GB2190095A - Method for purification of fats and oils - Google Patents

Abstract

A method for physical purification of crude fats and oils containing both free fatty acids and diglyceride components which comprises blowing steam into the fats and oils at a steam distillation temperature of not higher than 240 DEG C in a temperature rise stage to make the acid value of the fats and oils not more than 1, and then raising the temperature to a predetermined degree.

Description

SPECIFICATION Method for purification of fats and oils The present invention relates two a method for purification of fats and oils. More particularly, it relates to a method for preventing formation of isomers in a deodorization step during physical purification of crude fats and oils containing both free fatty acids and diglyceride components.

Heretofore, for purification of crude fats and oils, there have been employed so-called chemical purification wherein deacidification is carried out by neutralization with an alkali, and so-called physical purification wherein free fatty acids are removed by steam distillation in a deodorization step.

In chemical purification, generally, crude fats and oils are purified by treating fats and oils with warm water oran acid such as phosphoric acid for degumming; neutralizing the degummedfats and oilswith an alkali such as sodium hydroxide to remove free fatty acids for deacidification; treating the deacidification fats and oils with activated clay to absorb and remove coloring materials for bleaching; and then subjecting the bleached fats and oils to steam distillation to remove volatile materials causing order orflavorfor deodorization.On the other hand, in physical purification, degum med crude fats and oils are subjected to dehydration and bleaching and then the fats and oils thus treated are subjected to steam distillation to remove both volatile materials causing odourorflavor and freefatty acids. The step of deacidification with an alkali in chemical purification is omitted in physical purification.

Although chemical purification is more popularthan physical purification,the latter is also often employed because it has various advantages in addition to the steps thereof being simplerthan those of the former. For example, loss of neutral fats and oils is decreased because of omission of a deacidification step, and fatty acids can be effectively utilized. Further, problems in drainage can be reduced.

However, physical purification is not always a preferred purification method for fats and oils such as hard butter wherein the amount of isomers oftriglycerides significantly affects quality thereof, although such purification does not cause any trouble in purification for fats and oils such as cooking oils (e.g., salad oil, frying oil, etc.) and those for margarine or shortening and the like wherein isomers oftriglycerides do not affect quality thereof. That is, there is a correlation between the amount of isomers oftriglycerides and a cooling curve and, as the amount of isomers increases, the curve shifts toward the low temperature side and its maximum temperature is lowered.In fats and oils used for chocolate production, it is well known that, as the maximum temperature of a cooling curve becomes lower, tempering properties of chocolate are deteriorated and this is undesirable. Forexample, when fats and oils containing as their main triglycerides 2-unsaturated-l 3-disaturated triglycerides (hereinafter referred to as SUS) are purified with physical purification, the amount of isomers such as 2-disaturated-3 (or 1)-unsaturated triglycerides (hereinafter referred to as SSU) increases in comarison with chemical purification. As a result, the quality as a hard butter of the product thus purified is reduced because of a drop of the maximum temperature in the cooling curve as mentioned above.

The present inventors have studied intensively to solve the above problems in physical purification offats and oils, and have found thatfree fatty acids and diglyceride components have an important influence in the deodorization step. Further, it has been found that, when free fatty acid components are distilled off atthe initial stage of the deodorization step, the problems can be solved or mitigated.

According to the present invention, there is provided a method for physical purification of crude fat or oil containing both free fatty acids and diglyceride components, which comprises blowing steam into thefat oroil at a steam distillation temperature of not higher than 240'C while raising the temperature to make the acid value of the fat or oil no more than 1, and then raising the temperature to a predetermined degree.

The fats and oils to be subjected to the method of the present invention are not limited to specific ones, but the method of the present invention is particularly useful for natural or synthetic fats and oils containing as the main triglycerides 2-unsaturated-l ,3-disaturated triglycerides (SUS) which can be used as starting materials for hard butter products, or their modified products such as fractionated fats and oils. Examples of these fats and oils include paim oil, shea fat, mango oil, sal fat, kokum fat, Borneo tallow, illippe fat, mowrah fat, cacao fat, enzymatically interesterified fats and oils, and theirfractionated fats and oils.

In general, for carrying outthe method of the present invention, firstly, crude fat or oil is degummed by contacting it with warm water or an acid, for example, an inorganic acid, e.g. phosphoric acid, or an organic acid, e.g. citric acid. Generally, after dehydration, the fat or oil is then bleached with activated clay under reduced pressure. Thereafter, deodorization is carried out by steam distillation, generally under reduced pressure. In the present invention, it is important to remove free fatty acids in fats and oils as much as possible in the stage of steam distillation during which temperature rises.According to the present invention, steam is blown into the fats and oils at not higherthan 240"C in atemperature risestageto make the acid value ofthe fats and oils not more than 1 and then the temperature is raised to a predetermined degree to deodorize the fat or oil. Thereby, formation of isomers during the deodorization step can be inhibited.

Usually, in a commonly employed Girdlertype semi-continuous deodorization device, fats and oils are heated with steam to about 170'C in a lsttray undervacuum of2- 6 mmHg (usually, 2-3 mmHg) andthen heated with high pressure steam to about 250 - 260"C in a 2nd tray. Thereafter, steam is blown into the fats and oils in 3rd and 4th trays to distill offmaterialscausing odourorflavour. Then, the fats and oils are cooled to 50- 60"C in a 5th tray and are discharged to complete deodorization.

According to the present invention, as seen from the following Experiments, increase in the amount of isomers during purification of fats and oils takers place only in the deodorization step and it is significant in the presence of a relatively larger amount of both free fatty acids and diglycerides.

Experiment 1 Crude palm oil was dissolved in hexaneto prepare a hexane micelle of 20% oil content. The m iceile was passed through a silica gel column to effect absorption treatment. After hexane was removed,0.1 (% by weight based on the oil, hereinafter merely referred to as %) of phosphic acid was added. The mixturewas stirred with a homomixer at 85 - 900C for 3 minutes and centrifuged. Further, 5% of warm water was added and the mixture was stirred with a homomixer at 85 - 90"C for 3 minutes and centrifuged to effect degumming.

Then, according to a standard manner, alkaline deacidification was carried out by using 18 Baume degree sodium hydroxide solution. 2% of activated clay was added and the mixture was stirred at 11 0 for 10 minutes under reduced pressure of 5 - 10 mmHg to effect bleaching. The mixture was filtered and the resulting bleached oil was heated under reduced pressure of 2-3 mmHg.When the temperature reached 240 C, a small amount of steam was blown into the oil so that the oil was stirred and then 5% of steam was blown into the oil at about 260 over 90 minutes to effect steam distillation. Thereafter, the oil was cooled two complete deodorization.

Experiment2 The same procedure as in Experiment 1 was repeated exceptthat alkaline deacidification was omitted.

Experiment 3 (chemical purification) The same procedure as in Experiment 1 was repeated except that silica gel absorption treatment was omitted.

Experiment 4 (physicalpurification) The same procedure as in Experiment 1 was repeated exceptthat both alkaline deacidification and silica gel absorption treatment were omitted.

In each Experiment, the acid value, the diglyceride content and the isomer increase rate of the oil at each treatment step were determined. The isomer increase rate was calculated from the following equation.

Isomer (Amount of isomer (Amount of isomer increase= intreatedoil) - in crude oil) x 100 rate (%) (Amount of isomer in crude oil) The results are shown in Table 1.

TABLE 1 Isomer Diglyceride in crease Acid value content { /O) rate (%) Crude starting oil 6.87 5.6 0 Exp. 1 Oilafterabsorption 6.40 1.0 0.4 treatment Degummedoil 6.41 1.0 1.5 Deacidifiedoil 0.14 0.9 0.6 Bleached oil 0.14 0.8 0.9 Deodorized oil 0.04 1.2 9.1 Exp. 2 Oil after absorption 6.40 1.0 0.4 treatment Degummedoil 6.41 1.0 1.5 Deacidified oil Bleached oil 6.10 0.8 1.5 Deodorized oil 0.04 1.3 12.7 Isomer Diglyceride increase Acid value content (%) rate (%) Exp.3 Oil after absorption treatment Degummedoil 6.85 5.2 1.8 Deacidified oil 0.13 3.5 1.2 Bleached oil 0.10 3.4 1.7 Deodorized oil 0.05 3.5 13.6 Exp.4 Oil after absorption - - treatment Degummedoil 6.85 5.2 1.8 Deacidified oil - Bleached oil 6.83 5.5 1.7 Deodorized oil 0.05 5.7 26.9 As can be seen from Table 1, although the amount of isomers scarcely varies from the beginning to the bleaching step, it increases in the deodorization step.When both the acid value and the diglyceride content are low, the increase in the amount of isomers is relatively small (Experiment 1). And, when the acid value is high and the diglyceride content is low, orvice versa, the increase in the amount of isomers is also relatively small (Experiments 2 and 3). However, when both the acid value and the diglyceride content are high (Experiment4), the increase in the amount of isomers is significant in comparison with other experiments.

Thus, when either or both of the acid value and the diglyceride content are low, the increase in isomers caused by physical purification is about the same as that by chemical purification. However, as described hereinabove, when both the acid value and the diglyceride content are high, the increase in isomers is significant.

This increase in isomers becomes rapid in the initial stage of the deodorization step and, when the acid value is made not more than 1 by blowing steam into fats and oils atatemperature rise stage of not higherthan 240"C, the rapid increase in isomers can be prevented.

Experiment5 According to the same procedure as in Experiment 4, bleached oil was obtained from crude palm oil and it was heated under reduced pressure of 2 -3 mmHg. When the temperature reached 240"C, a minimum amount of steam was blown into the oil so that the oil was stirred and then thetemperaturewas raised to 260'Cand steam was blown into the oil to effect deodorization.

Experiment6 The same procedure was followed as in Experiment 5 except that blowing of steam was started at 180and then the temperature was raised to 2600C to effect deodorization.

In each Experiment, the acid value, the diglyceride content and the isomer increase rate ofthe oil at each temperature in the deodorization were determined. The results are shown in Table 2.

TABLE 2 Isomer Diglyceride increase Acid value content (%) rate (%) Crude starting oil 6.87 5.6 0 Exp. 5 reached to 2600C 3.90 5.5 3.5 after30rnin.at2600C 0.08 5.2 17.7 after90min.at260 C 0.04 5.4 25.0 after 150 min. at 260"C 0.04 6.1 38.7 after 270 min. at 260"C 0.03 6.6 52.2 Isomer Diglyceride increase Acidvalue \ content (%) rate (%) Exp. 6 reached to 1800C 6.77 5.4 1.2 reached to 210"C 4.58 5.3 1.8 reached to 240"C 0.80 5.4 2.1 reached to 260"C 0.45 5.5 2.5 after30min.at260 C 0.06 5.5 6.2 after90min.at260 C 0.04 5.6 13.4 As seen from Table 2, in the case that both the acid value and the diglyceride content are high when the temperature reaches 260"C, the increase in the amount of isomers after 30 minutes is significant (Experiment 5). However, when the acid value is made not more than 1 in temperature rise stage at not higher than 240"C, the rapid increase in the amount of isomers is not observed even in the initial stage of deodorization at 260"C.

Thus, as described hereinabove, when starting fats and oilsforthe production of hard butter products are purified by physical purification, the quality of hard butter products deteriorates because of the increase in the amount of isomers. However, according to the foregoing description, fats and oils in good quality can be obtained by physical purification which is more advantageous than chemical purification.

The following example further illustrates the present invention in detaii but is not to be construed to limitthe scope thereof. In the example, all "%'s" and "parts" are by weight unless otherwise stated.

Example Phosphoric acid (0.1% based on the oil) was added to crude palm oil (100 parts) having an iodide valueof 52.5, acid value of 6.89, diglyceride content of 5.5% and isomer content of 11.2%. The mixture was stirred with a homomixer at 85 - 90"C for 3 minutes and centrifuged. Further, 5% of warm water was added and the mixture was stirred with a homomixer at 85-90"C for 3 minutes and centrifuged to effect degumming. The oil was dehydrated by heating at 11 00C for 10 minutes under reduced pressure of 5 - 10 mmHg.Then activated clay (2% based onthe oil) was added and the mixture was stirred at 1 10'Cfor 10 minutes under reduced pressure of5-10 mmHg to effect bleaching. The bleached oil was heated under reduced pressure of 2 -3 mmHg. When the temperature reached 1 80"C, steam blowing was started and the temperature was further raised. 1% of steam was blown into the oil until the temperature was raised to 2400C and the temperature was further raised to 260 C.4% steam was blown into the oil at the same temperature over 90 minutes to effect steam distillation.

Thereafter, the oil was cooled to complete dedorization to obtain deodorized oil having an acid value of 0.04, diglyceride content of 5.6% and isomer content of 12.6%.

Claims (8)

1. A method for the physical purification of crude fat or oil containing both free fatty acids and diglyceride components, which comprises blowing steam into the fat or oil at a steam distillation temperature of not higherthan 240"chile raising the temperature to make the acid value of the fat or oil not more than 1,and then raising the temperature to a predetermined level.

2. A method according to claim 1, wherein the fat or oil is a natural or synthetic fat or oil containing asthe main triglycerides 2-unsaturated-1,3-disaturated triglycerides (SUS) which can be used as a starting material .or hard butter products, or a modified product thereof such as a fractionated fat or oil.

3. A method according to claim 2, wherein the fat or oil comprises palm oil, shea fat, mango oil, sal fat, kokum fat, Borneo tallow, illippe fat, mowrah fat, cacao fat, enzymatic interestified fat or oil, or a fractionated fat or oil thereof.

4. A method according to any one of the preceding claims, wherein the predetermined temperature is 260 C.

5. A method according to claim 1 and substantially as hereinbefore described.

6. A method for the physical purification of crude fat or oil substantially as hereinbefore described in the Example.

7. Fat or oil whenever purified using a method according to any one ofthe preceding claims.

8. Chocolate made with a fat or oil according to claim 7.