Research - (2020) Volume 11, Issue 3
Received: 23-Mar-2020
Published:
27-Jun-2020
, DOI: 10.37421/2150-3494.2020.11.209
Citation: Samuel Echioda, Salisu Salisu, Amina Abdulraheed, Omogbeme Judith, and Hadiza Rita Sule. "Variations on the Physiochemical, Microbiological and Selected Heavy Metals of Different Palm Oil Samples Sourced From Galadima, Tarauni, Sabon-Gari, Yan-Kura of Kano State and Samples from Kogi and Edo States of Nigeria". Chem Sci J 11 (2020) doi: 10.37421/CSJ.2020.11.209
Copyright: �© 2020 Samuel E, et al. This is an open-access article distributed under the terms of the creative commons attribution license which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.
This study involves the physiochemical, microbiological and selected heavy metals variations of palm oil samples sourced from galadima, tarauni, yan-kura markets of kano state and samples from Kogi and Edo States of Nigeria. The samples were evaluated using standard documented procedures. The result showed; samples from Edo had: oil acid value 0.73 ± 0.13, iodine value 29.25 ± 0.09, peroxides value 2.68 ± 0.09, saponification value 194.31 ± 2.21, moisture content 1.13 ± 0.56, ester value 195.04 ± 2.08. The samples from Kogi had; acid value 0.88 ± 0.11, iodine value 11.54 ± 0.24, peroxides value 5.79 ± 0.62, saponification value 187.49 ± 0.56, moisture content 1.60 ± 0.10, ester value 186.61 ± 0.45. The sabon-gari samples had; oil acid value 0.86 ± 0.17, iodine value 30.37 ± 0.34, peroxides value 3.25 ± 0.95, saponification value 188.66 ± 1.88, moisture content 1.19 ± 0.59, ester value 187.8 ± 1.71. Galadima samples had: acid value 0.89 ± 0.14, iodine value 29.31 ± 0.47, peroxides value 6.8 ± 0.16, saponification value 182.62 ± 3.65, moisture content 1.82 ± 0.67, ester value 181.73 ± 3.5. Taruani samples had; acid value 0.56 ± 0.13, iodine value 29.63 ± 0.81, peroxides value 5.79 ± 0.62, saponification value 194.07 ± 0.47, moisture content 1.43 ± 0.71, ester value 193.51 ± 0.44. Yan-kura samples had: acid value 0.98 ± 0.09, iodine value 30.78 ± 0.26, and peroxides value 6.2 ± 0.14, and saponification value 184.045.00, and moisture content 1 21 ± 0.60, ester value 183.06 ± 4.91. The microbiological analysis of the samples revealed sabon-gari samples had 1.0 × 10-5, galadima 7.6 × 10-3, Tarauni 7.2 × 10-4, Kogi 1.2 × 10-5, Yan-kura 1.1 × 10-5 and Edo 6.8 × 10-3 cfu/ml respectively. The heavy metals analysed were cadmium (Cd), arsenic (As), mercury (Hg) and lead (Pb). The concentrations of Cd ranged between 0.001 (ppm) Tarauni to 0.019 (ppm) Galadima, As (ppm) ranged between 0.01 Edo and Kogi to 0.047. Hg (ppm) 0.01 Edo to 0.19 galadima and Pb (ppm) 0.05 Kogi to 0.18 galadima. From the results obtained, it shows that Yan-kura has the most polluted oil due to the exposure to the environment. The samples collected are safe for consumption as at time of analysis, however continuous monitoring is required.
• Palm oil • Physiochemical • Microbiological • Heavy metals
Palm oil is derived from the mesocarp of the fruit of the oil palm. It has light yellow to red color. Red palm oil get its name from its characteristic dark red color, which come from carotenes, such as alpha-carotene, betacarotene and lycopene which are responsible for high vitamin A content, [1]. The oil palm (Elaeis guinensis) is West Africa’s most important oil producing plant. The fruit produces two distant type of oil. The orange to red crude palm oil which is extracted from the mesocarp and brown light yellow crude palm kernel oil extracted from the seed (kernel). The former consists of mainly palmitic and oleic acids and the latter, mainly lauric acid. Both oils are important in the world trade. Crude palm oil (CPO) is the richest natural source of carotenoilds and cotrienols. While it’s semi-solid consistency at a tropical room temperature is mainly due to the presence of triacylgycerols of palmitic and oleic acid [2]. Human use oil palm as far as 5,000 years back, in the late 1800s archaeologists discovered a substance that they conducted was originally palm oil in a tomb at Abydos dating back to 3,000 BC. It is believed that traders brought oil palm to Egypt.
The work is aimed at ascertaining the physiochemical, microbiological and selected heavy metals of different palm oil sample consumed from different markets of Galadima, Tarauni market, Sabon-Gari, Yan-Kura of Kano state and sample from Kogi and Edo states.
Materials
The following materials were used for the study; wijis solution, thiosulphate solution, glacial acetic acid (BDH Chemicals England), Concentration nitric (Merck Chemicals), Sulphuric acid (BDH Chemicals), hydrogen peroxide (BDH Chemicals England), Hot air oven (Gellenkamp, UK), desiccators, Atomic absorption spectrometer (Shimadzu, Model- AA7000 with air acetylene flame at 324.8 nm), Incubators, Muffle furnace (Gellenkamp, UK), colony counters (Hanna, USA).
Sampling
The palm oil samples that were used for the study were collected in triplicate from oil market in size locations namely: Galadima, Tarauni, Sabongari, Yan-kura, in Kano state, Kogi and Edo state Nigeria.
Determination of acid value
The oil sample (1.0 g) was boiled with 50.0 cm3 ethanol, and then was allowed to cool and two drops of phenolphthalein indicator was added. The resulting solution was titrated against 0.1 mol/dm3 NaOH until a pink colour was obtained
The acid value was calculated using equation;
The oil sample (1.0 g) was boiled with 50.0 cm3 ethanol, and then was allowed to cool and two drops of phenolphthalein indicator was added. The resulting solution was titrated against 0.1 mol/dm3 NaOH until a pink color was obtained [3].
The acid value was calculated using equation
(1)
V is the titre value and W is the weight of oil, M is the molar mass NaOH.
Determination of iodine value
The method described by Marshall et al., was adopted. About (0.5 g) will be placed in 250.0 cm3 conical flask and 10.0 cm3 of anhydrous chloroform was added. This was followed by 30.0 cm3 of solution and the flask was stopped and allowed to stand in the draw for 30 minutes and which potassium iodine (10.0 cm3 of 15% v/v) was added to the content of the flask so as to wash down any iodine that might present on the stoppard. The resulting solution was titrated with sodium thiosulphate solution (0.14 M) until the light yellow colour form disappears. The determination for the blank will be conducted in the same manner but without the oil. The iodine value was calculated as:
(2)
B and S was titre value of blank and sample respectively, M is molarity of sodium thiosulphate, 12.69 is the conversion factor from meq sodium thiosulphate to gram molecular weight of iodine and W is the weight of oil.
Determination for peroxide value
One gram of oil sample was weighed into a clean dry boiling tube. While still liquid, one gram of powdered potassium iodide and 20 cm3 of solvent mixture (2.0 volumes of glacial acetic acid and 2.0 volume chloroform.) were added. The tube was placed in boiling water so that the liquid boils within 30 sec. and allows boiling vigorously for not more than 30 seconds.
The content was placed quickly into a flask containing 20.0 cm3 of potassium iodide solution (5.0%) the tube was will beheld twice with 25.0 cm3 water and was titrated with 0.002 mol sodium thiosulphate using starch indicator.
A blank will be performed at the same time. The peroxide value was calculated using equation.
(3)
Where B and S titre values of blank and sample respectively, M is the Molarity of Na2S2O3.
Determination of saponification value
Two grams of the oil sample was weighed into clean dried conical flask and 25.0 cm3 of alcohol potassium hydroxide will be added. The flask was heated for an hour with frequent shaking. 1.0 cm3 phenolphthalein indicator was added and the hot excess alkali titrated with 0.5 mol/dm3 hydrochloric acid (HCl) until it reaches the end point where it turns colorless.
A blank titration was carried at the same time. The saponification value was calculated using equation:
(4)
Where S = Sample titre value, B = Blank titre value, M = Molarity of HCl (0.5 M) and 56.1 = Molecular weight of potassium hydroxide.
Unsaponifiable matter
After the titration of the saponification value, the resultant solution was made alkaline again with 1.0 cm3 of aqueous 3.0 M potassium hydroxide solution. And was then transfer to a separator and washed in with water. The solution was extracted while still just warm three times with 50.0 cm3 quantities of diethyl ether and also poured into separator containing 20.0 cm3 water. After the third extract was added, the combined ether extracts was shacked with the first 20 ml of wash water and vigorously with another 20.0 cm3. The third was washed twice with 20.0 cm3 of aqueous 0.5 M potassium hydroxide solution and at least twice with 20.0 cm3 quantity of water until the wash water is no longer alkali to phenolphthalein. The ether extract was poured until a weighed flask, the solvent was evaporated off and the residue dried at about 550°C, cooled and weighed.
Refractive index
The refractive index was determined using Abbe’s refractor meter. The Abbe’s refractor meter was reset with a light compensator (20°C) the oil sample was smeared on the lower prism of the instrument and closed. Light was passed by means of angled mirror, the reflected light appear in form of a dark background. The fine adjustment of telescope tube was used until the black shadow appears at central in the cross wire indicator. The refractive index was read off and recorded.
Determination of rancidity
The rancidity of the oil sample was determined qualitatively using Kries Test. About 5.0 cm3 of the oil samples was placed in 100.0 cm3 test tube and then mixed vigorously with 5.0 cm3 of universal indicator and 5.0 cm3 of concentrated HCl for about 20 seconds. The presence of pink colour indicates incipient rancidity.
Determination of pH value
The pH of the oil sample was determined using a pH meter, about 30.0 cm3 of the oil sample was poured into a beaker, then the pH meter electrode was immersed into the beaker containing the oil sample and the pH values was recorded [4].
Determination of moisture content
Gravimeter method was used for moisture determination. About 5.0 g of sample was weighed into evaporation dish. It was placed in an oven and maintained at 105°C for 3 hours interval. After drying to a constant weight, the sample was cooled in a desecrator and re-weighed using analytical balance.
(5)
Where b = weight of crucible and sample
c = weight of crucible and dried oil
a = weight of crucible only.
Determination of ester value
The ester was determined by subtracting acid value from saponification value [5].
Adulteration is very common among palm oil sellers especially in this part of the world, understanding the physical and chemical content of palm oil is therefore important. The results of the study indicate the suitability of the palm oil samples for both domestic and industrial uses. Current study highlight the need of implementation of food safety law at all level of palm oil processing specially within supply chain to ensure safe product to the consumers. Some microorganisms found in palm oil often lead to deterioration in their chemical quality. Hence the presence or absence of micro-organisms can be considered as quality determinant of palm oil. The microbial quality of palm oil is essential because of the adverse role played by most lipophilic micro-organisms in human and animal health.
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