EFFECT OF LONG STORAGE TIME OF PALM KERNEL ON THE CHARACTERISTICS OF PALM KERNEL OIL



  A PROJECT WORK SUBMITTED TO THE DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
FACULTY OF AGRICULTURE AND NATURAL RESOURCES MANAGEMENT

IN THE PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREE (B.Sc.) IN FOOD SCIENCE AND TECHNOLOGY


ABSTRACT
Studies were conducted to determine the effect of long storage time of palm kernel on the physiochemical properties of palm kernel oil. In this work, palm kernels stored at various length of time were used to produce palm kernel oil (p k o) by solvent extraction using n-hexane as solvent. The physiochemical properties of the oil determined includes: the specific gravity, the refractive index, the freezing point, the acid value, iodine value, saponification value, the moisture content and free fatty acid. The result obtained from the analysis show that for storage time up to 22 months, the specific gravity of palm kernel oil increased form 0.88 to 0.94, the freezing point increased from 17.3 to 22.330c, the refractive index did not noticeably changed with storage time, the moisture content decreased from 5.5% to 2.04 and later increased to 4.7%. On the chemical properties, the results obtained shows that the iodine value increased from 5.094g/100g to 25.078.9/100g, the peroxide value increased from 4.73 mEq/kg to 17.66 mEq/kg, the acid value increased form 49.38 mgKOH/g to 78.56 mgKOH/g, the saponification value increased from 185.14 mgKOH/g to 802.25 mgKOH/g while the free fatty acid increased from 24.83 to 39.40 mgKOH/g. however, the storage time of palm kernel heavily affected the palm kernel oil characteristics. Generally, specific gravity, increased slightly with storage time of the palm kernel the freezing point decreased with storage time and later increased. The iodine value, peroxide value, saponification value and Acid value/free fatty acid (FFA) increased with storage time of palm kernel. The findings in this work, therefore recommends that palm kernel oil (pko) should be produced from fresh palm kernel, but if palm kernel oil was produced from stored palm kernel, the oil should be refined.

CHAPTER THREE
MATERIALS AND METHODS

3.0       SOURCE OF SAMPLE
The sample (palm kernel) was obtained from palm fruits gotten from palm trees in Enugu, Enugu state. The palm kernel was obtained from the palm fruits after the production of palm oil from the fruits using the, solven (by soaking) process. The palm kernel has been stored for one year and seven months.

3.1 SAMPLE PREPARATION
200g of the sample (palm kernel) will be measured using mettler balance model (P 1210), in the chemistry laboratory of food science and technology of Ebonyi state university, Abakaliki, Ebonyi State. The weighted sample will be crushed at Eke market Ezzangbo. The sample will be reduced to smaller sizes to easy the oil extraction. After size reduction of the sample, it will be soaked in 600m1 of n- Hexane in the food science and technology chemistry laboratory for 24 hours.

3.2                   FLOW PROCESS OF THE OIL EXTRACTION
Raw material
Weigh
Crushing
Soaking (600ml hexane)
Filtering - Palm kernel cake (meal)
Oil in Hexane - (Mixture)
Pour into Soxhlet apparatus
Hexane - Heat at 700C (using heating mantle)
Crude palm kernel oil
Packaging

3.3 METHOD OF OIL EXTRACTION
Soxhlet method of oil extraction will be used to extract the oil. The oil extracted will be subjected to the following analysis:
1.         Specific gravity/density;
2.         Moisture content;
3.         Acid / F.F.A;
4.         Saponification value;
5.         Peroxide value;
6.         Iodine value;
7.         Freezing point;
8.         Refractive index;
9.         Viscosity;

3.3.1 SPECIFIC GRAVITY/DENSITY
The method described by G.I Onwuka (2005) will be used for the determination of density. The pycometer bottle (5Oml) will be
washed with detergent, water and Detroleum ether, dry.and /
re weigh. After drying the bottle,it will be felled with Hgo & weigh, then day and fill it with the oil sample and weigh.
Calculation:
The density will be calculated as follows:
Density          =          Weight  of oil
  Volume
Kirk (1965 developed a formular for calculating density of fat using other fatty indices).
3.3.2 MOISTURE CONTENT
The moisture content of the oil will be determined using the AOAC (1984) hot air oven method.
A petri-dish will be washed, dried, cooled and weighed as w1.
5g of the sample (oil) will be weighed into the dried petri-dish as w2. The dish with the oil will be transferred into the electric oven and set at a temperature of 100°C-105°C and allow for one to two hours.
The dish and the oil will be transferred into dessicator to cool as w3 (w3 will be maintained at constant weight).
 
% moisture    =          w2-w3       x   100
W2-w1             1
Where w1       =          weight of petri-dish,
w2                    =          weight of dish an4oil,
w3                    =          weight of petri-dish and dried oil.

3.3.3 ACID VALUE/FREE FATTY ACID (F.F.A)
G.I Onwuka’s procedure (2005) will be used to determine the acid value:
25m1 (diethyl ether will be mixed with 25ml alcohol and imi phenolphthalein solution (1%) and carefully neutralized with 0.lm NaOH.
Dissolve 1-lOg of the oil in the mixed neutral solvent and titrate with aqueous O.lm NaOH shaking constantly until a pink colour which persists for 15 second is obtained.
Calculation:
Acid value = titre value (ml) x 5.61
 Weight of sample used

3.3.4 SAPONIFICATION VALUE
The G.I Onwuka procedure (2005) will be employ to determine the saponification value. 2g of the oil will be weighed into a conical flask and add exactly 25m1 of the alcoholic potassium hydroxide solution. Attach a reflux condenser and heat the flask in boiling water for 1 hour, shaking frequently. Add 1ml of phenolphthalein (1%) solution and titrate both the excess alkali with 0.5m hydrochloric acid (titration = aml).
Carry out a blank at the same time (titration = bml).
Calculation:

Saponification value = (b-a) x 28.05

Wt (g) of sample

3.3.5 PEROXID VALUE
The method of G.I Onwuka (2005) will be used.
ig of oil will be weighed into a clean dry boiling tube, while still liquid, ig of powdered potassium iodine and 2ml of solvent mixture (2 vol. flacial acetic acid + 1 vol chloroform will be added.
The tube will be placed in boiling water so that the liquid boils within 30secs. And allow to boil vigorously for not more that than 30 seconds. Pour the contents quickly into a flask containing 20m1 of potassium iodine solution (5%), wash out the tube twice with 25m1 water and titrate with 0.002N sodium thiosuiphate solution using starch. Perform a blank at the same time

 3.36 IODINE VALUE
G.I Onwuka (2005) will be used to determine the iodine value.
The oil sample will be poured into a small beaker add a small rod and weigh out a suitable quantity of the sample by difference into a dry glass — stopped bottle of about 250m1 capacity. The approximate weigh in g of the oil to be taken can be calculated by diving 20 by the highest expected iodine value. lOmI of carbon tetrachloride will be added to the oil and dissolve.
Add 20m of Wiji’s solution, insert the stopper (previously moistened with potassium iodine solution) and allow to stand in the dark for 30 minutes.
15ml of potassium iodine solution (10%) and lOOmI water, mix and titrate with O.lm thiosulphate solution using starch as indicator just before the end-point (titration = aml).

Carry out a blank at the same time commencing with lOmI of carbon tetrachloride (titration = bml)

Iodine value = (b-a) x j.26g

Wt (g) of sample

3.3.7   FREEZING POINT
The oil will be poured into the bottle and placed in the refrigerator and monitor closely from time to time. The temperature of the oil will be noted immediately it start to freezing.

3.3.8   REFRACTIVE INDEX
The method of G.I Onwuka (2005) will be used to determine the refractive index.
The refractometer will be rested with a light compensator (water at
20°C).  Smear the oil sample on the lower prism of the instrument and close. Light will be passed by means of the angled minor; the rejected light appears in a form of a dark background. Using the fine adjustment move the telescope tube until the black shadow appears central in the cross wire indicator read off the refractive index.

3.3.9 VISCOSITY
The oil will be poured into the l00 mI beaker. The viscometer spindle speed will be set at 65r.p.m after 5 seconds the spindle will be immersed in the oil at temperature of 25°C. The viscometer reading will be recorded when it will be steady for 5 seconds.

3.3.10 STATISTICAL ANALYSIS
The data collected will be tested using product — moment formula for the linear correlation coefficient from Schaum’s out lines third edition (1998).
The data generated will be, analyzed using analysis of variance (ANOVA) (Steel and Torrie, 1980).

REFERENCES
- Malaysain palm oil council
- Mayochilinc corn.
- USDA national nutrient database for standard reference
- American palm oil council.
Sron, B. (2005) palm oil’s track record global oil and fats 2: 24: 25
Tang, S.T and Teoh, P.K (1995). Palm kernel oil extraction.
The Malaysian experience paper, presented to the world conference on processing of palm, palm kernel and coconut oils, Kuala Lumpur, Malaysia. Journal of the American oil chemist society 62 (2) 255.
Onwuka, G.I., (2005). Food analysis and instrumentation theory
and practice Naphtli prints A division of HG support Nig. Ltd 6 Adeniyi Jones close Surulere, Lagos, Nigeria. 102-103.
Leong W.L (1992). The refining and fractionation of palm oil.
Palm oil mill Engineers- Executives training course 14th semester 1. PORIM.
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