Technical Field The present invention relates in general to a method for preparing a hydrogenated vegetable oil having a reduced hydrogenation odor and containing or not containing conjugated linoleic acid (hereinafter, called "CLA"), and to the use of the hydrogenated vegetable oil as a food ingredient. More particularly, the present invention relates to a method for preparing a hydrogenated vegetable oil significantly reduced in volatile compounds that are causative of the hydrogenation odor from the oil and usually formed during the purification of a crude vegetable oil.

CLA is an unsaturated fatty acid of 18 carbon atom, and is known as having an excellent efficacy, such as a lowering of a blood cholesterol concentration in an adult, a reduction in body fat, an anticancer function, and the like. Such a CLA can be formed during a hydrogenation of a vegetable oil under certain conditions. The hydrogenated vegetable oil containing so formed CLA is, however, limited in use in applications, such as foods, medical supplies, and the like, due to a hydrogenation odor emitted by volatile compounds formed during the hydrogenation of the crude vegetable oil.

Fig 1 shows the conventional method for the purification of various oils. As shown in Fig. 1, the conventional purification procedure includes first degumming a crude vegetable oil which was extracted by expression, neutralizing the degummed oil, bleaching the

neutralized oil using an bleaching earth (acid activated bleaching earth), hydrogenating the bleached oil, and finally deodorizing the hydrogenated oil.

The hydrogenated vegetable oil (containing or not containing CLA) prepared through the conventional purification method is problematic in that it contains a significant amount of volatile compounds, such as aldehyde, alcohol, various acids esters, and the like, that are causative of the hydrogenation odor. However, there is not suggested a clear solution to solve this problem. In addition, if the hydrogenated vegetable oil produced according to the conventional purification method is applied to foods as such, it adversely affects the flavor of the resulting foods due to its hydrogenation odor, thereby causing a decrease in value of the foods as goods.

Disclosure of the Invention We have studied to solve the problem with the conventional method for the preparation of hydrogenated vegetable oil containing or not containing CLA. As a result of that, we have found a fact that, when certain minor components directly associated with a promotion and increase in production of volatile compounds causative of a hydrogenation odor were removed prior to a hydrogenation of a crude vegetable oil, the volatile compounds could be decreased in production to a significant extent. On the basis of this fact, we have perfected the present invention.

It is therefore an object of the present invention to provide a method for the preparation of a hydrogenated vegetable oil (containing or not containing

CLA) which was improved in flavor to a significant extent. This object is accomplished by removing, prior to hydrogenation, minor components directly associated with the promotion and increase in production of the hydrogenation odor-causative volatile compounds so that the volatile compounds are minimized in their production during the hydrogenation so as to reduce the hydrogenation odor to a significant extent.

It is other object of the present invention to use the hydrogenated vegetable oil decreased in the hydrogenation odor, as an ingredient the prepared foods as goods is increased, thereby contributing to a development in the food industry.

A method of the present invention for the preparation of the hydrogenated vegetable oil includes treating a crude vegetable oil with an adsorbent combination of a bleaching earth and a suitable amount of magnesium silicate, in a bleaching step of the crude vegetable oil, unlike the conventional purification method using only the bleach earth in the bleaching step.

The hydrogenation odor emitted from the hydrogenated vegetable oil is resulted from a gummy material, to which various minor components contained in a crude vegetable oil, such as phospholipid, protein, calcium ion (Ca2+), magnesium ion (Mg2+), iron ion (Fe2), 2+), and the like, are bonded. These minor components promote and increase the production of materials that are directly causative of the hydrogenation odor, such as aldehyde, alcohol, ketone, ester, and the like.

The method of the present invention includes, in the bleaching step during the purification process of

the crude vegetable oil, a removal of the minor components directly associated with the promotion and increase of production of aldehyde, alochol, ketone and ester. As a result, the method of the present invention allows the production of the hydrogenation odor- causative materials in the vegetable oil to be inhibited.

Brief Description of the Drawings The method of the present invention for the preparation of the hydrogenated vegetable oil containing or not containing CLA will now be described in detail with reference with the accompanying drawings.

Fig. 1 is a flow chart showing the conventional purification method of a crude vegetable oil.

Fig. 2 is a flow chart showing a method for the preparation of a vegetable oil according to the present invention.

Fig. 3 is a gas chromatogram showing a CLA content in a hydrogenated vegetable oil prepared according to the present invention.

Fig. 4 is a gas chromatogram for volatile compounds isolated from a hydrogenated soybean oil containing CLA prepared according to the conventional purification method.

Fig. 5 is a gas chromatogram for volatile compounds isolated from a CLA-containing hydrogenated vegetable oil prepared according to the present invention.

Best Mode for Carrying Out the Invention Fig. 2 is a flow chart showing a method for the

preparation of a hydrogenated vegetable oil (containing or not containing CLA) according to the present invention, which may be used as an ingredient for the preparation of foods. As shown in Fig. 2, the method of the present invention includes the steps of degumming a crude vegetable oil, and washing and drying the degummed oil to be neutralized. Then, the neutralized oil is bleached with an bleaching earth, while removing, by adsorption, the minor components in the oil with a magnesium silicate, and the like. After this, the oil is filtered. Next, the bleached oil is hydrogenated, and the hydrogenated vegetable oil (containing or not containing CLA) is stripped with dry steam, thereby to be deodorized.

Among the steps as described above, the degumming step is carried out to remove impurities in the crude vegetable oil, such as phospholipid, a gummy material, carbohydrate, protein, and the like, using an aqueous solution of oxalic and phosphoric acids. For this purpose, the crude vegetable oil is added with a phosphoric acid at the amount of 0.1 to 0.3 % by weight relative to the weight of the crude vegetable oil.

Subsequently, the mixture is stirred at a temperature of 75 to 95 °C for 20 minutes to one hour, thereby removing the impurities.

The vegetable oil treated in the degumming step contains a free fatty acid. The free fatty acid is hence removed from the oil in the subsequent neutralization step. The removal of the free fatty acid is achieved by washing the oil through the addition of sodium hydroxide (20 Baume) to the vegetable oil at 20% excess relative to an acid value of the oil, and then drying the oil.

Thereafter, the bleaching step of the neutralized oil is performed to remove minor components, a natural pigment, such as chlorophyll, and other pigment, such as carotin, from the oil, by a physical adsorption. For this purpose, the physical adsorption is carried out under vacuum (10 mmHg) using an adsorbent combination consisting of a bleaching earth for the removal of pigments in the crude oil, and magnesium silicate for the removal of other minor components which can promote the off-flavor formation during hydrogenation. As a result, the pigments and the minor components are removed.

Subsequently, the hydrogenation step is carried out to hydrogenate unsaturated fatty acids in the oil using a catalyst. In order to particularly induce the formation of CLA in the oil, this hydrogenation needs to be performed at a temperature of 160 to 230 °C under a pressure of 0.5 to 5 kg/cm3 in the presence of a nickel catalyst (0.3 to 0.5%). From Fig. 3, it can be confirmed that the vegetable oil treated by the hydrogenation step contains CLA.

Finally, the deodorization step is a final step of the purification to remove oily odor-emitting components and other volatile components in the hydrogenated vegetable oil (containing or not containing CLA), thereby obtaining a hydrogenated vegetable oil with low level of odorous compounds. In this deodorization step, the hydrogenated oil is stripped with dry steam at a temperature of 165 to 230 °C under a vacuum level of 2 to 4 mmHg for about 25 minutes, such that the oily odor- emitting components and other volatile components in the oil are removed. In this way, the hydrogenated vegetable

oil (containing or not containing CLA) having a reduced hydrogenation odor is obtained.

In the conventional method for the purification of the crude vegetable oil, the crude vegetable oil is treated with only the bleaching earth in its bleaching step. On the other hand, the bleaching method of the present invention utilizes an adsorbent combination consisting of the bleaching earth, as a first adsorbent component serving to remove pigments in the oil, and a suitable amount of magnesium silicate as a second adsorbent component serving to remove the minor components which can promote formation of volatile odorous compounds during hydrogenation, in the bleaching step. Thus, according to the method of the present invention, the minor components are removed prior to the hydrogenation of the vegetable oil, so that an effect of deodorizing the vegetable oil is maximized.

Moreover, as an alternative to magnesium silicate as the second adsorbent component, it is also possible for the method of the present invention to use other adsorbents, such as silica or silicic acid, as the second adsorbent component, such that the minor components in the crude vegetable oil are removed by adsorption with the second adsorbent component. In addition, the second adsorbent component serving to remove minor components, i. e., magnesium silicate, silica, and silicic acid, may be also preferably used in their mixture.

The second adsorbent component, i. e., magnesium silicate, silica, silicic acid, or a mixture thereof, is not especially limited in its use amount. It is, however, preferred that the second adsorbent component

is used, in combination with the bleaching earth, at the amount of 0.2 to 10 % by weight based on the weight of the vegetable oil, in order to maintain its adsorbablity at an excellent level. Moreover, the effect of the present invention is not significantly influenced by the use amount of the acid earth used as the first adsorbent component for the removal of the pigments. It is, however, preferred for the practice of the present invention that the acid earth is used at the amount of 1.5 to 8% by weight based on the weight of the vegetable oil.

Examples of the vegetable oil suitable for use in the practice of the present invention include general vegetable oils, as well as vegetable oils containing CLA, such as soybean oil, corn oil, cottonseed oil, canola oil, sunflower seed oil, rice bran oil, safflower oil and the like. Among these vegetable oils, the soybean oil is most preferred in the practice of the present invention, since it is excellent in the ability to form CLA.

The hydrogenated vegetable oil (containing or not containing CLA) produced according to the method of the present invention is good in flavor. As a result, the hydrogenated vegetable oil of the present invention may be used as an ingredient for the preparation of foods, such as fried instant noodles, processed milks, yogurt, snacks, ice-cream products, water ices, processed chocolates, shorting margarines, confectionaries, breads, frozen foods, and the like, so that it can produce foods having a significantly enhanced sensory attribute.

The present invention will now be described in

detail with reference to the following examples. Note, however, that the examples are included herein for only explanation purposes and they are not restrictive of the present invention.

Example 1 To a crude soybean oil, which was extracted by expression from soybeans, was added a phosphoric acid at the amount of 0.3% by weight relative to weight of the crude soybean oil. The mixture was stirred at 85°C for 30 minutes to remove impurities, such as phospholipid, a gummy material, carbohydrate, protein, and the like.

Thereafter, the resulting oil was added with sodium hydroxide (20 Baume) at the amount of 0.3% by weight relative to the weight of the oil to remove free fatty acids, washed with water, and then dried at 105 °C, thereby to be neutralized. Next, the neutralized oil is subjected to a physical adsorption for 30 minutes under vacuum (10 mmHg) using an adsorbent combination, so that pigments and minor components were removed from the oil, thereby bleaching the oil. At this point, the adsorbent combination used in the above adsorption consists of an bleaching earth of 8% by weight relative to weight of the oil, and magnesium silicate of 0.2 % by weight relative to weight of the oil. Then, the bleached oil was hydrogenated at 230 °C under 0.5 kg/cm3 in the presence of a nickel catalyst (0.5%) to yield a hydrogenated soybean oil containing CLA. Fig. 3 is a gas chromatogram indicated for the hydrogenated soybean oil produced as described above. From Fig. 3, it could be confirmed that the hydrogenated soybean oil contains CLA at the amount of 50.45 mg per gram of the oil.

Then, the hydrogenated soybean oil containing CLA was stripped with dry steam at 230 °C under a vacuum of 4 mmHg for 25 minutes to remove oily odor-emitting components and other volatiles components, thereby deodorizing the oil.

Example 2 The same procedure as described in Example 1 was carried out to obtain a hydrogenated vegetable oil containing CLA, except that 0.5% by weight of magnesium silicate having an excellent adsorbability was used in the bleaching step of the crude oil, in order to remove the minor components promoting the production of the hydrogenation odor-emitting materials.

Example 3 The same procedure as described in Example 1 was carried out to obtain a hydrogenated vegetable oil containing CLA, except that 2% by weight of magnesium silicate having an excellent adsorbability was used in the bleaching step of the crude oil, in order to remove the minor components promoting the production of the hydrogenation odor-emitting materials.

Example 4 The same procedure as described in Example 1 was carried out to obtain a hydrogenated vegetable oil containing CLA, except that 5% by weight of magnesium silicate having an excellent adsorbability was used in the bleaching step of the crude oil, in order to remove the minor components promoting the production of the hydrogenation odor-emitting materials.

Example 5 The same procedure as described in Example 1 was carried out to obtain a hydrogenated vegetable oil containing CLA, except that 10% by weight of magnesium silicate having an excellent adsorbability was used in the bleaching step of the crude oil, in order to remove the minor components promoting the production of the hydrogenation odor-emitting materials.

Test Example 1 : Identification and quantitative measurements for volatile compounds in the hydrogenated soybean oil The volatile compounds, that are known to be causative of the hydrogenation odor, were isolated from the CLA-containing hydrogenated soybean oil obtained in Example 3, and the hydrogenated soybean oil containing CLA, as a control, produced by the conventional purification method, respectively, as described below.

Then, the isolated volatile compounds were identified and determined with respect to their content in each of the hydrogenated vegetable oils, as follows.

Operation Conditions of Gas Chromatograph Two samples each containing volatile compounds were extracted from the CLA-containing hydrogenated soybean oils obtained in Example 3 of the present invention, and from the CLA-containing hydrogenated soybean oil of the conventional purification method, respectively, by a solid phase microextraction (SPME).

Next, the respective samples were subjected to separation by gas chromatography. At this point, a fiber

used in the microextraction of the samples was a 75 mm Carboxen-PDMS.

More concretely, the above microextraction and gas chromatography were performed as follows.

5.0 g of the hydrogenated soybean oil containing CLA was introduced into a serum bottle of a 30 ml capacity, which was then closed and sealed with a silicon-lined rubber septum and an aluminum cap.

Thereafter, the serum bottle was heated on a hot plate at 100°C for 60 minutes. Next, the 75 mm Carboxene-PDMS fiber was injected into the serum bottle through the septum and kept in the bottle for 10 minutes for the adsorption of the volatile compounds. Then, the Carboxene-PDMS fiber, on which the volatile compounds were adsorbed, was transported into a feeder of a gas chromatograph in which the adsorbed volatile compounds were desorbed at 250 °C for 1 minutes and introduced into the gas chromatograph for analysis with a carrier gas.

An oven of the gas chromatograph was maintained at 50 °C for one minute, and then increased in temperature to 200 °C at a rate of 4 °C/minute. At this point, a capillary column was used in the gas chromatography, and the carrier gas was helium. Also, a flame ionization detector (FID) was used at 260 °C for the calculation of a peak area. A gas chromatography-mass spectroscope was used for the identification of the volatile compounds.

In addition, for the confirmation of the kind and intensity of odors emitted from the separated volatile compounds, a snipping port was used which was installed in the gas chromatography.

Figs. 4 and 5 show results analyzed by the gas chromatography for the hydrogenated soybean oil

containing CLA of the present invention and the hydrogenated soybean oil containing CLA produced by the conventional purification, respectively.

Moreover, Table 1 below shows results identified for the volatile compounds isolated from the CLA- containing hydrogenated soybean oil produced by the conventional purification method, as well as the property and intensity of odor emitted from the volatile compounds.

Table 1 : Identification of volatile compounds isolated from CLA-containing hydrogenated soybean oil produced by the conventional purification method.

Comp. Odor No. Compound Name Peak Odor Description Intensity 1 Methoxy ethane 785 2 Pentenal + unknown 954 Oxidized fat ++ 3 Hexanal 1068 Grass ++ 4 4-pentanal 1139 5 1-butanol 1151 6 Heptanal 1210 Fat, butter, medicinals + 7 (E)-2-hexanal 1275 Fat + 8 1-pentanol 1305 9 Octanal 1359 Oxidized fat ++ 10 2,3-octandion 1411 11 (E)-2-heptanal 1424 Fat ++ 12 1-hexanol 1446 13 4-azido-heptane 1456 Butter +++ 14 3-methyl-1, 5-pentadiol 1494 Rubber, oxidized fat ++ 15 2-octenal 1536 Fat, butter ++++ 16 1-octene-3-ol 1559 Fat ++

17 1-heptanol 1567 Fat, butter ++ 18 1, 1-heptandiol, diacetate 1588 Fat ++ Table 1 (Continued) Comp. Odor No. Compound Name Peak Odor Description Inten sity 19 Decanal 1610 20 Hexanoic acid, pentyl ester 1616 21 (E, E)-2,4-heptadienal 1629 Oxidized fat + 22 (E)-2-nonenal 1654 Oxidized fat ++++ 23 Unknown 1660 Oxidized fat ++++ 24 1-Octanol 1670 Oxidized fat ++ 25 4-methyl-l-heptanol 1705 26 (Z)-2-decenal 1744 Fat + 27 1-nonanol 1755 28 Heptyl hexanoate 1773 29 (E)-2-undecenal 1819 Fat, margarine ++++ 30 3,4-dimethyl-2,5-furandione 1838 Fat ++ 31 (E, E)-2, 4-decadienal 1853 Fat + 32 Hexanoic acid 1881 33 Heptanoic acid 1834- 34 Octanoic 1980 35 Nonanoic acid 2020 In Table 1, 35 kinds in total of volatile compounds were identified, being mostly aldehyde, alocohol, acid, ester, and the like. Among these volatile compounds, 15 compounds were shown to be medium (++) or more in odor intensity, and 5 compounds (Compound Nos. 13,15,22,23, and 29) were shown to be strong (+++) or more. The 5 compounds having the strong odor intensity were found to be 4-azido heptane, 2-

octenal, (E)-2-nonenal, unknown compound, and (E)-2- undecenal, respectively, and to be predominant in odor of the hydrogenated soybean oil containing CLA.

Table 2 shows peak areas measured by gas chromatography for the volatile compounds in the CLA- containing hydrogenated soybean oil produced by the present invention and in the CLA-containing hydrogenated soybean oil produced by the conventional purification method.

Table 2: Comparison of peak areas of volatile compounds in CLA-containing hydrogenated soybean oil produced by the conventional purification method, with those in the CLA-containing hydrogenated soybean oil produced by the present invention Compound Peak Area (Electron Counts) No. CLA Soybean Oil CLA Soybean Oil (Conventional Method) (Invention) 1 11, 049 11,864 2 55,911 28. 150 3 42,851 17, 073 4 6, 064 2, 247 5 5,722 2, 106 6 27, 528 12,564 7 13,218 4,661 8 19,427 8, 454 9 46, 343 22, 578 10 97,084 22,578 11 60,304 33,239 12 6,828 2,337 13 <100 <100 14 23,901 12,480 15 12, 289 5, 377 Table 2 (Continued) Compound Peak Area (Electron Counts) No. CLA Soybean Oil CLA Soybean Oil (Conventional Method) (Invention) 16 1,645 321 17 4,783 1,674 18 9,617 4,403 19 3,522 1,107 20 2,251 1,167 21 2,936 1,035 22 5,893 2,055 23 2,588 2, 014 24 11,073 5,419 25 1,459 720 26 5,458 2,769 27 597 <100 28 673 328 29 6,130 3,496 30 4, 312 3, 315 31 656 120 32 26,424 22,020 33 5,654 3,141 34 3,923 2,204 35 8,690 4,828 Total 513, 493 302, 011 As is clear from the comparison indicated in Table 2, the content of the volatile compounds in the CLA- containing hydrogenated soybean oil produced by the present invention was very low as compared with that in

the CLA-containing hydrogenated soybean oil produced by the conventional purification method. The total peak area of the volatile compounds 1 to 35 was 513,493 for the CLA-containing hydrogenated soybean oil produced by the conventional purification. On the other hand, for the CLA-containing hydrogenated soybean oil produced by the present invention, the total peak area was 302,011 corresponding to about 58.8% of the conventional CLA- containing soybean oil. Moreover, the total peak area for five volatile compounds having a strong odor intensity (+++ and ++++) was 27,000 for the CLA- containing hydrogenated soybean oil produced by the conventional purification. However, for the CLA- containing hydrogenated soybean oil produced by the present invention, the total peak area for the five compounds having a strong odor strength was 13,042 corresponding to about 48.3% of that for the conventional CLA-containing soybean oil. These results demonstrate that the method of the present invention produces the hydrogenated soybean oil containing CLA, having significantly reduced volatile compounds.

Furthermore, these results correspond with results of sensory evaluation for fried instant noodles (Table 3) prepared using the hydrogenated soybean oil containing CLA of Example 3, which evaluation was conducted with 25 adults of either sex as the evaluating persons.

Test Example 2: Preparation of fried instant noodles Wheat flour and starch were mixed in a mixer, to which water was added. Next, the mixture was kneaded to form a dough. The dough was formed into a sheet using a

roller, and the formed sheet was cut into noodle strings using a slitting equipment. The noodle strings were steamed in a steam box with steam of 100 °C. The steamed noodle strings were cut and introduced into a retainer which was then positioned in a fryer. Thereafter, the noodle strings in the retainer were fried at 145 °C for 90 seconds, using the CLA-containing hydrogenated soybean oil of the present invention and the CLA- containing hydrogenated soybean oil obtained by the conventional method, respectively, and cooled to prepare fried instant noodles. With respect to the fried instant noodles prepared using the soybean oil of the present invention, they contained 18% by weight of the hydrogenated soybean oil containing CLA. Also, the content of CLA in the fried instant noodles prepared using the oil of the present invention was 0.9 g per 100 g of the noodles. For reference, current studies show that the intake of 0.6 to 6 g/day of CLA by an adult produces an anticancer effect, as well as a diet effect that reduces body fat.

Table 3: Result of sensory evaluation Kind of Oil Odor Intensity Sensory Evaluation CLA hydrogenated soybean oil by the 7.8 2.87 conventional method CLA hydrogenated soybean oil by the present 4.7 4.18 invention Note: Odor intensity: 1= very weak, 3= weak, 5= medium, 7= strong, 9= very strong.

Sensory evaluation (five scales): 1= very bad, 2= bad, 3= medium, 4= good, 5= very

good.

Number of the evaluating persons: 25 adults of either sex.

Results in Table 3 correspond with results of sensory evaluation, as shown in Table 4, for milks prepared by emulsifying the conventional CLA-containing hydrogenated soybean oil and the CLA-containing hydrogenated soybean oil of Example 3, in skimmed milk, respectively. The evaluation in Table 4 was conducted with 25 adults of either sex, as the evaluating persons.

Test Example 3: Preparation of Milks A skimmed milk was prepared by separating a butter fat from a raw milk, and to which, sucrose fatty acid ester was added at the amount of 0. 1% by weight based on the weight of the milk. The mixture was heated to a temperature of 65 to 70 °C with stirring. Meanwhile, two kinds of the CLA-containing hydrogenated soybean oils produced by the present invention and by the conventional method, respectively, were heated to a temperature of 65 to 70 °C with stirring. After which, glycerine fatty acid ester was added to each of the oils at the amount of 0.2% by weight based on the weight of the oil. The skimmed milk mixture was mixed with each of the CLA-containing hydrogenated soybean oil mixtures, and stirred for five minutes. Then, each of the resulting mixtures was homogenized at a temperature of 65 to 70 °C, sterilized at 95 °C for five minutes, and cooled to 4 °C, thereby obtaining finished milk products.

With respect to the milk product prepared using the soybean oil of the present invention, it was found to contain 154 mg of CLA per 100 g of the finished milk

product.

Table 4: Result of sensory evaluation Kind of Oil Odor Sensory Intensity Evaluation CLA hydrogenated soybean oil by the conventional 5.9 1.68 method CLA hydrogenated soybean oil by the present 3.2 4.2 invention method Note: Odor intensity : 1= very weak, 3= weak. 5= medium, 7= strong. 9= very strong.

Sensory evaluation (five scales): 1= very bad, 2= bad, 3= medium, 4= good, 5= very good.

Number of the evaluating persons: 25 adults of either sex.

Industrial Applicability As apparent from the above description, the present invention provides the hydrogenated vegetable oil (containing or not containing CLA) which is significantly reduced in content of various volatile compounds causative of the hydrogenation odor, and which is therefore enhanced in flavor. Moreover, prepared foods using the hydrogenated vegetable oil (containing or not containing CLA) produced by the present invention are significantly reduced in the hydrogenation odor which causes persons to feel reluctant to use them. As a result, the hydrogenated vegetable oil results in the foods having a considerably enhanced flavor, and thus increased in value as goods.

Although the preferred embodiments of the invention have been disclosed for illustrative purposes,

those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.