newobetaproject corrected desired
TRANSCRIPT
Effect of drying Condition on the physicochemical properties of oil
extracted from two varieties of tiger nuts from Northern Nigeria.
ABSTRACT
Two varieties of tiger nuts grown in Northern Nigerian were studied to
determine the effect of drying temperatures on the physicochemical
properties of oil extracted from the nuts; to compare the parameters and
evaluate the qualities and quantities of the oil at the drying conditions and
also determine varietals and geographical impacts on those parameters. The
drying protocol used were sun drying, and oven drying at 600C, 1200C, and
1800C. The following physicochemical parameters were evaluated: Free fatty
acid, peroxide value, Iodine value, percentage oil yield, specific gravity and
smoke point. Results from this study revealed that the free fatty acid,
peroxide value, Iodine value, percentage oil yield, specific gravity and smoke
point of oil from the two varieties ranged from (0.01-0.03%) as oleic, (0.63-
2.83) meq/kg, (124-131) wijs, (8.20-12.77%), (240-263oC) respectively.
However, there was general decrease in the free fatty acid, peroxide value,
Iodine value and smoke point of oil from the two varieties tiger nut tuber
after exposure to different temperature conditions which indicates an increase
in the quality of the oil. There was also a significant difference in the
physicochemical properties of the oil from the two varieties of tiger nut tuber
which shows that varietal differences and difference in geographical location
had a significant effects on the oil. The values from the free fatty acid and
peroxide values of the oil from both varieties confirm that the oil is edible
and can be consumed directly without further processing. There is also
possibility of using the oil from both varieties for deep frying and other
industrial applications without further processing of the oil. There were
significant difference at (P<0.05) of the percentage oil yield of oil from the
two varieties of tiger nut tubers.
CHAPTER ONE
INTRODUCTION
The demand for vegetable oils has ever been widening in Nigeria as
industrialists rely mostly on the popular vegetable oils like palm kernel oil,
groundnut oil and soybean oil for the preparation of various products
(Akintayo, 2004).
The study of the physicochemical properties of food (oil) is fundamental in
the analysis and design of the unit operations involved in the food industry
and also in determining the suitability of the final product for human
consumption and other subsidiary uses (Arubi, 2009). These properties
influence the handling and treatment received during processing and they
allow for a better control of both product and processing (Ramos and Ibarz,
1998). Operations such as heating, transportation, packaging, extraction and
milling can be applied with ease in food system if the data on
physicochemical properties such as specific gravity, % oil yield, smoke point,
iodine value, free fatty acid and peroxide value are available.
Seed oil are known to deteriorate when processed inadequately with the
principal decomposition reaction being oxidation. Oxidation of seed oil
occurs through a free radical mechanism, initially characterized by the
emergence of unpleasant odour and flavour which becomes progressively
worse until it attains a characteristic smell of rancid fat (Gouveia et al; 2004).
Heating is one of most commonly used methods of food preparation in the
home and industries and prolong use of oil for this purpose causes change in
its physicochemical properties ( Morette and Fett, 1998).
Under the influence of temperature, fats and oils are susceptible to oxidation
primarily leading to formation of hydroperoxides. Due to their high
reactivity, these hydroperoixde especially at high temperatures rapidly react
with secondary oxidative products e.g aldehydes, ketones, peroxides,
hydrocarbons as well as cyclic compounds that exhibit very different possible
toxic or carcinogenic properties (Kowalki, 1995).
Tiger nut (Cyperus esculentus) a grass like plant of the family cyperaceae
(sedge family), order cyperales or Graminates (Takhatajah, 1992) and genus
Carex (Swiff 1989) is widely distributed in many parts of northern
temperature locations (Anon, 1992) within South Europe as its probable
origin (Childers, 1992). Like other sedges the plant is most frequently found
in wet marshes and edges of streams and pounds where it grows in coarse
tufts (Swiff, 1989). In most countries, the plant is grown as a weed of
cultivation to serve as sand or soil binder.
Tiger nut produces rhizomes from the base with somewhat spherical tubers.
In Egypt, it is used as a source of food, medicine and perfumes (Devries and
Feuke, 1999). Tiger nut is commonly known as earth almond, chufa, yellow
nut sedge and zulu nuts. In Nigeria where three varieties (black, brown and
yellow) are cultivated, it is known as “Ayaya” in Hausa, “Ofio” in Yoruba
and “Akiausa” in Igbo (Umerie et al., 1997). Among these three varieties,
only two (yellow and brown) are readily available in the market. Tiger nut
can be eaten raw, roasted, dried, baked or made into a refreshing beverage
called “Hochata De Chufa” or tiger nut milk (Oladele and Aina, 2007). Also,
it can be used as a flavouring agent for ice cream and Biscuit (Cantetejo,
1997).
Tiger nut oil can be used naturally with salads or for deep frying. Tiger nut
oil can be used in preparation of therapy for some cardiac and intestinal
pathologies, because of its high content of monounsaturated fatty acids (Oleic
acid) and vitamin E (natural antioxidant) ( Adejuyitan et al; 2009). It has also
been reported that the tubers contain about 25% oil, 50% digestible
carbohydrate, 4% protein and 9% crude fibre (Shilenkoo et al; 1979,
Emmanuel and Edward 1984).
Tiger nut tuber can be processed for solvent extraction in different ways such
as sun drying, oven drying and other drying techniques (such as vacuum
drying, solar drying, and continuous or batch atmospheric drying ). It is
expected that these drying techniques influences the physicochemical
properties which eventually affects the quality of the oil. Several works have
been carried out on tiger nut oil but no attempt was made to study the effect
of drying conditions on the physicochemical properties of oil from tiger nut
tuber.
OBJECTIVE
The objectives of this work therefore are:
i. To determine the effect of drying temperatures on the
physicochemical properties of oil extracted from two different
varieties of tiger nuts,
ii. To compare free fatty acid, peroxide value, iodine value, specific
gravity, percentage oil yield and smoke point of the oil from the two
varieties tiger nut tubers and evaluate their qualities and quantities at
different temperature conditions.
iii. To study drying temperatures of nuts in relation to varietals
differences and geographical location.
CHATER TWO
LITERATURE REVIEW
2.0 TIGERNUT (ORIGIN AND DISTRIBUTION)
Tiger nut, also called nut sedge (Cyperus esculentus ) is a perennial
grass-like tropical plant that has a rhizomious growth habit. It produces nuts,
which are attached to its fibrous root endings under the ground. About 90
general of the family cyperaceae are known. Two varieties of tiger nuts are
available in Nigeria and they either grow wild or are domesticated. (Arubi,
2009).
wikipedia (2000), reported that this tuber ranks among the oldest
cultivated plants in Ancient Egypt although nothing that “Chufa” was no
doubt an important food element in ancient Egypt during dynastic times, its
cultivation in ancient times, seems to have remained (totally or almost
totally) an Egyptian specialty. They were used to make cakes in ancient
Egypt.
Presently, they are cultivated mainly, at least for extended and common
commercial purposes, in Spain, where they were introduced by Arabs, almost
exclusively in the Valencia region. They are found extensively in California
and were grown by the paiute in Owens valley. ( wikipedia, 2000).
Egypt through North Africa, before reaching the Iberian peninsula and
sicily with the influx of Islamic culture during the middle Ages (13th century).
Islamic culture was also responsible for the expansion of the cultivation of
tiger nut in the Mediterranean areas of the Valencia region, as well as the
introduction of revolutionary techniques that were, at the time far ahead of
those employed in the agricultural sector. Thus its growth in most savannah
region of Africa like Ghana, Burkina Faso and Mali. No wonder why its
growth in Nigeria mostly concentrated in the middle belt and Northern parts
which have the highest percentage of Islamic believers.
2.0.1 SCIENTIFIC CLASSIFICATION OF TIGERNUT
kingdom: Planatae
(Unranked): Angiosperms
(Unranked): Monocots
(Unranked): Commelinids
Oder: Poales
Family: Cyperaceae
Genus: Cyperus
Species: Esculentus
Binomial name: Cyperus Esculentus
Also, in Nigeria tiger nut nut has a specific name given to it by a
particular tribe as shown below:
Housa: Ayaya
Yoruba: Ofio
Igbo: Akiausa
2.0.2 TIGERNUT
Tiger nut (Cyperus esculenturs) unlike a great variety of nuts, which
are fruits or seeds that have a hard and dry shell, which encloses a kernel
(Mac Daniels, 1987), the nuts of Cyperus esculentus are rhizomes, which are
enlarged storage organs at the fibrous root endings of the plant. The tubers
are edible, with a slightly sweet, nutty flavour, compared to the more bitter
tasting tuber of the related cyperus rotundus (purple Nutsedge). They are
quite hard and are generally soaked in water before they can be eaten, thus
making them softer and giving them a better texture. (http://online.
Wsj.com/article/sb1250180464983695.html).
The kinds of oil produced by plants are non-volatile oils and the
essential volatile oil. The first kinds of oils are food reserve and are by far the
most important in commerce. The second kinds of oils are aromatic and are
commercially important in scents and perfumes. Millions of tones of non-
volatile vegetable oils are consumed as food or used in industry each year.
They are used either as fluid or converted into edible fats source as
margarine. (Onwueme and Sinha, 1991). Edible oils are converted into fats
by a process of catalyzed hydrogenation in which relatively unsaturated oils
become saturated by combining them with hydrogen. Large quantities of
vegetable oils are used to make soap and detergent. Vegetable oils are also
used as lubricants and the least saturated of them are used in paints and
varnishes and to make linoleum. Currently, a lot of efforts have been made on
the production of biodiesels from vegetable oils. Tiger nut oils also contain
minerals, the composition of which are shown below.
Table 2.1: MINERAL CONSTITUENTS/COMPOSITION OF TIGERNUT FLOUR (MG/100G FLOUR).
MINERAL ELEMENT YELLOW VARIETY BROWN
VARIETY
Calcium 155 140
Sodium 245 235
Potassium 216 255
Magnesium 51.2 56.3
Manganese 33.2 38.41
Phosphorus 121 121
Iron 0.65 0.80
Zinc 0.01 0.01
Copper 0.02 0.01
Source: Oladele and Anina (2007)
2.1 IMPORTANCE OF TIGERNUTS
2.1.1 AGRICULTURAL IMPORTANCE
Tiger nut as a grass-like plant serves as a good forages for support of
livestock pastures and range grazing lands and also for hay and silage crops.
(Robert, 2001). Oladele and co-workers, (2009) reported that raw tigernut
contains 4.27% crude protein, 13.5% crude fibre, 2.32% ash and 47.9%
carbohydrate, thus making the tiger nut cake an excellent source of basal
feeds for livestock specifically monogastric animals. Tiger nut is equally used
as a fishing bait. For instance, the boiled nuts are used in Uk as a bait for carp
and have high reputation for success. It has also been reported by Bamgbose
(2003) that tiger nut meal (TaN) could serve as a replacement for maize in
the diets of cockerel starters especially at 33.33% level.
2.1.2 SUBSIDIARY USES TIGERNUT
Apart from the used of tiger nut meal in animal feed as pig feed in parts
of the Southern USA, it has other application or uses in industries. Tiger nut
is used in the following ways:
i. As a confectionary: tiger nuts are sometimes used in certain types of
confectionary, often as a substitute for almonds.
ii. As a coffee and cocoa adulterant: the ground tubers are sometimes
used as a substitute or adulterant of coffee and cocoa.
iii. As a source starch: tiger nut tubers are potentially a rich source of
starch which may be extracted after the oil has been removed from
the tubers. This serves as a major raw material for textile industries.
iv. Flour: the tubers can be ground to produce nutritious flour, which
can be mixed with wheat flour in baking. It has the following
composition: protein 3.4%, fat 27%, starch 38%, ash 2.4 (Bailey,
2006).
v. Alcohol: tiger nut tuber can be used for the production of alcohol by
fermentation in silily, a cultivars with a very high sucrose content is
grown and used commercially for this purpose.
vi. Leaves: it has been suggested that the leaves of the tiger nut could
be utilized for paper making, simple digestion with soda Lye will
give a yield of 35-40% of a deep-yellow coloured pulp.
2.1.3 MEDICINAL VALUE AND HEALTH BENEFITS OF TIGER
NUT
Tiger nuts have long been recognized for their health benefits as they
are high in fibre, proteins and natural sugars. They have a high content of
soluble glucose and oleic acid. Along with a high energy content (starch, fat,
sugar and proteins), they are rich in minerals such as phosphorus and
potassium and in vitamins E and C.
It is believed that they help to prevent heart attacks, thrombosis and
caners especially of the colon. They are thought to be beneficial to diabetics
and those seeking to reduce cholesterol or lose weight. The high fibre content
combined with a delicious taste, make them ideal for healthy eating. Tiger
nut milk can be used in conjunction with other foods, to fight cardiovascular
diseases (Djomdi and Ndjouenken, 2006). The tiger nut has 20-30% oil
which helps in the nourishment of the epidermis, nullifies hard-knots in the
stomach and acts as a coolant to hot flushes associated with premature
menopause. The high fibre content of the tiger nut also makes it a wonderful
colon evacuator and cleanser. Other medicinal benefits of the tiger nuts are:
1. It prevent constipation
2. It contains necessary essential minerals; calcium, magnesium and
iron necessary for bones, tissues repairs, muscles and the blood
stream.
3. It contains enough protein and carbohydrate
4. Tiger nut contains a good quality of vitamin B, which assists in
balancing the central nervous system and helps to encourage the
body to adapt to stress.
5. It supplies the body with enough quantity of vitamin E, very
essential for fertility in both men and women.
6. It is excellent for colitis and assists proper digestion in China, tiger
nut juice is used as a liver tonic heart stimulant, drank to heal
serious stomach pain, to promote normal menstruation, to heal
mouth and gum ulcers, use in Ayurvedic medicines, and is a
powerful aphrodistiac (sexual stimulant).
7. The black specie of the tiger nut is an excellent medicine for breast
lumps and cancer (any type of internal concretion and
inflammations). It can be used as eye compress and to bandage
wounds.
8. Tiger nuts give a heating and drying action to the digestive system
in general and this gives it the potency to alleviate flatulence.
9. Tiger nut promotes the production of urine, this is why it is a
preventive measure for cyst, prostrate hernia, rectum deformation
and prolapsed (anal feature-small painful flesh and the tip of the
anus) and to prevent endometriosis of fibrosis as well as blockage of
the tip of the fallopian tube.
Martinez, (2003) reported that tiger nut have high content of oleic with
positive effect on cholesterol level due to the high content of vitamin E. thus,
the nut was found to be ideal for children, older persons and sportsmen.
2.1.4 NUTRITIVE VALUE OF TIGERNUT
Tiger nut is one of the nutritionally underutilized tubers especially here
in Nigeria. Since such factors like non-availability of nutritional information
and presence of antinutritional factors in the nut, its use in food formulating
is yet to gain popularity (Oladele et al, 2009).
However, it has been reported that processing techniques such as
soaking, roasting and germination improve the nutritional value and reduces
the antinational factors in the nut (Oladele and co-workers, 2009).
The federal institute of Research Oshodi has reported their success in
the development of a technology for the production of ice cream from tiger
nut milk. According to the consejo regulator de Chufa Valencia (Regulating
council for Valencia’s Tiger nut), the nutritional composition/100ml of a
classical horchata de Chufas, or orxata de xufes in Valencia language,
contains energy content around 66kcal, proteins around 0.5g, carbohydrates
over 10g with starch at least 1.9g, fat at least 2g. Even though too low in
proteins and in fats and tool high in carbohydrate, to be considered equal to
milk, Horchata de Chufa (Tiger nut milk) can be useful in replacing milk in
the diet of people intolerant to lactose to a certain extent.
Tiger nuts have excellent nutritional qualities. Arubi, (2009) reported
that the nut has a percentage fat of 19.6%, thus a good source of energy. It
has also been reported that tiger nut has fat composition similar to olives. The
oil of the tuber was found to contain 18% saturated (palmitic acid and stearic
acid) and 82% unsaturated (Oleic acid and linoleic acid) fatty acids.
(http://online.wsj.com/article/sb125051804649836445.html). Oladele and
Aina (2007) also reported that tiger nut is very rich in minerals especially
sodium and potassium. These minerals (sodium and potassium) play vital
roles in normal cell function including neurotransmission, muscle contraction
and maintenance of acid – based balance of the body (Okaka, 2005).
Table 2.2 shows the nutritive values of two different varieties of tigernut.
Nutrient Variety of tiger nut
Creamy yellow Dark brown
Crude protein (%) 2.62 + 0.13 2.54 + 0.08
Fat (%) 19:71+ 0.08 19.5 + 0.06
Moisture (%) 23.26 + 0.04 23.46 + 0.02
Fibre (%) 15.46 + 0.17 17.63 + 0.05
Ash (%) 2.80 + 0.14 3.82 + 0.15
Carbohydrate (%) 36.15 + 0.06 33.05 + 0.07
Reducing sugars (mg/100g) 25.00 + 0.25 18.63 + 0.34
Sucrose (mg/100g) 21.18 + 0.16 16.22 + 0.09
Energy value (Kcal/100g) 332.47 + 47 0.13 317.86 + 0.05
Ascorbic acid (mg/100g) 1.60 + 0.12 1.54 + 0.06
Source Arubi (2009)
Footnote values are means + SD. Standard Deviation.
2.1.5 VEGETABLE OILS
Oil is classified as lipid. Lipids are hertogeneous collection of
biochemical substances which are soluble in organic polar solvent such as
ethanol, hexane and diethyl ether. Chemically, oils are mixtures of fatty acid
esters of the trihydroxy alcohol, glycerol (Morris, 1999). The fatty acid
composition of common vegetable oils and their physicochemical
characteristics are given in table 2.3 and 2.4 respectively. Oil is very
important in our daily life activities. It is used as raw material for the
manufacture of margarine, mayonnaise shortening and cosmetics. One
important role of oil in our diet is their supply of essential fatty acids and they
are good sources of energy. Examples of the essential fatty acids are linoleic,
linolenic and arachidonic. These fatty acids play key roles in the maintenance
of tissue integrity and in spermatogenesis. (Okaka et al, 2006).
Vegetable oils are derived from the seeds, and fruits of plants, which
growths in many different parts of the world. Several hundred varieties of
plants are known to have oil bearing seeds but in fact only about a dozen are
significant commercially (Table 2.3) are soybeans, palm kernel, cottonseeds,
groundnut, sunflower, coconut, linseeds, olive, sesame, rapeseed, fung and
castor. (Elaine and Moore, 1973).
2.1.6 IMPORTANCE OF VEGETABLE OILS
The chief importance of vegetable oil lies in their food value. Oil and
fat are recognized as essential nutrients in both human and animal diets.
Nutritionally, they are good sources of energy (9cal/gram), they provide
essential fatty acids which are the building blocks for the hormones needed to
regulate bodily systems, and they are carries for fat soluble vitamins A, D, E
and K. They enhance the foods we eat by providing texture and mouth feel,
imparting flavour, and contributing to the feeling of satiety after eating.
(Okogeri, 2009). In resent years, vegetable sources of oil and fat have
accounted for about three-fifths of the world’s consumption; the rest comes
from animal and marine oil.
These edible oils, are the mixed triglycerides of fatty acids, so treated
as to be wholesome foods (Morris, 1999), are consumed in various ways in
their natural liquid state, they are used in warmer climates for cooking. In the
West world they are eaten chiefly in spread able form, and the main demand
for them comes from margarine industry. Other food industries, which need
vegetable oils, use it in the manufacture of cooking fats and oils, salad
dressings and ice-cream. In addition, oils are equally important functionally
in the preparation of many food products such as bread, cakes, biscuits where
they acts as tenderizing agents and shortener, facilitating aeration, carry
flavours and colours, and provide a heating media for food preparations.
In addition to their value as a source of oil, the seeds of several of these
plants as well as their nuts have a huge protein content, in particular
groundnut and soybean. For this reason, the residue after the oil has been
extracted in many cases serve as animal feed. Outside the realm of food
manufacture, vegetable oils feature in a wide variety of industries, ranging
from soap manufacture, (by far the most important) to the production of
paints, varnishes, lubricants and plastics (Elaine and Moore, 1973).
All oils used in industry must be refined, and the degree of refining
depends on the intended use of the oil. No vegetable oil is equally suitable for
all purposes, since each oil has unique characteristics. Nevertheless, it is
possible to divide them into tree broad groups, firstly, those which are used
mainly for edible purposes examples include soybeans, groundnut, cotton
seeds, sunflowers, rapeseed, sesame and olive. Secondly, those suitable for
both edible and other industrial purposes, examples palm kernel oil, palm oil,
tiger nut and coconut oils. Thirdly, those suitable only for other industrials
purposes, examples linseed, fung and castor seed oils.
Vegetable oils can be obtained commercially from oil seeds by one of
the three basic methods, which can be modified or combined to suite specific
conditions. These are batch hydraulic pressing, expelling method and solvent
extraction (Wesis, 1983).
2.1.7 METHOD OF OIL EXTRACTION FROM TIGERNUT
Solvent extraction in the oil seed processing plant is principally the
same as extraction processes used in the chemistry laboratory. A material to
be extracted is placed into a container with solvent, agitated for a time, and
then the solvent with dissolved oil is removed by filtration or centrifugation.
The residue may be repeatedly extracted with fresh solvent to increase the
yield.
Alternatively, the material may be placed in a percolating column and
solvent poured in through it. This method results in more complete removal
of oil with a lower usage of solvent and is the basis for most commercial
solvent extraction plant today. This method has been described by Thieme
(1968) as the most efficient method of oil extraction. This is because while
mechanical pressed oil cakes still contains about 4-5% of oil, the solvent
method has about 1% or as low as 0.5% in the residue.
The theory of solid-liquid extraction involves the removal of a desired
component (the solute) from a food using a liquid (i.e suitable solvent like
Hexane, ethanol, petroleum ether, methanol etc), which is able to dissolve the
solute. This involves mixing the food (i.e after drying, crushing and flaking
of the raw material) and solvent together, either in a single stage or in
multiple stages, holding for a pre-determined time and then separating the
solvent. During the holding period there is mass transfer of solutes from the
food material to the solvent, which occurs in three stages:
1. The solute dissolves in the solvent.
2. The solution moves through the particle of food to its surface.
The solution becomes dispersed in the bulk of the solvent. During
extraction, the holding time should therefore be sufficient for the solvent to
dissolve sufficient solute and for the changes in composition to approach
equilibrium. The time require depends on the solubility of a given solute in
the solvent selected and also on the following factor such as temperature of
extraction, the surface area of solid exposed to the solvent, the viscosity of
the solvent and finally the flow rate of the solvent. (Fellows, 2009). Oil
produced by this method is of high quality because very little treatment is
required. (Thieme, 1968).
Table 2.3 Typical percentage composition of fatty acid of vegetable fats
and oils
Fatty acid Carbon Cocoa Coconut Corn Cotton Olive Palm Palm
Peanut Rapeseed Saf- Secame Soy Sun
Atoms butter seed kernel
flower bean flower
Cprylic 8 - 6 - - - - 3 -
- - - - -
Capric 10 - 6 - - - - 4 -
- - - - -
Lauric 12 - 44 - - - - 51 -
- - - - -
Mytistic 14 - 18 - - - 1 17 - -
- - - -
Palmitic 16 24 11 13 24 13 48 8 6 4
8 10 12 8
Palmitolic 16 - - - 1 1 - - - -
- - - -
Stearic 18 35 6 4 3 2 4 2 5
2 3 5 2 5
Oleic 18 39 7 29 18 75 38 13 61 19
13 40 24 21
Linoleic 18 2 2 54 53 9 9 2 22 14
75 43 54 66
Linolenic 18 - - - - - - - - 8
1 2 8 -
Arachidonic 20 - - - - - - - 2 -
- - - -
Gadoleic 20 - - - - - - - - 13
- - - -
Behenic 22 - - - - - - - 3 -
- - - -
Frulic 22 - - - - - - - - 40
- - - -
Lignoleric 24 - - - - - - - 1 -
- - - -
Iodine value - 37 9 127 109 84 51 16 101
104 146 114 134 134
Source: Norman and Hotchkiss (2007).
TABLE 2.4: CHEMICAL AND PHYSICAL CONTESTANTS OF
VEGETABLE OILS AND FAT
Oil Specific 130C Specification Iodine Acid value
Refractive Unsaponitiable Reichert Hehner
Gravity 150C value value 250C index
at matter mess value value
Almond 0.914-0.921 183-207 183-207 93-103
1.4593-1.4646a 0.75 0.5 96.0
Coconut 0.926 253-262 6-10 2.5-10 1.4477-
1.4495a 0.2 6.6-8.4 82.3-905
Cocoa butter 0.950-0.974 192-202 33-42 1.1-1.9
1.4537-1.4580a - 0.3-1 94-95
Corn 0.921-0.928 187-193 111-128 1.4-2.0
1.4733-1:477 1.5-2.8 4.3 93-95
Cotton seed0.918-0.923 194-195 89-103 - -
- - 96
Olive 0.915-0.920 185-196 79-90 0.3-1.0
1.4657-1.4667 0.4-10 0.6-15 95
Palm 0.923-0.924 196-204 49-59 10 1.4603-
1.4639a - 0.9-1.9 94-97
Peanut 0.917-0.926 186-194 85-100 0.8
1.4620-1.4653a 0.5-0.9 0.5 95-96
Poppy seed 0.924-0.926 190-195 128-141 2.5 1.4739-
1.4743 0.4 0.6 95-96
Rape 0.913-0.917 168-179 94-105 0.4-1.0
1.4649-11.4659a 1.5 1.1 95
Sesame 0.921-0.925 188-193 103-117 9.8
1.4723-1.4756 1.3-1.5 0.5-28 93-95
Soya 0.924-0.927 189-194 122-134 0.3-1.8
1.4723-1.4756 1.3-1.5 0.5-28 93-95
Sun flower 0.924-0.926 188-194 120-136 11.2 1.4659-
1.4721a 0.3 0.5 95
Tea seed 0.911-0.927 188-196 88-90 - 1.4707
- - -
White mustard 0.912-0.916 171-174 94-98 5.4
1.4649 - - 96-97
Morris (1999). At 400C
2.1.8 COMPONENTS OF CRUDE OILS
According to Thieme (1968) crude oil produced by rendering
expression or solvent extraction contains reliable amount of non-glyceride
components which add up to 5%, and include:
1. Free fatty acids resulting from partial hydrolysis of oil
2. Sterols
3. Carotenoid pigments
4. Phosphatides
5. Carbohydrate and its derivatives
6. Tocopherols
7. Protein fragment and
8. Various resinous and mucilaginous materials some of these
compound are desirable while others are undesirable and are
removed during various stages of processing.
i. Sterol-colourless, heat stable and for all practical purposes
inert. They are not noticed except when they are present in
large amount.
ii. Tocopherols-protects the oil from oxidation by stabilizing
hydroperoxy and other tree radical whose presence in oil gives
it off-flavour. (i.e Tocols acts as a natural antioxidant).
All other non-triglyceride components undesirable since they cause some
changes in the oil, which includes:-
a. Acceleration of deteriorative process (rancidity)
b. Promotion of undesirable colour of the oil (i.g dark coloured)
c. Promotion of foaming or smoking of the oil
d. Promotion of precipitation in the course of processing especially when
the oil is heated.
2.1.9 OIL REFINING
The aim of refining oil is to remove all unwanted substances that may
have harmful effects on the consumers and to improve oil quality (Ojeh,
1981). The crude fats and oils obtained from oilseeds and animal tissues can
vary from pleasant-smelling to quite offensive-smelling, only a few of the
crude fats and oils are suitable for edible purposes without undergoing
processing in some manner. Processing techniques allow us to refine fat and
oils, make them melt more slowly or rapidly, change their crystal habit,
rearrange their molecular structure, and literally take them apart and put them
back together again to suit our requirement of the moment. (Okogeri, 2009).
The process of refining is done by four major processes which include
degumming, Alkali Refining, leaching and deodorization (Ojeh, 1981).
2.1.10 PHYSICAL AND CHEMICAL PROPERTIES
A number of physical and chemical “constant” have been established
for the purposes of assessing quality and purity as well as for identification of
fats and oils. Although many of them are empirical, others are quite specific
in measurements of the fats (see table 2.4).
The most commonly used to establish identities are:
Saponification value, iodine value, refractive index and reichert-polensk-
kissecher values. Other data are determined on the oil and fat in order to
assess quality. They include free fatty acid, peroxide value and
unsaponitiable residue.
2.7.1 SPECIFIC GRAVITY
This is the ratio of the density of a substance to the density of a
reference substance. For solids and liquids, specific gravity is numerically
equal to its density since the reference substance for solids and liquid is
usually 1g/cm3, it can be used to exclude certain compounds from the list of
possibilities. It varies with the composition as well as the structure of the
compound positioning of the double bond nearer the middle of the molecules
and also presence of functional groups cause an increase in the specific
gravity. Generally, compounds containing several functional groups
especially those groups that promote association have a specific gravity more
than 1.0 (Hawley, 1981). If a compound contains no halogen and has a
specific gravity less than 1.0 it probably does not contain more than a single
functional group in addition to the hydrocarbon or other portions. And if
heavier than water, it is probably polyfunctional.
2.1.12 SMOKE POINT
When oils are heated to increasingly high temperature, they reach a
point at which they begin to smoke. This is a factor in choosing oils for deep-
frying application. Thus, oil smoke as a result of the decomposition of
volatile compounds from the oil followed by the production of a blue haze or
smoke and a characteristic burnt odour usually at a temperature above 2000C.
In general, vegetable oils have a higher smoke point than animal fats (Gaman
and Sherrington, 1977). Decomposition of the triglyceride produces small
quantities of glycerol and fatty acids. The glycerol decomposes further
producing a compound called acrolein. This decomposition is irreversible and
when using a fat or oil for deep frying, the frying temperature should be kept
below the smoke-point. Repeated heating will also produce oxidative and
hydrolytic changes in the fat and result in the accumulation of substance
giving undesirable flavours to the food fried in the fat.
In the analytical test the sample is heated while being held in a
chamber. A strong beam of light is shined horizontally above the surface of
the sample, and the analyst looks through this beam at a white background.
Detection of the first wisps of smoke is the end point and depends on the
visual acuity and experience of the person running the test. Nevertheless, it is
a useful characterizing test.
2.1.13 IODINE VALUE
Is a measure of the properties of unsaturated acid present. The degree
of unsaturation of the fatty acids in a fat or oil can be qualitatively expressed
by the iodine value (Norman and Hotchikiss, 2007). The unsaturated
glycerides of an oil or fat have the ability to absorb a definite amount of
iodine especially when aided by a carrier such as iodine chloride or iodine
bromide, and thus form saturated compounds. The quantity of iodine
absorbed is a measure of the unsturation of an oil or fat. The iodine value is
generally expressed as the number of grams of iodine absorbed by 100g of
the oil, (Morris, 1999). Since the iodine reacts at the sites of unsturation,
much as would hydrogen in hydrogenation, the higher the iodine value the
greater the degree of unsaturation in the fat (Norman and Hotchikiss, 2007).
The two methods usually employed for the estimation of the iodine
value are the Hanus method using iodine bromide as the carrier and the Wijs
method using chloride as the carrier. The preparation of iodine bromide
solution is easier than the Wijs reagent, thus Hanus method is often used.
However, there is some difference in the iodine values obtained by these two
methods, but the difference is not greater than the variation in the iodine
values of the oil or fat themselves.
2.1.14 ACID VALUE OR FREE FATTY ACIDS
This is the measure of the amount of free fatty acid present in a fat. Oil
and fats contain more fatty acids according to the conditions of manufacture,
age and storage. The glycerides are hydrolyzed to a small degree by enzymes,
air, and possibly bacteria. The increase in free fatty acids is generally
accompanied by a rancid odour, although the odour itself is not due to the
rancidy. The acid value is the number of milligram of potassium hydroxide
required to neutralize the fatty acids in 1g of the oil or fat (Morris, 1999).
According to Norman and Hotchikiss, (2007), fats also are degraded by
the process of hydrolysis, which in the presence of moisture splits
triglycerides into their basic components of glycerol and free fatty acids. The
free fatty acids, especially if they are of short-chain length, cause off odour
and rancid flavour in fat and oils. This type of deterioration, referred to as
hydrolytic rancidity does not require oxygen to occur but is favoured by the
presence of moisture, high temperatures and natural lipolytic enzymes. The
term acid value refers to a measure of free fatty acids present in a fat.
2.1.15 PEROXID VALUE
This measure is usually used as an indicator of deterioration of fats and
oils. According to Norman and Hotchikiss (2007), the degree of oxidation
that has taken place in a fat or oil can be expressed in terms of peroxide
value. When the double bonds of unsaturated fats become oxidized peroxides
are among the oxidation products formed. Under standard conditions. These
peroxide can liberate iodine from potassium iodine added to the system. The
amount of iodine liberated is then a measure of peroxide content, which
correlates with the degree of oxidation already experienced by the fat and
probable tendency of the fat to subsequent oxidative rancidity. Oxidative
rancidity results from the liberation of odourous products during breakdown
of unsaturated fatty acids. These commonly include such compounds as
aldehydes, ketones and shorter-chain fatty acids. This is the type of fat
deterioration that can often be prevented or minimized by the addition of
chemical antioxidants such as butylated hydroxyanisole (BHA) and butylated
hydroxytoluene (BHA). This peroxide value can be used therefore to estimate
oxidation levels (De Bussy, 1975, ihekoronye and Ngoddy, 1985). Hence,
peroxide value is an index of quality and stability of an oil.
2.1.16 DETERIORATION OF FATS AND OILS
Deterioration of fats and oils is produced by the auto-oxidation of the
unsaturated components. The reaction proceeds with the addition of
molecular oxygen to the double bonds of the unsaturated acids with the
production of labile peroxides which then further isomerize or decompose
spontaneously into, series of products including aldehydes, ketones, and acids
of lower molecular weight (Morris, 1999).
After processing, oxidation is the main problem affecting fats and oils,
leading to formation of peroxides which in turn decomposes to products
(aldhydes, ketones alcohols and others) which impart objectionable flavours
and odoures. Generally, the rate of oxidation depends on the degree of
unsaturation of the oil, its temperature and the presence of antioxidants.
Oxidation occurs at varying rates throughout the life of the oil: during storage
and distribution of the oil, and during food preparation and storage of the
final food product, (Okogeri, 2009).
2.1.17 AUTOXIDATION
Autoxidation is the direct reaction of atmospheric oxygen with the
unsaturated fatty acids attached to triglyerides, under mild conditions.
(Okogeri, 2009). Fats and oils absorb oxygen at a very slow rate, but
depending on atmospheric condition (temperature, humidity, light), presence
or absence of an antioxidant, and degree of unsaturation, the rate of oxygen
absorption can increase significantly, leading to rapid formation and
decomposition of hydroperoxides. Autoxidation reaction proceeds by a free
radical chain mechanism, which can be described in terms of initiation,
propagation and termination stages.
Initiation
RH R. + H.
Propagation
R. + 02 ROO .
ROO. + R1H ROOH+R1
Termination
ROO. R1OO. ROOR1 + O2
RO. + R11. ROR11
2.1.18 PHOTOXIDATION
The oxidation of unsaturated fats is accelerated by exposure to light.
Direct photoxidation is due to free radical produced by ultraviolet light
irradiation, which catalyses the decomposition of hydroperoxide (ROOH) and
other compound such as peroxides (RCOR), or other oxygen complexes of
unsaturated lipids. This type of oxidation proceeds by normal free radical
chain reactions and can be inhibited by chain-breaking antioxidants, or by
ultraviolet deactivators (e.g o-hydroxybenzophenone) that absorb irradiation
without formation of free radicals.
2.1.19 PHOTOSENSITIZED OXIDATION
Photoxidation provide an important way to produce hydroperoxides from
unsatureated fatty acids in the presence of oxygen, light energy and a
photosensitizer. Pigments in foods (e.g. chlorophyll) can serve as a
photosensitizer by absorbing visible or near-UV light to become
electronically excited. Sensitizers have two excited states: by absorption of
light, the singlet (1sens) is converted to the triplet state (3sens), which has a
longer life-time and initiates photosensitized oxidation. Pigments initiating
photosensitized oxidation in foods include chlorophyll, heme protein and
riboflavin (Okogeri, 2009).
CHAPTER THREE
MATERIALS AND METHOD
3.0 SOURCE OF RAW MATERIALS
The two varieties of tiger nut tuber (Cyperus esculentus) yellow and
Brown varieties used for this work were purchased from Mafara market
and Wuruko market in Gusou Zafara state and Markudi Benue state
respectively.
3.1 PREPARATION OF SAMPLES
Fresh yellow and brown varieties of tiger nut tuber were used. The two
varieties were pre-processed by sorting and washing, after which each
variety was divided into four samples of the same quantity, making a total
of eight samples for the two varieties (four from each variety). The samples
from the yellow variety were coded YDS, YD60, YD120, YD180, while samples
from the Brown variety were coded BDs and BD60, BD120, and BD180.
Samples YDs and BDs were sun dried; samples YD60 and BD60 were oven
dried at 600C; samples YD120 and BD120 were oven dried at 1200C; and
samples YD180 and BD180 were oven dried at 1800C which took 1month,
12hrs, 6hrs ,4hrs respectively to dry to a constant weights, after which the
samples were milled into flour using harmer mill.
Extraction of oil from nuts was carried out according to AOAC method
(1980). Precisely, 100g of milled sample was weighed into a labeled separate
plastic containers with lid. The sample was mixed with 400ml of n-hexane
and then covered and sealed with a masking tape. The mixture was allowed
to stand under environmental conditions for 48 hours with periodic shaking;
then filtered through a sieve cloth and further through a 12.5mm filter paper
to remove the fine particles from the solvent mixture. The filtrates subjected
to distillation to recover the solvent (n-hexane) . The oil obtained was
heated in a water bath set at 70oC to remove residual hexane. The
percentage oil content was calculated using the formular :
% oil content = B-A x 100 Oil Content (%) =
W 1
Where A = weight of container in grams
B = weight of container and extracted oil samples in grams
W = weight of samples in grams
3.2 ANALYSIS OF THE SAMPLES
The oil samples extracted from each variety of tiger nut tuber were
evaluated for : Free fatty acid (FFA), Peroxide value, Iodine value, specific
gravity and smoke point.
3.2.1 DETERMINATION OF FREE FATTY ACID (FFA)
The method described by Onwuka (2005) was used for the
determination. precisely 25ml of diethyl ether, 25ml of alcohol, and 1ml of
phenolphthalein solution (1%) were mixed together and carefully neutralized
with 0.1M NaOH by titration. .Precisely 1g of oil from each sample was
weighed in a conical flask and the neutralized solvent was added to the
sample and then titrated with aqueous 0.1M NaOH shaking constantly until a
pink colour which persisted for 15 second was obtained. This was repeated
for the rest of the samples and % FFA, expressed as oleic acid was
calculated as follows:
FFA (as % Oleic acid) = Titration (ml) X 0.0282
Weight of sample used
FFA (%) =
Where:
V = volume of NaOH used during titration (ml)
W = weight of sample (g)
3.2.2 DETERMINATION OF PEROXIDE VALUE
The method described by Onwuka (2005) was adopted for the
determination.Precisely 1g of oil was weighed into a dry conical flask and 1g
of powdered potassium iodide and 20ml of solvent mixture ( acetic
acid/chloroform, 2:1 (v/v)) were added to the sample). the flask was placed
in a water bath set at 100oC for 30 minutes. In continuation, the contents
mixture was transferred to a titrating flask containing 20ml of potassium
iodide solution (5%) and the flask was washed twice with 25ml water and
added into the titrating flask. The mixture was then titrated with 0.002M
Sodium thiosulphate solution using starch as indicator. The blank was also
performed at the same time.
Calculation:
Peroxide value = 2 V Meg/kg
Where V = volume of Na2S2O3 used during titration (ml)
3.2.3 DETERMINATION OF IODINE VALUE
The method described by Morris (1999) was used for the
determination.Precisely 0.5g of the oil sample was weighed into a glass
stopper bottle of about 250ml and 15ml of chloroform was added to it and
then 25ml of Wij’s iodine solution, with the aid of a safety pipette, which was
allowed to drain for a definite time. The stopper bottle was placed in a dark
place and was allowed to stand for 30 minutes. At the end of the period, 20ml
of 15 percent potassium iodide solution was stopped and shaked thoroughly.
The sides of the bottle and the stopper was washed down with 100ml of
distilled water. The mixture was titrated with standard 0.1 N sodium
thiosulphate solution of which the reagent was added with constant shaking
until the yellow colour of the iodine almost disappeared. About 2ml of 1
percent starch solution was added and the titration was continued until the
blue black coloration disappeared. Blank determination on an equal portion
of the wijs reagent was also carried out of which the pipette was also allowed
to drain for the same length of time.
Calculation:
Iodine value = (b-a) x 1.269 Iodine Value =
Weight of sample in grams
Where a = volume of the standard sodium thiosulphate used for the
sample (ml).
b = volume of the standard sodium thiosulphate used for the
blank (ml).
W= weight of sample (g).
3.2.4 DETERMINATION OF SPECIFIC GRAVITY
The specific gravities of the oil samples were determined using the
method described by Onwuka (2005). A 50ml pyconometer bottle was
thoroughly washed with detergent and water and then dried and weighed. The
bottle was filled with water and weighed after which the bottle was dried and
filled again with oil sample and then weighed again. This was repeated for
the rest of the oil samples.
Calculation:
Specific gravity = weight of Xml of oil
Weight of Xml of water
3.2.5 DETERMINATION OF SMOKE POINT
The method described by Onwuka (2005) was adopted. About 20g of
the oil was poured inside an evaporating dish with a thermometer suspended
at the centre of the dish ensuring that the bulb just dipped inside the oil
without touching the bottom of the dish. The dish was placed on a stove and
gradually, the temperature of the oil was raised. The temperature at which the
oil samples gave off a thin bluish smoke continuously was noted as the
smoke point in 0C.
CHAPTER FOUR
4.0 RESULT AND DISCUSSION
The effect of drying temperatures conditions on the physicochemical
properties of oil extracted from yellow and brown varieties of tiger nut tuber
obtained from Zafara and Benue state were studied; as well as the
relationship between drying conditions and varietal difference of these tiger
nuts.
Table1: Effect of drying on physicochemical parameters.
Sample FFA
(%)
PV
(Meq/kg)
IV
(Wijs)
oil
yield
(%)
Specific
gravity at
300c
Smoke
point
(oC)
Yds 0.034a 2.833 a 129.861 b 10.900 b 0.863 c 263.000 a
YD60 0.019 b 2.267 b 129.523 cd
9.267 e 0.857 cd 247.333 c
YD120 0.015 c 1.867 c 128.930 de
10.767 c 0.853 df 241.667 ef
YD180 0.012 c 1.807 cd 124.024 h 9.433 d 0.863 c 240.000 fg
BDs 0.013d 1.873 c 131.299 a 14.767a 0.860 cd 252.667 b
BD60 0.0010 1.473e 129.607 8.200 h 0.877 ab 244.000
d bc d
BD120 0.009e 0.793f 128.846 ef 8.833f 0.883 a 241.333 ef
BD180 0.007 e 0.633 g 125.716 g 8.333 g 0.877 ab 240.333 fg
The values are means of triplicate determinations. Means in the same
column with different superscripts are significantly different at (P<0.05).
Where : YDs = Yellow variety tiger nut tuber sun dried
YD60 = yellow variety tiger nut tuber oven dried at 600C
YD120 = yellow variety tiger nut tuber oven dried at 1200C
YD180 = yellow variety tiger nut tuber oven dried at 1800C
BDs = Brown variety tiger nut tuber sun dried
BD60 = Brown variety tiger nut tuber oven dried at 600c
BD120 = Brown variety tiger nut tuber oven dried at 1200c
BD180 = Brown variety tiger nut tuber oven dried at 1800c
4.1.1 FREE FATTY ACID
Free fatty acid is one of the products of odour and rancid flavour in fat
and oil especially when they are more of short-chain length ( Norman and
Hotchkiss, 2007 , Ogundele et al; 2006). Thus, it is a measure of hydrolytic
rancidity of an oil (Arawande, 2008, Ihekoronye & Ngoddy, 1985 ). The free
fatty acid of oil extracted from the yellow and brown variety of tiger nut
tuber subjected to sun drying and oven drying at 60, 120, and 180
respectively are shown in table 1 above. Results from this table reveal that
the free fatty acid values were in the range of 0.70 – 3.4 % with oil from the
sun dried yellow variety tiger nut tuber having the highest FFA value among
all the samples. However the FFA values decreased when the tubers from
both variety were dried at 60. and maintained a liner trend of decrease in the
FFA of the oil extracted from the two variety as the drying temperatures was
increased. The stability could be attributed to the high content of
4.1.2 PEROXIDE VALUE
According to Norman and Hotchikiss (2007) the degree of oxidation
that has taken place in a fat or oil can be expressed in terms of peroxide
value. The results in table 1 show that the peroxide values of the oil samples
ranged between 1.807 – 2.833 Meq/kg of oil. The peroxide values of all four
samples decreased with increase in drying temperature however, the oil
extracted from sun dried tiger nut tuber recorded the highest value. This can
be probably attributed to prolonged sun drying of the tiger nut tuber which
may have promoted enzymatic hydrolysis, and therefore increase in FFA .
The peroxide value of 10 meq/kg of oil has been recommended by SON
(2000), as standard for fresh vegetable oil . All the oil samples conformed to
this standard. This shows that all the oil samples would have stable shelf life
as rancid taste often begins to be noticeable when peroxide value is between
20 and 40 meq/kg (Pearson, 1976, Oderinde and Ajayi 1998). . Under the
influence of temperature, fat and oils are susceptible to oxidation primarily
leading to the formation of hydroperoxides. Due to their high reactivity, these
hydroperoxides especially at high temperature rapidly react with secondary
oxidative products e.g. aldehydes, ketones, peroxides, hydrocarbons as well
as cyclic compounds that may exhibit possible toxic or carcinogenic
properties (Kowalki, 1995). The values were equally lower than codex
standard values of (10Meq/kg and 20Meq/kg) allowed for refined and
unrefined olive oil respectively (FAO/WHO, 1993). However, the recorded
PV values are higher than the value of 0.3 meq/kg reported by Shaker and
coworkers (2009) for tiger nut oil.The different could be do the fact that PV
values of oils depends on a number of factors such as the state of
oxidation( quantity of oxygen consume), the method of oil extraction used
and the type of fatty acid present in the oil (Oluba and co-worker, 2008).
Statistically, the peroxide value of sample YDs and YD60 differed
significantly at (P<0.05) however, there was no significant difference
between sample YD120 and YD180 at (P>0.05). Also from table 1, the peroxide
value of the oil samples from brown variety tiger nut tuber ranges from 0.633
– 1.873 meq/kg of oil. The results reveal that the peroxide values of all the
samples decreased as the temperature was increased however, sample YDs
recorded the highest value which suggest hydrolytic deterioration which must
have probably taken place during the long period of sun drying of the tiger
nut tuber. According to Kowalki (1995), fat and oils under the influence of
temperature are susceptible to oxidation primarily leading to the formation of
hydroperoxide which further reacts with secondary oxidative products like
Ketones, aldehydes etc that is responsible for rancid and off flavour found in
a rancid oil. However, the result in table 1 did not agree with this report and
is probably attributed to the high content of monounsaturated fatty acid
(Oleic acid) and tocopherol (gamma tocopherol) present in tiger nut oil (Tiger
nut Traders, 2008). Reported from Tiger nut Traders (2008) equally shows
that tiger nut oil does not show any important change in its structure when
subjected to high temperature which could also be the reason why the
peroxide value decreased as the oven temperature was increased. Thus, tiger
nut oil can be used in prevention and therapy of some cardiac and intestinal
pathologies (www.tigernut.com). Statistically, all the oil samples differed
significantly at (P<0.05) at the end of the drying process.
4.1.3 IODINE VALUE
The degree of unsaturation of fatty acids in a fat or oil can be
quantitatively expressed by the iodine value (Norman and Hotchikiss, 2007).
From table 1, it shows that the iodine value of the oil samples extracted from
tiger nut tuber subjected to different temperatures ranges from 124.024 –
129.861 wijs. It was discovered from the results that the iodine values of all
the samples decreased with an increase in temperature.
The decrease in iodine values of the oil samples as the temperature was increased suggest the
loss of unsaturation in the fatty acids of the triacylglycerols (Nzikou et al; 2010). The quantity of
iodine absorbed is a measure of the degree of unsaturation of an oil or fat. Hence, the iodine
value is generally expressed as the number of grams of iodine absorbed by 100g of the oil
(Morris, 1999). Since the iodine reacts at the sites of unsaturation, much as would hydrogen in
hydrogenation, the higher the iodine value the greater the degree of unsaturation in the fat and oil
(Norman and Hotchikiss 2007). The iodine values of all the oil samples were very close to the
value (131 wijs) reported by Alasela (2006). However, the values were higher than values
reported by Shaker et al; (2009) and Ezebor et al; (2005). The high values obtained suggest the
presence of unsaturated fatty acid and this places the oil in the drying groups (Nzikou et al;
2010). Also, the values were above the range of codex standard values (80 – 106 Wijs) for
groundnut oil however, the values were within the codex standard
values (124 – 139 wijs) for crude soybean oil (FAO\WHO, 1993). Statistically, all the samples
were significantly different at (P<0.05) at the end of the drying. Table 1 also reveal that t
he iodine values of oil samples from brown variety tiger nut tuber varied from 125.716 – 131.299
wijs. The result shows that the iodine value decreased as the temperature was increased,
however, sample BDs had the highest iodine value of 131.299 wijs. This suggest that
temperature of the sun has little if any effect at all on the iodine value of Brown variety tiger nut
oil. Also, sample oven dried at 600c,1200c, and 1800c had the same trend of decrease in iodine
value as the temperature was increased which was in agreement with the report from Nzikou and
co-worker; (2010) which suggest loss of unsaturation in the fatty acids of the triacylglycerols.
However, the values were higher than the value (104.2 wijs) reported by Ezebor et al; (2005) but
were in agreement with the value (131 wijs) reported by Alasela (2006). The values equally
conformed to the codex standard value (124- 139 wijs) for crude soybean oil (FAO/WHO, 1993).
The high iodine values obtained in the oil samples suggest the presence of unsaturated fatty acid
and this places the oil in the drying groups (Nzikou et al; 2010). Statistically, all the oil samples
from the brown variety tiger nut tuber differed significantly at (P<0.05) at the end of the drying.
4.1.4 PERCENTAGE OIL YIELD
This can be seen as the quantity of extractable oil present in a given
quantity of an oil seed expressed in percentage. From table 1, the percentage
oil yield ranges from 9.267 – 10.900%. The values did not follow a particular
linear trend which could be traced to method of oil extraction (cold
extraction method) adopted. According to fellows (2009), solid-liquid
extraction involves the removal of a desired component (the solute)from a
food sample (oil seed) using a liquid (i.e. suitable solvent like Hexane,
ethanol, petroleum ether, methanol etc.) which is able to dissolve the solute.
Further studies by fellow (2009) indicates that extraction rate (% oil yield) is
dependent on the temperature of extraction, the surface area of solid exposed
to the solvent, the viscosity of the solvent and finally the flow rate of the
solvent. Report by Ezebor et al; (2005) shows that yellow variety tiger nut
tuber had a percentage oil yield of 22.3% after the solvent extraction. Which
was higher than the values in table 1. This suggests that soxhlet extraction
method is more efficient than cold extraction method since there were a
significant difference between the percentage oil yields from both methods.
Also, the values were not in agreement with the specification of codex
Alimentarius commission of 20% oil content for edible oil (Pearson 1976).
Since the percentage oil yield from the cold extraction method is low, it may
limit the utilization of the method in vegetable oil industries. Statistically, all
the samples were significantly different at (P<0.05) at the end of drying.
Table 1 also reveal that the percentage oil yield from the brown variety tiger
nut tuber ranges form 8.333-14. 767%. The decrease in percentage oil yield
from the tiger nut tuber did not follow a particular linear trend also which
could be attributed to the inefficiency of the cold extraction method adopted.
However, sample BDs recorded the highest percentage oil yield of 14.767%.
This suggests that sun drying increases the percentage oil yield than over
drying in the brown variety tiger nut tuber. The percentage oil yield from the
entire sample fell below the codex alimentarius commission specification of
20% oil content for edible vegetable oil (Pearson, 1976). The yields were also
below the value (20.4%0 reported for brown variety tiger nut tuber by Arubi
(2009). This implies that cold extraction method is not a reliable means of oil
extraction to be adopted by commercial oil processors. Fellow (2009)
reported that percentage oil yield depends on the temperature of extraction,
the surface area of the solid exposed to the solvent, the viscosity of the
solvent as well as the flow rate of the solvent statistically, the result obtained
from the percentage oil yield of the brown variety tiger nut tuber shows that
all the samples differed significantly at (P < 0.05) at the end of the drying
process.
4.1.5 SPECIFIC GRAVITY
This is the ratio of the density of a substance to the density of a
reference substance otherwise know as relative density. Table 1 shows that
the relative density of the oil samples varied from 0.863 – 0.853. The values
decreased as the temperature of the oven was increased however, when the
tuber was subjected to a temperature of 1800c, there was an increase in the
specific gravity of the oil. This suggests that there was no direct relationship
between the temperature and specific gravity of oil extracted from yellow
variety of tiger nut tuber. The values also suggests that the oil is less dense
than water. According to Codex Alimentarius Commission, specific gravity
of 0.919 – 0.925 at 200c have been recommended for soybean oil
(FAO/WHO, 1993). However, the values were lower than the above
specification but is within the range 0.86g/ml reported for water melon seed
oil by Taiwo and co-workers(2008). This shows that the oil contains lower
molecular weight of fatty acid (Mowla et al; 1990, Ching Kilang cho 2000).
According to Hawley (1981), compounds containing several functional
groups especially those groups that promote association have a specific
gravity more than 1.0. Since all the oil samples had specific gravity less than
1.0 it implies that the samples were made up of fewer functional groups
within the triglyceride structures. Statistically, there was no significant
difference at (P>0.05) among the samples at the end of drying. Table 1
equally shows that the relative density of the oil samples from the brown
variety tiger nut tuber varies from 0.860- 0.883. The result revealed that there
was no particular pattern or trend followed by the oil sample as the
temperature was increased. This suggest that temperature has little or no
direct relationship with the specific gravity of oil samples extracted from
brown variety of tiger nut tuber. However, there was an increase in specific
gravity as the temperature was increase to 600C, 1200C but later deceased
when the tiger nut tuber was dried at 1800C. t The results from table 1 were
equally below the codex alimentarius commission specification (0.919-0.925
at 200C) for soybean oil (FAO/WHO, 1993). This suggest that the brown
variety tiger nut oil contains low molecular weight of fatty acids (Mowla et
al; 1990, ching Kuang Cho 2000). This also indicates the possible use of the
oil in soap manufacture (Arubi 2009). Statistically, sample BDs and BD60
differed significantly at (P < 0.05) while sample BD120 and BD180 did not
differ significantly at (P > 0.05) at the end drying processes.
4.1.6 SMOKE POINT
When a fat or oil is heated to a certain temperature, it starts to
decompose producing a blue haze or smoke and a characteristics acrid smell.
The temperature at which this occurs is known as smoke point (Gaman &
Sherrington, 2001). The smoke points of different oil samples in table 1
ranges from 240.000 – 263.0000c. The smoke point of all the samples
decreases with increase in the oven temperature. According to Onwuka
(2005), the smoke point is used in determining the thermal stability of the oil.
A good quality palm oil will have a smoke point at least 215 – 3330c when
fresh but this can be lowered by the free fatty acid present. The values of the
smoke points of the oil samples were in agreement with this report.
Studies from Ezigbo (2009), indicates that smoke point vary with the chain
length of free fatty acid. Hence sample YDs and YD60 with smoke points
(263.0000c and 247.0000c) respectively had higher free fatty acid values
which is in agreement with the report. However, the degree of unsaturation of
oil has little, if any effect on its smoke point (Hui, 1996). Sample YDs and
YD60 were significantly different at (P<0.05) while there was no significant
difference at (P>0.05) between sample YD120 and YD180. Table 1 also shows
that the smoke point of oil of oil
Samples extracted from brown variety tiger nut tuber ranges form 240.333-
252.6670C. The result also reveal that the smoke points of the oil samples
Decreased as the temperature was increased. However, sample BDs had the
highest smoke point of 252.6670C. According to report from Ezigbo (2009),
smoke point vary with the chain length of the free fatty acid which was in
agreement with the result in table 1. The values were equally within the range
(215-3330C) reported by Onwuka (2005) for a good quality palm oil.
Statistically, sample BDs and BD60 differed significantly at (P <0.05) while
there was not significant difference between sample BD120 and BD180 at (P>
0.05).
FFA as %
oleic
PV meq/g IV Wijs’ % oil yield Specific
gravity
Smoke point
Y B Y B Y B Y B Y B Y
0.034a
0.019b
0.015c
0.012c
0.013d
0.0010
d
0.009e
0.007e
2.833a
2.267b
1.867c
1.807cd
1.873c
1.473e
0.793f
0.633g
129.861
b
129.523
cd
128.930
de
124.024
h
131.299
a
129.607
bc
128.846
ef
125.716
g
10.900
b
9.267e
10.767
c
9.433d
14.767
a
8.200h
8.833f
8.333g
0.863c
0.857cd
0.853df
0.863c
0.860cd
0.877ab
0.883a
0.877ab
263.000
a
247.333
c
241.667
ef
240.000f
g
Table 2. Relationship between drying condition and variety
The values are mean of triplicate determination. Means in the same column
with different superscript are significant difference at (P < 0.05)
Where y = yellow variety tiger nut tuber
B = Brown variety tiger nut tuber
Ds = Sun dried
D60 = Oven dried at 600C
D120 = Oven dried at 1200C
D180 = Oven dried at 1800C
4.3.1 FREE Fatty Acid
Free fatty acid is one of the products of odour and rancid flavour in fat
and oils especially when they are more of short-chain length
(Norman and Hatchikiss, 2007, Ogundele et al; 2006). Thus, it is a measure
of hydrolytic randicty of an oil (Arawande 2008, Ihekoronye & Ngoddy
1985).
Table 2 shows the relationship between drying conditions and variety on the
physicochemical properties of tiger nut oil from two varieties of tiger nut
tuber. The data obtained for free fatty acid of the two varieties indicate that
the free fatty acid varies form 0.007-0.034%. The results indicate that oil
from sun dried tiger nut tuber had highest free fatty acid content among the
samples but the FFA of the oil from sun dried yellow variety tuber (0.034%
oleic) was higher than the oil form sun dried brown variety tuber (0.013%
oleic). Generally, the rest of other oil samples maintained a linear trend of
decrease as the temperature was increased. This suggest that oils form brown
variety tiger nut tuber are more hydrolytically stable than the yellow variety
and thus will have a higher shelf life (Oyedeji et al; 2006). The difference in
the results between the oil from the two varieties could be probably traced
from the difference in their fatty acid composition, tocopherol content, soil
type as well as agronomic practices. The data obtained were below the values
(0.3 and 0.4% oleic) reported by Arubi (2009) for oil from yellow and brown
variety tiger nut tuber respectively. This is probably attributed to difference
in conditions of manufacture, age and storage (Morris 1999). Statistically, oil
samples YDs and YD60 differed significantly at (P < 0.05) while oil samples
(YD120 and YD180, BDs and BD60, BD120 and BD180) did not differ significantly
at (P > 0.05) respectively.
4.3.2 PEROXIDE VALUE
Is the measure of primary product of lipid oxidation (oxidative
rancidity) (Rossel, 1994). Seed oil or nuts are known to deteriorate when
processed inadequately with the principal decomposition reaction being
oxidation which occur by free radical mechanism, initially characterized by
the emergence of a sweetish and unpleasant odour which becomes
progressively worse until it attains a characteristic smell of rancid fat
(Grouveia et al; 2004). Data obtained in table 2 reveal that peroxide value of
oil form the yellow and brown variety tiger nut tuber varied from 0.63-2.83
meg/kg. The result also indicates that the oil from the yellow variety tiger nut
tuber had higher peroxide values (1.81-2.83 meq/kg) than the oil from brown
variety tiger nut tuber which had peroxide values (0.63-1.87Meq/kg).
Generally, all the oil samples from the two varieties recorded a linear trend of
decrease in peroxide value as the temperature was increased but was more
pronounced in the oil from sun dried tubers which had peroxide values (2.833
and1.873meq/g) respectively. This suggest that tiger nut oil is more prone to
hydrolytic rancidity than oxidative rancidity since there was a decrease in the
peroxide values of oil from other samples as the temperature was increased.
The high peroxide values recorded in the oil from the sun dried tubers
samples could be attributed to prolong period of sun drying which must have
promoted hydrolytic rancidity in the tiger nut tuber. It was also discovered
from the result in table 2 that the oil form the brown variety tiger nut tuber
were thermally and hydrolytically more stable than the oil from the yellow
variety tiger nut tuber since all the oil samples from the yellow variety tiger
nut tuber had a peroxide values higher than the oil from the brown variety
tiger nut tuber. The low peroxide value recorded in oil samples from brown
variety tiger nut tubers as the temperature was increased also indicates slow
oxidation of the oil samples according to Damain (1990). It also suggests that
the oil will have a high induction period than the yellow variety. The
variance could be probably attributed to their differences in fatty acid
composition, vitamin E content (Tocopherol), soil type as well as agronomic
practices. Nevertheless, all the oil samples from the two variety tiger nut
tubers had peroxide values below the codex standard (10meq/kg) for freshly
refined vegetable oil. This suggests the edibility and freshness of tiger nut oil
even without refining (Tiger nut Traders, 2008). The result of the statistical
analysis revealed that there was no significant difference among the oil
samples (YD120, YD180 and BDs) at (P >0.05) while oil samples (YDS, YD60,
BD120 and BD180) differed significantly at (P < 0.05)
4.3.3 IODINE VALUE
This is the measure of the degree of unsaturation in oil and it is an
identity characteristic of native oil which is an indicatives of the degree of
unsaturation in the fatty acid of triacylglycerol which can be used to quantify
the amount of double bonds present in an oil and evaluate the susceptibility
of oil to oxidation (Nzikou et al; 2010 ). Result from table 2, indicates that
the iodine values of oil form the two varieties
tiger nut tuber varies from 124.024-131.299 wijs. The result from the two
varieties were comparable however, the oil from the brown variety tiger nut
tuber recorded higher iodine values than the oil from the yellow variety tiger
nut tuber. Also, there was a linear trend of decrease in the iodine value as the
temperature was increased. This suggests the loss of degree of unsaturation in
the fatty acids of the triacylglycerols (Nzikou 2010). According to Arawande
and Ademulegun (2009) report, the increase in Iodine value is always
accompanied with decrease in peroxide value owing to more C = C
unsaturated double bond that are present in the oil that is left to be oxidized
therefore leaving more C =C unsaturated double bond in the oil for iodination
reaction during Iodine value determination. The results in table 2, is not in
agreement with this report probably because oil from tiger nut tuber is
hydrolytically and thermally stable. The difference in the results of Iodine
values of tiger nut oil from the two varieties could be attributed to varietals
differences as well as difference in agronomic practices. From statistical
analysis, sample (YDs, BDs, YD180 and BD180) different significantly at (p <
0.05) while sample (YD60, YD120, BD60, and BD120) were significantly the
same at (P > 0.05).
4.3.4 PERCENTAGE OIL YIELD
Apart from the use of hydraulic pressing machine, use of solvent
extraction method which involves the process of leaching out soluble
constituent (non-polar) present as a solid or liquid from a solid or from a
liquid by means of a solvent (Richardson 1993). According to Mcclement
(2003), solvent extraction technique is one of the most commonly used
methods of isolating lipids from food samples and of determining the total
lipids content (percentage oil yield). Table 2 shows that the percentage oil
yield of oil from two varieties of tiger nut tuber ranges from 8.333-14.767%.
The sun dried samples from both variety (YDs and BDs) had the highest % oil
yield of (10.9000 and 14.767 %) respectively while oven dried samples
recorded a low % oil yield when the tubers were dried at 600C. However,
when the tubers were dried at 1200C, there was an increase in % oil yield
which later decreased again when the tubers were dried at 1800C. This
indicates that there was no linear trend in the percentage oil yield as the
temperature was increased. However, the result from the two varieties
followed the same pattern of rising and falling as the temperature was
increased. All the data generated from the two varieties tiger nut oil fell
below the codex alimentarius commission standard of 20% oil content
(percentage oil yield) for edible vegetable oil (Pearson 1976). The results also
fell below the values reported by Ezebor and co-worker (2005), Arubi (2009).
This could be attributed to the difference in methods of oil extraction used.
The results also indicate that cold extraction method is not a reliable method
of extracting oil from tiger nut tubers. Sample BDs was closer to the value
(15% oil content) reported by Tiger nut Traders (2008) for mechanically
pressed tiger nut oil. From statistical analysis, all the oil samples from the
two varieties were significantly different at (P < 0.05).
4.3.5 SPECIFC GRAVITY
Is one of the physical analyses used in predicting the quality of oil
extracted from an oil seed or nut. It has a linear relationship with the
saponification value of oil and can be used in predicting the suitability of an
oil for soap and shampoo manufacture (Karim 2009). Data obtained in table 2
revealed that the specific gravity of oil samples extracted from the two
varieties of tiger nut tubers varied from 0.853-0.883. the result of the specific
gravity of oil from the two varieties were comparable however there was no
specific pattern of increase or decreases as the temperature was increased
among the samples. Nevertheless, when the tiger nut tuber from the brown
variety was oven dried at 600C and 1200c, there was an increase in specific
gravity of the oil while sample from the yellow variety decrease when
subjected to the same temperatures. But when the temperature was increased
to 1800C sample from the brown variety decreased while sample from the
yellow variety increase in the specific gravity of their oil. Also, all the
specific gravities of all the oil samples from the two varieties did not fall
within the codex specification (0.919-9.25) for soybean (FAO/WHO, 1993) .
the differences could be attributed to temperature difference, geographical
location, as well as differences in agronomic practices.
However, the values were similar to the values (0.86) reported by Taiwo and
co-workers (2008) for water melon seed oil. Sample (YDs, YD60, YD120,
YD180 and BDs) and sample (BD60, BD120 and BD180) were significantly the
same at (P > 0.05).
4.3.6 SMOKE POINT
This is one of the factors used in the selection of oil for deep-frying
application. Oil smoke as a result of the decomposition of volatile
compounds from the oil followed by the production of a blue haze or smoke
and a characteristic burnt odour usually at a temperature above 2000C
(Gaman and sherrington, 1977). Table 2 shows the comparison of the smoke
points of oil extracted from the two varieties of tiger nut tubers subjected to
different drying temperatures. The result revealed that the smoke point of the
oil samples from the two varieties were within the ranges 240.000-263.0000C.
The values from the two varieties were comparable.
The data from the two varieties for smoke point also showed a linear
trend of decrease in their smoke points as the temperature was increased
which is in agreement with the report by Ezigbo (2009). This implies that the
smoke point of the oil samples from the two varieties tiger nut tubers varies
with their chain length of free fatty acid. The results were equally within the
range (215-3330C) reported by Onwuka (2005) for a good quality palm oil.
This suggests that the oil samples from the two varieties were thermally
stable and could be used for deep –frying operations (Gaman and Sherrington
1977). The difference among the smoke points of the oil from the two
varieties could be attributed to their differences in fatty acid composition,
Varietal differences, geographical difference, differences in soil types as well
as agronomic differences. Oil samples from (YDs, BDs, YD60 and BD60) were
significantly different at (P < 0.05) however, there was no significant
difference among sample (YD120, BD120, YD180 and BD180 at (P > 0.05).
CONCLUSION AND RECOMMENDATION
This study showed that oven drying tiger nut tubers especially at 1800C
is the best temperature for drying tiger nut tubers for oil extraction since the
results revealed that at this temperature, oil samples from the two variety
had the lowest value of peroxide value and free fatty acid which are
important variable in considering the quality of an oil because the lower the
values ( PV and FFA) the better the quality of the oil. The varietal differences
as well as differences in geographical locations had the least significant effect
on the quality of the oil samples from the two varieties at that temperature
also. The oil samples from the brown variety tiger nut tuber are preferred
because of its low PV and FFA values.
This implies generally, that the tiger nut oil from both varieties can be
rated as one of the best oil suitable for deep-trying, long term storage, soap
making and other industrial applications since they are hydrolytically and
thermally stable.
RECOMMENDATION
Based on findings from this work, the use of oven drying instead of sun
drying should be encouraged as a preparatory step in processing of tiger nut
tubers for oil extraction.
Further studies should be carried out to determine the effect of drying
temperatures and time on the induction time, chemical kinetics, fatty acid
composition and vitamin E content of tiger nut oil from tiger nut tubers so as
to evaluate the overall stability and behaviours of the oil at different
temperatures and times.
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APPENDIX 1
Table 4: STATISTICAL ANALYSIS OF FREE FATTY ACID
Replica
t
YDs YD60 YD120 YD180 BDs BD60 BD120 BD180 Sum of
Sample
s
1 0.03
4
0.02
0
0.014 0.014 0.01
1
0.00
8
0.008 0.006 0.115
2 0.03
4
0.01
7
0.014 0.011 0.01
4
0.01
1
0.011 0.006 0.118
3 0.03
4
0.02
0
0.017 0.011 0.01
4
0.01
1
0.008 0.008 0.123
Total 0.10
2
0.05
7
0.045 0.036 0.03
9
0.03
0
0.027 0.020 0.356
Mean 0.03
4
0.01
9
0.015 0.012 0.01
3
0.01
0
0.009 0.007
SD 0.00
0
0.00
2
0.002 0.002 0.00
2
0.00
2
0.002 0.001
Correction factor (CF) = Grand total of sum of Samples
rt
where r = number of replication = 3
t = number of treatment/samples = 8
CF = 0.356 2 = 0.127
3X8 24
= 0.0052917
Sum of squares sample (SSS)
= 0.102 2 + 0.057 2 + 0.045 2 …+ 0.020 2 – CF
3
= 0.0205240 – 0.0052917
3
+-
= 0.0068413 – 0.0052917
= 0.0015496
Sum of Square Total (SST)
= 0.0342 x 3 + 0.0202 x 2 +0.0172 x 2 … + 0.0142 x 5 + 0.0062 x 2 – CF
= 0.0068800 – 0.0052917
= 0.0015883
Sum of Square Error (SSE) = SST – SSS
= 0.0015883 – 0.0015496
= 0.0000387
Total Degree of Freedom (TDF)
= Total number of samples (n) – Mean degree of freedom (1)
= n-1
= 24 – 1
= 23
Total degree of samples (TDS)
= Number of samples – Mean Degree of freedom
= 8-1
= 7
Error Degree of freedom (EDF) = TDF – TDS
= 23 – 7
= 16
Treatment Mean Square (TMS) = SSS
TDS
= 0.0000387
16
= 0.000024
Variance Ratio of the F-statistics
F-cal of sample i.e F-treatment
= TMS = 0.0002214
EMS 0.0000024
= 92.25
Variance Ratio table at 5% level distribution
F- tab for sample = Error degree of freedom under total degree of sample
= 16 under 7
= 2.59
Table 5: ANOVA TABLE
Sources
of
DF SS MS F-cal F-tab
variance
Sample 7 0.0015496 0.0002214 92.25D 2.59
Error 16 0.0000387 0.0000024
Total 23 0.0015883
Since F_cal > F-tab, there is significant difference among the sample at 5% level
of significance. Hence, mean separation.
Least significant Difference, LSD
= Error d.f X Sd
Error d.f from t-table, t05/2, 16 = 2.120
Sd = Standard Error =
Where S2 = M. S for Error = 0.0000024
r = number of replications = 3
2 = constant for equal replication
Sd = =
= 0.0012649
LSD = Error d.f X Sd
= 2.120 x 0.0012649
= 0.0027
2S 2 r
2 x 0.000024 3
0.0000016
Any 2 sample differing by 0.0027 or more is significantly different at 5%
level of probability.
Arranging the means in the order of magnitude
YDs YD60 YD120 BDs YD180
0.034 0.019 0.015 0.013 0.012
BD60 BD120 BD180
0.010 0.009 0.007
Mean Difference LSD
0.034 0.007 0.027 0.0027 D
0.034 0.009 0.025 0.0027 D
0.034 0.010 0.024 0.0027 D
0.034 0.012 0.022 0.0027 D
0.034 0.013 0.021 0.0027 D
0.034 0.015 0.019 0.0027 D
0.034 0.19 0.015 0.0027 D
0.019 0.007 0.012 0.0027 D
0.009 0.010 0.0027 D
0.010 0.009 0.0027 D
0.012 0.007 0.0027 D
0.013 0.006 0.0027 D
0.015 0.004 0.0027 D
Mean Difference LSD
0.015 0.007 0.008 0.0027 D
0.015 0.009 0.006 0.0027 D
0.015 0.010 0.005 0.0027 D
0.015 0.012 0.003 0.0027 D
0.015 0.013 0.002 0.0027 N.S
0.013 0.007 0.006 0.0027 D
0.009 0.004 0.0027 D
0.010 0.003 0.0027 D
0.012 0.001 0.0027 N.S
0.012 0.007 0.005 0.0027 D
0.009 0.003 0.0027 D
0.010 0.002 0.0027 N.S
0.010 0.007 0.003 0.0027 D
0.009 0.001 0.0027 N.S
0.009 0.007 0.002 0.0027 N.S
YDs YD60 YD120 BDs YD180
0.034a 0.019b 0.015c 0.013d 0.012c
BD60 BD120 BD180
0.010d 0.009e 0.007e
YDs = Difference BDs and YD180 = same
YD60 = Difference BD120 and BD180 = same
Statically, the free fatty Acid of the samples (YDs and YD60) differed
significantly at 5% level of significant. However, sample (YD120 and BD180)
were significantly the same.
Appendix 2
STATISTICAL ANALYSIS OF PEROXIDE VALUES
Table 6: ANOVA TABLE
Source of
variance
(SOV)
DF SS MS Fcal Ftab
Sample 7 11.056800 1.5795429 599.83D 2.59
Error 16 0.0421333 0.002633
Total 23 11.0989333
YDs YD60 BDs YD120 YD180
2.833a 2.267b 1.873e 1.867c 1.807cd
BD60 BD120 BD180
1.473e 0.793f 0.633g
YDs = diff BD60 = diff BD180 =
diff
YD60 = diff BD12 = diff BDs =
same
YD120=
same
YD180 = same
APPENDIX 3
STATISTICAL ANALYSIS OF IODINE VALUE
Table 7: ANOVA TABLE
Source of
variance
(SOV)
DF SS MS Fcal Ftab
Sample 7 120.153 17.1647143 62.07D 2.59
Error 16 4.4243060 0.2765191
Total 23 124.5773060
BDs YDs BD60 YD60 YD120
131.299a 129.861b 129.607bc 129.523cd 128.930de
BD120 BD180 YD180
128.846ef 125.716g 124.024h
BDs = diff
YDs, BD60 and YD60 = same
YD120 and BD120= same
BD180 = diffenernce
APPENDIX 4
STATISTICAL ANALYSIS OF PERCENTAGE OF OIL YIELD
TABLE 8: ANOVA TABLE
Source of
variance
(SOV)
DF SS MS Fcal Ftab
Sample 7 96.9762500 13.8537500 5541.50D 2.59
Error 16 0.0400000 0.002500
Total 23 97.0162500
BDs YDs YD120 YD180 YD60
14.767a 10.900b 10.767c 9.433d 9.267e
BD120 BD BD60
8.833f 8.333g 8.200h
BDs =diff YDs = diff YD120 =diff YD180 = diff
YD60 =diff BD120=diff BD180=diff BD60=diff
APPENDIX 5
STATISTICAL ANALYSIS OF SPECIFIC GRAVITY
Table 9: ANOVA TABLE
Sources of
variance
(SOV)
DF SS MS F-cal F-tab
Sample 7 0.0024666 0.0003524 8.46D 2.59
Error 16 0.0006667 0.0000417
Total 23 0.0031333
BD120 BD60 BD180 YDs YD180
0.883a 0.877ab 0.877ab 0.863c 0.863c
BDs YD60 YD120
0.860cd 0.857cd 0.853df
BD120, BD60 and BD180 = same
YDs, YD180 and BDs = same
YD60 and YD120 = same
APPENDIX 6
STATISTICAL ANALYSIS OF SMOKE POINT
Table 10: ANOVA TABLE
source of
variance
(SOV)
DF SS MS F-cal F-cal
Sample 7 1341.624667 191.6606667 176.92D 2.59
Error 16 17.3333330 1.0833333
Total 23 1358.958000
YDs BDs YDs BD60 YD120
263.000a 252.667b 247.333c 244.000d 241.667ef
BD120 BD180 YD180
241.333ef 240.333fg 240.000fg
YDs = diff YD60 = diff YD120 and BD120 = same
BDs = diff BD60 = diff BD60 and YD180 = same