ABSTRACT
This
work evaluates the antioxidant potential of Monodora myristica (African
nutmeg). Monodora myristica extract
was obtained by solvent extraction using n-hexane and used as treatment on
freshly prepared crude palm kernel oil and palm oil. Equal volume of oil
samples were subjected to different concentration of extract treatment
(0.2ml,0.4ml, 0.6ml, 0.8ml, 1.0ml using syringe. These oil samples were equally
divided into two groups SS and SR. Group SS was stored under the sun and group
SR was stored in the room for three
weeks. These treated oil samples were analyzed on weekly basis at two different
parameters: Acid value (AV) of free fatty acid and thiobarbituric acid (TBA)
value, using standard methods. The main effect of extract was determined using
ANOVA. For the two varieties of oil, the acid value of free fatty acid
increased significantly (P<0.05) as the period extends for group SS without
extract while those for group SR showed no significant increase. But AV of oil
samples treated with higher extract concentration decreased significantly
(P<0.05) for both groups SS and SR. TBA value also showed the same trend of
AV. Hence, monodora myristica extract
yielded reducing effect in the oxidative level of the oil varieties.
TABLE
OF CONTENTS
Title
page
Approval
page
Dedication
Acknowledgement
Abstract
Table
of content
List
of tables
List
of figure
Abbreviation
CHAPTER ONE
1.0 Introduction
1.1 Significance of study
CHAPTER TWO
2.0 Literature Review
2.1 African nutmeg (Monodora myristica)
2.1.1 Scientific classification
2.1.2 Habitat/ ecology of Mondora myristica
2.1.3 Characteristics/morphology of monodora myristica
2.2 Oil Palm
2.2.1 Scientific classification
2.2.2 Origin and description of palm oil
2.2.3 The Chemical composition of palm oil
2.2.4 Physical characteristics of palm oil
products
2.3 Palm kernel oil
2.3.1 The chemical composition of palm kernel
oil
2.4 Modern uses of palm oil and palm
kernel oil
2.5 Lipid oxidation
2.5.1
Lipid oxidation pathway
2.5.2
Mechanism of oxidation
2.6 General antioxidant action
2.6.1 Mechanism of antioxidant action
2.6.2
Antioxidant molecules
2.7 General review of photochemistry of monodra myristica
2.7.1 Alkaloids
2.7.2 Flavonoids
2.7.3 Glycosids
2.7.4 Saponins
2.7.5
Tannins
2.8 Application of vegetable oils
2.8.1
Factors that cause oxidative
rancidity in vegetable oil
2.9 Nutritional signification
CHAPTER THREE
3.0 Materials and methods
3.1 Equipment/apparatus
3.2 Procurement of raw materials
3.3 Study design
3.4 Sample preparation
3.5 Chemical analysis
3.5.1 Determination of acid value (Av)
3.5.2 Determination of thiobarbituric acid
number
3.6 Statistical analysis
CHAPTER FOUR
4.0 Result and Discussion
4.1 Changes in Acid value of Palm Kernel
and palm oil
4.2 Changes thiobarbituric acid value of
palm kernel and palm oil
4.3 Effect of monodora myristica extract on the
chemical indices of oil on storage
CHAPTER
FIVE
5.0 Summary
and conclusion
5.1 limitations
5.3 Future recommendation
References
Appendix I
Appendix II
Appenedix III
LIST OF TABLES
Table 1: Fatty acid composition of palm oil (palm oil)
Table 2: Fatty
acid profile of palm kernel oil (palm kernel )
Table
3: Acid value for palm
kernel oil
Table
4: Acid value for palm oil
Table
5: Thiobarbituric acid value for
palm kernel oil
Table
6: Thiobarbituric acid value for
palm oil
LIST OF FIGURES
Figure 1: African
nutmeg seeds (Monodora myristica)
Figure
2: Africa Oil palm fruits (Elaeis
guinesis)
Figure
3: Lipid oxidation pathway
Figure
4: Dried seed kernels of Afican nut meg.
Figure
5: Transverse section of palm fruit
Figure
6: n-Hexane extract of Monodora mystica
Figure
7: Crude palm oil
Figure
8: Crude palm kernel oil
ABBRERVIATIONS
AOCS: Association of America Chemistry
Society
AV: Acid value
FFA: Free
fatty acid
PV: Peroxide value
PKO: Palm kernel oil
PO: Palm oil
PUFA: Polyunsaturated fatty acid
ROS: Reactive oxygen specie
SR: Storage in room
SS: Storage in sun
TBA: Thiobarbituric acid
CHAPTER ONE
1.0
INTRODUCTION
Lipid
oxidation is one of the major reasons that food deteriorate and is caused by
the reaction of fat and oil with molecular oxygen, leading to off-flavours that
are generally called rancidity(Basturk et al., 2007). Exposure to light,
pro-oxidants and elevated temperature will accelerate the reaction (Kubow,
2009). Lipid oxidation and resultant flavour impairment has seriously limited
the storage potential of most fat containing foods (Ihekoronye and Ngoddy, 1985).
Rancidity
covers a wide range of biological activities where the effect is to “make
things worse” and thus adversely affect man’s economy. Free radicals
and microorganisms are known to cause chemical characteristics that lead to
oxidation and deterioration in quality of vegetable oils derived from the seeds
or fruits pulps of plants (Basturk et al, 2007). The keeping quality of
the oils is basically dependent on their chemical compositions, for instance,
the percentages of the degree of unsaturation. Rancidity is
associated with off-flavour and odour of the oil. There are two causes of
rancidity. One occurs when oil reacts with oxygen and is called oxidative
rancidity. The other cause of rancidity is by the combination of enzymes and
moisture. Enzymes such as lipase liberate fatty acids from the triglyceride to
form di and/or monoglycerides and free fatty acids and such liberation of fatty
acid is called hydrolysis, hence hydrolytic rancidity.
The oxidation of
fats is an important deteriorative reaction with significant commercial
implications in term of product value. The initial oxidation products that
accumulate are hydroperoxides, which may subsequently break down to form
lower-molecular weight compounds such as alcohols, aldehydes, free fatty acids
and ketones, leading to autoxidative rancidity. The peroxide content present in
alimentary fats attests to its state of primary oxidation and thus its tendency
to go rancid. Unsaturated fatty acids, in fact, react with oxygen forming
peroxides, which determine a series of chain reactions whose end result is
volatile substances having the characteristic smell of rancidness. These
reactions are accelerated by high temperatures and by exposure to light and
oxygen (Yildiz et al., 2002). The lower the peroxide and acid values,
the better the quality of the alimentary fats and their state of preservation.
Although simple,
procedures of acid value (AV) or
peroxide value (PV) determination are cumbersome, destructive to the sample,
costly, require potentially hazardous solvents, substantial personnel time,
glassware and accurate preparation of reagents and are dependent on a visual
endpoint (Ismail et al., 1993; Van de Voort et al., 1994).
Oxidation is concerned mainly with
unsaturated fatty acids. Oxidative rancidity is of special interest as it leads
to the development of off-flavour that can be detected early on in the
development of rancidity (Basturk et al., 2007)
Some slight deterioration at least is to expected in any
commercial oil-bearing material and is, in fact, inherent in the process by
which fat is formed (Morel,1997). In the living plants and animals, fats,
carbohydrates and proteins are synthesized in a complicated series of steps
with the aid of certain enzymes. These enzymes are capable of assisting the
reverse as well as the forward reactions and hence under proper conditions may
promote the oxidation and degradation of the very substances that, they have
previously been instrumental in synthesizing (Basturk et al., 2007)
Oils in general are known to be susceptible to oxidation
and microbial attack. The composition of the various oils determines the extent
of oxidation and type of organisms likely to thrive in them (Chow et al.,
2000). Several studies have demonstrated that environment factors
affect not only the fatty acid composition of vegetable oil, but also, although
apparently indirectly, the spatial arrangement of those acids on the triacylglycerol
molecule (Tay et
al., 2002). Triacylglycerol composition and structure are important
in the areas of nutrition, oil stability and possible physiological effects.
Palm
oil is extracted from the mesocarp of the fruit of the oil palm, Elaeis
guineensis. crude palm oil (CPO) has a deep orange-red colour due to the
high content of carotenoids and is a rich source of vitamin E consisting of
tocopherols and tocotrienols (Nesaretnam and Muhammad, 1999). Both beta
carotenes and vitamin E are well known nutritional antioxidants.
Palm oil is
known to support the growth of fungi and bacteria especially when it contains
moisture (Cornellus, 2001).. Their lipolytic enzymes are so active that even
under unfavorable conditions palm oil is seldom produced with a free fatty acid
content (FFA) of less than 2% and under favorable conditions of processing, the
free fatty acid content of this oil reaches 20%and higher. When the fruit is
bruised, lipolytic action occurs and a near maximum FFA (8-10%) is reached
within 40 minutes. The FFA of unbruised fruits may increase only 0.2% or less
in the course of 4 days (Cornellus, 2001).
The
exposure in the sun is made under radiations of weak temperatures, varying
daily, creating an environment favourable to the chemical and enzymatic
reactions of hydrolysis and oxidation (Tan et
al., 2002).
This study is aimed at examining the oxidative and
biodeteriogenic effects of free radicals contaminating the oils from the
varieties of the oil palm (Elaeis guineensis) and palm kernel oil
and the chemical components of the oils and the effect of solvent extract of
ehuru (African nutmeg).
Oil
palm is indigenous to the Nigerian coastal area. It was discovered by European
explorers in the early 1400’s and was distributed throughout tropical Africa by
humans who practiced shifting agriculture about 5000 years ago. The palm plant
originated from the jungle forest of East Africa and about 5000 years ago, palm
oil was used by the pharaohs for cooking and lighting. The cultivation of oil
palm is restricted to the eastern sub zones where its growth is favoured
environmentally and climatically. Besides, it is a major cash crop in this region.
The first oil palm plantation was established at Sumatra in 1911 and at
Malaysia in 1917. About this time it was simultaneously established in West
Africa and tropical America.
Over the years, a little attention was
paid to the industrial use of palm kernel oil. Nevertheless, recent studies
have indicated that apart from their domestic uses that they can be used as
engine lubricants, as replacement for biodiesel if their properties are
enhanced.
Although
high in saturated fats, it is a different oil to extract from the nut or kernel
of palms which has a yellowish white colour and a pleasantly mild flavor
similar to coconut oil in fatty oil acid composition and properties.
Crude palm kernel oil (CPKO) is extracted from palm kernels with palm kernel
cake as a by-product. The physical and chemical properties of the various palm
oil products have been reviewed by Nesaretnam and Muhammad, (1999).
Monodora
myristica is a widespread and attractive small tree with very decorative
flowers appearing just before the leaves. The fruit is suspended on a long
green stalk with numerous seeds embedded in whitish sweet smelling pulp. The
seed is oblong and pale brown when fresh with a thin seed coat and hard kernel
(Nesaretnam and Muhammad, 1999). The seed production is seasonal occurring
between April to June. The fruits are globular and ovoid; 3-4 inch long and
about 3-5 inch diameter. The wood is hard. The seeds are contained in a hard
shell and have a very strong aroma . This plant is commonly called Orchid
flower tree in English, Ehuru Ofia in lgbo (Okafor, 2003). Monodora
myristica is a specie of calabash nutmeg, the edible seeds yield a
nutmeg-flavoured oil which is used in West Africa for cooking (Eggeling, 2002).
Plants that belong to Annonaceae family are rich in flavonoids and
bioflavonoids and are known to have antioxidant activity (Shahidi et al.,
2009). Monodora myristica seed extract contains important pharmacological
compounds, alkaloids, flavonoids, and vitamins A and E as well as many
important lipids; arhinolipids, free fatty acids, glycolipids, phospholipids
and sterols. The plant is widely used in ethnomedicine, especially to relieve
toothache as well as in the treatment of dysentery. When roasted and ground,
the seeds are rubbed on the skin for (unspecified) skin diseases (Irvine,
2000). This suggests that the seeds of Monodora myristica plant could be
germicidal or antiseptic. The roasted ground seeds are chewed, then spat into
the hand and then rubbed across the forehead to relieve headache. The seeds are
also crushed and used as insecticide, while the root relieves toothache when
crushed (Ogtinein unet al., 1999).
Monodora
myristica seeds are also used for the treatment of constipation and as a
stimulant (Irvine, 2000). The essential oil from Monodora myristica seed
is used in pharmaceutical and dental preparation (Talalaji, 1999).
In this study, we have monitored characteristic
parameter, namely acid value and thiobarbituric acid value during storage of
palm kernel oil and palm oil at different environmental conditions treated with
different concentration of seed extract of Monodora myristica. Whereby,
the acid value and thiobarbituric acid value, were assessed by the conventional
method and the UV-spectra were registered for each sample. Although simple,
procedures of acid value (AV) or peroxide value (PV) determination are
cumbersome, destructive to the sample, costly, require potentially hazardous
solvents, substantial personnel time, glassware and accurate preparation of
reagents and are dependent on a visual endpoint (Ismail et al., 1993;
Van de Voort et al., 1994).
1.1 SIGNIFICANCE OF RESEARCH
The
aim and objective of this research is to:
1. To carryout solvent extraction of Monodora myristica
2. To
investigate the antioxidant effect of Monodora myristica extract
on palm kernel oil and palm oil at different environmental conditions.
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