WO2012050423A1

WO2012050423A1 - Process for fractional crystallisation of palm-based diacylglycerol fat

Info

Publication number: WO2012050423A1
Application number: PCT/MY2011/000188
Authority: WO
Inventors: Darby Malaysia Berhad Sime; Putra Malaysia Universiti; Abdul Latip Razam; Azwani Ab. Karim Nur; Seong Koon Lo; Suria Affandi Yusoff Mohd.; Oi Ming Lai
Original assignee: Darby Malaysia Berhad Sime; Univ Putra Malaysia; Abdul Latip Razam; Nur Azwani Ab Karim; Seong Koon Lo; Mohd Suria Affandi Yusoff; Oi Ming Lai
Priority date: 2010-10-12
Filing date: 2011-08-15
Publication date: 2012-04-19
Also published as: MY165832A

Abstract

The present invention provides a method for fractionating an oil composition containing at least 80% by weight of diacylglycerol into a solid fraction and a liquid fraction, which heats the oil composition to an elevated temperature, cools the oil composition to deposit crystals at a cooling rate of 0.05°C/min to 3.00°C/min to an end-temperature in the range of 30°C to 50°C while stirring to obtain crystal slurry, and fractionating the crystal slurry into a solid fraction and a liquid fraction.

Description

PROCESS FOR FRACTIONAL CRYSTALLISATION OF PALM-BASED

DIACYLGLYCEROL FAT

Field of the Invention

The present invention relates to a method for dry fractionation of an oil composition. More particularly, the present invention relates to a method for dry fractionation of an oil composition containing at least 80% by weight of diacylglycerol into a solid fraction and a liquid fraction.

Background of the Invention

In recent years, medical professions have sought to prevent obesity. Researchers have found that obesity can be more effectively prevented by controlling not only body weight, but also body fat. In particular, researchers have found that decreasing visceral fat is effective in preventing various diseases such hypofunction of heart, hypertension and arteriosclerosis and is generally good for the health of an individual. Researchers have further found that diacylglycerol having a saturated or unsaturated acyl group having 12 to 22 carbon atoms as a constitutive acyl group is a useful agent for preventing and treating fatty liver (Japanese Patent Application laid-open no. 04-300828, titled "Preventive or Therapeutic Agent for Fatty Liver", published on 23 October 1992). In order to achieve the inhibitory effect of diacylglycerol on accumulation of body fat by daily eating habit, edible oil (or triacylglycerol) must be replaced with diacylglycerol enriched oil. This replacement can be achieved by using diacylglycerol enriched oil as cooking oil or using diacylglycerol enriched oil as a food additive in place of edible oil.

In the past, various methods have been put forth for the preparation of diacylglycerol enriched oil for use in food additives. One method is by an ester exchange reaction of an oil, such as soybean oil, rapeseed oil, and/or palm oil with glycerol. Another method is by an esterification reaction of a fatty acid derived from such an oil through hydrolysis, with glycerol. The resultant mixture may then undergo some purification treatments such as molecular distillation and deodorization to arrive at the desired diacylglycerol enriched oil.

However, diacylglycerol oil has a higher melting point than triacylglycerol oil, and it also crystallizes at a low temperature. Therefore, diacylglycerol oil is not easily poured out of a bottle, or has an unpleasant appearance. In addition, when diacylglycerol oil is used in products that must be stored in refrigerator, diacylglycerol oil crystallizes causing the fat to solidify and/or separation of the oil from the food products. To overcome this problem, it is preferable to remove the high-melting portion of diacylglycerol from the oil to lower the melting point.

Taking the different melting points into consideration, separation by chromatography and distillation have been considered. However, such processes involve problems of low productivity, high costs, deterioration of quality of the oil composition produced thereto, etc.

Another method which can be employed to remove the high-melting portion of diacylglycerol is to fractionate a solid fraction of the diacylglycerol having a high melting point from a liquid fraction of the diacylglycerol having a lower melting point. Many methods of fractionation of oils and fats are known in the art. It is known to fractionate fats in the presence of organic solvent such as acetone or hexane. Such fractionation procedure is highly efficient but expensive. Another method known in the art is to add a lipophilic polyglycerol fatty acid ester to an oil to fractionate the oil into a solid portion and a liquid portion (Japanese Patent Application laid-open no. 01-289897, titled "Production of Liquid Fat", published on 21 November 1989, and Japanese Patent Application laid-open no. 03-031397, titled "Fractionation Promoter of Fat and Oil", published on 12 February 1991 ).

It is also known to fractionate fats or oils without using solvent. However, such processes often involve additional step(s) to fluidize a crystal slurry formed during crystallisation before the crystal slurry is subjected to fractionation. For example, in US Pat. No. 5,045,243, titled "Method For Dry Fractionation of Fats And Oils" issued to Fuji Oil Company, Limited on 3 September 1991 , a crystal slurry formed during crystallisation is crushed to fluidize the slurry prior to fractionating the slurry into a solid fraction and a liquid fraction. Such additional steps often increase production costs. In order to fractionate diacylglycerol enriched oil into a solid fraction and a liquid fraction to obtain a diacylglycerol oil with a lower melting point, diacylglycerol oil must be cooled to crystallize a high-melting portion of the diacylglycerol.

One proposed process for fractionating a diacylglycerol enriched oil is given in US Pat. No. 6,630,189, titled "Solid-Liquid Fractionation Process of Oil Composition" issued to Kao Corporation on 7 October 2003 that discloses a high-melting diacylglycerol and a low-melting diacylglycerol are separated via fractionation from at least 50% by weight of diacylglycerol produced from soft oil. However, this described process becomes feasible only by cooling the oil composition to deposit crystals in the case where an emulsifier is added.

In the past, diacylglycerol and monoacylglycerol are often treated as impurities which inhibit the crystallization of oil, see Yu Kagaku (Oil Chemist), 28, 700-708 (1979); and Oil Palm News, 22, 10-18 (1997). Those skilled in the art often consider diacylglycerol oil to be difficult to crystallize and dry fractionate without using any solvent or additive. Thus, those skilled in the art are constantly striving to provide a process to fractionate diacylglycerol oil to produce a product usable in cooking that is cost effective and efficient.

Summary of the Invention

The above and other problems are solved and an advance in the art is made by a method for dry fractionation of an oil composition in accordance with this invention. It is an advantage of a method in accordance with this invention that the method provides dry fractionation of an oil composition containing at least 80% by weight of diacylglycerol under controlled cooling and controlled temperature, into a solid fraction and a liquid fraction without using any solvent or additive. A second advantage of this invention is that a liquid fraction obtained in accordance with the method of the invention has an iodine value in the range of 55 to 60 and/or a solid fat content of 0.10 to 10.00% by weight, preferably in the range of 0.50 to 8.50% by weight, at a temperature of 35°C. The liquid fraction thus obtained preferably has a preferable texture and is suitable for use in solid fat application such as margarine, shortening, and other food products. In accordance with some embodiments of this invention, the method is performed in the following manner. The method begins by heating the oil composition to an elevated temperature. The oil composition is then cooled at a cooling rate of substantially 0.05°C/min to substantially 3.00°C/min to an end-temperature in a range of 30°C to 50°C. The oil composition is stirred during the step of cooling. The cooling and stirring of the composition produce crystal slurry. The crystal slurry is then fractionated at the end-temperature into a solid fraction and a liquid fraction.

In accordance with some embodiments of this invention the oil composition is a diacylglycerol enriched oil. In particular, in one of these embodiments, the diacylglycerol enriched oil is derived from palm oil.

In accordance with some embodiments of this invention, the stirring is carried out at a speed of approximately 30 to 110 rpm, preferably 90 to 110 rpm.

In accordance with some embodiments of this invention, the end-temperature in the cooling step is in the range of approximately 30°C to approximately 50°C. In accordance with other embodiments, the end-temperature of the cooling step is in a range of approximately 33°C to approximately 37°C. In accordance with some of the embodiments, the cooling rate in the cooling step is in a range of approximately 0.05°C/min to approximately 1.00°C/min.

In accordance with some embodiments of this invention, the resulting liquid fraction comprises low-melting diacylglycerol and a solid fat content. In accordance with some of these embodiments, the solid fat content at 35°C is at least 0.80% by weight of the liquid fraction. In accordance with other of these embodiments, the liquid fraction comprises a solid fat content of at least 0.50% by weight when the end- temperature is at approximately 35°C. In accordance with some embodiments of this invention, the fractionation of the crystal slurry is completed by performing filtration under pressure on the crystal slurry.

In accordance with some embodiments of this invention, the liquid fraction has an iodine value in the range of approximately 55 to approximately 60. In accordance with some of these embodiments, the liquid fraction has a solid fat content at 35°C in the range of approximately 0.50 to approximately 8.50% by weight.

Detailed Description of the Preferred Embodiments

The present invention relates to a method for dry fractionation of an oil composition containing at least 80% by weight of diacylglycerol under controlled conditions into a solid fraction and a liquid fraction. The oil composition used in the present invention is preferably derived from palm oil and/or its products.

The method of the present invention may be applied to both edible and non-edible vegetable oils, animal and marine fats, their fractionations and hydrogenated and interesterified derivatives and their constituent fatty acids, for example, tallow, palm, sunflower, safflower, groundnut, soybean and lauric oils.

In a preferred embodiment, the oil composition containing at least 80% by weight of diacylglycerol is prepared by mixing palm oil having the intended constitutive fatty acids with glycerol in the presence of a lipase to allow an ester exchange reaction to take place. The resultant reaction product obtained is then subjected to purification treatments, such as molecular distillation treatment, to obtain a desired oil composition containing at least 80% by weight of diacylglycerol. The amount of free fatty acid present in the oil composition is less than 1.0% by weight, and is preferably at most 0.5% by weight. The remaining components present in the oil composition include triacylglycerol in an amount of less than 2.0% by weight. Palm oil, such as refined bleached deodorized palm oil (RBDPO), is used in preparing the oil composition. However, one skilled in the art will recognize that other palm oil products and oil compositions derived from other sources may be used without departing from this invention. In accordance with one embodiment of this invention, an oil composition containing at least 80% by weight of diacylglycerol, prepared as described above, is heated to a temperature sufficient enough to cause all fat crystals to be destroyed, in a 1 -litre double-jacket crystallizer equipped with an anchor stirring blade. Preferably, the oil composition is heated to a temperature of at least 70°C to 90°C. The oil composition is stirred or agitated at a speed sufficient enough to destroy the fat crystals present in the oil composition. Preferably, the oil composition is stirred or agitated at a speed of 90 to 100 rpm. The oil composition is heated and stirred or agitated to obtain a homogeneous oil composition.

The resulting homogeneous oil composition is then cooled at a cooling rate of approximately 0.05°C/min to approximately 3.00°C/min, or more preferably approximately 0.05°C/min to approximately 1.00°C/min, while stirring the composition to deposit crystals comprising high-melting diacylglycerol. Preferably, the oil composition is stirred at a speed of 30 to 1 10 rpm and more preferably, at a speed of 90 rpm.

Preferably, the method of the present invention is carried out in situ during stirring or agitation. In the preferred embodiment, the oil composition is stirred continuously during heating the oil composition and cooling the oil composition until deposition (or crystallisation) of the crystals is completed. One skilled in the art will recognize that other stirring speeds may be employed while heating and cooling the oil composition without departing from this invention

The apparatus used in the method of the present invention preferably comprises a stirring chamber fitted with an anchor blade stirrer with a smooth profile and cooling means for cooling the contents of the chamber. Preferably, the cooling is applied through the walls of the chamber and the stirrer. In preferable embodiments, the stirrer does not scrape the walls of the cooling chamber as a stirrer that scrapes the walls of the chamber does not provide homogeneous agitation of the composition. The oil composition is agitated during cooling to form large crystals with a high efficiency of filtration.

The cooling rate is affected by the temperature differential between the cooling surface of the apparatus and the oil material. Large temperature differential promotes rapid cooling but with formation of micro-crystalline growth. Small temperature differential, on the other hand, produces larger crystals but at a much slower rate. Thus, the exact cooling rate within the desired range is left as a design choice to those skilled in the art to account for variations in the desired resulting product and production facilities. Temperature differentials specified in this specification are measured proximate the centre of the liquid. A temperature differential of approximately 1°C to approximately 20°C, or more preferably approximately 1°C to approximately 3°C, is preferably maintained between the coolant and the body of the oil composition undergoing the cooling, at least until the crystals appear. Thereafter, a higher differential may be provided. However, the differential preferably should not exceed approximately 25°C and more preferably be in a range of approximately 10°C to approximately 20°C.

The oil composition of the present invention is cooled until the oil composition reaches a desired end-temperature in the range of approximately 30°C to approximately 50°C; or preferably approximately 33°C to approximately 37°C at which the crystals are fully deposited, forming crystal slurry. The crystal slurry is fractionated into a solid fraction and a liquid fraction at the desired end-temperature. In the preferred embodiment, fractionation is carried by a method of filtration under pressure. The pressure and duration employed in the filtration method is approximately 2 bar (200kPa) for at least 10 minutes, approximately 4 bar (400 kPa) for at least 10 minutes, or approximately 6 bar (600kPa) for at least 10 minutes.

The solid fraction obtained by the method in accordance with this invention comprises high-melting diacylglycerol and the liquid fraction obtained comprises low- melting diacylglycerol.

The liquid fraction obtained by the method in accordance with the invention preferably has a solid fat content at 35°C of less than 10% by weight. The liquid fraction is suitable for use in solid fat application such as margarine, shortening, or other food products. Apart from the low-melting diacylglycerol, the liquid fraction also contains a relatively large amount of oleic acid in the range of 45% to 50% by weight, resulting in a higher iodine value in the range of 55 to 60 in comparison to the commercial solid fat products.

The method in accordance with the present invention allows an oil composition enriched with diacylglycerol to be readily fractionated by employing controlled cooling and controlled temperature conditions in fractionating the oil composition without using any solvent or additive. The method provides separation efficiency and reducing fractionation costs. The method is also more environmentally friendly as compared to solvent fractionation processes. The following Examples and Comparative Examples further illustrate the present invention in detail but are not to be construed to limit the scope thereof. EXAMPLE 1

Margarine was produced from a fat blend consisting of 91 % by weight of a mixture of palm oil and palm stearin (93:7) and 9% by weight of palm kernel oil. A w/o emulsion was produced from 80% by weight of the fat blend and 20% by weight of an aqueous phase containing 2% salt, 0.2% Myverol, 0.0055% flavour and 0.032% carotene.

The emulsion was fed through a rotator to obtain a margarine having the properties as Comparative 1.

Shortening was produced from a fat blend consisting of 60% by weight of palm oil and 40% by weight of palm stearin with properties of Comparative 2.

Table 1

Iodine Fatty acid Solid fat content (%) Value composition (%)

(Wij's) C16 C18:1 20°C 30°C 35°C

Comparative 47.78 43.86 36.07 30.87 12.19 7.55

1

Comparative 44.90 51.14 34.57 48.54 23.25 15.60

2

EXAMPLE 2 After a 15kg pilot plant reactor was charged with raw oil (10kg) as in Table 2, glycerol (10%) and 1 ,3-position-selective, immobilized lipase ("Novozymes 435", product of Novo Nordisk Bioindustry Co.; 5%) were mixed to conduct an esterification reaction for 6 hours under conditions of 70°C. The resultant reaction product was subjected to molecular distillation treatment to obtain a partial acylglycerol-containing oil composition having a composition shown in Table 3. The diacylglycerol oil, with properties given in Table 3, was transferred to a crystallizer and heated to 70°C thereby preparing uniform liquid, as a whole. Thereafter, the liquid was cooled to a desired end-temperature at a cooling rate of 0.5°C/min and stirred at a speed of 5 90rpm.

The resultant crystal slurry was then fractionated into a solid fraction and a liquid fraction by pressure filtration method. The properties of the liquid compositions obtained thereto are shown in Table 4.

Examples 1 to 5 are all liquid oil compositions, and deposition of crystals was observed when the oil compositions were left at 20°C. Examples 1 and 2 are completely melted at body temperature (35°C) while Examples 3, 4 and 5 completely melted at above body temperature. As compared to Comparative Example 1 which has a solid fat content of at least 7.55% by weight at 35°C, Examples 1 to 4 have a lower solid fat content of at least 0.78% by weight and at most 2.82% by weight at 35°C. Thus, Examples 1 to 4 provide better mouth-feel characteristics which are important in solid fat application such as margarine, shortening and other food products. Furthermore, the degree of unsaturation of the liquid fraction obtained by the method in accordance with the present invention is higher than the commercial solid fat products due to the high content oleic acid of 45% to 50% by weight present in the liquid fraction. Thus, the liquid fraction obtained by the method in accordance with the present invention provides health benefits such as lowering of body fat level. Table 2

Composition (%) Iodine Fatty acid Solid fat content (%)

Raw oil Value composition (%)

FFA MG DG TG (Wij's) C16 C18:1 20°C 30°C 35°C

RBDPO 0.024 2.01 97.99 52.72 43.26 40.29 27.41 9.31 4.97

Table 3 Oil Composition (%) Iodine Fatty acid Solid fat content (%)

Value composition (%)

FFA MG DG . TG (Wij's) C16 C18:1 20°C 30°C 35°C

Diacylglycerol oil 0.16 - 97.89 2.64 49.86 44.08 39.86 34.70 22.09 19.00

Table 4

End Composition (%) Iodine Fatty acid Solid fat content (%)

Temp Value composition

(°C) (Wij's) (%)

FFA MG DG TG C16 C18:1 20°C 30°C 35°C

Example 1 30 0.30 96.23 3.78 59.97 33.53 49.1 1 22.13 2.01 0.90

Example 2 35 0.25 96.13 3.88 59.74 34.31 48.35 24.16 1.59 0.78

Example 3 40 0.21 96.42 3.57 59.73 34.89 47.81 24.73 3.71 2.42

Example 4 45 0.18 90.72 9.30 57.64 36.73 46.22 23.83 4.61 2.82

Example 5 50 0.28 96.72 3.27 55.41 38.65 44.55 31.27 11.34 8.32

EXAMPLE 3

5

Using the same diacylglycerol oil as in Example 2, crystallization to an end- temperature of 35°C was performed with stirring speed of 90 rpm using different cooling rate. The resultant crystal slurry was fractionated into a solid fraction and a liquid fraction by pressure filtration method. The properties of the liquid compositions 10 obtained are shown in Table 5.

Examples 6 to 12 are all liquid oil compositions, and deposition of crystals was observed when the compositions were left at 20°C. The solid fat content increases as the cooling rate increased from 0.05°C/min to 2.00°C/min (Examples 6 to 10), 15 resulted in higher solid fat content. However, at a cooling rate of 2.50°C/min

(Example 6), the solid fat content is reduced and increases again as the cooling rate increases to 3.00°C/min (Example 7).

Examples 6, 7 and 8 have a solid fat content of almost zero at 35°C, hence providing 20 better mouth-feel characteristics as compared to commercial solid fat products such

as margarine, shortening and other food products. The degree of unsaturation of Examples 6 to 12 is also high, ranges from 57 to 58, as compared to Comparative Examples 1 and 2. Table 5

Cooling Composition (%) Iodine Fatty acid Solid fat content (%) rate Value composition

(°C/min) (Wij's) (%)

FFA MG DG TG C16 C18:1 20°C 30°C 35°C

Example 6 0.05 0.051 0.30 78.04 21.66 58.83 34.98 47.10 18.87 2.81 0.48

Example 7 0.50 0.051 0.40 78.06 21.54 58.44 34.44 47.53 18.65 2.86 0.50

Example 8 1.00 0.051 0.25 68.00 31.75 58.45 35.27 46.91 15.61 2.84 0.64

Example 9 1.50 0.052 0.40 77.66 21.94 58.38 35.60 46.59 20.35 5.23 2.30

ExamplelO 2.00 0.051 0.25 80.34 19.41 57.32 37.19 45.28 22.11 7.94 4.82

Example 2.50 0.051 0.40 78.59 21.01 58.19 36.12 46.17 20.80 5.55 2.60

1 I 1 I

Example 3.00 0.052 0.32 79.30 20.38 57.17 36.35 45.94 21.78 6.63 3.50

As described above, according to the present invention, oil composition containing at 5 least 80% by weight of diacylglycerol can be readily fractionated into a solid fraction

and a liquid fraction by varying the end-temperature and/or the cooling rate, at which the liquid fraction can be used to prepare a fat blend with good mouth-feel characteristics.

10 The above is a description of the subject matter the inventors regard as the invention

and is believed that others can ahd will design alternative processes that include this invention based on the above disclosure.

Claims

CLAIMS:

1. A method for fractionating an oil composition containing at least 80% by weight of diacylglycerol, comprising:

heating the oil composition to an elevated temperature;

cooling the oil composition at a cooling rate of 0.05°C/min to 3.00°C/min to an end-temperature in a range of 30°C to 50°C;

stirring the oil composition during the step of cooling wherein the cooling and stirring produce a crystal slurry; and

fractionating the crystal slurry at the end-temperature into a solid fraction and a liquid fraction.

2. The method according to claim 1 , wherein the oil composition containing at least 80% by weight of diacylglycerol is derived from palm oil.

3. The method according to claim 1 , wherein the stirring is carried out at a speed of 30 to 1 10 rpm.

4. The method according to claim 1 , wherein the end-temperature is in the range of 30°C to 35°C.

5. The method according to claim 1 , wherein the oil composition is cooled at a cooling rate of 0.05°C/min to 0.50°C/min.

6. The method according to claim 1 , wherein the liquid fraction comprises low- melting diacylglycerol and a solid fat content wherein the solid fat content at 35°C is at least 0.80% by weight of the liquid fraction.

7. The method according to claim 6, wherein the solid fat content at 35°C is at least 0.50% by weight of the liquid fraction.

8. The method according to claim 6, wherein the solid fat content at 35°C is in the range of 0.50% to 8.50% by weight of the liquid fraction.

9. The method according to claim 1 , wherein fractionating of the crystal slurry comprises:

performing filtration under pressure on the crystal slurry.

10. The method according to claim 1 , wherein the liquid fraction has an iodine value in the range of 55 to 60 when the end-temperature is in the range of 30°C to 50°C.

11. The method according to claim 1 , wherein the liquid fraction has an iodine value in the range of 55 to 60 when the end-temperature is in the range of 33°C to

37°C.

12. A liquid fraction obtainable according to claim 1 , wherein the liquid fraction has an iodine value in the range of 55 to 60 and/or a solid fat content at 35°C in the range of 0.50 to 8.50% by weight of the liquid fraction.

13. The liquid fraction according to claim 12, wherein the liquid fraction is obtained by fractionating the crystal slurry at the end-temperature in the range of 30°C to 50°C.

14. The liquid fraction according to claim 12, wherein the liquid fraction is obtained by fractionating the crystal slurry at the end-temperature in the range of 33°C to 37°C.