WO2016171541A1 - Method for the extraction of palm kernel oil (pko) and coconut oil (co) from various palm kernel sources and copra utilizing supercritical carbon dioxide (sc-co2) to obtain defatted palm kernel fibre - Google Patents

Abstract

This patent details a method for the extraction of palm kernel oil (PKO) and defatted palm kernel fibre from various sources of palm kernel. Three sources of palm kernel are outlined: raw palm kernel with testa, palm kernel without testa and palm kernel cake (PKC). This patent also details a method for the extraction of coconut oil (CO) from copra. Supercritical carbon dioxide (SC-CO₂) is used as a solvent in the extraction process to extract the PKO and CO from the palm kernel and copra matrix. Parameters governing the SC-CO₂ extraction process, namely; temperature, pressure, SC-CO₂ flow rate and palm kernel particle size, are set at levels which allow the maximum amounts of PKO and CO to be extracted from the palm kernel and copra matrix. Once the extraction process is completed, two products are obtained from palm kernel: palm kernel oil and defatted palm kernel fibre. In the case of copra, two products are also obtained namely virgin coconut oil (VCO) and defatted coconut flesh fibre. Removal of the testa from palm kernel before the oil extraction step results in the extraction of colourless oil. The patent also details the testa removal process form palm kernel.

Description

Method for the extraction of palm kernel oil (PKO) and coconut oil (CO) from various palm kernel sources and copra utilizing supercritical carbon dioxide (SC-CO?) to obtain defatted palm kernel fibre Field of the Invention

The present invention relates to a process for the extraction of palm kernel oil from palm kernel with testa, palm kernel without testa and palm kernel cake using supercritical carbon dioxide. The present invention also relates to a process for the extraction of coconut oil form copra using supercritical carbon dioxide. The present invention relates to methods and processes for obtaining palm kernel oil and palm kernel fibre from various palm kernel sources: palm kernel with testa, palm kernel without testa and palm kernel cake using supercritical carbon dioxide, particularly for obtaining refined bleached palm kernel oil and defatted palm kernel fibre. The present invention also relates to the methods and processes for obtaining defatted coconut flesh fibre using supercritical carbon dioxide.

Background

The oil palm, Elaeis guineensis, is a major industrial crop in both Malaysia and Indonesia. It originated in Guinea, Africa and was first introduced by the Dutch to Java in 1848. The oil palm was introduced to Malaya by the British in 1910 via William Sime and Henry Darby. In 1995, Malaysia produced most of the world's palm oil, totalling 51% of the total output. Malaysia in 1998 produced about 2.4 million metric tonnes of palm kernel, from which was extracted 1.1 million metric tonnes of crude palm kernel oil. However, in 2007 Indonesia surpassed Malaysia as the world's main producer, producing 50% of the global output.

As its name suggests, the oil palm is cultivated for the oil produced by the plant, which is extracted from the pulp of its fruit and also from the kernel of the fruit. The fruit pulp surrounds a nut, which consists of a kernel enclosed by an outer shell. Oil extracted from the pulp of the fruit is termed "palm oil" while oil extracted from the kernel is termed "palm kernel oil".

The fruits of the oil palm are carried on a large, compact bunch. Circa 22 kg of palm oil and 1.6 kg of palm kernel oil is typically extracted from 100 kg of oil palm fruit brunch. World production of PKO was 3236 metric tons in 2003, of which 1644 metric tons was produced in Malaysia (MPOB, 2003). Palm kernel cake (PKC) is the by-product which is produced after oil extraction from palm kernels using the screw-press technique. However this technique is not able to extract the oil completely leaving an average residual oil content of 10% with mean moisture content of 7.1% (Pasha, 2007).

The global production of this by-product is increasing annually as the oil palm industry continues to expand in many parts of Asia and Africa. More than four million metric tons of PKC was produced globally in the year 2002 (Atasie and Akinhanmi, 2009). Malaysia, as one of the world's greatest palm oil producers, generated about 2 million metric tons of PKC in 2004. PKC has been used as feed for a variety of animals such as ruminant animals due to its crude protein content of about 18.6%, dry matter 90.8%, total of dietary fiber, 37% crude fiber and ash 4.5% (Ramachandran et al., 2007; Akpan et al., 2005). The main problem for utilizing PKC for human consumption is the residual oil that is left in its matrix after mechanical screw-pressing extraction, which gives it its bad taste after a time period of storage and makes it lose its potential as a food additive for human consumption (N.N. Ab Rahman et al., 2012).

High fibre foods are increasingly gaining attention in the food industries due to their potential health benefits in decreasing the risks of many diseases such as cancer and diabetes, as well their effects in lowering cholesterol levels, weight loss management, the prevention of constipation and many more. The recommended total daily fibre intake for adults is circa 30 to 40 g. But most people get only about 10 g of fibre a day. Finding a new cheap source of fibre that can be utilized as a source for high fibre food additive in products such as breads, pastries, pasta, cakes and many other food products has become a target for food companies to enhance their products and attract customers. According to a study conducted by N.N. Ab Rahman et al. (2011), raw PKC has a total dietary fibre content of about 60.71% and crude fibre content of 15.17%. Raw palm kernel with the testa still intact has a total dietary fibre content of 61.58% and a crude fibre content of 8.99%. Raw palm kernel which has had the testa removed contains 57.78% of total dietary fibre and 7.29% of crude fibre. The higher crude fibre found in PKC is due to the presence of residual shells up to 10% in composition of the meal, which in turn contributes to the total fibre content to increase to a range from 16 to 18%. PKC has greater than 60% of fibre which is comprised of cell wall components which are mainly mannans, cellulose and xylans. These components are what make it suitable for ruminants and less apt for non- ruminants (Jaafar and Jarvis, 1992). Since raw palm kernel (both with and without testa) and PKC contain high dietary fibre and crude fibre levels, and the main problem in the application of these sources of palm kernel as food additives for human consumption is the oil content within the kernels, the removal of palm kernel oil (PKO) from the various sources of palm kernel would facilitate its subsequent application for human consumption.

There are three conventional methods being used in Malaysia for extracting PKO from palm kernel:

a. ) mechanical extraction using high pressure screw press;

b. ) direct solvent extraction; and

c.) pre-pressing followed by solvent extraction (MPOB, 2003).

However, these methods require much time, are costly and require organic solvents like hexane, which are often toxic, to obtain refined, bleached and deodorized palm kernel oil. Furthermore, if solvents such as hexane are used to extract PKO from palm kernel, the solvent will remain within the matrix of the palm kernel, which means the solvent must be completely removed before the palm kernel can even be considered for human consumption. Therefore, if both the PKO and palm kernel are to be applied for human consumption, a method of extraction is required which:

a. ) utilizes a non-toxic solvent to extract the PKO from the palm kernel matrix, and b. ) is easily removed from the palm kernel matrix after extraction of the PKO.

An alternative processing method is supercritical carbon dioxide (SC-C0₂) fluid extraction. Carbon dioxide (C0₂) is employed as a supercritical fluid because it has a low critical temperature (31.1°C) and pressure (7.28 MPa), which makes it an ideal solvent for extracting thermally sensitive materials. SC-C0₂ is also non-toxic, non-flammable, easily available and relatively low in cost, which in turn makes SC-C0₂ a suitable solvent for food products (McHugh and Krukonis, 1994; Saldana et al., 1999). As mentioned previously, conventional solvent-extracted products must be desolventized before they are suitable for consumption, whereas products obtained by SC-C0₂ extraction are completely free of solvent residues. This particular quality of SC-C0₂ makes it an ideal solvent for extracting PKO from the various sources of palm kernel, be it raw palm kernel or PKC, since both the PKO and palm kernel matrix will be free of any solvent residue after the extraction process has been completed.

Several studies have been conducted on the separation of PKO from palm kernel matrix, as well as the extraction and fractionation of PKO from ground palm kernel, using SC-C0₂ (Hassan et al., 2000; Norulaini et al., 2004a, Norulaini et al., 2004b; Omar et al., 1998; Rahman et al., 2001 ; Zaidul, 2003; Zaidul et al., 2006). PKO has good solubility in SC- C0₂ at high pressures (>30 MPa) and temperatures (>350 K). Thus, extraction of PKO requires relatively high pressures and temperatures for separation from palm kernel matrix as palm kernel is hard and compact, and has an intricate honeycombed cellular structure, as shown in Figure 1 and Figure 2 (Bharath et al., 1992; Bharath et al., 1993; Hassan et al., 2000; Norulaini et al., 2004a; Norulaini et al., 2004b; Rahman et al., 2001 ; Zaidul, 2003; Zaidul et al., 2006).

According to studies that have been conducted on the extraction of PKO from palm kernel utilizing SC-C0₂, an increase in the extraction temperature and pressure will result in an increase in the yield of PKO (Hassan et al., 2000, Norulaini et al., 2004b, Zaidul et al., 2006, Zaidul et al., 2007). Hassan et al. (2000) carried out the SC-C0₂ extraction of PKO from palm kernel at temperatures of 40°C to 80°C and pressures ranging from 20.7 MPa to 48.3 MPa and found that the highest solubility of PKO was obtained at 80°C and 48.3 MPa, which was 20 g PKO/100 g C0₂. Norulaini et al. (2004b), meanwhile, utilized pressures ranging from 27.6 to 48.3 MPa but limited the temperature to two levels of 40°C and 80°C to extract PKO. Zaidul et al. (2006) and Zaidul et al. (2007) also carried out SC- C0₂ extraction at pressures of 20.7 MPa to 48.3 MPa and extraction temperatures of 40°C and 80°C. Norulaini et al. (2004b) found that the yield of PKO obtained at an extraction temperature of 80°C and extraction pressures of 27.6, 34.5, 41.4 and 48.3 MPa for 30 minutes extraction time was 28.2, 33.7, 41.0 and 44.75%, respectively. Zaidul et al. (2006) found that the highest PKO extraction yield of 99.6%, as compared to the amount obtained by Soxhlet extraction, was obtained at the extraction temperature and pressure of 80°C and 48.3 MPa, which was the highest temperature and pressure levels in the study. The same maximum temperature and pressure levels of 80°C and 48.3 MPa utilized in another study by Zaidul et al. (2007) gave a maximum PKO yield of 49 g PKO/100g palm kernel, which was close to the PKO yield obtained by Soxhlet extraction.

The composition of PKO extracted utilizing SC-C0₂ in the study carried out by Hassan et al. (2000) and Norulaini et al. (2004b) is presented in Table 1, alongside the composition of commercial PKO and virgin coconut oil (VCO). VCO is rich in lauric acid (C12) and myristic acid (C|₄), which constitutes about 45 to 56% and 16 to 21%, of the total fatty acids found in the oil, respectively. There are significant health benefits associated with the consumption of VCO which stem from its fatty acid content. Lauric acid has been cited as having many health benefits, amongst them being antiviral, antibacterial, antiplaque, anticaries and antiprotozoal qualities (German and Dillard, 2004). Studies have also shown that consumption of solid fat rich in lauric acids resulted in a more favourable serum lipid profile in human subjects compare to consumption of solid fat containing trans-fatty acids (De Roos et al., 2001)

Table 1: Composition of palm kernel oils taken from different studies and compared with composition of virgin coconut oil.

Data taken from APCC Standards for Virgin Coconut Oil, Hassan et al. (2000), and Nik Norulaini et al. (2004b).

As can be seen from the results given in Table 1, the composition of PKO extracted utilizing SC-C0₂ is comparable to commercial PKO extracted via conventional means. The composition SC-C0₂ extracted PKO is also closely similar to VCO. Due to the almost identical fatty acid profile, the consumption of SC-CO2 extracted PKO potentially confers the same health benefits as those conferred by the consumption of VCO. Therefore, the production and marketing of SC-C0₂ extracted PKO as a high value-added product with numerous health benefits, which are equal to VCO, is a rich, untapped market with enormous potential. SC-C0₂ extracted PKO may also be marketed as an alternative to VCO. A study was carried out by N.N. Ab Rahman et al. (2012) in which SC-C0₂ was used to extract the residual oil in PKC and it was found the PKO extraction improved with the increase in pressure and temperature and with the reduction in particle size. The maximum extracted oil yield was 9.261% at 41.36 MPa and 70°C while the sample size, extraction time and SC-C0₂ flow rate was 150μπι, 60 minutes and 2.0 ml/min, respectively. According to the study, after the SC-C0₂ extraction had been carried on the PKC, the residual oil which was extracted was yellowish in colour while the PKC itself was lighter in colour and looser in structure. The study demonstrated that it is possible to utilize SC- C02 to extract residual oil from PKC and obtain two products: namely, PKO that still has commercial value and defatted PKC that can be used as food fibre additive for high fibre food products.

In another study by N.N. Ab Rahman et al. (2011), SC-C0₂ was used to extract PKO from two different samples: palm kernel with testa and palm kernel without testa. The highest yields of PKO that was extracted for palm kernel with testa and palm kernel without testa were 54.9% and 33.9%, respectively. These PKO yields were achieved at a temperature of 80°C, pressure of 41.36 MPa, particle size of 500 μιη and SC-C0₂ flow rate of 1 ml/min. Before SC-C0₂ extraction, the palm kernel with testa samples contained total dietary fibre and crude fibre percentage of 61.58% and 8.99%, respectively. After SC-C02 extraction, the defatted palm kernel with testa samples contained total dietary fibre of 63.03% and crude fibre of 8.49%. In the same study, prior to SC-C0₂ extraction, the palm kernel without testa samples had a total dietary fibre content of 57.78% and a crude fibre content of 7.29%. After SC-C0₂ extraction, the defatted palm kernel without testa samples contained total dietary fibre and crude fibre percentage of 58.96% and 7.23%, respectively. Raw PKC sourced from palm oil mill has a total dietary fibre content of 60.71% and a crude fibre content of 15.17%. A comparison of the total dietary fibre values of defatted palm kernel with testa and defatted palm kernel without testa (both of which have been defatted with SC-C0₂) with raw PKC shows that, in addition to removing the PKO from the palm kernel matrix, the SC-C0₂ extraction process also slightly improved total dietary fibre percentage of the two samples.

Figures 3 and 4 show the SEM images of palm kernel before and after SC-C0₂ extraction, respectively. The presence of starch globules can be observed in the cellular structure of the palm kernel shown in both images. This shows that the SC-C0₂ extraction, while extracting the PKO, does not affect the starch components of the cellular structure, which still remain within the palm kernel fibre after extraction has taken place.

Similarly, in Figure 5, it can be observed that the starch components of the cellular structure still remain in the palm kernel cake fibre after the palm kernel cake has been subjected to SC-C0₂ extraction of PKO. Since the starch components still remain in the cellular structure of the palm kernel fibres after SC-C0₂ extraction of PKO has taken place, this means that the palm kernel fibres are highly suitable for incorporation as a high- fibre food additive into products which require starch as an important component, particularly flour. Flour which has been incorporated with palm kernel fibre as a high-fibre food additive will in turn yield food products high in dietary fibre, when used for making other food products such as breads, pastry and cakes.

N.N. Ab Rahman (201 1) also reported that the palm kernel with testa sample had a protein content of 15.61 before SC-C0₂ extraction and 14.40% after SC-C0₂ extraction. The palm kernel without testa samples had a protein content of 15.01% before SC-C0₂ extraction and 14.06% after SC-C0₂ extraction. When these values are compared with the protein content of raw PKC, which is 13.56%, it shows that the SC-C0₂ extraction process that the palm kernel samples undergo, does not dramatically change their nutrient composition and still keeps their protein content at levels higher than PKC, with the added advantage that the palm kernel samples (both with and without testa) have been defatted, and are therefore more suitable for human consumption.

Based on the results of studies that have been conducted, the SC-C0₂ extraction of PKO from various types of palm kernel samples will yield two types of products:

a.) palm kernel oil (PKO).

b.) defatted palm kernel fibre.

Both of these products are completely free of any solvent residue due to the nature of the SC-C0₂ extraction process, and are therefore suitable for application as or into food products for human or animal consumption. A flowchart showing the process is given in Figure 6.

Summary of the Invention

The invention involves the application of supercritical carbon dioxide (SC-CO₂) extraction upon palm kernel from different sources to obtain two different products, namely; palm kernel oil (PKO) and defatted palm kernel fibre. The invention also involves the application of SC-C0₂ extraction to obtain coconut oil (CO) from copra. Since the defatted palm kernel fibre or copra must contain as little PKO or CO as possible, the parameters governing the efficiency of the SC-C0₂ must be optimized so that the maximum amount of PKO or CO is extracted. The SC-C0₂ extraction of PKO from palm kernel, or CO from copra, is influenced by the extraction temperature, pressure, SC-C0₂ flow rate and the particle size. Therefore, these extraction variables must be set at levels which allow for the maximum amount of oil to be extracted. Brief Description of Drawings

Figure 1 shows Scanning electron microscopy (SEM) image of cellular structure of palm kernel at 50X magnification.

Figure 2 shows Scanning electron microscopy (SEM) image of cellular structure of palm kernel at 100X magnification.

Figure 3 shows SEM image of palm kernel cells before SC-C0₂ extraction (3000X magnification).

Figure 4 shows SEM image of palm kernel cells after SC-C0₂ extraction (500X magnification).

Figure 5 shows SEM image of palm kernel cake cells after SC-C0₂ extraction (1000X magnification).

Figure 6 shows Flowchart detailing process of SC-C0₂ extraction of palm kernel oil from different sources of palm kernel and subsequent products obtained.

Figure 7 and Figure 8 show the palm kernels before and after the testa removal process, respectively.

Figure 9 shows a schematic diagram showing the apparatus used in SC-C0₂ extraction of PKO from palm kernel.

Figure 10 and Figure 1 1 shows copra and fresh coconut flesh, respectively. Detailed Description

The first part of the invention involves the preparation of the raw materials, for the SC- C0₂ extraction process. As mentioned in the 'Background' section, in addition to copra, the invention covers two possible sources of palm kernel:

a.) raw palm kernel. b.) palm kernel cake (PKC) from palm kernel mill.

For raw palm kernel, the first necessary consideration is the testa of the palm kernel. Testa of the raw palm kernel may be removed using a testa removal method so that the palm kernels that are obtained are free of the testa covering. The palm kernel testa removal method will be described in the following section.

The testa removal process

The first step of the process involves immersion of the palm kernels within a solution of sodium carbonate (Na₂C0₃). The concentration of the Na₂C0₃ solution should be 30% (w/v). A 30% (w/v) solution of Na₂C0₃ means that the concentration of the solution is equivalent to 30 g of Na₂C0₃ per every 100 mL of water. For example, if 10 litres 30% (w/v) of Na₂C0₃ solution were needed to be prepared, then 3 kg of Na₂C0 powder would have to be dissolved in 10 litres of distilled water to obtain such a solution.

The solution should be heated at a constant temperature of 90°C. The volume of sodium carbonate solution should be enough to ensure that the surfaces of the palm kernels are constantly in contact with the solution during the heating process. The heating period should be from 60 to 80 minutes long. During the heating process, it is recommended that the solution is occasionally stirred so that the kernels may be distributed evenly within the solution to ensure greater surface exposure to the solution.

After the palm kernels have undergone the first step of immersion and heating in sodium carbonate at a given temperature and time period, the palm kernels are taken out of the sodium carbonate solution and the excess solution still adhering to the kernels is allowed to drain from the kernels for duration of about 1 minute. The colour of the sodium carbonate solution after the first step of the process has been executed will be dark purple.

The second step of the process involves immersion of the palm kernels within a solution of hydrogen peroxide (H₂0₂). The concentration of the hydrogen peroxide solution should be between 30% (w/v). Since H₂0₂ is usually available on the market in 30% (w/v) concentration, no dilution process need be carried out.

The temperature of the solution should be constant at 85°C while the heating period should be between 30 to 60 minutes long. Similar to the first step of the process, the volume of the hydrogen peroxide solution should be enough to ensure that the surfaces of the palm kernels are constantly in contact with the solution during the heating process and the solution should be stirred occasionally during the process to ensure even distribution of the kernels for greater surface exposure to the solution. After the palm kernels have undergone the second step of immersion and heating in hydrogen peroxide at a given temperature and time period, the palm kernels are taken out of the solution and the excess solution still adhering to the kernels is allowed to drain from the kernels for duration of about 1 minute. It will be observed that the testa will be a lighter shade of brown compared to its colour before treatment. The kernels are then immersed again in the 30% Na₂C0₃ solution for 5 minutes to neutralize any H₂0₂ still adhering to the palm kernels. After that the palm kernels may be washed under running water to remove any Na₂C0₃ solution still adhering to the palm kernels.

After the palm kernels have been washed of chemicals, the testa, which is now much softer, may be easily removed by mechanical means. However, it is extremely important to note that the removal of the testa must be done as soon as possible after the treatment process has been carried. This is because storage of the treated kernels will result in phenolic constituents from the testa leaching onto the kernels and dying the surface of the palm kernels, resulting in colouring of the palm kernels.

The SC-CO? extraction process

The second consideration of the process, for both raw palm kernel and palm kernel with the testa removed, is the size reduction of the palm kernels. This step is essential in the SC- C0₂ process to obtain the maximum amount of PKO from the palm kernel matrix and so ensure that the subsequent palm kernel fibre which is obtained is as free of residual oil as possible. To accomplish a reduction in the size of the palm kernels, physical mechanical grinding using various types of grinding mills is well suited for this purpose. However, for PKC, no size reduction of the raw material is necessary since this step has already been accomplished during the PKO extraction stage using mechanical screw-press. However, the PKC may be sieved through sieves of differing diameters to separate and standardize the particle size of the PKC and also to separate foreign bodies from the PKC. Additional size reduction of the PKC may be carried out if smaller particle sizes are needed.

After the grinding process of the palm kernels, the next step is the actual SC-C0₂ extraction. SC-C0₂ extraction is carried out on the grounded palm kernels or PKC to extract as much of the PKO as possible. This is achieved by setting the parameters which govern the SC-C0₂ extraction process at levels which allow for maximum extraction of the PKO by the solvent. The parameters which influence the efficiency of the SC-C0₂ extraction of PKO from palm kernel are: a. ) Temperature.

b. ) Pressure.

c. ) SC-C0₂ flow rate.

d. ) Palm kernel particle size.

A schematic diagram showing the apparatus used in SC-C0₂ extraction of PKO from palm kernel is shown in Figure 7.

Figure 9 shows a schematic diagram showing the apparatus used in SC-C0₂ extraction of PKO from palm kernel (Zaidul et al., 2006). Temperature exerts an influence on the SC- C0₂ extraction process via two factors: the vapour pressure of the solute (PKO) and the density of the solvent (SC-C0₂). An increase in extraction temperature will generally improve the SC-C0₂ extraction of PKO by increasing the vapour pressure of PKO which in turn facilitate its dissolution into the SC-C0₂ fluid. However, an increase in temperature will also have a detrimental on the extraction process by increasing the density of the SC- C0₂ fluid, which in turn decreases the solvating power of the fluid. However, this negative effect of an increase in temperature upon the density of the SC-C0₂ fluid may be counteracted by increasing the extraction pressure.

An increase in the extraction pressure generally exerts a positive influence on the extraction process by increasing the SC-C0₂ solvent density. When the density of the SC- C0₂ fluid is increased, the dissolution of the PKO into the SC-C02 fluid is enhanced due to the greater interaction between the solute and solvent. According to Reverchon and De Marco (2006), the solvent power of SC-C0₂ is often expressed in terms of its density given operating conditions. Therefore, the SC-C0₂ extraction of PKO from palm kernel and PKC may be increased via high extraction temperature and pressure. For example, Zaidul et al. (2006) found that the highest PKO extraction yield of 99.6%, as compared to the amount obtained by Soxhlet extraction, was obtained at the extraction temperature and pressure of 80°C and 48.3 MPa (7000 psi), which was the highest temperature and pressure levels in the study. Similarly, Norulaini et al. (2004b) utilized pressures ranging from 27.6 MPa (4000 psi) to 48.3 MPa (7000 psi) but limited the temperature to two levels of 40°C and 80°C to extract PKO. The highest yield of PKO found in the study, 44.75%, was also achieved at the highest temperature and pressure in the study which was 80°C and 48.3 MPa, respectively. Zaidul et al. (2006) carried out extraction for 40 min while Norulaini et al. (2004b) carried out extraction for 30 min, which could explain the disparity in the PKO yield. N.N. Ab Rahman et al. (2011) conducted SC-C0₂ extraction on ground palm kernel, both with testa and without testa, and also found that the highest PKO yields for both types of sample was obtained at the highest temperature and pressure levels utilized in the study , which was 80°C and 41.4 MPa (6000 psi), respectively. In this study, the highest PKO yield was 54.9% for palm kernel with testa and 33.9% for palm kernel without testa. As for PKC, according to N.N. Ab Rahman et al. (2012), the maximum yield of PKO extracted from PKC using SC-C0₂ was also at the highest temperature and pressure levels used in the study. The highest yield of PKO in the study was 8.61% at 70°C and 41.4 MPa (6000 psi).

Based on the results of the studies which have been carried out, it can be surmised that to get good recoveries of PKO from palm kernel with testa, palm kernel without testa and PKC, higher temperatures and pressures must be utilized in the SC-C0₂ extraction process. An extraction temperature of 80°C is preferable. However, good recoveries of PKO may be obtained for temperature ranges of 70°C to 90°C. Higher temperature ranges beyond 90°C are not recommended due to potential scorching of the palm kernel matrix by high temperatures, which will adversely affect its application as a high-fibre food additive. Extraction pressures in the range of 34.5 MPa to 48.3 MPa (5000 psi to 7000 psi) are recommended for good recoveries of PKO from the palm kernel samples. Higher pressures than 48.3 MPa (7000 psi) may cause compaction of the palm kernel matrix and thus hinder the SC-C0₂ extraction of PKO from the palm kernel matrix.

SC-C0₂ flow rate is another important parameter governing the extraction of PKO from palm kernel. N.N. Ab Rahman et al. (2012) tested the effects of SC-C0₂ flow rates of the 1.00, 2.00 and 3.00 ml/min on the extraction of PKO from PKC and found that the best yield of 9.26% of PKO was obtained at 2.00 ml/min for 120 min. Increasing the SC-C0₂ flow rate will generally lead to higher PKO recoveries since more solvent is available for solubilising of the PKO. When the flow rate increased, the mass transfer resistance decreases and SC-C0₂ fluid will be saturated with PKO, and this will lead to equilibrium conditions and maximum extraction will be obtained. However, any additional flow rate increment will lead to the loss of the equilibrium condition, and the exiting solvent will be unsaturated even with the high mass transfer rate. Furthermore, when the SC-C0₂ flow rate is increased, it flows through the sample at high velocities and instead of diffusing through the palm kernel matrix, it flows around the matrix through channels, thus limiting the contact necessary for extraction of PKO, a phenomenon known as "channelling". Therefore, the SC-C0₂ should be neither too low nor too high. Generally, an SC-C0₂ flow rate between 1 ml/min to 3 ml/min should be sufficient for an extraction time of 60 min. Palm kernel particle size is also an important parameter that must be set at certain levels to ensure maximum recoveries of PKO during SC-C0₂ extraction. Hassan et al. (2000) and Norulaini et al. (2004b) used ground palm kernel of less 2 mm in diameter particle size in their study. Zaidul et al. (2006) used ground palm kernels of 0.5 to 1.5 mm. N.N. Ab Rahman et al. (2011) ground both palm kernel with testa and palm kernel without testa and passed them through an aperture sieve to get particle sizes of 0.5 mm. A reduction in the particle size of the palm kernel will result in higher PKO recoveries due to higher surface to volume ratio of smaller particles, which results in more solute being available for contact and interaction with SC-C0₂. Reducing the sample particle size of plant materials also ruptures the cell walls, which may otherwise hinder the diffusion process of the solute of interest into SC-C0₂ (Goodrum et al., 1996). According to Reverchon and De Marco (2006), in smaller particles, the length of diffusion of a solvent is shorter, which results in lower internal mass transfer resistance. However, extremely small particle size can have a negative impact due to very compact packing of extremely small size particles in the extraction chamber. When this occurs, channeling effects will occur as part of the SC-C0₂ will travel through channels formed inside the sample, instead of penetrating through the sample matrix. The channelling phenomenon in SC-C0₂ extraction will result in inefficient extraction due to reduced contact between the solvent and the sample (Reverchon and De Marco, 2006). In general, palm kernel particle sizes of 0.5 mm to 1.0 mm should be sufficient for good recoveries of PKO from the palm kernel matrix.

N.N. Ab Rahman (2011) also reported that the palm kernel with testa sample had a protein content of 15.61% before SC-C0₂ extraction and 14.40% after SC-C0₂ extraction. The palm kernel without testa samples had a protein content of 15.01% before SC-C0₂ extraction and 14.06% after SC-C0₂ extraction. When these values are compared with the protein content of raw PKC, which is 13.56%, it shows that the SC-C0₂ extraction process that the palm kernel samples undergo, does not dramatically change their nutrient composition and still keeps their protein content at levels higher than PKC, with the added advantage that the palm kernel samples (both with and without testa) have been defatted, and are therefore more suitable for human consumption.

Furthermore, according to Moftah ben Nama (2013), the total dietary fibre content for raw palm kernel (PKt), palm kernel without testa (PKw) and palm kernel cake (PKC) is 61.58%, 57.78% and 60.71%, respectively. According to Moftah ben Nama (2013), the application of SC-C02 extraction to extract the residual oil from these sources of palm kernel improved the dietary fibre content of the palm kernel. When raw palm kernel was submitted to SC-C02 extraction (SC-PKt), the dietary fibre content increased from 61.58% to 63.03 %, while when palm kernel without testa was submitted to SC-C02 extraction (SC-PKw), the dietary fibre content increased from 57.78% to 58.69%. It is abundantly clear, therefore, that palm kernel is a good source of dietary fibre and the application of SC-C02 extraction to extract PKO improves the dietary fibre content of palm kernel fibre, as can be seen in Figure 10.

Furthermore, in a study carried out by Nik Norulaini et al. (2009), SC-C0₂ extraction was executed upon dried coconut (Cocos nucifera L.) flesh (copra) to extract VCO.

The SC-C0₂ extractions were carried out at pressures and temperatures ranging from 20.7 MPa to 34.5 MPa and 40°C to 80°C, respectively. The results of the study confirmed that for 99% of the oil content in copra can be extracted by utilizing SC-C0₂ extraction method. SC-C0₂ extraction is therefore an effective method for the acquisition of VCO from copra and is also appropriate for the production of defatted coconut flesh fibre, since it removes close to 100% of the oil content of copra.

Claims

Claims

1. A method for the extraction of coconut oil from copra, or for the extraction of palm kernel oil from palm kernels or palm kernel cakes, comprising:

a.) removing the oils completely from the matrix of the copra, or the matrix of the palm kernel, or the matrix of the palm kernel cake.

b. ) the reduction in size of the copra or palm kernels using physical means such as grinding, milling, pulverising etc.

c. ) extracting the coconut oil from copra, or palm kernel oil from the palm kernel matrix us

d. ) the extraction temperature of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel matrix, or coconut oil from copra, using supercritical carbon dioxide as a solvent.

e.) the extraction pressure of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel matrix, or coconut oil from copra, using supercritical carbon dioxide as a solvent.

f. ) the flow rate of the of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel matrix, or coconut oil from copra, using supercritical carbon dioxide as a solvent.

g. ) the reduction of the size of the palm kernels or copra using physical means such as grinding, milling, sieving, etc., for the purpose of obtaining palm kernel oil from the palm kernel matrix, or coconut oil from copra, using supercritical carbon dioxide as a solvent.

2. A method for the extraction of palm kernel oil from palm kernels or palm kernel cakes for the purpose of obtaining defatted palm kernel fibre which involves:

a.) the reduction in size of the palm kernels using physical means such as grinding, milling, pulverising etc.

b.) the use of supercritical carbon dioxide as a solvent to extract the palm kernel oil from the palm kernel matrix to obtain defatted palm kernel fibre. c. ) the extraction temperature of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

d. ) the extraction pressure of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

e. ) the flow rate of the of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

f. ) the reduction of the size of the palm kernels using physical means such as grinding, milling, sieving, etc., for the purpose of extracting palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

g. ) The subsequent application of the defatted palm kernel fibre as a food product in itself, or as a food additive, or as flour or for subsequent incorporation into flour products.

3. A method for the extraction of coconut oil from copra for the purpose of obtaining defatted coconut flesh fibre which involves:

a. ) the reduction in size of the copra using physical means such as grinding, milling, pulverising etc.

b. ) the use of supercritical carbon dioxide as a solvent to extract the coconut oil from the copra matrix to obtain defatted cocnut flesh fibre.

c. ) the extraction temperature of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting coconut oil from the copra matrix using supercritical carbon dioxide as a solvent, to obtain defatted coconut flesh fibre.

d. ) the extraction pressure of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting coconut oil from the copra matrix using supercritical carbon dioxide as a solvent, to obtain defatted coconut flesh fibre.

e. ) the flow rate of the of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting coconut oil from the copra matrix using supercritical carbon dioxide as a solvent, to obtain defatted coconut flesh fibre.

f. ) the reduction of the size of the palm kernels using physical means such as grinding, milling, sieving, etc., for the purpose of extracting coconut oil from the copra matrix using supercritical carbon dioxide as a solvent, to obtain defatted coconut flesh fibre.

g. ) The subsequent application of the coconut flesh fibre as a food product in itself, or as a food additive, or as flour or for subsequent incorporation into flour products.

4. A method for the extraction of palm kernel oil from palm kernels which involves:

a.) the reduction in size of the palm kernels using physical means such as grinding, milling, pulverising etc., which is carried out after the removal of the palm kernel testa from the palm kernels via physical and chemical means,

b.) the use of supercritical carbon dioxide as a solvent to extract the palm kernel oil from the palm kernel matrix.

c.) the extraction temperature of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent.

d. ) the extraction pressure of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent. e. ) the flow rate of the of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent.

f.) the reduction of the size of the palm kernels using physical means such as grinding, milling, sieving, etc., which is carried out after the removal of the palm kernel testa from the palm kernels via physical and chemical means, for the purpose of obtaining palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent.

5. A method for the extraction of colourless palm kernel oil from palm kernels which involves:

a. ) the removal of the palm kernel testa from the palm kernels via physical and chemical means before the extraction of the colourless palm kernel oil.

b. ) the reduction in size of the palm kernels using physical means such as grinding, milling, pulverising etc., which is carried out after the removal of the palm kernel testa from the palm kernels via physical and chemical means.

c. ) the use of supercritical carbon dioxide as a solvent to extract the palm kernel oil from the palm kernel matrix.

d. ) the extraction temperature of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent.

e. ) the extraction pressure of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent. f. ) the flow rate of the of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent.

g. ) the reduction of the size of the palm kernels using physical means such as grinding, milling, sieving, etc., which is carried out after the removal of the palm kernel testa from the palm kernels via physical and chemical means, for the purpose of obtaining palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent.

6. A method for the extraction of palm kernel oil from palm kernel for the purpose of obtaining defatted palm kernel fibre which involves:

a.) the removal of the palm kernel testa from the palm kernels via physical and chemical means before the extraction of the palm kernel oil. b. ) the reduction in size of the palm kernels using physical means such as grinding, milling, pulverising etc., which is carried out after the removal of the palm kernel testa via physical and chemical means.

c. ) the use of supercritical carbon dioxide as a solvent to extract the palm kernel oil from the palm kernel matrix to obtain defatted palm kernel fibre.

d. ) the extraction temperature of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

e.) the extraction pressure of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

f. ) the flow rate of the of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

g. ) the reduction in size of the palm kernels using physical means such as grinding, milling, pulverising sieving, etc., which is carried out after the removal of the palm kernel testa from the palm kernels via physical and chemical means, for the purpose of extracting palm kernel oil from the palm kernel matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

h. ) The subsequent application of the defatted palm kernel fibre as a food product in itself, or as a food additive, or as flour or for subsequent incorporation into flour products.

7. A method for the extraction of palm kernel oil from palm kernel cake which involves: a. ) the palm kernel cake being a result of palm kernels undergoing a physical process to extract the palm kernel oil from the palm kernel matrix, which in turn leads to reduction of the size of the palm kernels.

b. ) the use of supercritical carbon dioxide as a solvent to extract the palm kernel oil from the palm kernel cake matrix. c. ) the process of outlined in 5a.) occurring before the use of supercritical carbon dioxide as a solvent to extract the palm kernel oil from the palm kernel matrix. d. ) the extraction temperature of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel cake matrix using supercritical carbon dioxide as a solvent.

e. ) the extraction pressure of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel cake matrix using supercritical carbon dioxide as a solvent.

f. ) the flow rate of the of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of obtaining palm kernel oil from the palm kernel cake matrix using supercritical carbon dioxide as a solvent. g. ) the reduction of the size of the palm kernel cake particles using physical means such as grinding, milling, pulverising, sieving, etc., for the purpose of obtaining palm kernel oil from the palm kernel cake matrix using supercritical carbon dioxide as a solvent.

8. A method for the extraction of palm kernel oil from palm kernel cake for the purpose of obtaining defatted palm kernel fibre which involves:

a. ) the palm kernel cake being a result of palm kernels undergoing a physical process to extract the palm kernel oil from the palm kernel matrix, which in turn leads to reduction of the size of the palm kernels.

b. ) the use of supercritical carbon dioxide as a solvent to extract the palm kernel oil from the palm kernel cake matrix to obtain defatted palm kernel fibre.

c. ) the process outlined in 6a.) occurring before the use of supercritical carbon dioxide as a solvent to extract the palm kernel oil from the palm kernel matrix to obtain defatted palm kernel fibre.

d. ) the extraction temperature of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting palm kernel oil from the palm kernel cake matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre. e. ) the extraction pressure of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting palm kernel oil from the palm kernel cake matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

f. ) the flow rate of the of the supercritical carbon dioxide extraction process being a variable parameter which is controlled for the purpose of extracting palm kernel oil from the palm kernel cake matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

g. ) the reduction of the size of the palm kernel cake particles using physical means such as grinding, milling, pulverising, sieving, etc., for the purpose of extracting palm kernel oil from the palm kernel cake matrix using supercritical carbon dioxide as a solvent, to obtain defatted palm kernel fibre.

h. ) The subsequent application of the defatted palm kernel fibre as a food product in itself, or as a food additive, or as flour or for subsequent incorporation into flour products.