GB2177715A - Method for fractionation of fats and oils - Google Patents

Abstract

A method of fractionation of fats and oils wherein the fat or oil is dissolved in a solvent having low polarity, cooled and separated into a liquid fraction and a solid fraction, the solvent is removed from the solid fraction which is then further fractionated using a polar solvent. The solid fraction thus obtained may be used as a cocoa butter substitute.

Description

SPECIFICATION Method for fractionation of fats and oils The present invention relates to a method for fractionation of fats and oils. More particularly, it relates to a method for separation of natural and/or synthesized fats and oils containing triglyceride components having different melting points into liquid and solid fractions of good qualities in good yields.

Heretofore, fractionation of triglyceride components having different melting points contained in fats and oils have been carried out by using a solvent such as acetone or hexane, for example. When fats and oils are separated into plural fractions by multistage fractionation, usually, a single solvent is used throughout the entire fractionation stages without changing the solvent to another solvent in the course of fractionation because continuous fractionation can be readily conducted, or fractionation can be carried out at a low cost. For example, Japanese Patent Laid Open Publication No. 84009/1978 discloses such a fractionation and, in all the Examples of this publication, separation of fats and oils into desired liquid and solid fractions is carried out by using a single solvent.

In the last few years, demands for fractions of more improved quality have become greater and greater. However, it is difficult to separate fats and oils into liquid and solid fractions of improved qualities according to conventional fractionation methods using a single solvent as described above. That is, even if a desired liquid fraction of good quality is obtained, the quality of the other desired solid fraction is inferior or, depending upon a particular kind of a solvent used, vice versa. In this respect, it is desired to develop an improved fractionation method of fats and oils which can provide liquid and solid fractions both of which are of improved qualities.

There are both advantageous and disadvantageous points in a conventional fractionation method using a single solvent such as hexane or acetone, for instance. For example, when hexane which is known as a solvent having low polarity is used, it is advantageous that the ability for fractionation of triglyceride components into individual components based on the difference between melting points of the components such as low, middle and high melting points is superior to that of acetone which is known as a polar solvent; and, even if a fraction is contaminated with water, it can be readily removed because hexane is immiscible with water.On the other hand, when using hexane, it is disadvantageous that the ability for separation of impurities such as diglyceride components is inferior to that of acetone; and separation requires a large-scale cooling equipment and high cost because separation should be effected at a low temperature. To the contrary, when acetone which is a polar solvent is used, it is advantageous that the ability for separation of impurities such as diglyceride components is superior to that of hexane; and separation does not require a large-scale cooling equipment equipment and high cost because separation can be effected at a relatively high temperature.On the other hand, when using acetone, it is disadvantageous that the ability for fractionation of triglyceride components into each component is inferior to that of hexane; a resulting liquid fraction of a low melting point has less stability when it is used as frying oil and the like, because impurities such as diglyceride components are concentrated therein; and conditions for fractionation are varied according to the degree of contamination of water because acetone is miscible with water.

It would be desirable to provide a method for fractionation of fats and oils into liquid and solid fractions of improved qualities in comparison with those obtained by conventional fractionation methods in good yields.

According to the present invention, there is provided a method for fractionation of fats and oils, wherein a starting fat or oil material is separated into triglyceride components based on the difference between melting points by using a solvent, characterized in that the starting fat or oil material is firstly separated into a liquid fraction and a crystalline portion by using a solvent having low polarity; a solid fraction of a high melting point is separated and removed from the crystalline portion, if necessary; all or a part of the solvent is removed; and then the crystalline portion is further separated into a solid fraction and an additional liquid fraction by using a polar solvent.

The invention includes product prepared using a fat or oil obtained by the above method, especially foodstuffs containing such fats or oils, e.g. mayonnaise or chocolate.

In the method of the present invention, it is necessary to firstly separate a desired liquid fraction of a low melting point from the starting fat or oil material by using a solvent having low polarity. By effecting this treatment at the first stage of fractionation, it is possible to obtain the liquid fraction of good quality hav ing a high iodine value in a good yield. To the contrary, when using a polar solvent, a liquid fraction of good quality which meets current severe requirements can be hardly obtained because the fraction is contaminated with a large amount of impurities such as diglyceride components, gums and the like.Further, when fractionation is carried out by firstly separating a solid fraction of a high melting point, and then a solid fraction of a middle melting point and a liquid fraction of a low melting point, only a liquid fraction of poor quality having a low iodine value is obtained regardless of the particular kind of a solvent used.

Normally, since a liquid fraction is more stable than a liquid oil such as salad oil, it is used for frying oil or mayonnaise, for example.

For this purpose, it is desired to use a stable fat or oil having an iodine value as high as possible and containing a small amount of impurities such as diglyceride components and gums. The low melting point liquid fraction obtained by the method of the present invention can meet these requirements.

Then, if necessary, a high melting point solid fraction is separated and removed from a crystalline portion which is the remainder after separation of the low melting point liquid fraction from the starting fat or oil material. In the present invention, it is preferable to effect this removal of a solid fraction of a high melting point because impurities such as diglyceride components, gums and the like can be removed, even if the amount thereof is very small and, thereby, a desired solid fat fraction of improved quality is obtained in the subsequent stage.

After removal of the high melting point solid fraction, or without removal thereof, the solvent having a low polarity firstly used is removed by a standard method, e.g. distillation, and the crystalline portion is again fractionated by using a polar solvent. All the solvent firstly used is not necessarily removed and a part of the solvent firstly used may be mixed with a polar solvent freshly added. However, it is preferabie to replace all the solvent firstly used with a polar solvent. Thus, the crystalline portion is separated into a desired solid fraction and an additional liquid fraction. The desired solid fraction thus obtained contains only a slight impurities such as diglyceride components and gums and is of improved quality which is suitable for use as a hard butter fraction. In addition, the yield thereof is very high.

Impurities are concentrated in the additional liquid fraction and removed.

Examples of the solvent having a low polarity used in the present invention include hydrocarbon solvents such as petroleum ether, hexane, heptane, octane or nonane, for Example. They can be used alone or in a combination thereof.

As the the polar solvent, there can be used acetone or methyl ethyl ketone, for example.

Examples of the starting fat or oil material include natural fats and oils such as shea fat, palm oil, sal fat, mango kernel oil, aceituno fat, mowrah fat, kanya fat and the like and synthesized- fats and oils such as enzymatic interesterified fats and oils and the like. The starting fat or oil material may be subjected to degumming, refining or partial separation of a solid fraction of a high melting point prior to fractionation of the present invention. Particularly, the starting fat or oil material having an acid value of not higher than 5 is preferred.

As described hereinbefore, according to the method of the present invention, it is possible to obtain the desired liquid and solid fractions of improved qualities in good yields by multistage fractionation of fats and oils with sequential use of a solvent having low polarity and then a polar solvent. Particularly, in solvent fractionation, it is very advantageous from the economic viewpoint to improve the yield of a desired solid fraction of a middle melting point which is of high utility value, even an increase in yield of 1%. Accordingly, a great deal of effort has been expended to improve the yield, even if the increase in yield is very slight.In this regard, according to the method of the present invention, the solid fraction of a middle melting point of improved quality which is suitable for use as a hard butter component can be obtained in a yield of several % higher than that in a conventional method as shown in the Comparative Example 2 hereinafter.

The following Examples and Comparative Examples further illustrate the present invention in detail. In the Examples and Comparative Examples, all the "parts" and "%'s" are by weight, unless otherwise stated.

Example 1 Palm olein (1 part) having a diglyceride content of 7.7% and an iodine value of 57.2 was dissolved in hexane (1 part) and the resulting micellar colloid was cooled with stirring to separate out crystals. After being kept at - 15% for 1 hour, the mixture was filtered to separate into a filtrate portion and a crystalline portion. The crystalline portion was washed with hexane at -15"C (1 part) and again filtered. The filtrate was combined with the filtrate portion. The solvent was removed from the crystalline portion to recover a fat in a yield of 39.0% (based on the starting palm olein, hereinafter merely referred to as yield) The fat had an iodine value of 39.9 and a diglyceride content of 6.8%. A desired liquid fraction was recovered from the filtrate portion in a high yield of about 61.0%.The liquid fraction had an iodine value of 68.4, a diglyceride content of 8.4% and a low cloud point of about 2"C and was suitable for use as frying oil.

On the other hand, the fat (1 part) recovered from the crystalline portion by removal of the solvent was dissolved in acetone (9 parts) and cooled to 5"C with stirring. After being kept at this temperature for 20 minutes, the mixture was filtered to separate into a filtrate portion and a crystalline portion. The crystalline portion was washed with acetone at 5"C (1 part) and filtered. Then, the solvent was removed from the crystalline portion to obtain a desired solid fraction, i.e., palm mid fraction in a yield of 25.7%. The mid fraction had an iodine value of 33.4 and a diglyceride content of 1.2%.A mixed fat of this palm mid fraction (50 parts) and shea stearin having an iodine value of 39.0 (50 parts) had a considerably high maximum attainable temperature in the Jensen cooling curve (Tmax) of about 28.9"C and a rapid crystalline transformation rate and, therefore, it was suitable for use as a hard butter.

Example 2 The crystalline portion obtained by fractionation with hexane in the first stage of Example 1 was dissolved in hexane with heating. The fat concentration of the resulting micellar colloid was adjusted to 33% and cooled to 5"C.

After being kept at this temperature for 20 minutes, crystals separated out were filtered off to obtain a crystalline portion. After removal of the solvent, a solid fraction of a high melting point was obtained in a yield of 1.9%.

The fraction had an iodine value of 30.0 and a diglyceride content of 30.2%.

After removal of the solvent from the filtrate, the residue was dissolved in acetone (9 parts). The resulting micellar colloid was cooled with stirring to 4"C and maintained at this temperature for 20 minutes. The mixture was filtered to separate into a crystalline portion and a filtrate portion. The crystalline portion was washed with acetone (1 part) and the solvent was removed therefrom to obtain a desired solid fraction having an iodine value of 35.0 and a diglyceride content of 1.2% in a yield of 26.6%. A mixed fat of the solid fraction (50 parts) and shea stearin having an iodine value of 39.0 (50 parts) had a very high Tmax of such as 29.4"C and, when it was used as a hard butter in chocolate, it showed excellent mold release characteristics and retraction.

Comparative Example 1 The fat concentration of the filtrate portion resulted from filtration of the crystalline portion to remove the solid fraction of a high melting point from the micellar colloid in hexane in Example 2 was adjusted to 10% without removal of the solvent. The filtrate portion was cooled with stirring to - 1 20C and maintained at this temperature for 20 minutes.

Crystals separated out were filtered off. The crystalline portion was washed with hexane (1 part). The solvent was removed from the crystalline portion to obtain a solid fraction, i.e., palm mid fraction in a yield of 26.6% by weight. Although this palm mid fraction had an iodine value of 34.4, its diglyceride content was 5.2% which was much higher than those of the mid fractions of Examples 1 and 2.

When a mixed fat was prepared by using this mid fraction and shea stearin according to the same manner as in Examples 1 and 2, it showed low Tmax such as 27.8"C. When the mixed fat was used as a hard butter in chocolate, mold release characteristics and retraction thereof under similar conditions were inferior to those of the mixed fats in Examples 1 and 2.

Comparative Example 2 The same palm olein as that used in Example 1(1 part) was dissolved in acetone (4 parts) and the resulting micellar colloid was cooled with stirring to 3"C and maintained at this temperature for 1 hour. A crystalline portion was filtered off and washed with acetone at 3"C (1 part). The washings were combined with the filtrate portion and the solvent was removed therefrom to obtain a liquid fraction in a yield of 46.5% which was lower than that in Example 1 using hexane. Further, the liquid fraction had a low iodine value such as 67.0 and a high diglyceride content of such as 12.3%. When the liquid fraction was allowed to stand at room temperature (about 20"C) for a week, it was clouded.

On the other hand, the crystalline portion was molten with warming and a micellar colloid thereof containing 10% of the fat in acetone was prepared. The micellar colloid was cooled with stirring to 7"C and maintained at this temperature for 1 hour. This was separated into a crystalline portion and a filtrate portion. The crystalline portion was washed with acetone at 7"C and the solvent was removed to obtain a palm mid fraction having an iodine value of 35.0 and a diglyceride content of 0.8% in a yield of 22.3%. A mixed fat of this fraction (50 parts) and shea stearin (50 parts) had a high Tmax of such as 29.2"C.

However, as described above, the yield thereof was 22.3% which was considerably low in comparison with the yields in Examples 1 and 2.

As will be appreciated from the foregoing, it has been found that fats and oils can be separated into liquid and solid fractions both of which are of improved qualities by changing a solvent to another kind of a solvent in the course of fractionation to utilize advantageous points of both kinds of solvents. Further, unexpectedly, it has been also found that desired liquid and solid fractions of improved qualities can be obtained in good yields by changing a solvent in the course of fractionation.

Claims (9)

1. A method for fractionation of fats and oils, wherein a starting fat or oil material is separated into triglyceride components based on the difference between melting points by using a solvent, characterized in that the starting fat or oil material is firstly separated into a liquid fraction and a crystalline portion by using a solvent having low polarity; a solid fraction of a high melting point is separated and removed from the crystalline portion, if necessary; all or a part of the solvent is removed; and then the crystalline portion is further separated into a solid fraction and an additional liquid fraction by using a polar solvent.

2. A method according to claim 1, wherein the solvent having low polarity is a hydrocarbon solvent.

3. A method according to claim 2 wherein the hydrocarbon solvent is petroleum ether, hexane, heptane, octane, nonane or a mixture thereof.

4. A method according to any one of the preceding claims, wherein the polar solvent is acetone or methyl ethyl ketone.

5. A method according to any one of the preceding claims, wherein the starting fat or oil material has an acid value of no more than 5.

6. A method according to claim 1 substantially as hereinbefore described.

7. A method for fractionation of fats and oils substantially as hereinbefore described in Example 1 or Example 2.

8. A fat or oil whenever obtained by a method as claimed in any one of the preceding claims.

9. A product prepared using a fat or oil as claimed in claim 8.