Field of the Invention The present invention relates to a method for the removal of the testa from palm kernels. More particularly, the present invention relates to a method of removing testa from palm kernel seed in order to produce colourless palm kernel oil.

Background of the Invention

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. 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. The seed of the oil palm is the nut which remains after the mesocarp has been removed from the fruit. The nut consists of an endocarp, or outer shell, and a kernel. It is the kernel that constitutes the seed proper from a botanical perspective. However, the term "seed" is commonly used to refer to the nut, which constitutes both endocarp and kernel. This is due to the fact that in agriculture, it is the nut of the palm fruit which is stored, germinated and planted. The kernel lies within the endocarp and is constituted of greyish-white endosperm surrounded by a dark- brown testa covered with a network of fibres. The endosperm is hard and contains palm kernel oil. Palm kernel contains about 47 to 50% oil on a wet basis. 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.

In Malaysia, palm kernel oil is often extracted using the screw press method which yields 40 to 43% (g oil/100 g kernel), or using hexane solvent extraction, which yields 44.5 to 46.5%. Generally the unremoved testa gives the colour of the oil extracted, which requires refining. Palm kernel oil contains about 48.3% lauric acid (C ₁₂ ), 15.6% myristic acid (C ¹⁴ ) and 15.1 % oleic acid (C _18:1 ). This composition gives palm kernel oil a solid consistency at cool ambient temperatures, however the oil still melts below 30°C.

Palm kernel oil is regarded as high-quality oil suitable for food use and is commonly used in cosmetics and cooking due to the fact it remains stable at high temperatures and can be stored longer compared to other vegetable oils. Extraction of palm kernel oil via the screw-press technique will yield a by-product named "palm kernel cake" (PKC). PKC is commonly used as feed for animals such as ruminants due to its crude protein content of roughly 18.6%, total dietary fibre content of 37% and fibre and ash content of 4.5%. It is made up of 90.8% dry matter, contains an average residual oil content of 10% and also essential elements such as magnesium, ferum and zinc. As feedstock, PKC is ranked higher than copra cake and cocoa pod husk. However, it is ranked lower compared to fish meal and groundnut cake, especially in its protein value. Palm kernel meal obtained from un- dehulled palm kernel is dark brown in colour due to the presence of testa, the presence of which has been reported by several studies to lower its acceptability by animals (Babatunde et al., 1975; Barry and Duncan, 1984; Cornelius, 1983; Sreedhara and Kurup, 1998).

The tannins and phenolic compounds within the palm kernel testa contribute to its characteristics as animal feed. For example, tannins act as a defence against insect consumption and can react and bind with proteins within the kernel (Barry et al., 1989; Yu et al., 1995). Also, quinones, which result from the oxidation of phenolic compounds within the testa, form insoluble complexes with thiol and amino groups of proteins within the kernel (Pierpoint, 1969; Siebert et al., 1996; Sosulski., 1979; Vitayathil and Gupta, 1981 ). The reactions of these tannin and phenolic compounds with proteins within the kernels thus lower the availability of the proteins for intake when consumed by agricultural livestock (Griffith, 1981 ; Oh et al., 1980; Wolffram et al., 1995).

Sreedhara et al. (1992) developed a method for the removal of testa from palm kernel which involves treating the palm kernels with hydrochloric acid (HCI) at high temperatures followed by mechanical action to remove the testa. This method was employed in a subsequent study by Sreedhara and Kurup (1998) where it was found that rats that were fed palm kernel meal with the testa removed absorbed more protein compared to rats that were fed palm kernel that included the testa. Hence, protein digestibility of palm kernel meal appeared to improve with HCI treatment to remove the testa (Sreedhara and Kurup, 1998). Moftah Ben Nama (2013) found that removing the testa from palm kernel resulted in a significant decrease in the levels of anti-nutrients. Untreated palm kernels were found to possess a tannin content of 0.42 mg/g while the treated palm kernels had tannin levels that were undetectable altogether, indicating that the removal of the testa from palm kernel resulted in a virtual elimination of tannins from the palm kernels.

However, HCI is a highly corrosive acid, which poses a hazard when handling. A process for the removal of palm kernel testa which utilizes less harmful materials is therefore desirable.

Uvarova and Barrera-Arellano (2005) produced two types of palm kernel flour: one type from palm kernels with the testa intact and a second type from palm kernel that had undergone treatment with hydrochloric acid to remove the testa. The study reported that removal of the testa resulted in a decrease of the polyphenol content of the palm kernel flour. Also, the flour produced from palm kernels which had undergone testa removal was a light cream colour. In an earlier study, Sreedhara and Kurup (1998) treated palm kernels with acid to remove the testa and found that the resulting palm kernels, as well as the flour produced from them, were pearl- white in colour. Such results would seem to suggest that very little of the compounds which contribute to pigmentation are found within the palm kernel itself, with the majority of the pigmentation being concentrated within the testa in the form of phenolic compounds. Oil extracted from palm kernel which has undergone treatment to remove the testa should, therefore, be relatively colourless. Virgin coconut oil (VCO) is rich in lauric acid (C ₁₂ ) and myristic acid (C ₁₄ ), which constitutes about 45 to 56% and 16 to 21 %, of the total fatty acids found in the oil, respectively. There are significant healths 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. Studies have also shown that consumption of solid fat rich in lauric acids result in a more favourable serum lipid profile in human subjects compare to consumption of solid fat containing frans-fatty acids (De Roos et al., 2001 ). It is interesting to note that VCO and palm kernel oil (PKO) have very similar fatty acid profiles. PKO is rich in lauric acid, C ₁₂ (48.3%) and other major fatty acids are myristic, C ₁₄ (15.6%) and oleic acids, C _18:1 (15.1 %) (Nik Norulaini et al., 2004). Due to the almost identical fatty acid profile, the consumption of PKO potentially confers the same health benefits as those conferred by the consumption of VCO. Therefore, the production and marketing of PKO as a high value-added product with numerous health benefits, which are equal to VCO, is a rich, untapped market with enormous potential. PKO may also be marketed as an alternative to VCO.

Table 1 : Comparison of fatty acid content between virgin coconut oil and palm kernel oil

Data taken from APCC Standards for Virgin Coconut Oil and Nik Norulaini et al.

(2004)

The colour of vegetable oil greatly influences its acceptability by consumers. Clear or colourless oils are often perceived of as being more pure and are more attractive to consumers. The production of clear or colourless PKO directly from palm kernels would also render the use of any bleaching earth in oil refining process unnecessary. Currently, impurities and pigments are removed from vegetable oils via the application of bleaching earth (also termed "fuller's earth"). Bleaching earth is a sedimentary clay or clay-like earthy material used to decolorize, filter, and purify animal, mineral, and vegetable oils and greases. Bleaching earth tends to consist of montmorillonite, attapulgite or a mixture of the two. Sometimes, calcite, dolomite and quartz may also be present within bleaching earth. Montmorillonite is also called "swelling clay" due to its property of being able to swell in water, with an absorption capacity of two to seven times its volume. Montmorillonite has a general formula of AI ₂ Si ₄ 0io(OH) ₂ . However, the montmorillonite which is used in the industrial vegetable oil refining has undergone acid-activation to allow the bleaching earth to swell in oil rather than water. Bleaching earth that has been utilized for the absorption of impurities and pigmentation from vegetable and animal oil is termed "used bleaching earth" (UBE) or alternatively, "fat-containing bleaching earth". Residual oil trapped within the bleaching earth is technically recoverable. The high costs of doing so, however, make the recovery uneconomical, which results in up to 10 000 metric tonnes of UBE being disposed of as waste yearly. UBE is a hazardous environmental pollutant due to the fact that oil and fats trapped within the UBE matrix are combustible (Hertrampf and Piedad-Pascual, 2000). By bypassing the refining stage and thus precluding the use of bleaching earth in the production of PKO, economic and environmental advantages will be accrued in the form of reduced production costs and waste reduction.

In view of the above shortcomings, it is advantageous to provide an improved process for removing palm kernel testa from palm kernel seed, which is effective in producing colourless palm kernel oil.

Summary of the Invention The present invention provides a method for the removal of testa from palm kernels, which comprises the steps of: i. immersing the palm kernels in a solution of sodium carbonate (Na ₂ C0 ₃ ); ii. heating the solution of step (i) at 85 to 95°C;

iii. removing the palm kernels from the heated solution of step (ii);

iv. allowing the solution of Na ₂ C0 ₃ to drain from the palm kernels for a period not exceeding 1 minute;

v. immersing the palm kernels of step (iv) in a solution of hydrogen peroxide (H ₂ 0 ₂ );

vi. heating the solution of hydrogen peroxide (H ₂ 0 ₂ ) in step (v) at 80 to 90°C; vii. removing the palm kernels from the heated solution of hydrogen peroxide (H ₂ 0 ₂ ) in step (vi);

viii. allowing the solution of hydrogen peroxide (H ₂ 0 ₂ ) to drain from the palm kernels;

ix. immersing the palm kernels in Na ₂ C0 ₃ to neutralize any remaining H ₂ 0 ₂ on the palm kernels;

x. removing the palm kernels from the solution of step (ix);

xi. washing the removed palm kernels; and

xii. removing the testa from the palm kernels.

Preferably, the solution of sodium carbonate (Na ₂ C0 ₃ ) is having a concentration of 20 to 30%.

Preferably, the heating steps (ii) and (vi) are carried out for 70 to 100 minutes, and 40 to 70 minutes, respectively.

Preferably, the hydrogen peroxide (H ₂ 0 ₂ ) solution is having a concentration of 20 to 30%. The reaction of the hydrogen peroxide with the sodium carbonate present in the layer between the testa and the kernel facilitates loosening of the testa from the palm kernel. After the palm kernel has undergone the treatment with hydrogen peroxide, the testa may be removed manually, for example using mechanical means, such as tweezers or knife, or manually using hand.

It is an advantage of the present invention to provide a method of removing testa from palm kernel, which does not involve the use of corrosive or harmful chemicals, such as hydrochloric acid. Furthermore, both sodium carbonate and hydrogen peroxide are well-known ingredients already commonly used in the food industry for various purposes, and are available in 'food-grade' quality.

Another advantage of the present invention is the use of hydrogen peroxide in the process, which provides the effect of killing a variety of microorganisms including algae, fungi and spore-forming bacteria, thus functioning as a sterilizing agent as well. It is another advantage of the present invention to provide a method that is capable of removing testa from palm kernel at a short period of time, without involving the use of expensive chemical or equipment. It is also another advantage of the present invention to provide a method of removing testa from palm kernel, which in turn, yields clear or colourless palm kernel oil that is often perceived of as being more pure and are more attractive to consumers. Brief Description of the Drawings

Figure 1 illustrates an apparatus used to carry out soxhlet extraction on the treated palm kernels and the untreated palm kernels, according to an embodiment of the present invention;

Figure 2 illustrates the results of the soxhlet extraction carried out on untreated palm kernels, according to an embodiment of the present invention; and

Figure 3 illustrates the results of the soxhlet extraction carried out on treated palm kernels, according to an embodiment of the present invention.

Detailed Description of the Invention

The present invention will now be described in further detail by way of non-limiting examples.

Example 1 Testa Removal

The first step of the process involves immersion of the palm kernels in a solution of sodium carbonate (Na ₂ C0 ₃ ). The concentration of the Na ₂ C0 ₃ solution is preferably between 20% (w/v) and 30% (w/v). A 30% (w/v) solution of Na ₂ C0 ₃ means that the concentration of the solution is equivalent to 30 g of Na ₂ C0 ₃ per every 100 mL of water. For example, if 10 litres 30% (w/v) of Na ₂ C0 ₃ solution were needed to be prepared, then 3 kg of Na ₂ C0 ₃ powder would have to be dissolved in 10 litres of distilled water to obtain such a solution.

The mixture of palm kernels and sodium carbonate (Na ₂ C0 ₃ ) is heated at a constant temperature ranging from 85 to 95°C. The volume of sodium carbonate solution should be enough to ensure that the surfaces of the palm kernels were constantly in contact with the solution during the heating process. The heating period ranges from approximately 70 to 100 minutes. During the heating process, it is preferred 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, 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 approximately 1 minute. The colour of the sodium carbonate solution after completion of the first step is dark purple.

The second step of the process involves immersion of the palm kernels in a solution of hydrogen peroxide (H ₂ 0 ₂ ). The concentration of the hydrogen peroxide solution is preferably between 20% (w/v) and 30% (w/v). A 20% (w/v) solution of H ₂ 0 ₂ means that the concentration of the solution is equivalent to 20 g of H ₂ 0 ₂ per every 100 mL of water. However, since H ₂ 0 ₂ is usually available on the market in 30% (w/v) concentration, some dilution process must be carried out to prepare solutions with concentrations lower than 30% (w/v). For example, to prepare 10 litres of 20% (w/v) H ₂ 0 ₂ , about 6.666 litres of 30% (w/v) H ₂ 0 ₂ solution is taken and then topped up to 10 litres with distilled water.

The mixture of palm kernels and hydrogen peroxide (H ₂ 0 ₂ ) are heated at a temperature ranging from 80 to 90°C for approximately, 40 to 70 minutes. 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 the given temperature and time period, the palm kernels are taken out of the solution and the excess H ₂ 0 ₂ solution still adhering to the kernels is allowed to drain away for approximately 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 once more into 30% Na ₂ C0 ₃ solution to neutralize any remaining H ₂ 0 ₂ solution still adhering to the kernels. For this step, a time period of 5 to 10 minutes is sufficient. After the immersion in Na ₂ C0 ₃ is complete, the kernels may be washed under running water or immersed in room-temperature or hot water. However, immersion in hot water for a few minutes is preferred since the testa may be softened further.

After the palm kernels have been washed to remove unwanted chemicals, the kernels may be allowed to dry by air. However, it must be noted that air-drying is an optional step, and not essential to the palm kernel testa removal process. After the palm kernels have been air-dried, the testa, which is now much softer, may be easily removed by mechanical means. For example, the testa can be removed using tweezers, knife, any sharp object or by hand. The testae may also be removed from the palm kernels while still wet, immediately after the washing step has been completed.

In an embodiment, the softened and loosened palm kernels with testa are dipped momentarily in liquid nitrogen and the testa can be separated from the kernel by rotating 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. Also, drying of the kernels in an oven must be avoided. It has been observed that drying the kernels in an oven after the treatment process results in the testa re-adhering to the surface of the kernels, rendering them unremovable. However, if testa removal is unable to be carried out after the treatment process and the kernels need to be stored, then storing the kernels while still wet in a refrigerator at temperatures of 0°C and below may be done since it has been observed that the testae will still be removable when taken out of the refrigerator. However, the surface of the palm kernels may be coloured due to leaching of phenolic compounds from the testa onto the surface of the palm kernels.

Example 2 Test Analysis

Conventional soxhiet extraction was carried out on the treated palm kernels and the untreated palm kernels to determine if there were any significant differences in the colour of the oils extracted via such a process. Before the soxhiet extractions were carried out, the raw palm kernels were subjected to the treatment described in Example 1 and the testae were subsequently removed by hand. These palm kernels are referred to as 'treated palm kernels'. Raw palm kernels that were not subjected to the treatment described in the preceding section are referred to as 'untreated palm kernels'. The untreated palm kernels were merely washed in water to remove dirt and particulate matter. The treated palm kernels were ground into small particles with a kitchen blender. The untreated palm kernels were ground into small particles using a grinding mill.

Soxhiet extraction is essentially a hybrid continuous-discontinuous solvent extraction technique. In soxhiet extraction, a specific amount of the sample is placed within a cellulose extraction thimble, which is in turn placed within the soxhiet extraction chamber. An extraction flask containing the solvent of choice is connected to the bottom part of the extraction chamber, while a condenser is connected to the top part of the extraction chamber. The flask is then placed into a heating mantle. The heating mantle will slowly heat the solvent, which will then volatilize and flow into the condenser, where the solvent vapours will then condense and flow into the soxhiet extraction chamber. The soxhiet extraction chamber will slowly be filled with the extraction solvent. Solid-liquid extraction will slowly take place between the sample within the cellulose thimbles and the extraction solvent. When the solvent reaches the designated overflow level, it will then aspirated via a siphon back into the flask. As long as the entire apparatus is connected to the heating mantle, the entire process will repeat itself (De Castro and Garcia-Ayuso; 2000).

Figure 1 illustrates an apparatus used to carry out soxhlet extraction on the treated palm kernels and the untreated palm kernels, according to an embodiment of the present invention. The apparatus basically, is made up of a condenser 102, an extraction chamber 104 comprising a cellulose thimble 106 and an extraction solvent 108, and a heating mantle 110. In the case of the soxhlet extraction process carried out on the treated and untreated palm kernels, the solvent of choice was hexane, which has been shown in previous studies to be an effective solvent in extracting oil from palm kernels. The extraction time was set at 3 hours. After the extraction process was complete, the solvent was then evaporated using a vacuum evaporator, leaving behind the palm kernel oil.

The results of the soxhlet extraction carried out on untreated palm kernels revealed that oil extracted from them was coloured yellow, as shown in Figure 2. Oil extracted from treated palm kernel however, was clear and colourless, as shown in Figure 3. The removal of the testae from the palm kernels therefore, also removed the compounds which contributed to the colour of the oil, which are the phenolic compounds located within the testa.

The treated palm kernels may be applied advantageously to different applications within the industry. As the results of the soxhlet extraction procedure indicate, oil extracted from the treated palm kernel is colourless. Therefore, treating the palm kernels using sodium carbonate and hydrogen peroxide to remove the testa from palm kernels, and subsequently extracting oil from the palm kernels, is a way to obtain colourless oils without the need to refine the oils without using bleaching earths, which are expensive and produce large amounts of environmental waste. Furthermore, both sodium carbonate and hydrogen peroxide are well-known and common ingredients already in extensive use within the food industry and are available in 'food grade' quality, which is safer and more suitable for food processing applications. Another advantageous application of the treated palm kernels is using the defatted treated palm kernels to produce palm kernel flour. The flour produced from defatted treated palm kernel is nutritionally superior to flour produced from untreated palm kernels. This is due to the fact that although phenolic compounds in the testae of plant seeds may exert strong antioxidant effects, they also exert strong anti- nutritional effects which in turn affect foods that are derived from the seeds of such plants. Sreedhara and Kurup (1998) utilized the method developed by Sreedhara et al. (1992) to produce defatted palm kernel flour by treating raw palm kernels in 4M HCI (hydrochloric acid) for 6 to 7 minutes at 95°C. After treatment, the palm kernels were subsequently defatted with hexane. When compared to untreated palm kernel flour, it was found that treated palm kernel flour had higher protein content, with the untreated palm kernel flour containing 183 g/kg protein and the treated palm kernel flour having a protein content of 198 g/kg (Sreedhara and Kurup, 1998). Sreedhara and Kurup (1998) attributed the difference in protein content between the treated and untreated samples to the absence of testa in treated palm kernel flour.

Sreedhara and Kurup (1998) also conducted in vivo digestibility studies, which were conducted on rats fed a diet containing either pure casein, treated palm kernel meal or untreated palm kernel meal, all for a period of 10 days. It was found that rats fed the casein diet absorbed 94% of food nitrogen, while for rats that were fed diets containing treated and untreated palm kernel meal, 80% and 65% of food nitrogen was absorbed, respectively. Rats fed the casein diet had the highest gains in body weight, gaining an average of 64.2 g. Rats fed the treated palm kernel meal had an average body weight gain of 59.5 g while rats that were fed untreated palm kernel meal had average body weight gain of 42.5 g. The increase in the protein content of the treated palm kernel flour when compared to untreated palm kernel flour, as well as increased protein absorption and weight gain in rats when fed treated palm kernel meal compared to untreated palm kernel meal, all indicate that treatment to remove palm kernel testa from palm kernel improved the flour and meal that was subsequently manufactured from the kernels.

According to the available literature, the removal of the testae from palm kernels improves the nutritional quality of the kernels as well its absorption when fed to animals. The method described in this patent differs from the method used by Sreedhara and Kurup (1998). Whereas Sreedhara and Kurup (1998) removed the palm kernel testae using 4M HCI, which is a highly corrosive and hazardous chemical, the method described in the present invention uses sodium carbonate and hydrogen peroxide which are available in food grade quality, The flour produced from treated palm kernels using the present method will therefore be less hazardous, safer to produce and subsequently consumed. Palm kernel flour produced from the treated palm kernels can be used to produce breads, biscuits, cakes and other forms of food.

Currently, as feedstock, palm kernel cake, which is produced from palm kernel, is ranked higher than copra cake and cocoa pod husk. However, it is ranked lower compared to fish meal and groundnut cake, especially in its protein value (Wong and Wan Zahari, 1997). The treated palm kernels can therefore, also be used to produce high-quality palm kernel cake, which in turn can be used as high-quality animal feed, as removing the testae from the palm kernels will also improve its nutritional absorption when consumed by animals.