Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 3, Pages: 143-147
143
Physicochemical Characteristics and Microbial Population of Palm
Oil Sold in Major Markets in Yenagoa Metropolis, Bayelsa States,
Nigeria
Elijah Ige Ohimain
1
and Sylvester Chibueze Izah
2
*
1- Food and Industrial Microbiology Research Unit, Department of Biological Sciences,
2- Faculty of Science, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria
Abstract
Palm oil has found application in both food and several industries. This study evaluated some physicochemical quality and
microbial population of palm oil sold in some major markets in Yenagoa metropolis, Bayelsa State, Nigeria. A total of twenty
eight palm oil samples were obtained from seven markets, four being from each market. Standard procedures were employed to
enumerate the microbial population and physicochemical quality of palm oil. The microbial population ranged from 3.802- 4.858
Log cfu/ml and 2.287 – 3.792 Log cfu/ml for bacteria and fungi respectively. The results of the physicochemical ranged from
4.503 - 8.467 (free fatty acid i.e. FFA), 2.600 - 9.275 Meq/kg (peroxide value), 3.775 – 12.000% (Impurity level), 0.550– 2.425%
(moisture content) 191.50– 203.05mgKOH/g (saponification value) and 0.9250 - 0.9875 (Specific gravity). The Analysis of
variance showed that there were significant differences (P < 0.05) in all the physicochemical in most of the markets apart from
saponification value. Parameters such as FFA, impurity, moisture, specific gravity, saponification value were not within the
recommended limits, while the microbial population was within the maximum range recommended by Nigerian Agency for Food
and Drug Administration Control (NAFDAC) for vegetable oil.
Key words: Bayelsa state, Market, microbial population, physicochemical properties, quality
1 Introduction
1
Palm oil is the most exploited and applied vegetable oil
in Nigeria. Quality assessment of palm oil is an important
index in evaluating its applications. About 55% of palm oil
consumed in Nigeria is produced domestically and the rest
45% deficit are met through importation from major
producing nation such as Indonesia and Malaysia.
Presently, Malaysia and Indonesia account for about 89%
of global palm oil, while Thailand, Columbia and Nigeria
account for about 6% and the rest of the oil palm producing
nations account for 5%.
Palm oil is semi-solid and saturated at room
temperature and can tolerate high level of heat and resists
oxidation. Palm oil contain natural antioxidants. Palm oil is
orange red to brownish and/ or yellowish-red in colour [1,
2] and is insoluble in universal solvent such as water and
soluble in organic solvents like trichloromethane and
alcohol [3]. Palm oil is widely used as food or as an input
in feed production. Palm oil has also found application in
industries such as pharmaceutical, detergent and soap,
confectionaries, margarines, cosmetics and biofuel such as
biodiesel.
The quality of palm oil processed in Nigeria is
influenced by the level of hygiene practiced by the
processors in the processing mills. The imported palm oil
often gets impaired due to prolong storage and /or transfer
Corresponding author: Sylvester Chibueze Izah, Faculty
of Science, Niger Delta University, Wilberforce Island,
Bayelsa State, Nigeria, E-mail: sylvesterizah@yahoo.com
in unhygienic condition/container. Poor palm oil quality
with regard to microbial and physicochemical properties
affects some of its down streams applications. The
physicochemical quality affects the industrial use of the
palm oil such as biodiesel production [4]. The microbial
composition influences its food application and in
traditional medicine, hence causing health related effects.
Several microorganisms are capable of flourishing in the
palm oil. The type of microbial species and population pose
danger to individual that consumes raw palm oil. Though,
during cooking heat is applied which often eliminates or
reduce the microbial populations, but some individuals still
consumes raw palm oil especially in the rural areas.
Majority of palm oil microbial species is part of normal
flora which could have been introduced into the palm oil
from the field and during processing especially by
individuals under poor hygienic conditions. Some of these
microorganisms often cause diseases on ingestion of raw
palm oil. The microorganisms that have been widely
reported to be found in palm oil include Enterobacter,
Bacillus, Proteus, Micrococcus, Staphylococcus,
Aspergillus, Candida, Mucor and Penicillium species [3, 5,
6], Trichphyton schoenleinii and Microsporium canisas [7].
These microbes are known to cause disease conditions. For
instance, Proteus species is capable of causing urinary tract
infection [3], Aspergillus species is capable of causing
aspergillosis, endophthalmitis, meningitis, pulmonary
osteomyelitis, endocarditis, myocarditis; Candida and
Mucor species causing candidiasis and mucormycosis
respectively [5]. Enterobacter species often causes
respiratory tract infections, septicemia and meningitis [6].
Journal web link: http://www.jett.dormaj.com
J. Environ. Treat. Tech.
ISSN: 2309-1185
Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 3, Pages: 143-147
144
Some species of Micrococcus can degrade sweats to
produce unpleasant odors; some Penicillium species can
cause keratitis, otomycosis; some species Staphylococcus
can cause bacteremia, genitourinary disease among
sexually active person especially females; some species of
Pseudomonas such as Pseudomonas aeruginosa can cause
skin and soft tissue infections, urinary tract infections,
gastrointestinal tract, bone and joint infections, respiratory
infections, endocarditis, central nervous infections,
necrotizic enterocolitis and giving port of entry for
septicemia and bacteremia. These microorganisms are
opportunistic in nature are capable of affecting individuals
that have suppressed immune system.
Physicochemical parameters such as free fatty acid
(FFA) increase due to long storage and microbial
infestation prior to processing. This basically causes
rancidity in the palm oil, which reflects in the taste and
odour of the palm oil. Other physicochemical quality
parameters of palm oil include peroxide value, moisture
content, iodine value, saponification value, impurity level
etc. The quality of palm oil processed from various palm
oil mills in Nigeria has been widely reported in Literature
[1, 3, 5, 8 – 11]. Also the palm oil sold in some major
market in different states in Nigeria abound in Literature;
Delta state [12], Jos metropolis, Plateau state [6], Abia state
[13], Ibadan, Oyo state [14] and Kogi state [7]. The
microbial population and physicochemical quality of palm
oil sold in major markets in Yenagoa metropolis has not
been documented, hence the need for the study.
2 Materials and Methods
2.1 Study site
This study was carried out in Yenagoa metropolis, the
Bayelsa state Capital. The state has several markets that
trade nearly every day of the week. Nearly all the markets
are located along the express way (i.e stretching across
Igbogene, Akenfa, Agudama-Epie, Tombia, Opolo,
Kpansia and Swali). Some of the palm oil dealers do sell in
more than one market depending on the day it trade.
Basically, the population of the state has been increasing
due to urbanization and industrialization. Hence, the
number of people that consumes palm oil on daily basis is
also increasing.
2.2 Sample collection
Four samples of oil palm displayed for sales were
purchased from seven different markets in Yenagoa
metropolis. The sample meant for microbial analyses were
transferred into sterile McCartney bottles.
2.3 Enumeration of total heterotrophic bacteria and fungi
counts
The Microbial population from the palm oil samples
was enumerated using serial dilution pour plate method
described by Pepper and Gerba [15]. About 1.0ml of the
sample suspension was serially diluted with sterile distilled
water and aliquots of the dilutions were aseptically plated
into Nutrient Agar for bacteria and Potato Dextrose Agar
for fungi. The agar plates were inverted and incubated at
35°C for 24– 48 hours and 30°C for 72- 120 hours for
bacteria and fungi respectively. The colonies that grew on
the medium were counted and expressed as colony forming
units (cfu)/ml of the palm oil samples.
2.4 Physicochemical properties of the palm oil
The physicochemical parameters studied include
specific gravity, FFA, saponification value, moisture
content, impurities level and peroxide value. Specific
gravity and saponification value were determined using the
method described by Akinola et al. [1], Ohimain and Izah
[4], Ohimain et al. [3]. Free fatty acid was determined
based on the method described by Tagoe et al. [16], Aletor
et al. [9], Ohimain and Izah [4], Ohimain et al. [3, 11].
Impurity content were similarly determined based on the
method described by Tagoe et al. [16], Ohimain and Izah
[4]. Moisture and peroxide value analyzed based on method
describe by Ohimain et al. [3, 11].
2.5 Statistical Analysis
SPSS software version 16 (SPSS Inc, Chicago) was
used to carry out the statistical analysis on the microbial
load and the physicochemical parameters of the palm oil. A
one-way analysis of variance (ANOVA) was carried out at
α = 0.05, and Duncan’s multiple range test was used to
determine the source of the observed differences.
Microbial population densities were log transformed prior
to ANOVA. Pearson’s correlation matrix was used to
identify the relationship among the physicochemical
parameters of the palm oil.
3 Results and Discussion
Table 1 presents the microbial population of palm oil
sold in major markets in Yenagoa metropolis. The total
heterotrophic bacteria ranged from 3.802-4.858 Log cfu/ml
being significantly not different (P> 0.05) among the
various markets. Total fungi ranged from 2.287 - 3.792 Log
cfu/ml. The microbial population recorded in this study is
in agreement with other studies. For instance, the microbial
load of palm oil sold in Jos metropolis, Plateau state
Nigeria ranged from 9.4 x 10
4
to 1.61 x 10
4
cfu/ml [6],
8.0×10
3
to 3.7×10
4
cfu/ml for mould load [14]. However,
the result obtained in the current study is far from microbial
count of 7.6 Log cfu/ml reported for palm oil sold in some
markets in Nigeria after 8 months of storage [17]. The
microbial population recorded in the current study is
however comparable to the microbial load of palm oil
produced by smallholder’s processors in Rivers state,
Nigeria [5] and semi-mechanized processors in Bayelsa
state [3]. The microbial population from the palm oil
samples was within the minimum standard microbiological
population (10
4
cfu/ml) recommended by the Nigerian
Agency for Food and Drug Administration (NAFDAC) [6].
The population of the microbes could be associated with
the duration of storage after processing.
The physicochemical quality parameters of the palm oil
samples sold in Yenagoa metropolis are presented in Table
2, while Table 3 presents Pearson’s correlation coefficient
matrices for the analyzed physicochemical parameters. The
FFA ranged from 4.503 to 8.467 being significantly
different among the markets (P<0.05) apart from Swali and
Agudama-Epie that were not significantly different
(P>0.05). FFA significantly correlated (P < 0.01) with
peroxide value (r=0.493), specific gravity (r=0.639),
Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 3, Pages: 143-147
145
moisture content (r=0.798) and impurity level (r=0.889)
(Table 3). The results of this study were higher than
previous findings. Okechalu et al. [6] sampled palm oil
sold within Jos Metropolis and found that the FFA ranged
from 2.67 – 4.20%. Enemuor et al. [7] reported FFA of
palm oil sold in Anyigba Market, Kogi state, Nigeria as
6%. Also, the FFA content of palm oil processed from
some palm oil mills in some Nigeria states including Kogi
[10], Osun and Ondo [1] and Imo [8] were lesser than this
study. The findings from these studies were also not in
consonance with other study. Olorunfemi et al. [14]
reported FFA of palm oil sold in Ibadan in the range of
13.93 to 19.00%. The FFA content recorded in this study
was similar to values obtained in other studies in southern
Nigeria including Delta state [9], Rivers [11] and Bayelsa
[3]. The range of percentage FFA from this study indicates
that the palm oil sold in Yenagoa is of poor quality.
Table 1: Microbial population of palm oil sold in major markets in Yenagoa metropolis, Bayelsa state, Nigeria
Markets
Total Heterotrophic Bacteria, Log cfu/ml
Total fungi, Log cfu/ml
Swali
4.783±0.142b
3.792±0.285c
Agudama-Epie
4.416±0.293b
3.298±0.028b
Tombia
4.858±0.039b
3.279±0.018b
Akenfa
4.697±0.025b
3.294±0.006b
Igbogene
4.400±0.246b
3.306±0.002b
Kpansia
3.802±0.012a
2.287±0.006a
Opolo
4.763±0.003a
3.304±0.005b
Each value is expressed as mean ± standard error (n = 4). Different letters in each column indicate significant differences at P< 0.05 according to the Duncan Multiple
Range Test
Table 2: Physicochemical properties of palm oil sold in major markets in Yenagoa metropolis, Bayelsa state, Nigeria
Markets
FFA, %
Peroxide value,
Meq/kg
Specific gravity
Moisture, %
Swali
8.467±0.463e
9.275±0.155f
0.9875±0.005b
2.400±0.158c
Agudama-
Epie
8.253±0.410e
9.000±0.238f
0.9770±0.008b
2.425±0.193c
Tombia
6.730±0.646d
4.450±0.185c
0.9645±0.005b
1.575±0.111b
Akenfa
5.320±0.408b
5.450±0.150d
0.9350±0.014a
1.525±0.155b
Igbogene
4.503±0.112a
7.300±0.212e
0.9250±0.010a
0.950±0.087a
Kpansia
6.223±0.312cd
2.600±0.158a
0.9743±0.006a
1.425±0.179b
Opolo
5.840±0.408bc
3.400±0.196b
0.9660±0.006b
0.550±0.065a
Each value is expressed as mean ± standard error (n = 4). Different letters in each column indicate significant differences at P< 0.05 according to the Duncan Multiple
Range Test
Apart from palm oil from Swali and Agudama-Epie,
the peroxide values were significantly different (P<0.05)
ranging from 2.600 - 9.275 Meq/kg. Peroxide value
significantly correlates (P < 0.01) with moisture content
(r=0.638) and impurity level (r=0.703) (Table 3). The
result from this study is in agreement with other studies.
Agbaire [12] reported peroxide value from palm oil sold in
some markets in Delta state as 7.8 – 8.4Meq/kg. Udensi
and Iroegbu [13] reported peroxide value of palm oil sold
in some major markets in Abia state, Nigeria in the range of
7.9 – 8.8Meq/kg. The peroxide value of palm oil processed
in some Nigeria states including Kogi [10], Bendel (now
Delta) [9], Osun and Ondo [1], Rivers [11], Bayelsa [3] and
Imo [8] are comparable to the values obtained in this study.
However, high peroxide value has been reported in some
literature. Okechalu et al. [6] reported peroxide values of
23.2 – 35.5 meq/kg from palm oil sold in major markets in
Jos metropolis, Plateau state. Ohimain et al. [3] also
reported high peroxide value from palm oil processed from
semi-mechanized palm oil mill in Bayelsa state, which
were not comparable to the findings of this study. The
peroxide value of palm oil from this study is within the
permissible limit of 10MeqO
2
/kg of standard specified by
World Health Organization [18] and Standard Organization
of Nigeria [19]. Basically, peroxide value is an indication
of the stability and or rancidity of fat by reason of the
amount of lipases, stages of oxidation and extent of
spoilage [11].
Table 3: Pearson’s correlation matrix of the physicochemical quality parameters of palm oil sold in Yenagoa metropolis, Bayelsa
state, Nigeria
Parameters
FFA,%
Saponification value,
mgKOH/g
Peroxide value,
Meq/kg
Specific
gravity
Moisture
content, %
Impurity level, %
FFA,%
1
Saponification value,
mgKOH/g
-0.164
1
Peroxide value, Meq/kg
0.493
**
0.180
1
Specific gravity
0.639
**
-0.388
*
0.083
1
Moisture content, %
0.798
**
-0.162
0.638
**
0.387
*
1
Impurity level, %
0.889
**
-0.152
0.703
**
0.613
**
0.792
**
1
**. Correlation is significant at the 0.01 level (2-tailed).
*. Correlation is significant at the 0.05 level (2-tailed).
N=28; n=4
Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 3, Pages: 143-147
146
The level of impurities of the palm oil sold in major
markets in Yenagoa metropolis ranged from 3.775 –
12.000%, being significantly different (P<0.05) from all the
markets. Impurities level from this study is higher than
previous report. Agbaire [12] reported level of impurity
from palm oil sold in some markets in Delta state as 0.11 –
0.14%. Enemuor et al. [7] reported impurity content of
palm oil sold in Anyigba Market, Kogi state, Nigeria as
0.2%. Also, the findings were higher that the impurity
value reported from palm oil from mills in some Nigerian
states including Kogi [10], Imo [8]. The impurity content
were comparable to the value reported in palm oil from
palm mills in Rivers state as reported by Ohimain et al.
[11]. Higher impurity level (19.87%) has been detected in
palm oil from semi-mechanized palm oil mill in Bayelsa
state [3]. The impurity content observed in the current
study were higher than 0.01% recommended for maximum
impurity limit [18]. The high impurity level of the palm oil
could be associated to poor hygienic disposition of the
processors and palm oil marketers. The impurity content
could also has been increased by the addition of second
grade oil to the palm oil during processing. This is a major
practice of smallholder oil palm processors in Nigeria [2,
3].
The moisture content of the palm oil sold in major
markets in Yenagoa metropolis ranged from 0.550–
2.425%. Moisture content significantly correlated (P <
0.01) with impurity level (r=0.792) (Table 3). The results
from this study were higher than previous findings. Udensi
and Iroegbu [13] reported moisture content of 0.14 to
0.16% for palm oil sold in some major markets in Abia
state. Agbaire [12] similarly reported moisture content of
0.14 – 0.17% for palm oil sold in some markets in Delta
state. Enemuor et al. [7] reported moisture content of palm
oil sold in Anyigba Market, Kogi state, Nigeria as 0.3%.
The finding of this study is in consonance with other
reports. Okechalu et al. [6] reported moisture content of
1.09 – 1.27% for palm oil sold in Jos Metropolis, Plateau
state, Nigeria. Olorunfemi et al. [14] reported moisture
content of palm oil sold in Ibadan in the range of 1.2 –
2.0%. Also, the moisture content were close to the finding
of Akubor and Ogu [10], Aletor et al. [9], Onwuka and
Akaerue [8] from palm oil processed from palm oil mills in
some Nigerian states. The values obtained were relatively
higher than the limits of 0.29% recommended by SON
[19].The relatively high moisture content from this study
could be attributed to poor heating during clarification.
High moisture content makes the palm oil susceptible to
microbial attack, thereby contributing to the high free fatty
acid content [16].
The saponification value of the palm oil obtained from
major markets in Yenagoa metropolis were not different
significantly (P>0.05) ranging from 191.50–
203.05mgKOH/g. Saponification exhibited negative
relationship with specific gravity (P<0.05). The findings of
this study are comparable to other studies. Udensi and
Iroegbu [13] reported saponification value of 191.64 –
198.03 mgKOH/g for palm oil sold in some major markets
in Abia state. Agbaire [12] reported saponification value of
195.76 – 198.75 mgKOH/g for palm oil sold in some
markets in Delta state. Also, the results of this study is
similar to the saponification value reported in palm oil
processed in some Nigerian states including Bayelsa [3],
Osun and Ondo [1]. But the findings of this study were not
in consonance with other study. Olorunfemi et al. [14]
reported saponification value of palm oil sold in Ibadan in
the range of 221.87 – 234.83 mgKOH/g. Akubor and Ogu
[10], Onwuka and Akaerue [8] reported saponification
value that exceeded the results of this study. However,
apart from palm oil from Swali and Agudama-Epie, the
saponification value reported in the current study was
within the permissible limit of 195 – 205 mgKOH/g
recommended by SON [19].
The specific gravity of the oil in the current study
ranged from 0.9250 - 0.9875. Specific gravity significantly
correlated with moisture content (r=0.387P < 0.05) and
impurity level (r=0.613 P<0.01) (Table 3). The results of
this study were slightly higher than previous studies.
Udensi and Iroegbu [13] reported specific gravity of 0.832
– 0.880 for palm sold in major markets of Abia state.
Agbaire [12] reported specific gravity of 0.859 –0.885 for
palm oil sold in major markets of Delta state. However,
results obtained in this study were comparable to the
specific gravity content reported by Akinola et al. [1] for
palm oil obtained from Osun and Ondo states. Also,
Ohimain et al. [3] reported specific gravity higher than the
result of this study from semi-mechanized palm oil mill in
Bayelsa state, Nigeria.
4 Conclusions
Some physicochemical properties and microbial
population of palm oil sold in some major markets in
Yenagoa metropolis Bayelsa state were evaluated. The
bacterial and fungal populations were found to be within
the specified range of x10
4
specified by SON. Some
physicochemical parameters such as FFA, moisture
content, impurities level, specific gravity were higher than
the permissible limits. However, Peroxide value were
within the maximum limit specified by WHO. Also, apart
from palm oil from Swali and Agudama-Epie, the
saponification value of the palm oil analyzed during the
current study was within the recommended limit.
Acknowledgement
The authors wish to thank Rohi Biotechnologies
Limited, Port Harcourt, Nigeria for providing the
laboratory facilities for carrying out this study.
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