JPWO2007086389A1 - Water-soluble polysaccharide derived from rice bran, process for producing the same, and emulsifier using the same - Google Patents

Abstract

In order to make effective use of rice bran, an object was to efficiently extract water-soluble polysaccharides. In addition to its function as a dietary fiber, the purpose was to examine whether it could be used as a functional material to improve the physical properties and functions of food. Rice bran was extracted under acidic conditions under high temperature conditions, and the knowledge that functional polysaccharides that are cell wall constituents can be efficiently extracted was obtained. In addition, the present inventors have found that the water-soluble polysaccharide of the present invention functions as an emulsifier in addition to the function as a dietary fiber.

Description

  The present invention relates to a water-soluble polysaccharide derived from rice bran and a method for producing the same. And usage.

  Currently in Japan, 1 million tons of rice bran is discharged during the milling process. About 40% of rice bran is used as a raw material for oil extraction, but the defatted rice bran produced in the process has been treated as industrial waste or incinerated without being effectively utilized so far.

  As a method for extracting polysaccharide components from rice bran, a method of extracting with an aqueous solvent and a method of extracting by partially decomposing a cell wall by an enzyme treatment have been reported. In the case of extraction with an aqueous solvent, when extraction is performed at normal pressure, the extraction efficiency is as low as 3.5 to 8% by weight regardless of pH conditions (Patent Documents 1 and 2). In addition, the yield is low as well at room temperature even under high pressure conditions of 100 MPa or more (Patent Document 3). Even under high temperature and pressure conditions such as 130 ° C. and 2 MPa, polysaccharides could not be efficiently obtained unless the sample was sheared with an extruder or the like if the pH was not adjusted (Patent Document 4). Even under high temperature and pressure conditions, the extraction efficiency under neutrality is poor, and a combination of enzymatic decomposition is required (Patent Document 5). These conventional rice bran polysaccharides have many uses as dietary fiber reinforcement (dietary fiber), and the functionality which improves the physical property and function of food is not found.

Japanese Patent Publication No.6-11764 Japanese Patent Laid-Open No. 5-112455 Japanese Patent No.3098553 Japanese Patent Publication No. 2-100644 Japanese Patent Laid-Open No. 5-219976

  In order to make effective use of rice bran, water-soluble polysaccharides were efficiently extracted, and in addition to the function as a dietary fiber, the problem was to use it as a functional material that improves the physical properties and functions of food.

  As a result of diligent research to solve the above problems, rice bran was extracted under acidic conditions under high temperature conditions, and it was found that functional polysaccharides that are cell wall constituents can be efficiently extracted. In addition, in addition to the function as a dietary fiber, the water-soluble polysaccharide of the present invention has come to the knowledge that it functions as an emulsifier without performing further hydrolysis treatment with an enzyme, for example. The present invention has been completed based on such findings.

That is, the present invention
(1) A method for producing a water-soluble polysaccharide, wherein a water-soluble fraction is extracted from rice bran by treatment at pH 2.5 or more and pH 4 or less and 95 ° C. or more and 140 ° C. or less.
(2) The method for producing a polysaccharide according to (1), wherein desalting and purification are performed after the treatment.
(3) A water-soluble polysaccharide obtained by extracting a water-soluble fraction from rice bran by treatment at pH 2.5 to pH 4 and 95 ° C. to 140 ° C.
(4) An emulsifier comprising the water-soluble polysaccharide according to (3) as an active ingredient.
It is.

  By extracting from rice bran under acidic conditions at a high temperature of 95 ° C. or higher, a water-soluble polysaccharide could be obtained efficiently, and the obtained water-soluble polysaccharide had a function as an emulsion stabilizer. Moreover, the food excellent in the said function was able to be obtained by using the polysaccharide of this invention.

  The rice bran used in the present invention refers to all rice bran produced as a by-product when rice is polished, and includes defatted rice bran and the like. Rice bran contains a large amount of fats and oils rich in unsaturated fatty acids, and becomes a peroxide and easily causes a problem in flavor. Therefore, defatted rice bran obtained by defatting lipids with hexane or the like in advance is preferred as a raw material.

  The method for producing rice bran polysaccharide will be described in detail as follows. Rice bran is crushed as it is or pulverized, and water is added to the rice bran. When the pH is lower, hydrolysis of the polysaccharide is promoted, the ratio of reducing sugar in the total sugar becomes very high, and the yield of the polymer fraction decreases. In addition, when the extraction temperature is below 95 ° C., the yield deteriorates, and the obtained extract increases impurities such as ash. The yield increases as the temperature increases, but the hydrolysis of the polysaccharide proceeds, so extraction is performed at a temperature range of 95 ° C to 140 ° C, preferably 105 ° C to 140 ° C, more preferably 110 ° C to 130 ° C. It is desirable to do. Heating exceeding 100 ° C. is performed under pressure in a pressurized container or the like. The extraction time is not particularly limited, but is preferably about 2 minutes to 2 hours.

  There are no particular restrictions on the acid used to adjust the pH during high-temperature extraction, and any acid can be used. However, in order to achieve acidic conditions, inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, or acetic acid, citric acid, lactic acid, Organic acids such as oxalic acid can be used.

  The pH of the obtained extract is arbitrarily adjusted, and the water-soluble fraction is separated by centrifugation or the like. In this pH adjustment, an alkali such as sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia or the like can be used. The polysaccharide thus obtained can be dried and used as it is, but it is preferable to carry out further purification in order to remove mixed impurities.

  Examples of the desalting and purification treatment include precipitation using a polar organic solvent such as methanol, ethanol, isopropanol, and acetone, electrodialysis, ion exchange resin or hydrophobic resin, and membrane fractionation using a UF membrane. . One of these methods or two or more methods can be used in combination. Of these, the precipitation method using a polar organic solvent is efficient and preferable, and ethanol is particularly preferable. The purified rice bran polysaccharide solution is dried by freeze drying, spray drying or the like to obtain a powdered rice bran polysaccharide.

  The viscosity of the polysaccharide solution obtained in the present invention is not particularly limited, but it is a low-viscosity of 5 wt% solution at 50 ° C., preferably 20 cP · s or less at 20 ° C. As a result of analyzing the constituent sugars of the rice bran water-soluble polysaccharide by the method described in JP-A-11-049682, glucose and arabinose are used as constituent sugars. All the obtained polysaccharides have a molecular weight of 1 million or less, preferably 500,000 or less, as analyzed by gel filtration HPLC (TSKgel-G-5000 PWXL; TOHSO). The average molecular weight of this polysaccharide is a value measured using a standard substance pullulan (Showa Denko KK) as a standard substance.

  The water-soluble polysaccharide of the present invention can be used alone as an emulsifier. Other quality improvers and emulsifiers can also be used in combination. Although this emulsifier can make an emulsion in any pH range, it is preferable to make an emulsion at pH 4 to pH 9, and a neutral pH range of pH 6 to pH 8 is more preferable. The addition amount is not particularly limited, but the addition amount in the emulsion is 0.05 to 25% by weight, preferably 0.1 to 15% by weight, and the emulsion has an oil content of 5 to 50% by weight. Can be made. The addition timing of the water-soluble polysaccharide is not particularly limited, but an emulsion can be obtained by dissolving in advance in the aqueous phase or dispersing in the oil phase.

  Hereinafter, the present invention will be described by way of examples, but these are examples and the contents of the present invention are not limited by these examples. In the examples, “%” means a weight basis unless otherwise specified.

  150 g of commercially available defatted rice bran was added to 3 kg and adjusted to pH 2-7 using hydrochloric acid. These were heated under pressure at 110 ° C. for 90 minutes to extract water-soluble polysaccharides. After adjusting the pH to 7, the obtained slurry was centrifuged (8000 G × 30 minutes, room temperature), and ethanol was added to the supernatant to a concentration of 60%. The precipitate was collected by centrifugation (8000 G × 30 minutes, room temperature) and lyophilized. Table 1 shows the compositional analysis values of the rice bran polysaccharides obtained by this example. As a composition analysis method for these polysaccharides, the total sugar was quantified using the phenol-sulfuric acid method, the starch was quantified by the iodine starch method, the reducing sugar was quantified by the Sommoji Nelson method, the uronic acid was quantified by the Blumenkrantz method, and the crude protein was quantified by the Kjeldahl method. The water-solubilization rate is the ratio of the solid content that has been water-solubilized after heat extraction to the solid content of the raw material, and the eta precipitation yield is the ratio of the solid content of ethanol precipitation to the solid content of the raw material It is a value expressed in%.

[Table 1] Composition analysis values at each pH at 110 ° C extraction

  Thus, at pH 5 or higher, both the water-solubilization rate and etaprecipitation yield are low, and the purity of all sugars, ie polysaccharides, is also low. In addition, since the protein content increased near neutrality, the range suitable for extraction was judged to be pH 4 or lower. When extracted at pH 2, the water solubilization rate was high, but the eta precipitation yield of the obtained polysaccharide was as bad as 8%. Further, when the molecular weight distribution was measured by HPLC, it became clear that a polymer fraction could not be obtained, and it was considered that the decomposition was progressing under strong acid conditions (FIG. 1). Therefore, it was judged that the pH during extraction was 2.5 or more and 4 or less.

  5 g of commercially available defatted rice bran was added to 100 g and adjusted to pH 3 with hydrochloric acid. These were extracted for 90 minutes under conditions of 60 to 150 ° C. Heating was performed in a hot water bath at 100 ° C. or lower, and using an autoclave at 110 ° C. or higher. After adjusting the pH to 7, the obtained slurry was centrifuged (8000 G × 30 minutes), and ethanol was added to the supernatant to a concentration of 60%. The precipitate was collected by centrifugation (8000 G × 30 minutes) and lyophilized to obtain a powdered rice bran polysaccharide. Table 2 shows the compositional analysis values of the rice bran polysaccharides obtained by this example.

[Table 2] Composition analysis values at each temperature during pH3 extraction

As a result, when extracted under acidic conditions at pH 3, the water-solubilization rate was low at 60 ° C. and 80 ° C., the total sugar, that is, the polysaccharide purity was low, and the ash content was high. 110-130 ° C is preferable because of high etaprecipitation yield, but 135 ° C shows some tendency to increase reducing sugar and ash content due to hydrolysis. A decrease and an increase in reducing sugar were observed.
[Production Example 1]

  5 g of commercially available defatted rice bran was added to 100 g and adjusted to pH 3 with hydrochloric acid. These were extracted for 90 minutes at 110 ° C. using an autoclave. After adjusting the pH to 7, the obtained slurry was centrifuged (8000 G × 30 minutes), and ethanol was added to the supernatant to a concentration of 60%. The precipitate was collected by centrifugation (8000 G × 30 minutes) and freeze-dried to obtain powdered rice bran polysaccharide A.

Evaluation of emulsification stability After adding the oil phase to the aqueous phase with the composition shown in Table 3, an emulsion was prepared by ultrasonic treatment (5281 type vibrator; KAIJO DENKI) and stored at 4 ° C. In Table 3, “%” is volume%.

[Table 3] Formulation of emulsion

  The particle size of these emulsions was measured over time using a laser particle size distribution analyzer (SALD-2000; Shimadzu Corporation). Table 4 shows the average emulsified particle size after 0, 1, 7 days.

[Table 4] Particle size change of each emulsion

  As a result of the above, the emulsion using rice bran polysaccharide A as an emulsifier did not separate oil and maintained a stable emulsified state even after storage for one week. In particular, it maintained a stable emulsified state with a small particle size under neutral conditions, and had a very strong emulsifying power.

  Addition to the environment can be reduced by efficiently extracting water-soluble polysaccharides from rice bran or defatted rice bran originally treated as industrial waste. Further, by using the obtained polysaccharide as an emulsion stabilizer, it has become possible to produce a safe food that does not use a synthetic emulsifier.

Fig. 2 shows gel filtration of molecular weight distribution of water-soluble rice bran polysaccharides.

Claims (4)

A method for producing a water-soluble polysaccharide, characterized in that a water-soluble fraction is extracted from rice bran by treatment at pH 2.5 to pH 4 and from 95 ° C to 140 ° C. The method for producing a polysaccharide according to claim 1, wherein desalting and purification are performed after the treatment. A water-soluble polysaccharide obtained by extracting a water-soluble fraction from rice bran by treatment at pH 2.5 to pH 4 and at 95 ° C. to 140 ° C. The emulsifier which uses the water-soluble polysaccharide of Claim 3 as an active ingredient.

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