SK133097A3 - Separation method for solid fat material from partialy crystallized palm oil - Google Patents

Abstract

Fractionation of palmkernel oil using stirred crystallisation with a separation efficiency of more than 70 % by employing a sucrose polyester as a crystallisation modifying substance.

Description

A process for separating a solid fat material from a partially crystallized palm kernel oil

Technical field

The invention relates to a process for the fractionation of triglyceride oils, in particular lauric oils.

BACKGROUND OF THE INVENTION

The fractionation (fractional crystallization) of triglyceride oils is described by Gunston, Harwood and Padley in The Lipid Handbook, edition 1986, p. 213 to 215. Triglyceride oils are generally mixtures of different triglycerides with different melting points. The present invention relates to a specific lauric oil - palm kernel oil. The mixture of triglyceride oils may be treated, for example, by fractionation to give fractions with different melting points or solubilities.

One fractionation method is the so-called dry fractionation process, which involves cooling the oil until it crystallizes and separating the crystalline phase from the liquid phase. The liquid phase is referred to as the olein fraction, while the solid phase is referred to as the stearin fraction.

The phase separation is usually carried out by filtration, optionally by some method of applying pressure.

The main problem associated with separation in the dry fractionation process is the inclusion of a fairly large amount of liquid olein fraction into the separated stearin fraction. The olein fraction is included in the inter- and intracrystalline space of the crystalline mass of the stearin fraction. Therefore, the separation of the solid fraction from the liquid fraction is only partial.

The solids content of the stearin fraction is referred to as separation efficiency. In dry fractionation, the efficiency rarely exceeds 50 to 60%. This is unfavorable both for stearin quality and for olein yield. For a related solvent fractionation in which the fat to be fractionated crystallizes, for example, from a hexane or acetone solution, the separation efficiency can be up to 95%.

However, dry fractionation is a process that is more economical and more environmentally friendly than solvent fractionation. Increasing the separation efficiency of the dry fractionation is therefore highly desirable, especially for the commercially important palmoy oil.

For co-crystallization, it is known to add to the crystallizing oil a substance which is commonly referred to as a crystallization modifier. The presence of small amounts of such a substance in a refrigerated oil may accelerate, retard or stop crystallization. In some situations, the above substances are more accurately referred to as crystal habit modifiers. Known crystallization modifiers are, for example, the sucrose fatty acid esters described in US 3,059,010, US 3,059,011, JP 05/125389 and JP 06/181686 and the fatty acid esters of glucose and its derivatives described in US 3,059,011. These crystallization modifiers are effective in increasing the crystallization rate.

Other crystallization modifiers, for example as described in US 3,158,490 when added to cooking oils, have the effect of preventing or at least retarding solid fat crystallization. Other types of crystallization modifiers, particularly referred to as crystal habit modifiers, are often used as an additive to mineral fuel oils in which waxes are prone to crystallize at low temperatures. US 3,536,461 discloses the addition of a crystal habit modifier to fuel oil, with the effect that the temperature of the cloud point (or pour point) is reduced enough to prevent precipitation of the crystals. Alternatively, the formation of such different crystals is induced which, when formed, pass through the fuel filters and do not clog them. Other crystal habit modifiers are even capable of altering the habit of crystallized triglyceride fat crystals in such a way that, after crystallization, the crystals can be effectively separated from the liquid olein phase. Publications describing such crystal habit modifiers are, for example, GB 1,015,354, US 2,610,915, co-pending PCT application WO 95/04122, US 3,059,008, US 3,059,009 and US 3,059,010.

The separation efficiency also depends on the crystallization method, which may be static or with stirring. Often good results are obtained with static crystallization rather than with stirring crystallization. In view of the cost of the crystallization process, however, stirring crystallization is preferred.

Palm kernel oil crystallizes in the shape of needle-like crystals. The resulting crystalline agglomerates (see Fig. IA) readily include olein. Fractionation by crystallization with agitation is not possible because the hydrodynamic shear can break up the needles and produce a crystallisation slurry that cannot be separated into the stearin and olein phases. The stationary crystallization (static process) produces large, flaky crystals which can be separated provided a high pressure mode is used at a pressure of 2.5 to 3.0 MPa. Therefore, fractionation of palm kernel oil is only possible in a static arrangement which is very laboriously carried out. There is an urgent need for an effective crystallization modifier that allows fractionation with agitation.

SUMMARY OF THE INVENTION

It has been found that palm kernel oil can be crystallized by a process using agitation so that the stearin phase and the olein phase can be separated. Crystallization produces large and non-porous spherulites that are readily separated and - as when working in a static configuration - the separation efficiency is greatly increased. Accordingly, the present invention relates to a process for separating a solid fat material that crystallizes from palm kernel oil, comprising the steps of:

a. heating the oil until a substantial amount of solid triglycerides is no longer present in the oil,

b. cooling and crystallizing the triglyceride oil resulting in a solid stearin phase in addition to the liquid olein phase; and

c. obtaining the stearin phase by separating it from the olein phase, wherein a crystallization modifier is added to the triglyceride oil or to a solution of the triglyceride oil in an inert solvent prior to crystallization, characterized in that the crystallization is carried out with stirring.

The palm kernel oil to be fractionated is mixed with the crystallization modifier (additive) before crystallization commences, preferably before the oil is heated or dissolved in the solvent so that all the solid triglyceride fat and preferably also the modifying agent is liquefied.

The oil or solution is cooled to the selected crystallization temperature. A suitable temperature range is 15 to 35 ° C. Each temperature includes a specific composition of the olein and stearin phases.

The crystallization proceeds at the selected temperature until the crystallized oil stabilizes with a constant solid phase content. When more solid phase is required, the crystallization time is increased and the temperature is lowered. Typical times range from 4 to 16 hours. During crystallization, the oil is stirred, for example with a frame mixer.

The additive is a sugar polyester of fatty acids. Suitable polyesters are selected from the group consisting of sucrose polylaurane (100% laurate), sucrose polyester (75% laurane, 25% palmitate), sucrose polyester (50% laurane, 25% palmitate, 25% stearate), sucrose polyester (25% laurate, 35% palmitate, 40% stearate), sucrose polyester (75% caprate, 25% palmitate), sucrose polyester (75% myristate, 25% palmitate) and sucrose polypalmitate ( 100% by weight of palmitate), wherein the ratios are given in percent by weight. A sucrose polyester in the context of the present invention refers to a sucrose ester having on average at least four, preferably five to six, of the eight es5 hydroxyl groups modified with one or more types of fatty acids. The ester can be obtained by well known conventional procedures, such as esterification of sucrose with fatty acids or a mixture of fatty acids or reactive fatty acid derivatives. Sucrose with more than four free hydroxyl groups has insufficient oil solubility.

The sucrose polylaurane as mentioned herein is a highly esterified (50-100%) sucrose ester with a lauran content of 95% by weight. It is a readily available commercial product (e.g. Ryoto Sugar Ester L195, ex. MITSUBISHI).

The stearin and olein phases may be separated by filtration, but a high pressure membrane filter press is used to effectively separate the solid from the liquid phase. Suitable pressures are 0.3 to 5 MPa for 20 to 200 minutes. However, the invention allows low or moderate pressure. At a pressure of 0.6 to 1.2 MPa, obtaining a suitable separation of the stearin phase from the olein phase typically takes about 30 to 60 minutes.

The solids content of the crystallization slurry prior to separation and the obtained stearin phase after separation is measured by the known pulse NMR method (Fette, Seifen, Anstrichmittel 1978, 80, No. 5, pp. 180-186).

It is believed that the effect of the invention is due to a change in the crystalline structure or habitus of the crystalline stearin due to the additive. These can interfere in different ways with the growth of different crystal shapes.

In microscopic observation (see Fig. 1B), the effect of the additive shows that the crystals and crystalline aggregates formed in the oil are remarkably different from those obtained without the crystallization modifier (Fig. 1B). Instead of fragile acicular crystals, large and non-porous spherulites are formed. Since the stearin fraction with such crystals retains less olein fraction, also in low or light pressure filtration, the altered crystallization leads to a significant increase in separation efficiency and allows crystallization with agitation.

Although the invention is useful for solvent fractionation or detergent fractionation, the process is preferably performed as a dry fractionation process.

The sucrose polyester is suitably used in an amount of 0.005 to 2% by weight based on the total weight of the oil. A useful amount is about 1% by weight.

The invention will be illustrated by the following examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A shows agglomerates of acicular crystals of palm kernel oil obtained by static crystallization without additive.

Figure 1B shows the spherulites of palm kernel oil crystals obtained by crystallization under stirring in the presence of sucrose polylaurate.

DETAILED DESCRIPTION OF THE INVENTION

Examples 1 and 2

A sample containing 1000 g of palm kernel oil (neutralized, bleached, deodorized) and 10 g (1% by weight) of sucrose polylaurate was prepared. The sample was heated and stirred at 65 ° C until completely liquefied (containing no solid) and then cooled slowly. Crystallization was carried out in a static (0 οΐ / min) arrangement at the selected temperature of 23 ° C until a constant solid phase content was reached. The sample was filtered and pressurized at 12 bar for 30 minutes. After filtration and compression, the solid phase content (SE-separation efficiency) of the cake was measured by NMR. For comparison, fractionation was repeated, except that no sucrose polylaurane was added.

In Example 2, palm kernel oil was fractionated by the same procedure as described above, but in an agitated arrangement (5 rpm).

Examples 3 to 8

The dry fractionation process of Example 2 was repeated with various sucrose polyesters. Each experiment was performed with and without a crystallization modifier. Table I shows the SE and the relative improvements caused by the modifier.

The crystal habit modifiers used are:

# 3 sucrose polyester (75% laurane, 25% palmitate), # 4 sucrose polyester (50% laurane, 25% palmitate, 25% stearate), # 5 sucrose polyester (25% laurane, 35% wt palmitate, 40% stearate), # 6 polyester of sucrose (75% by weight of caprate, 25% by weight of palmitate), # 7 polyester of sucrose (75% by weight of myristan, 25% by weight of palmitate) and # 8 polypalmitate of sucrose, where ratios are expressed in weight percent.

The results in Table I show that the addition of various sucrose polyesters allows the fractionation of palm kernel oil with mixing with a surprisingly high separation efficiency.

Table I

# CHM r / min C SE δ 1 sucrose polylaurate 0 0.0 46 +59 1.0 73 2 sucrose polylaurate 5 0.0 n. d. 1.0 71 ++ 3 Sucrose polyester (75% lauran) 25% palmitate) 5 0.0 n. d. 1.0 69 ++ 4 sucrose polyester (50% lauran) 25% palmitate 25% stearate) 5 0.0 n. d. 1.0 73 ++ 5 sucrose polyester (25% lauran) 35% palmitate 40% stearate) 5 0.0 n. d. 1.0 73 ++ 6 Sucrose polyester (75% caprate) 25% palmitate 5 0.0 n. d. 1.0 60 ++ 7 Sucrose polyester (75% myristan) 25% palmitate 5 0.0 n. d. 1.0 72 ++ 8 polypalmitate sucrose 5 0.0 n. d. 1.0 48 ++

c in wt. rpm SE in mass δ in%

n. d.

% crystallization modifier concentration stirrer speed% separation efficiency increase SE due to blank test not done: impossible solid / liquid phase mo- ¢ / separation

Claims (5)

PATENT CLAIMS A method of separating a solid fat material from a partially crystallized palm kernel oil, comprising the steps of: a. heating the oil until a substantial amount of solid triglycerides is no longer present in the oil, b. cooling and crystallizing the triglyceride oil resulting in a solid stearin phase in addition to the liquid olein phase; and c. obtaining the stearin phase by separating it from the olein phase, wherein crystallization modifier is added to the triglyceride oil or to a solution of the triglyceride oil in an inert solvent prior to crystallization, characterized in that the crystallization is carried out with stirring and the process is used as a dry fractionation process. The method of claim 1, wherein the modifying agent is sucrose polyester. The method of claim 2, wherein the sucrose polyester is selected from the group consisting of sucrose polylaurane (100% lauran), sucrose polyester (75% lauran, 25% palmitan), sucrose polyester (50% lauran) , 25% w / w palmitate, 25% w / w stearate), sucrose polyester (25% w / w laurane, 35% w / w palmitate, 40% w / w stearate), sucrose polyester (75% w / w caprate, 25% w / w palmitate), sucrose polyester (75% w / w % myristate, 25% palmitate) and sucrose polypalmitate (100% palmitate), wherein ratios are indicated in percent by weight. Method according to claim 1 or 2, characterized in that the sucrose polyester has an average es10 degree of degree of 50 to 100%. Process according to claim 1 or 2, characterized in that the sucrose polyester is used from 0.005 to 2% by weight of the total amount of oil in the amount of