OIL PALM INDUSTRY REPORT | EFFECT OF ADDITIVES ON SOME PHYSICAL / CHEMICAL PARAMETERS OF PALM OIL

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.

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