
samples
|
1
|
Free
fatty acid [%]
MEAN
|
5.64
|
8.46
|
6.77
|
12.97
|
||
6.21
|
10.97
|
||
2
|
Iodine
value [%]
|
51.86
|
58.50
|
51.89
|
53.62
|
||
Mean
|
51.88
|
53.56
|
|
3
|
Moisture
content [%]
|
0.56
|
1.02
|
0.82
|
1.10
|
||
MEAN
|
0.69
|
1.06
|
|
4
|
Peroxide
value [meq]
|
9.00
|
10.46
|
8.05
|
10.47
|
||
Mean
|
8.53
|
10.49
|
|
5
|
Specific
density
|
0.90
|
0.92
|
4.1 PEROXIDE
VALUE
Peroxide value is a measure of the
degree of oxidation of oil, it determines the extent to which oil has undergone
rancidity, and thus it could be used as an indication of the quality and
stability of fats and oil [Ekwu and Nwagu, 2004]. When double bond of
unsaturated fat becomes oxidized peroxide value is among the products that are
formed.
Results from this study indicates
that the peroxide value of fresh and adulterated samples were 8.53 10.47 meq/kg
respectively. It further suggests that one increase in peroxide value of
adulterated sample maybe possibly due to components of red dye which were also
determined as peroxides or components, of dye which could rise to the formation
of peroxides. However, the peroxide value for both the fresh and adulterated
samples can be considered to be within the range [10meq/kg] recommended by SON
[2000].
4.2 FREE
FATTY ACID
The percentage free fatty acid on (table
2) is 6.21 and 10.72 respectively for fresh and adulterated samples. Generally
the free fatty acid shows level of rancidity taking place in the oil. Free
fatty acid should be 3.5% as recommended by SON [2000]. A high free fatty acid
value of the samples above maybe as a result of the processing step adopted
during the extended extraction period which may have led to formation of FFA
through hydrolysis; due to the high amount of water or storage conditions of
the oil, long storage in the presence of moisture can lead to hydrolysis of triglycerides
to yield FFA. The FFA of the fresh palm oil was different from the adulterated;
this may imply that dye increases the FFA of palm oil. FFA represents the fatty
acid molecules that have been free by lipase oxidation. The freedom of the
fatty acid molecule in the palm oil could therefore be influenced by the
addition of red dye, which might be due to the increase of lipase activity as
the moisture of the oil increases.
4.3 IODINE
VALUE
The
iodine value is a chemical parameter that characterizes oil based on the degree
of unsaturation of the fatty acids in the oil. The Standard Organization of
Nigeria [SON, 2000] stipulates that iodine value of palm oil should range form
45 to 55. The values of the control and adulterated samples are 31.88 and 53.56
respectively, this conforms to SON standard. Swern (1979) and Etuk (1998) have
reported that the higher the degree of unsaturation in an oil sample, the
higher the iodine value of that oil. It therefore follows that any substance
that can increase the degree of unsaturation in an oil sample will raise the
iodine value of the oil. The iodine values reported in table 2 for adulterated
and fresh [unadulterated] oils therefore signify that the adulterant has no
effect on the degree of unsaturation of the oil or the iodine value.
4.4 MOISTURE
CONTENT
The moisture content as shown in (table
2] for the control and adulterated samples were 0.69 and 1.06 respectively. The
moisture content of oil should be as low as possible since moisture leads to
hydrolysis and thus to increase of free fatty acid.
According to Scott (1956), moisture
content of any food material should be used as an index of stability and
susceptibility to fungi infection. The significant increase of moisture when
the red dye was added can be attributed to processing technique and combination
of the inherent moisture content of the plant. This also shows that fresh palm
oil will last longer than the adulterated oil because of the moisture content
which when high increases spoilage of the oil because it becomes rancid leading
to changes in colour, taste and odour:
4.5 SPECIFIC
DENSITY
The specific density of palm oil is
0.90 and when mixed with red dye is 0.92, there was no significant difference
between the palm oil and the adulterated palm oil; which indicates that
adulterants has no impact on the specific gravity of red palm oil.
The quality of palm oil can be
assessed by analyzing the oil samples for its chemical constants. A shift in
the value of any of these chemical constants from the expected range can be
used as an index of adulteration of the oil quality [Woodlatt, 1985]. This
constants are expressed in values which can be adapted to assed the quality of
the oil. The change in any of the parameters during the storage or handling of
palm oil signifies that there is change in the quality of palm oil.
4.6 SENSORY
DISCUSSION
FIGURE 1: Sensory characteristics of adulterated and
unadulterated samples.
Sensory
evolution was conducted using semi-trained panelist on the hedonic scale of 9
to 2; 9 being extremely liked as 1 extremely disliked. The differences
calculated are 1:1 for Aroma, 1.25 for colour, 1.4 for taste, 0.9 for mouth
feel and 1.2 for general acceptability.
During the sensory analysis, the fresh
palm oil was preferred in terms of aroma, colour, taste, mouth feel and general
acceptability. This is because this attributes appeals to the human sense
compared to the adulterated palm oil. It was also observed that the palm oil
with red dye is the one that looks like palm oil because people are used to
seeing this colour and buying that particular colour in the market. The sensory
evaluation conducted shows that fresh oil is preferred and should be used in
place of adulterated as it does not appeal even though the colour looks
attractive.
There is no much difference
statically in the sensory attributes.
CONCLUSION
From the study, the adulterant
considered increased the moisture content, free fatty acid and peroxide value
of the palm oil. This implies that the adulterant used has a potential of
adulterating palm oil. The addition of the adulterant to the palm oil before
marketing is usually aimed at increasing the market value and not the quality
value of palm oil.
It is recommended that the use of additives
in increasing the quantity of palm oil should be strongly discouraged through
proper legislation. Significant attempt should be made toward the control of
the quality of palm oil offered for sale.