INTRODUCTION

Coconut is high in fat (consists of over 80% saturated fat), with a fine oil which has been used extensively for edible and non-edible purposes all over the world such as cooking, cosmetics and other products. Most commercially available coconut oils are made from copra, which is basically the dried kernel or meat of the coconut fruit. If standard copra is utilized as a raw material for the process, the unrefined coconut oil extracted from it is not yet suitable for consumption and therefore must be purified or refined first. According to coconutdiet.com, The standard end product made from copra is RBD coconut oil. RBD stands for refined, bleached, and deodorized. High heat is used to deodorize the oil, and the oil is typically filtered through (bleaching) clays to remove impurities. Sodium hydroxide is generally used to remove free fatty acids and prolong shelf life. This is the most common way to mass-produce coconut oil. The older way of producing refined coconut oil was through physical/mechanical refining. More modern methods also use chemical solvents to extract all the oil from the copra for higher yields.

Nonetheless, coconut oil extraction can be done through traditional methods. With help from modern machinery, pressure, heat and motion are forces that are often used to separate the coconut oil from the white coconut meat (such as in this experiment). Depending on the type of extraction method used, the coconut oil extracted may be completely pure, or it may require additional refining processes. The most common mechanical method of extracting coconut oil is the expeller technique, in which the dried copra passes through a special screw press that compresses the coconut copra, squeezing about 75 percent of the oil from the coconut meat. For this experiment, the same extraction principle was used. For smaller amounts, a hand method using cheese cloth will also work. A website called livestrong.com reported Traditional aqueous coconut processing involves grating coconut into small pieces, adding water, squeezing the mixture by hand, leaving the resulting emulsion to stand, and then scooping off the oil-rich cream. The cream is then boiled to produce oil. The intermediate-moisture content aims to speed up the process by introducing a bridge-press to extract oil directly from partially-dried coconut gratings.

Mechanically extracted oil needs to be tested first before mass production or consumption. There are basically two tests which are used for coconut oil: the free fatty acids (FFA) test and the peroxide value (POV) test. Both methods come with a titration process that will then let the students get the values needed for the computations.

OBJECTIVES

This experiment aims to simulate the processes involved in the extraction of crude coconut oil. Students must conduct chemical tests typically done for oils and must be able to relate free fatty acid and peroxide levels of oils to oil quality and shelf life.

METHODOLOGY

There were 4 stages that had been performed in this experiment. The first stage was the extraction of the milk from the grated coconut mixed with water using a cheesecloth. The pH of the extract collected was then measured. The next step was the extraction of crude oil from the milk by heating it until all the water had evaporated and only the crude oil was left with the lump of solid matter. These two had been filtered afterwards to separate the crude oil completely. The weight of the solid matter and crude oil were then recorded separately as well as the pH of the crude oil. Thirdly, the determination of the free fatty-acids in the crude oil. In order to do this, a particular amount of crude oil was mixed with a free alcohol (ethanol) and drops of phenolphthalein were added. A blank had been prepared before performing the titration in order to have a comparison whether the solution was already neutralize. Sodium hydroxide was used to neutralize the solution. After recording the volume used. The FFA could now be calculated. The last stage was the determination of Peroxide Value. For this stage, another blank was prepared. A certain amount of the crude oil was added with acetic acid-chloroform solution and saturated Potassium Iodide. Distilled water had also been added to the solution. Titration with Sodium thiosulfate was then performed to the solution until the yellow color disappeared. Starch indicator was added to give blue color to the solution. However, there had been no color change. Hence, the peroxide value couldnt be determined. The third and fourth stages were repeated for the unknown oil.

RESULTS AND DISCUSSIONSFig 2-1: Crude coconut oil is a yellow liquid at room temperature

Crude Coconut Oil (CNO) is known as "basic industrial grade oil". Basically, CNO is an end-product of squeezing out the oil from Copra (dried coconut meat) by the use of expeller press and in industry, it is then refined to eliminate impurities/contaminants. It is unrefined, unfiltered and without any additives. The crude coconut oil that the group extracted is sweet smelling and has pleasant aroma.It is clear yellow liquid at room temperature and cloudy yellow solid when stored in refrigerator. It tasted strongly like coconuts.

Table 2-1 Extraction of coconut oil

Weight of coconut milk collected, grams979

ph of coconut milk6.9

Boiling temperature, C96

Total time of evaporation of water component, mins (basis: 500 g)25 mins

Weight if cooled coconut cake, grams71.767

Weight of crude coconut oil extract, grams86.103

pH of crude coconut oil6.1

% recovery8.79%

Table 2-2 Determination of free fatty acids

Total volume of NaOH used, mL2.0

% FFA as Oleic Acid0.80%

Table 2-3 Analysis of the Unknown

a. % Free Fatty Acid

Mass of the unknown, grams56.398

Total volume of NaOH used, mL1.7

% FFA as Oleic Acid0.085

b. POV

Mass of the unknown for POV, grams55.002

Fig 2-2: Analysis of FFA involves titration with NaOH with phenolphthalein a indication. The solution at the left shows the coconut oil sample, the one a the right is the blank solution.

The composition of crude coconut oil includes triacylglycerols, free fatty acids, partial glycerides, phospoholipids, sterols, tocopherols, pigments, volatiles, trace metals, and oxidised products. Triacylglycerolsof crude coconut oil constitue the major component (95%). Coconut oil must be very stable to oxidative deterioration when exposed to atmospheric oxygen. It differs from other vegetable oils that it contains a high degree (90%) saturated fatty acids. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28Fatty acids are usually derived fromtriglyceridesorphospholipids. When they are not attached to other molecules, they are known as "free" fatty acids. In this experiment, two tests were carried out to determine the level of unsaturated fatty acid in the crude coconut oil sample free fatty acid (FFA) and peroxode value tests. After titration with NaOH, it was revealed that the crude coconut sample contained high amount of free fatty acids at 0.80 as compared to the accepted value for edible oils of 0.1 maximum thus, this can not be considereed stable and will not last a longer shelf life. The unknown oil analyzed showed a considerably low amount of FFA at 0.085 and is most likely to last longer. Fig 2-3: Addition of starch solution and more Na2S2O3 did not turn the solution blue.

The shelf life declared by the coconut oil companies ranges from 18 months-2 years for refined coconut oil, and 2 years-4 years-beyond for virgin coconut oil. The test for peroxide value could have supported the FFA result but then during the addition of starch indicator in which the coconut oil with initial amount of Na2S2O3, the solution did not turn blue. Because of this, the accurate amount of Na2S2O3 which should have determined the peroxide value, was not obtained. Results could have been different if the starch solution was cooked. The peroxide index is the most common parameter used to characterize oils and fats. The number of peroxides present in vegetable oils reflects its oxidative level and thus its tendency to become rancid. Theoretically, coconut oil should exhibit a low rate of oxidation due to its low content of unsaturated fatty acids. Unsaturated fatty acids easily react with oxygen to form peroxides. Oils with high peroxide values are unstable and easily become rancid. The peroxide values obtained were relatively low, indicating that the samples were highly stable against oxidation.

Various methods have been developed to extract coconut oil, either through dry or wet processing. Dry processing is the most widely used form of extraction. Clean, ground and steamed copra is pressed by wedge press, screw press or hydraulic press to obtain coconut oil, which then goes through the refining, bleaching, and deodorizing (RBD) processes. Adding heat while pressing can give higher yield. Pressed coconut meat can also be drenched in coconut water and pressed again to extract more milk. Another method for extraction of a "high-quality" coconut oil involves the enzymatic action of alpha-amylase, polygalacturonases, and proteases on diluted coconut paste. Wet extraction, chilling, freezing and thawing techniques, and fermentation technique can also be considered. Wet processing or aqueous processing is the term used for the extraction of coconut oil directly from coconut milk. This method eliminates the use of solvent which reportedly may lower the investment cost and energy requirements. Heating and centrifugation, freezing and thawing, chilling and thawing the coconut cream obtained after centrifugation break the protein stabilized oil-in-water emulsion. Coconut milk emulsion can also be separated by adjusting pH of the coconut milk emulsion between pH 3 and 5.6 and inoculated with bacteria cultures used acetic acid treatments to destabilize coconut cream in coconut oil extraction. Treatment of 25% of acetic acid at level of 0.1, 0.2, 0.3 and 0.4% on coconut cream from 10 to 14 h of reaction time at room temperature had improved the quality of the oil extracted, with oil recovery up to 60%.

Most commercial grade coconut oils are made from copra. Copra is basically the dried kernel (meat) of the coconut. It can be made by: smoke drying, sun drying, or kiln drying , or derivatives or a combination of these three. If standard copra is used as a starting material, the unrefined coconut oil extracted from copra is not suitable for consumption and must be purified, that is refined. This is because the way most copra is dried is not sanitary. The standard end product made from copra is RBD coconut oil. RBD stands for refined, bleached, and deodorized. High heat is used to deodorize the oil, and the oil is typically filtered through (bleaching) clays to remove impurities. Sodium hydroxide is generally used to remove free fatty acids and prolong shelf life. This is the most common way to mass-produce coconut oil. The older way of producing refined coconut oil was through physical/mechanical refining. More modern methods also use chemical solvents to extract all the oil from the copra for higher yields.RBD oil is also sometimes hydrogenated or partially hydrogenated. This happens mostly in tropical climates, since the natural melting point of coconut oil is about 76 degrees F, and already naturally a solid in most colder climates. Since coconut oil is mostly saturated, there is little unsaturated oil left to hydrogenate. Hydrogenated oils contain trans fatty acids.

Virgin coconut oil (VCO) is obtained from fresh and mature kernel (12 months old from pollination) of the coconut (Cocos nucifera L.) by mechanical or natural means with or without the application of heat, which does not lead to alteration of the nature of the oil. VCO has not undergone chemical refining, bleaching or deodorizing. It can be consumed in its natural state without the need for further processing. Virgin coconut oil consists mainly of medium chain tryglycerides, which are resistant to peroxidation. The fatty acids in virgin coconut oil are distinct from animal fats which contain mainly of long chain saturated fatty acids. Virgin coconut oil is colorless, free of sediment with natural fresh coconut scent. It is free from rancid odor or taste.

SUMMARY AND CONCLUSIONS

Unlike animal fat, which is stored in fat cells, oilseeds do not have such a feature. Instead, the oil is stored in microscopic globules throughout the plant cells. Rendering will not be able to liberate the oil from the globules, and more mechanical processes such as grinding, flaking, rolling or pressing will be needed in order to break the cell walls in order to liberate the oil. The prepared meat from the oilseeds are then reduced into smaller sizes by grinding, then they are cooked and pressed in screw presses. At the base of the press is a drain, where the released oil is separated from the press cake (the pressed solid). The latter is discharged into conveyors for further processing. Further processing includes RBD -refining, bleaching, and deodorizing. High heat is used to deodorize the oil, and the oil is typically filtered through (bleaching) clays to remove impurities. Free fatty acid (FFA) and peroxide level signifies the amount of unsaturated fatty acid content of the coconut. These fatty acids easily react with oxygen to form peroxides which makes the oil rancid. Thus, oils with higher FFA and peroxide value (POV) are less stable and shorter shelf life.

REFERENCES

Ali, M. F., El Ali, B. M., & Speight, J. (2004). Handbook of Industrial Chemistry. Michigan: McGraw-Hill.Chow, C. K. (2008). Fatty Acids in Foods and their Health Implications,Third Edition. Boca Raton, FL: Taylor & Francis Group.Dayrit, F. M., Dimzon, , I., & Valde, M. (2011, August 11). Quality characteristics of virgin coconut oil: Comparisons with refined coconut oil. Retrieved July 2015, from http://pac.iupac.org/publications/pac/pdf/2011/pdf/8309x1789.pdfMoigradean, D., Poiana, M. A., & Gogoasa, I. (2012, October 2). Quality characteristics and oxidative stability of coconut oil. Journal of Agroalimentary Processes and Technologies, 18(4). Retrieved July 2015, from http://fos.ubd.edu.bn/sites/default/files/2000-Paper2.pdfRahman, H. (n.d.). The Chemistry of Coconut Oil. Retrieved July 2015, from http://fos.ubd.edu.bn/sites/default/files/2000-Paper2.pdfSmith, J. G. (2013). Organic Chemistry. New York, NY: McGraw-Hill.

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