CHAPTER THREE
MATERIALS AND METHODS
3.1 Source of Samples
The soybean seed was obtained from Kpiri-Kpriri market
Abakaliki,
Ebonyi State, Nigeria.
Ebonyi State, Nigeria.
Sample
preparation
Soybean oil was extracted from the soybean seed as
follows. The seed was cracked, adjusted for moisture content heated to 600- 88°C (140-
I 900F), grinded and solvent extracted using hexane.
The tallow was obtained from Fulani herds men, at
Amike-Aba Community in Abakaliki, Local Government Area of Ebonyi State,
Nigeria
and was extracted from cow tissue.
and was extracted from cow tissue.
They following analysis was carried out for
comparative evaluation
of the two (2) products, soybean oil and tallow.
of the two (2) products, soybean oil and tallow.
SOYBEAN SEEDS
Cleaning
Soaking (use of hexane) for 48 hours
Distillation
Soybean oil
Flow chart of soybean oil production
Tallow
Size reduction
Soaking (use of hexane) for 48 hours
Distillation
Tallow oil
Flow chart of tallow oil production
3.2 PEROXIDE VALUE
Peroxide value was determined
by the method describe by (Onwuka, 2005). About 1g of oil sample was
weighed into a clean dry boiling tube and 1g of powdered potassium iodine and
20ml of solvent mixture (20vol glacial+ 1vol chloroform) was added. The
tube was placed in water bath set at
100°C and allowed to boil vigorously for 30 minutes.
100°C and allowed to boil vigorously for 30 minutes.
In continuation, the mixture was transferred to
titrating flask containing 2Oml of potassium iodine solution (5%) and
the flask was washed twice with 25m1 of water and added into the titrating
flask. The mixture was titrated with 0.002M sodium thiosulphate solution using
starch as indicator. The blank will also be performed at the same time.
Calculation
Peroxide
value (meq/kg) 2v
Where
v = volume of Na2So3 use during titration
(ml).
3.3 IODINE VALUE
-
The method describe by Morris (1999) was used for the determination. Precisely 0.5g of oil sample was weigh into a glass stopper bottle of 250ml, exactly 15m1 of chloroform and 25ml of wiji’s iodine solution was added with the aid of pipette. The mixture was placed in the dark for 30minutes.At the end of the period 2Oml of 15% potassium iodide solution was added and shaken thoroughly. The side of the bottle was washed down with 100ml of distilled water. The mixture was titrated with standard O.1N sodium thiosulphate solution of which the was added with constant shaking until the yellow colour of iodine almost disappears. Then 2m1 of 1% starch solution was added and the titration was continued until the blue black coloration disappears. Blank determination on an equal portion of the Wiji’s reagent was also carried out which pipette will be also allowed to drain for the same length of time.
The method describe by Morris (1999) was used for the determination. Precisely 0.5g of oil sample was weigh into a glass stopper bottle of 250ml, exactly 15m1 of chloroform and 25ml of wiji’s iodine solution was added with the aid of pipette. The mixture was placed in the dark for 30minutes.At the end of the period 2Oml of 15% potassium iodide solution was added and shaken thoroughly. The side of the bottle was washed down with 100ml of distilled water. The mixture was titrated with standard O.1N sodium thiosulphate solution of which the was added with constant shaking until the yellow colour of iodine almost disappears. Then 2m1 of 1% starch solution was added and the titration was continued until the blue black coloration disappears. Blank determination on an equal portion of the Wiji’s reagent was also carried out which pipette will be also allowed to drain for the same length of time.
Calculation
Iodine value + (b-a) x 1.269
Iodine value + (b-a) x 1.269
W
Where
a volume of the standard thiosulphate solution used for the sample
(ml)
B = volume of the standard sodium thiosulphate used for the blank(ml)
(ml)
B = volume of the standard sodium thiosulphate used for the blank(ml)
W = weight
of sample (g)
3.4
SMOKE POINT
The method described by Onwuka (2005) was adopted.
About 20g of oil was poured into 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 sample was given off a thin bluish smoke continuously was noted as the
smoke point in oC.
3.5 FREE FATTY ACID (FFA)
The method described by Onwuka (2005) was used for the
determination, exactly 25m1 of diethylether, 25ml of alcohol and 1ml of
phenolpthalein solution (1%) was mixed together and carefully neutralized with
0.lrn NaOh by titration. In continuation 1g of the oil was weigh in a conical
flask and neutralized solvent was added to the sample and then titrated with
0.lm NaoH solution shaking constantly until a pink colour persisted for 15
seconds was obtained, % FFA (Expressed a palmitic acid) will be calculated as
follows:
FFA
(%) = V x 0.0282
w
Where,
V = volume of NaoH used during titration (ml)
W = Weight
of sample (g).
3.6 SPECIFIC
GRAVITY
The method described by Ishiwu et al Iwuno 2006 was
used for the
determination. Empty pyknometer bottle was weighed and recorded its weight (w1), and the dry pyknometer bottle was fill with oil sample. When the temperature has reached the ambient temperature at which the measurement was made, the volume of the oil was made, the volume of the oil was adjust to a fixed mark or density bottle was use, care was taken to insert the stopper in such a way that the capillary portion was completely filed with the oil. Which was weigh and record the weight (w2).
determination. Empty pyknometer bottle was weighed and recorded its weight (w1), and the dry pyknometer bottle was fill with oil sample. When the temperature has reached the ambient temperature at which the measurement was made, the volume of the oil was made, the volume of the oil was adjust to a fixed mark or density bottle was use, care was taken to insert the stopper in such a way that the capillary portion was completely filed with the oil. Which was weigh and record the weight (w2).
Calculation
Density - w2 - w1
VI
Where
V1 = volume of oil in pyknometer or density bottle in ml at
temperature t°c.
3.7
SAPONIFICATION VALUE
The
method described by lshiwu et al Iwouno (2006) was adopted.
‘I
About 2g of oil was weigh into a conical flask to within 0.001g and add
exactly 25ml of 0.5N ethanolic KOH solution. The flask was attach to the condenser. Boil gently, mixing from time to time. And heating stopped after 6Ominutes. 4-5 drops of phenolphthalein solution was added. And titrate the hot soap solution with O.5N hydrochloric acid solution.
‘I
About 2g of oil was weigh into a conical flask to within 0.001g and add
exactly 25ml of 0.5N ethanolic KOH solution. The flask was attach to the condenser. Boil gently, mixing from time to time. And heating stopped after 6Ominutes. 4-5 drops of phenolphthalein solution was added. And titrate the hot soap solution with O.5N hydrochloric acid solution.
Calculation:
Saponification
value 56.1 x N x (‘B-S)
w
where.
B = ml of hydrochloric acid solution used in blank test
B = ml of hydrochloric acid solution used in blank test
S = ml
of hydrochloric acid solution used for the sample
N = exact normally of the hydrochloric acid solution
N = exact normally of the hydrochloric acid solution
W = weight
in g of sample
3.8
MOISTURE CONTENT ‘I—
The method described by Karl Fischer was used for the
determination. Water was extracted from the oil sample into methanol and
titrate with Karl Fischer reagent (Pyridine. iodine in anhydrous methanol) and
the end point of the titration was detected visually or electrometrically.
CHAPTER FOUR
RESULT AND DISCUSSION
The
composition of oil extracted from fatty tissue and soybean seed are presented
in table four below.
TABLE
4-: Chemical composition of extracted oil from fatty tissue (from cow) and
soybean seed.
|
Sample
|
FFA(%)
|
PV
(Meq/kg)
|
Iv(wijs)
|
SV(mg/koH/g)
|
SG
|
SP(0C)
|
Moisture
content
|
|
Tallow
|
5.08a
|
27.33b
|
70.24b
|
185.28b
|
0.879b
|
2800C
|
2.00a
|
|
Soybean
oil
|
2.54b
|
52.00a
|
84.35a
|
291.17a
|
0.966a
|
2400C
|
2.03a
|
The
value are means of tiplicate analyses
4.1 FREE FATTY ACID - The free fatty acids are the acids in oil which not
esterified with glycerol to form glycerides, it is a relative measure of
Rancidity of oil. From table 4a the mean values obtained showed that the free
fatty acid recorded for tallow and soybean oil were 5.08% and 2.54%
respectively. This result shows that tallow recorded the highest free fatty
acid (5.08%) while the soybean oil had the lowest free fatty acid (2.54%).
Since hydrolysis that may occur in the presence of moisture, this reaction is
catalysed by some enzymes, acid bases and heat as reported Ihuria and Maliki
(2007), the high value of tallows may be as a result of hydrolysis that
occurred in the oil while less value of
free fatty acid in soybean oil could be due to reduced hydrolytic
activities. Free fatty acid is important in determining the suitability of oil
as edible oil, when the free fatty acid of oil is lower, more appeal the oil is
for consumer as reported by Coenen (1976). The result showed that there are
significant differences at (P< 0.05).
4.2
IODINE VALUE-: The Iodine value is a measure of fat stability and resistance to
oxidation, iodine is a measure of proportion of unsaturated fatty acid present
in given oil/ fat. Higher iodine value is attributed to high degree of unstauration
in the oil/ fat as reported by potter and Hotchkiss (1995) table 4. Revealed
that the iodine value of the samples tallow and soybean oil, were 70.24 and
84.35 respectively it can be observed from the same table 4 that the iodine
value was affected by the source of the
material/ oil used, as reported by Fokou et al(2009). It was observed that
soybean oil had the highest iodine value (84.35) there was significant
difference at (P< 0.05)The iodine value that was obtained from soybean oil
are less compared to the value reported by Ihekoronye et al (1985). Therefore
the lower in the value may be due to freshly of the oil; while tallow oil had
the highest iodine value than it’s stated by Ihekoronye and Ngoddy (1985) that
animal fatty are majorlly inoleic in nature and most of the tallow oil depend
on the specie of animal and its feed procedure since oxygen uptake (oxidation)
of unsaturated fatty acid in phospholipids occurs readily and isomerization
process usually lead to loss of unsaturation Ihuoria and Maliki (2007) than low
iodine value of oil could be beneficial
since it is always associated with good quality and a longer shelf life
of oil as reported by Ortega-nieblas etal (2007) and it prevent oxidative
deterioration in food the result obtained showed that these was significant different at (P< 0.05).
4.3 SAPONIFICATION VALUE-:
Saponification value of oil is inversely proportional to the mean molecular
weight of the glycerides in the oil. Saponification value is expressed as the
number of milligrams of potassium hydroxides required to saponify one gram of
fat/oil.
Saponification
value of the sample is presented in table 4. The result shows that
specification value of tallow and soybean oil were 185.58 and 291.17 mg/koH/g
respectively the soybean oil had the highest value (291.17). While tallow oil had
the lower value (185.58). The values obtained for tallow and soybean oil
indicate that the free fatty acids presents in the oil have high molecular
weight. This implies that soybean oil after hydrogenation could be substitute
for the conventional oil in soap making and shampoo industry like other oil
(Akintayo and Bayer 2002, Falade et al, 2008). This value actually measures the
amount of alkali which is required to compare with the fatty acids liberated by
the equivalent weight of the fatty acids
can be determined (Chamble and Harvey 1994). The soybean oil is made-up
of short chain saturated fatty acids,. This is supported by the fact that the
oil remained liquid at room temperature (28oC-300C) while
tallow oil remained solid at room temperature and thereby being made-up of long chain unsaturated fatty
acids. The saponificatuion value of tallow oil are almost comparable with
saponification value range of canarium schwnifurchii of African blank olive oil
which was ranged from mesocarp and endocarp and it is commonly used as cooking
oil by native people of Congo and Gabon (Abayeh et al 1999).
4.4
PEROXIDE VALUE (PV)-: Peroxide value
is usually used as indicator of detecting deterioration of fat and oil, thereby
oxidation takes place, double bonds in the unsaturated fatty acid are attacked
forming peroxide which further breakdown to produce secondary oxidation
products that may lead to off flavour and off dour in oil and fat (Ihekoronye
and Mgoddy, 1985) peroxide values of the sample tallow oil and soybean oil are
presented in table 4 above. The result show that the peroxide value of tallow
and soybean oil were 27.33 and 52.00 meg/kg. The peroxide value of soybean oil had the highest
value (52.00 Meq/Kg) while the tallow oil had the lower value (27.33 Meq/kg).
The different in the peroxide value may possibly depend on the varieties/
variation of the species of oil as the low peroxide value, indicate slow
oxidation of this oil.
According to Decmian (1990) the peroxide value is
frequently used to measure the deterioration of fat and oils. Therefore the low
peroxide value obtained for tallow oil showed period fort lasting of the
oil/shelflife of the oil before deterioration generally. Oils with peroxide
value less than 30 Meq/kg have been considered safe for human consumption
(Gotoh and Wada, 2006) while the soybean oil and tallow oil had higher values
compare to the reported by Wada and Gotoh and the do not have good oxidative
stability, the sample had their significant difference at (P< 0.05)
4.5
SPECIFIC GRAVITY-:The specific
gravity of the sample tallow and soybean oil is shown in table 4 from the table
the specific gravity of the sample were 0.879 and 0.9662 for tallow and soybean
oil respectively,. The results obtain show that the soybean oil had higher
specific gravity value of 0.9662. While the sample tallow oil had the lower
specific gravity value of 0.879. It was observed that the result of the specific
gravity of both tallow and soybean are low compare to the specific gravity
value reported by Singh and Singh (2010), but the values are within the range
reported by Onyeka et al (2005). The variation observed from the specific
gravity result could be because of the significant difference in their
saponification value) Molecular weight and degree of unsaturation) (Iodine
value ) Onyeka et al (2005) also reported that the density of an oil increases
with increase in their saponification
value iodine temperature free fatty acid and the water content the result
obtained showed that there are significant difference at (p<0.05)
4.6 SMOKE POINT – Smoke Point is one of the factors used in selection
of oil for deep frying application German and Sherrington (1977) from the
results presented in table 4, it was observed that the smoke point of fallow
and soybean oil were from 2400C and 2800C respectively.
The observation showed that the tallow oil had the highest smoke point value
280oC while the soybean oil had the lower smoke point value 2400C.
The soybean oil had the smoke point that fall within the recommended smoking
point for a good quality palm oil as reported by Onwuka (2005) while the tallow
oil were not within the recommended range. This suggested that soybean oil and
tallow that had high value compare to
other are not good mostly for deep frying processes.
The result obtained show that there
are significant difference at (p<0.05)
4.7 MOISTURE CONTENT: The moisture content of any food is an index of it
water activity (aw) as reported by Fraizier and Wertoll (1978) from
the result presented in table 4 moisture content values were 2.00 and 2.03 for
tallow and soybean oil respectively. It was observed that their had the same
ranged of result value. This implies that the value are good to prolong the
shelf life of the oil due to their low moisture content that cannot make the to
be oxidize when react.
CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
The soybean oil and tallow after
extraction using n-hexane as solvent for oil extraction. The result obtained
showed that physio-chemical properties of both oil are not the same. The result
also showed that soybean oil are from plant source and in ambient temperature
they are liquid and are better than other oil while the tallow are solid at ambient temperature and had
mostly higher chemical properties but when refined well it may serve as a good
source of material to be used in production of different food.
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