AU709185B2 - Fractionation of triglyceride oils - Google Patents

Description

(12) PATENT (11) Application No. AU 199887156 B2 (19) AUSTRALIAN PATENT OFFICE (10) Patent No. 709185 (54) Title Fractionation of triglyceride oils (51) 6 International Patent Classification(s) C11B 007/00 (21) Application No: 199887156 (22) Application Date: 1998.09.29 Priority Data (31) Number (32) Date (33) Country 93305924 1993.07.27 EP (43) Publication Date: 1998.12.03 (43) Publication Journal Date 1998.12.03 (44) Accepted Journal Date 1999.08.26 (62) Divisional of: 199474941 (71) Applicant(s) Unilever PLC (72) Inventor(s) Marcelle Van Den Kommer; Paul Raymond Smith; Adrianus Visser; Cornelis Winkel; Deryck Jozef Cebula (74) Agent/Attorney UNILEVER AUSTRALIA LIMITED,B F Jones,Private Mailbag 2,EPPING NSW 2121

AUSTRALIA

PATENTS ACT 1990

ORIGINAL

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COMPLETE SPECIFICATION STANDARD PATENT TITLE OF INVENTION FRACTIONATION OF TRIGLYCERIDE OILS Name and Address of Applicant: UNILEVER AUSTRALIA LIMITED of 20-22 CAMBRIDGE STREET, EPPING NSW 2121 The following statement is a full description of this invention, including the best method of performing it known to me:- 1 FRACTIONATION OF TRIGLYCERIDE OILS

DESCRIPTION

The present invention is concerned with a process for fractionating triglyceride oils.

The fractionation (fractional crystallisation) of triglyceride oils is described by Gunstone, Harwood and Padley in The Lipid Handbook, 1986 edition, pages 213-215. Generally triglyceride oils are mixtures of various triglycerides having different melting points. Triglyceride oils may be modified e.g. by separating from them by crystallisation a fraction having a different melting point or solubility.

One fractionation method is the so-called dry fractionation process which comprises cooling the oil until a solid phase crystallises and separating the crystallised phase from the 15 liquid phase. The liquid phase is denoted as olein fraction, while the solid phase is denoted as stearin fraction.

The separation of the phases is usually carried out by filtration, optionally applying some kind of pressure.

20 The major problem encountered with phase separation in the dry 9 fractionation process is the inclusion of a lot of liquid olein fraction in the separated stearin fraction.

The olein fraction is thereby entrained in the inter- and intracrystal spaces of the crystal mass of the stearin fraction.

Therefore the separation of the solid from the liquid fraction is only partial.

The solids content of the stearin fraction is denoted as the separation efficiency. For the dry fractionation of palm oil it seldom surpasses 50 This is detrimental to the quality of the stearin as well as the yield of the olein.

For the related solvent fractionation process, where the fat to be fractionated is crystallised from a e.g. hexane or acetone solution, separation efficiencies may be up to Dry fractionation is a process which is cheaper and more environmentally friendly than solvent fractionation. For dry fractionation an increase of separation efficiency is therefore much desired.

It is known to interfere with the crystallisation by adding to a crystallising oil a substance which will be generally indicated as crystallisation modifying substance. The presence of small quantities of such a substance in the cooling oil may accelerate, retard or inhibit crystallisation.

In certain situations the above substances are more precisely indicated as crystal habit modifiers. Known crystallisation modifiers are e.g. sucrose fatty acid esters, described in US 3,059,010 and fatty acid esters of glucose and derivatives, described in US 3,059,011. These crystallisation modifiers are effective in speeding up the crystallisation rate but are 15 not reported to increase the separation efficiency. They do

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not even allude to such an effect.

Other crystallisation modifiers, e.g. as described in US 3,158,490 when added to kitchen oils have the effect that solid fat crystallisation is prevented or at least retarded.

20 Other types of crystallisation modifiers, particularly referred to as crystal habit modifiers, are widely used as an ingredient for mineral fuel oils in which waxes are prone to crystallize at low temperatures. US 3,536,461 teaches the addition of a crystal habit modifier to fuel oil with the effect that the cloud point (or pour point) temperature is lowered far enough to prevent crystal precipitation. Or, alternatively, the solids are induced to crystallize in a different habit so that the crystals when formed can pass fuel filters without clogging them. Other crystal habit modifiers are actually able to change the habit of the crystallized triglyceride fat crystals in a way such that after crystallization the crystals, the stearin phase, can be more effectively separated from the liquid phase, the olein phase.

Publications describing such crystal habit modifiers are e.g.

GB 1 015 354 or US 2,610,915 where such effect is accomplished by the addition of a small amounts of a polymerisation product of esters of vinyl alcohol or of a substituted vinyl alcohol.

US 3,059,008 describes the use of dextrin derivatives for the same purpose. However, these crystallisation modifying substances are still far from ideal. In the former case after three days of crystallization an increase in olein yield from 71% to only 82% was reported. Although such improvement may seem fair, a need exists for more powerful crystallisation modifying substances which act faster and in a dry fractionation environment and which deliver still better improvements in olein yield. The selection of such habit modifiers is a problem, because it is not possible to predict which substances will successfully comply with these requirements.

15 STATEMENT OF INVENTION 0 o S. Polymers have been found which are suited as crystallisation ~modifying substances. In contrast to modifiers of the prior art, the present ones greatly increase the separation 20 efficiency.

**Accordingly the invention relates to a process employing such modifiers for separating solid fatty material from a triglyceride oil, which comprises the steps A. heating the oil or a solution of the oil in an inert solvent until no longer a substantial amount of solid material is present, B. adding a crystallisation modifying substance to the oil or to the solution of the oil, C. cooling the oil resulting in crystallising a solid stearin phase besides a liquid olein phase and D. recovering the stearin phase by separating it from the olein phase, characterized in that the crystallisation modifying substance is inulin or phlein of which 5-100% of the hydroxyl groups on the fructose subunits are connected to (C8-C24) unbranched alkyl chains and 0-95% of the hydroxyl groups have been esterified with a (Cl-C8)-alkyl containing fatty acid, preferably acetic acid.

At microscopic inspection the effect of the presence of such crystallisation modifying substance is that in the oil crystals and crystal aggregates are formed which are conspicuously different from the crystals obtained without crystallisation modifying substance. These crystals and aggregates can be filtered more effectively since the stearin fraction retains less of the olein fraction even at low or moderate filtration pressure. The altered crystallisation results therefore in a considerable increase of the separation 15 efficiency.

The found crystallisation modifying substances belong to a group of polymers having a backbone-chain of which at least a part of the carton atoms are connected to unbranched (C8-C24)- 20 alkyl side-chains. The chain is composed of a string of fructose units to which the (C8-C24)-alkyl chains are attached.

The molecular formula of the found crystallisation modifying substance has a comb-shape appearance with "teeth" which may be located at various distances and may have various lengths.

DETAILS OF THE INVENTION The oil to be fractionated is mixed with the crystallisation modifying substance before crystallisation starts, preferably before the oil is heated so that all solid triglyceride fat and preferably also the modifying substance is liquified.

Then the oil is cooled to the chosen crystallisation temperature. A suitable crystallisation temperature for e.g.

palm oil is 15-35 0 C. By choosing a different temperature the composition of the olein and stearin phases may change.

Crystallisation proceeds at the chosen temperature until a constant solid phase content is reached. The crystallisation time varies depending on the desired solid phase content.

Usual times are in the range of 4-16 hours. During crystallisation the oil may be stirred, e.g. with a gate stirrer. But stagnant crystallisation sometimes gives the best separation efficiency.

For the separation for the solid phase from the liquid phase generally a membrane filter press is used, because it allows rather high pressures. Suitable pressures are 3-50 bar, to be exerted for about 20-200 minutes. However, even with a low or moderate pressure the staerin phase obtained according to the present invention is easily separated from the olein phase.

15 As a rule it takes about 30-60 minutes to have both phases properly separated.

The solids content of the crystal slurry before separation and of the separated stearin phase is measured according to the 20 known pulse NMR method (ref. Fette, Seifen, Anstrichmittel 1978, 80, nr. 5, pp. 180-186).

The crystallisation modifying substances which are suited for the process of the invention are derivates of inulin or phlein. Inulin is a polyfructose comprising a terminal glucose subunit where the subunits are mutually connected via a 0-1,2 glycosidic linkage. Phlein is a polyfructose comprising a terminal glucose subunit where the subunits are mutually connected via a 0-2,6 glycosidic linage.

Preferably 5-100% of the hydroxyl groups of the polyfructoses have been esterified with a (C8-C24)-alkyl containing fatty acid, preferably palmitic acid and/or stearic acid, and 0-95% of the hydroxyl groups have been esterified with a (C1-C8)alkyl containing fatty acid, preferably acetic acid.

6 A preferred polymer from the previous group is an inulin fraction, having in non-esterified form a molecular weight of 4000-5500 Da, of which per subunit 1.5-3 hydroxyl groups have been esterified with myristic, palmitic acid or stearic acid, while the remaining hydroxyl groups are free or have been esterified with acetic acid.

By fully esterifying inulin with three palmitic acid per subunit molecules the molecular weight increases with a factor A particularly preferred group of crystallisation modifying substances is an inulin fraction, having in non-esterified form a molecular weight of 4000-5500 Da, of which per subunit 1.5-3 hydroxyl groups have been esterified with a mixture of 15 lauric and palmitic acid in a ratio of 9: 1 to 1: 9. This crystallisation modifying substance is particularly successful in stirred crystallisation.

The process of the invention preferably is carried out as a dry fractionation process, although the invention is useful too for solvent fractionation or detergent fractionation.

The process can be applied on triglyceride oils containing S relatively high melting fat such as palm oil, palm kernel oil, shea oil, coconut oil, cottonseed oil, butter oil, hydrogenated rapeseed oil, hydrogenated soybean oil or fractions of these oils or oils obtained from the previous oils by interesterification.

The process is particularly useful for fractionating palm oil.

The palm oil might be crude, but generally a refined quality is used.

The crystallisation modifying substance is suitably applied in an amount of 0.005-2 preferably 0.01-1 wt.% on the total amount of oil.

The invention comprises in particular the use as a triglyceride oil crystallisation modifying substance of all polymers as defined hereinbefore.

DRY FRACTIONATION OF PALM OIL Two samples were prepared each containing 1000 g of palm oil (neutralised, bleached, deodorised). The process is carried out as a common dry fractionation process, but to the first sample an inulin fraction fully esterified (DS=3) with palmitic acid and having as an ester a molecular weight of 27,000 Da was added as crystallisation modifying substance.

To the second sample no crystallisation modifying S substance was added. Both samples were heated at 70oC until 15 completely liquefied (no solid fat content) and then cooled in order to crystallise. Crystallisation proceeded without stirring (stagnant) at the chosen temperature of 23°C for 16 .hours until a constant solid phase content was reached. The S samples were pressed in a membrane filter for one hour. After filtration the separated fractions were weighted. The olein yield is the weight of the filtrate. The stearin yield is the weight of the crystal mass remaining on the filter. The yields of the measure stearin and olein fractions are given in Stable 1.

Table 1 Sample A Sample B wt.% modifier no modifier Temperature/ 0 C 23 23 Solid phase content slurry/% 13 13 Solid phase content cake/% 50 31 Olien yield/% 74 58

Claims (8)

1. Process for separating solid fatty material from a triglyceride oil, which comprises the steps a. heating the oil or a solution of the oil in an inert solvent until no longer a substantial amount of solid material is present, b. adding a crystallisation modifying substance to the oil or to the solution of the oil, c. cooling the oil resulting in crystallising a solid stearin phase besides a liquid olein phase and d. recovering the stearin phase by separating it from the olein phase, characterized in that the crystallisation modifying substance is a comb type polymer being inulin or phlein of which 5-100% of the hydroxyl groups on the fructose subunits are connected to (C8-C24) unbranched alkyl chains and 0-95% of the hydroxyl groups have been esterified with a (C1-C8)-alkyl containing fatty acid, preferably acetic acid.

2. Process according to claim 1, where the alkyl chains are connected to the polymer chain via an ester, an ester or an amide bridge.

3. Process according to claim 1, characterised in that the polymer is an inulin fraction having (without ester groups) a molecular weight of 4000-5500 Da of which per subunit 1.5-3 hydroxyl groups have been esterified with palmitic acid or stearic acid, while the remaining hydroxyl groups are free or have been esterified with acetic acid.

4. Process according to claim 1, characterised in that the polymer is an inulin fraction, having in non-esterified form a molecular weight of 4000-5500 Da of which per subunit 1.5-3 hydroxyl groups have been esterified with a mixture of lauric and palmitic acid in ratio of 9: 1 to 1: 9, while the remaining hydroxyl groups are free or have been esterified with acetic acid.

Process according to any one of claims 1-4, characterised in that it is applied as a dry fractionation process.

6. Process according to any one of claims 1-5, characterised in that the triglyceride oil to be fractionated is palm oil, palm kernel oil, shea oil, coconut oil, cottonseed 15 oil, butter oil, hydrogenated rapeseed oil, hydrogenated soybean oil or fractions of these oils or oils obtained from the previous oils by interesterification.

7. Process according to any one of claims 1-6, characterised 20 in that the crystallisation modifying substance is used in an amount of 0.005-2 preferably 0.01-1 wt.% on tthe total amount of oil. ago*

8. Use of an inulin or phlein polymer as defined in any one of the previous claims as a triglyceride oil crystallisation modifying substance. DATED qq SIGNED for and on behalf of UNILEVER PLC by Unilever Australia Limited F. J B. F. JONES, Com pny ecretary