JP4064548B2 - Rice bran oil production method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for purifying rice bran oil, and more particularly to a deoxidation method for efficiently leaving ferulic acid derivatives such as oryzanol and tocopherols (hereinafter also referred to as phenolic substances) in fats and oils.
[0002]
[Prior art]
Ferulic acid esters such as oryzanol contained in rice bran oil are widely used in cosmetic materials and pharmaceutical raw materials as natural physiologically active substances. Tocopherols and tocotrienols also have oxidative stability and in vivo antioxidant activity of fats and oils. It is a substance that is attracting attention. As the rice bran oil refining method, conventionally, an alkali refining method in which free fatty acids are neutralized with an aqueous caustic soda solution and a distillation deoxidation method in which fatty acids are physically removed by steam are used. The former alkali refining method is a general method from the viewpoint of removing free fatty acids, as in the case of soybean oil and rapeseed oil. However, this method also removes phenolic substances such as oryzanol, which are originally relatively abundantly contained in rice bran oil at 1 to 3%, and whose antioxidant and bioactive functions are noted. In many cases, it becomes 2% or less, and some of the tocopherols are also decomposed. As for the latter method, it is expected from the principle that phenolic substances such as ferulic acid esters are sufficiently left in the oil and fat. Examples include the method described in JP-A-6-340889. Requires a new special apparatus to perform steam distillation, and it is feared that tocopherols are also distilled depending on conditions. In addition, in the case of the distillation deoxidation method, since it is generally a high temperature treatment (180 to 250 ° C.), sufficient pretreatment such as impurities such as phospholipids must be completely removed from the fats and oils due to oil quality problems. A process is required. Furthermore, even when both methods are used in combination, phenolic substances such as ferulic acid esters are removed by alkali purification. Fats and oils (acid value 10-30) with extremely high acid value such as rice bran crude oil have a large loss of neutral oil, and hexane and alcohol described in JP-B-55-41679 as an improved alkali refining method to avoid this. In this method, active ingredients such as ferulic acid esters are removed in the same manner as free fatty acids, and the solvent removal process is unavoidable and consumes a large amount of heat energy. . Japanese Patent Laid-Open No. 7-26288 describes a method for alkali refining of rice bran oil using an indicator on the acidic side. However, it is required to manage the end point of neutralization by sampling and titration analysis of deoxidized oil. Control is necessary and complicated.
A method of extracting and purifying phenolic substances such as ferulic acid ester from rice bran oil alkaline deoxidized oil paddy and adding it to rice bran oil is also found in patents, but a new facility separate from the oil refining facility Is required.
[0003]
[Problems to be solved by the invention]
Due to its chemical properties, phenolic substances such as oryzanol are transferred from a neutral oil phase to an aqueous phase in the presence of a strong alkaline aqueous solution. Therefore, in the conventional alkaline deoxidation method using a caustic soda aqueous solution, It was difficult to leave phenolic substances in neutral oil in abundance. An object of the present invention is a method for producing rice bran oil, which is enhanced in quality and nutrition by leaving the active ingredient originally contained in abundantly in rice bran oil by improving the refining method. This is clearly different from the method of adding. That is, the present invention relates to a method for deoxidizing rice bran oil, while reducing the free fatty acid to the required level, ferulic acid esters such as oryzanol, which have been removed at the same time, and partial decomposition and removal proceed in the subsequent purification step. Tocopherols are included in fats and oils in high yield to provide rice bran oil rich in functionality.
[0004]
[Means for Solving the Invention]
As a result of intensive studies, the present inventors have used a weakly alkaline aqueous solution without using special equipment as in the distillation deoxidation method, so that the neutralization and removal efficiency of free fatty acids is not reduced. The inventors have found a deoxidation method in which a large amount of oryzanol and tocopherols is contained therein, and have completed the present invention. In addition, according to the present invention, even if the alkali amount (Na ⁺ conversion) necessary for neutralizing free fatty acid is excessively added, the yield is hardly affected, and a sufficient amount of the desired phenolic substance is contained. Quality deoxidized oil was obtained. Further, it has been found that the weak alkaline deoxidized oil keeps the reduction rate of those phenolic substances low even after the subsequent decolorization and deodorization step.
That is, the present invention is characterized in that (1): In the alkaline refining of rice bran oil, oryzanol in the raw material oil is allowed to remain in an amount of 80% by weight or more using a weak alkaline aqueous solution in removing the free fatty acid contained therein. (2): The production of rice bran oil according to (1), wherein the total tocopherol content remains 70% or more of the raw material oil even after the deodorizing step of the alkaline refined oil of (1) Method. ; (3): The method for producing rice bran oil according to (1), wherein the weak alkaline aqueous solution is an aqueous solution prepared from one or more weak alkaline compounds.
In the present invention, the raw material oil means degummed rice bran oil. The deodorization step is a step of removing mainly low-boiling components, which is performed after the alkali refining and after the decolorization step.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Details of the present invention will be described below. The above-mentioned strong alkaline aqueous solution refers to a conventionally used aqueous solution of caustic soda, caustic potash, etc., and the weak alkaline aqueous solution is an aqueous solution according to claim 3, specifically, sodium carbonate, potassium carbonate, sodium phosphate. And an aqueous solution such as sodium citrate or an alkaline buffer such as potassium chloride / caustic soda. The pH during weak alkaline deoxidation is preferably 7.5 to 10, and if it exceeds 10, the phenolic substance is easily removed as soda oil and does not remain in the crude oil. On the contrary, on the acidic side, free fatty acids are not removed and the degree of purification is low. For example, when sodium carbonate is used, the concentration is preferably about 1.2 to 1.5 times that of conventional caustic soda. In addition, this method can be used in combination with a conventional alkali refining method using a strong alkaline aqueous solution such as a caustic soda aqueous solution. For example, deoxidation with a strong alkaline aqueous solution having an acid value equivalent to that of rice bran crude oil is used as a primary treatment, and after the subsequent secondary treatment, deoxidation with a weak alkaline aqueous solution is used.
It goes without saying that if the alkali of the primary treatment is excessively added, the intended rice bran oil cannot be obtained because it becomes the same as the conventional refining method.
Oryzanol is a general term for ferulic acid derivatives, and is mainly an γ-oryzanol ester compound with an alcohol having ferulic acid as a core, such as triterpene alcohol, sterol, higher aliphatic alcohol, and linear alcohol. It is an ester compound of alcohols and ferulic acid. Tocopherols refer to tocopherol and tocotrienol.
The conditions such as the quality of the rice bran oil to be used, the structure of the apparatus, the processing temperature, and the processing time are not limited to the following. All percentages are by weight.
[0006]
【Example】
Example 1
36.1 ml of 32% sodium carbonate aqueous solution was added to 0.40 kg of degummed rice bran oil (acid value 24, γ-oryzanol content 1.9%). The pH at this time was 8.0 using the universal test paper. Alkali purification was carried out under the conditions of stirring at 85 ° C. and 180 rpm for 20 minutes, and after washing with water, 0.27 kg of deoxidized oil was obtained by centrifugation. The γ-oryzanol content of this deacidified oil as determined by spectroscopy (UV320 nm) was 1.9%.
[0007]
Comparative Example 1
All were carried out under the same conditions except that the alkaline solution of Example 1 was replaced with a 24% aqueous solution of sodium hydroxide (the molar concentration of Na ⁺ was the same as in the case of sodium carbonate of Example 1). The pH during alkali purification was 10.5. After washing with water, 0.24 kg of deoxidized oil was obtained by centrifugation. The deoxidized oil had an oryzanol content of 0.5%.
[0008]
Example 2
67 ml of 32% sodium carbonate aqueous solution was added to 0.40 kg of degummed rice bran oil (acid value 28, oryzanol content 1.3%). The pH at this time was 8.5 using a universal pH test paper. Alkali purification was performed under the conditions of 85 ° C., 20 min, 180 rpm, and 0.31 kg of deoxidized oil was obtained by centrifugation. The oryzanol content of this deoxidized oil as determined by spectroscopy was 1.3%.
[0009]
Comparative Example 2
All were carried out under the same conditions except that the alkaline solution of Example 2 was replaced with a 24% aqueous sodium hydroxide solution. The pH during alkali purification was 11.0 with universal pH test paper. Centrifugation after alkali purification gave 0.10 kg of deoxidized oil. The deoxidized oil had an oryzanol content of 0.3%.
[0010]
Example 3
570 ml of 24% sodium hydroxide aqueous solution was added to 8.0 kg of degummed rice bran oil (acid value 24, oryzanol content 1.6%, total tocopherol content 1210 ppm). The pH at this time was 9.0 with the universal test paper. Primary alkali purification was performed under the conditions of 85 ° C., 20 min, 450 rpm, then cooled to 30 ° C. for the purpose of dewaxing, and then 6.0 kg of deoxidized oil was obtained by centrifugation. Of this primary deoxidized oil, about 2.9 kg, 58 ml of 16% sodium carbonate aqueous solution was added, and secondary alkali purification was performed under conditions of 85 ° C., 20 min, 180 rpm, and 2.6 kg of deoxidized oil was obtained by centrifugation. It was. The oryzanol content of this deoxidized oil as determined by spectroscopy was 1.5%. The secondary deoxidized oil was dewaxed at 10 ° C., decolorized with 2.0% activated clay, 255 ° C., 90 min, and a vacuum of 3 torr. The properties of this final product oil were as follows.
[0011]
Oryzanol content 1.3% (spectroscopy)
Tocopherol content 1010ppm (including tocotrienol)
Acid value 0.09 (alkali blue method)
Peroxide value 0.1
Flavor Good [0012]
Comparative Example 3
The same procedures as in Example 3 were performed except that a 12% aqueous sodium hydroxide solution was used for refining the secondary alkali. After refining the secondary alkali, 2.5 kg of deoxidized oil was obtained by centrifugation. The oryzanol content of this deacidified oil as determined by spectroscopy was 0.3%. The secondary deoxidized oil obtained here was subjected to the same purification operation as in Example 3. The properties of this final product oil were as follows.
[0013]
Oryzanol content 0.2% (spectroscopy)
Tocopherol content 740ppm (including tocotrienol)
Acid value 0.07 (alkali blue method)
Peroxide value 0.1
Flavor Good [0014]
【The invention's effect】
According to the present invention, by using a weakly alkaline aqueous solution in the alkaline deoxidation step, phenolic substances having antioxidant and / or physiological activity can be distributed to deoxidized oil and thermally decomposed in the subsequent decolorization and deodorization step. As a result, it was possible to obtain rice bran oil which was rich in those active ingredients in deoxidized oil and was excellent in quality and nutrition. Further, compared with the conventional purification method, no special apparatus for distillation or extraction is required, which is advantageous in terms of cost. In addition, according to the present invention, even if a weakly alkaline aqueous solution is added excessively, the yield of deoxidized oil and the content of the above-mentioned phenolic substance are less affected, so the management of the amount of alkali added becomes easy. In addition to eliminating the need for sampling and titration for confirming the sum, there was an effect that the quality of the deoxidized oil could be kept constant at an excellent level.

Claims (3)

In alkali refining rice bran oil, upon removal of free fatty acids contained, and characterized by using a weak alkaline aqueous solution p H is 10 to 7.5, leaving the oryzanol in the feedstock 80 wt% or more To make rice bran oil. 2. The method for producing rice bran oil according to claim 1, wherein even after the deodorizing step, the total tocopherol content in the raw material oil remains at 70 wt% or more. claims p H is the weak alkaline aqueous solution is 10 to 7.5 and sodium carbonate, potassium carbonate, sodium phosphate, characterized in that one or aqueous solution prepared from two or more selected from sodium citrate Item 1. A method for producing rice bran oil according to Item 1.