Water-soluble soybean polysaccharides and method for producing the same

Abstract

To provide a material that can, in an acidic protein food or beverage such as an acidic protein beverage, disperse and stabilize protein particles even within a pH range of pH 4.2 or higher, i.e., around the isoelectric point of protein, and that has a low viscosity and can impart a refreshing taste.SOLUTION: The present inventors found that water-soluble soybean polysaccharides, wherein the ratio of arabinose / galactose, from among the components of constituting saccharides of the water-soluble soybean polysaccharides, satisfies the expression 0.15≤arabinose / galactose≤0.40 and the methyl esterification degree is 30% or lower, can disperse and stabilize milk proteins in an acidic protein food or beverage even within a pH range of pH4.2 or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-soluble soybean polysaccharide and a method for producing the same. [Background technology]

[0002] Acidic milk beverages are known in which milk protein is fermented with carbohydrates or dispersed in an aqueous solution of an organic acid. For these beverages, high-methoxy pectin, carboxymethyl cellulose, etc. have been used as dispersion stabilizers for the milk protein particles. Patent Document 1 discloses that water-soluble soybean polysaccharides, obtained by high-temperature pressurized extraction under acidic conditions using okara (soybean refuse), which is obtained by separating and removing fats, oils, and proteins from soybeans, as a raw material, can be used to stabilize the dispersion of milk protein particles in a very low viscosity state under acidic conditions of less than pH 4, which cannot be achieved with pectin, etc. This makes it possible to produce an acidic milk beverage with a refreshing and light taste that is unprecedented, unlike the heavy, pasty taste of beverages containing added pectin (Patent Document 2). Acidic milk beverages include those with high protein content and those made using fermented milk. When these beverages are prepared using water-soluble soybean polysaccharides at a pH below 4, they can end up with a very sour taste, or the low pH prevents lactic acid bacteria from growing, making it impossible to produce a live-type lactic acid bacteria beverage. On the other hand, the aforementioned water-soluble soybean polysaccharides do not exhibit sufficient dispersion stabilization ability for protein particles at pH levels above 4.2, or increasing the amount added can hinder a refreshing taste. Therefore, there is a need for water-soluble polysaccharides that can stabilize the dispersion of milk protein particles at pH levels above 4.2 and with low viscosity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-236759 [Patent Document 2] Japanese Patent Application Publication No. 7-059512 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional techniques are not necessarily sufficient in terms of the stability of acidic protein beverages such as acidic milk beverages in the pH range of 4.2 or higher, and further improvements are desired. The present invention aims to provide a material that can disperse and stabilize protein particles in acidic protein foods and beverages, such as acidic protein drinks, even in a pH range of 4.2 or higher, which is near the isoelectric point of the protein, and can impart a low viscosity and refreshing taste to the drink. [Means for solving the problem]

[0005] As a result of extensive research into solving the above problems, the present inventors have discovered that water-soluble soybean polysaccharides, among the constituent sugar components of which the arabinose / galactose ratio is in the range of 0.15≦arabinose / galactose≦0.40 and which have a degree of methyl esterification of 30% or less, can disperse and stabilize milk protein in acidic protein foods and beverages even in a pH range of 4.2 or higher, thereby completing the present invention.

[0006] That is, the present invention provides: (1) A water-soluble soybean polysaccharide in which the arabinose / galactose ratio of the constituent sugars of the water-soluble soybean polysaccharide is in the range of 0.15≦arabinose / galactose≦0.40 and the degree of methyl esterification is 30% or less. (2) The water-soluble soybean polysaccharide according to (1), wherein the arabinose / galactose ratio is 0.20≦arabinose / galactose≦0.35. (3) A method for producing water-soluble soybean polysaccharides having an arabinose / galactose ratio in the range of 0.15≦arabinose / galactose≦0.40 and a degree of methyl esterification of 30% or less, the method comprising heating a soybean raw material under conditions of pH 1.5 to 4.0, 40°C to less than 100°C, for 15 to 600 minutes to obtain a slurry containing the water-soluble soybean polysaccharides, adjusting the pH to 4.0 to 7.0, subjecting the slurry to solid-liquid separation, and deesterifying the resulting solution containing the water-soluble soybean polysaccharides, followed by purification. (4) The method for producing water-soluble soybean polysaccharides according to (3), wherein the soybean raw material is heated under conditions of pH 1.5 to 3.5, 60°C to less than 100°C, and 30 to 150 minutes. (5) A dispersion stabilizer for proteins containing the water-soluble soybean polysaccharide according to (1) or (2) as an active ingredient. (6) An acidic protein food or drink containing the dispersion stabilizer for protein according to (5). (7) The acidic protein food or drink according to (6), wherein the acidic protein food or drink is an acidic protein drink. is. [Effects of the Invention]

[0007] By using the water-soluble soybean polysaccharides of the present invention, proteins can be dispersed and stabilized at a pH of 4.2 or higher, which is near the isoelectric point of milk proteins, where stabilization power has traditionally been reduced, and acidic protein foods and beverages such as acidic protein beverages with low viscosity and a refreshing taste can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Water-soluble soybean polysaccharide) The water-soluble soybean polysaccharide of the present invention is characterized in that, among its constituent sugar components, the arabinose / galactose ratio is in the range of 0.15≦arabinose / galactose≦0.40, and the degree of methyl esterification is 30% or less. Due to these characteristics, when used as a stabilizer for acidic protein drinks, the polysaccharide exhibits protein stabilizing power with low viscosity, particularly in the high pH range of 4.2 to 4.6. The arabinose / galactose ratio is preferably in the range of 0.20≦arabinose / galactose≦0.35. In the present invention, the arabinose / galactose value is calculated from the arabinose and galactose contents (on a dry matter basis) obtained by analyzing the composition of neutral sugars described below.

[0009] (constituent sugar) The water-soluble soybean polysaccharide of the present invention contains galacturonic acid, an acidic sugar, as a constituent sugar. It also contains arabinose and galactose as major neutral sugars. Other neutral sugars may include glucose, rhamnose, xylose, and fucose. The galacturonic acid content is measured by colorimetric determination using the Blumenkrantz method. The neutral sugar composition is measured by ion chromatography (HPAEC-PAD) using an electrochemical detector after sulfuric acid hydrolysis, passing the sample through an anion removal cartridge and a 0.2 μm filter. Ion chromatography was performed using an ICS-3000 (DIONEX) column, a CarboPack PA1 solvent, a flow rate of 1.0 ml / min, and pulsed amperometry mode.

[0010] (Method for producing water-soluble soybean polysaccharides) The water-soluble soybean polysaccharide of the present invention is characterized by being obtained by heating a soybean raw material in an acidic pH range of 1.5 to 4.0 to obtain a slurry containing the water-soluble soybean polysaccharide, adjusting the pH to 4.0 to 7.0, preferably 4.5 to 6.0, followed by solid-liquid separation, and then deesterifying the resulting solution containing the water-soluble soybean polysaccharide and purifying it, as described in detail below.

[0011] (raw materials) As soybean-derived raw materials for water-soluble soybean polysaccharides, okara and defatted soybeans, which are produced as by-products in the production of tofu, isolated soybean protein, etc., can be used. When using okara as a raw material, it is preferable to use okara generated as a by-product in the process of producing isolated soy protein. Raw materials such as okara and defatted soybeans can be used alone or in combination.

[0012] (extraction) Water is added to the above soybean raw material, and the pH is adjusted to 1.5 to 4, preferably 1.5 to 3.5, and more preferably 2.0 to 3.0, using an acid such as hydrochloric acid, phosphoric acid, sulfuric acid, citric acid, oxalic acid, tartaric acid, or acetic acid. The mixture is then heated at a temperature of 40 to less than 100°C, preferably 60 to less than 100°C, and more preferably 80 to less than 100°C, for approximately 15 to 600 minutes, preferably 30 to 150 minutes, and more preferably 45 to 120 minutes to extract the water-soluble soybean polysaccharides, thereby obtaining a slurry containing the water-soluble soybean polysaccharides. Next, an alkali such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, or ammonia is added to the slurry to adjust the pH to 4.0 to 7.0, preferably 4.5 to 6.0, and then the slurry is subjected to solid-liquid separation using a filter press, a screw press, a centrifuge, or the like to obtain a solution containing water-soluble soybean polysaccharides.

[0013] (de-esterification) In the solution containing the water-soluble soybean polysaccharide, it is necessary to deesterify the methyl ester of galacturonic acid contained as a constituent sugar of the water-soluble soybean polysaccharide. The deesterification method can be carried out using an acid, alkali, or enzyme, but it is preferable to use an alkali from the viewpoint of simplicity and cost. Specifically, the pH of a solution containing water-soluble soybean polysaccharides is first adjusted to 9 to 14, preferably 11 to 13, using an alkali, and then heated. The heating conditions are 20°C or higher, preferably 30°C or higher, more preferably 40°C or higher, and 80°C or lower, preferably 70°C or lower, more preferably 60°C or lower. The heating time is 10 minutes or longer, preferably 20 minutes or longer, more preferably 30 minutes or longer, and 4 hours or shorter, preferably 3 hours or shorter, more preferably 2 hours or shorter, even more preferably 1.5 hours or shorter, and even more preferably 1 hour or shorter. The degree of deesterification is calculated by measuring the degree of methyl esterification. The degree of methyl esterification by deesterification is 30% or less, preferably 20% or less, and more preferably 15% or less. The degree of methyl esterification was determined by quantifying the amount of galacturonic acid and methyl esterified galacturonic acid using the Doesburg titration method, and the result was calculated using the following formula: Methyl esterified galacturonic acid ÷ total galacturonic acid × 100 (%) Calculated as follows.

[0014] (purification) The aqueous solution containing the water-soluble soybean polysaccharides can be used as is or after drying, but it is desirable to purify it by removing proteins and desalting it in order to make it more functional. Methods for removing proteins include adjusting the pH to aggregate proteins and then removing them by separation means such as press separation, centrifugation, filtration, or membrane separation; decomposing the proteins using any protease; and purifying the proteins by adsorbing and removing impurities using activated carbon or resin. Desalting methods may be any method that can separate and remove salts. Examples of desalting methods include precipitation using polar organic solvents such as methanol, ethanol, isopropanol, and acetone; electrodialysis; adsorption and removal using ion exchange resins; and membrane fractionation using UF membranes. It is preferable to use one or a combination of two or more of these methods.

[0015] The solution containing the purified or unpurified water-soluble soybean polysaccharides in this manner can be sterilized or dried, if necessary, to obtain the water-soluble soybean polysaccharides of the present invention.

[0016] (Dispersion stabilizer) The water-soluble soybean polysaccharide of the present invention is a dispersion stabilizer for proteins that can prevent aggregation of protein particles and maintain a stable dispersion state. Its pH range is broad, from around pH 3 to pH 4.6, which is a pH range exceeding pH 4.2. In particular, since the water-soluble soybean polysaccharide of the present invention is effective in the high pH range, the pH is preferably 4.2 to 4.6, more preferably 4.3 to 4.6. The dispersion stabilizer is suitable for acidic protein foods and beverages, particularly acidic protein beverages. The dispersion stabilizer of the present invention may consist solely of the water-soluble soybean polysaccharide of the present invention, or may further contain various substances such as other stabilizers. The content of the water-soluble soybean polysaccharide in the dispersion stabilizer may be 10 to 100% by weight, preferably 50 to 100% by weight, more preferably 90 to 100% by weight, and even more preferably 100% by weight.

[0017] The dispersion stabilizer of the present invention can be used in combination with various gums and proteins and their degradation products, if necessary. Examples of such combination products include polysaccharides such as starch, modified starch, various celluloses, agar, carrageenan, furcellan, guar gum, locust bean gum, tamarind seed polysaccharide, tara gum, gum arabic, tragacanth gum, karaya gum, pectin, xanthan gum, pullulan, and gellan gum, as well as proteins such as gelatin.

[0018] (Acidic protein food and drink) The acidic protein foods and beverages of the present invention are acidic foods and beverages containing proteins derived from animals and plants, regardless of whether the foods and beverages themselves are solid or liquid. The animal-derived proteins mainly refer to animal milks such as cow's milk and goat's milk, specifically cow's milk, skim milk, whole milk powder, skim milk powder, whey powder, sweetened milk, condensed milk, processed milk fortified with minerals such as calcium and vitamins, or fermented milk, while the plant-derived proteins mainly refer to soy milks obtained from soybeans, specifically soy milk, skim soy milk, powdered soy milk, powdered skim soy milk, isolated soy protein, or fermented products thereof. Acidic protein beverages are those made by fermenting beverages using animal milks, soy milks, etc., or by adding fruit juice, or organic acids such as citric acid or lactic acid, or inorganic acids such as phosphoric acid, to make the pH range acidic. Specific examples include pasteurized or live-bacterial lactic acid bacteria beverages, drinkable yogurts, and kefir. Acidic protein foods are those made from the animal milks, soy milks, etc., and include acidic ice creams made by adding organic acids or fruit juice to dairy-containing frozen desserts such as ice cream, acidic frozen desserts such as frozen yogurt, acidic desserts made by adding organic acids or fruit juice to gelled foods such as puddings and bavarois, as well as coffee drinks, acidic creams, and yogurt.

[0019] The water-soluble soybean polysaccharides produced by the present invention exhibit the function of stabilizing the dispersion of proteins, particularly in acidic protein beverages. They can stabilize proteins even in pH ranges near the isoelectric point of the protein, which conventional water-soluble soybean polysaccharides cannot. While any protein is effective, milk protein or soybean protein is preferred. Milk protein is the most commonly used protein for acidic foods and beverages, and the dispersion stabilizer of the present invention is most effective in this regard, making it the most preferred.

[0020] The protein dispersion stabilizer of the present invention is particularly effective in acidic protein foods and beverages with a protein concentration of 10% by weight or less, and by adding the water-soluble soybean polysaccharide to the acidic protein foods and beverages preferably in an amount of 0.05 to 3.0% by weight, more preferably 0.1 to 2.5% by weight, and even more preferably 0.2 to 2.0% by weight, the protein dispersion stabilizer exhibits good dispersion stability of the protein up to a pH range near the isoelectric point of the protein. For example, with milk protein, acidic protein foods and drinks with a pH of about 3.4 to 4.6 can be prepared, and in the present invention, aggregation can be effectively suppressed particularly in the high pH range of 4.2 to 4.6. [Example]

[0021] The present invention will be explained below by way of examples, in which parts and percentages are by weight unless otherwise specified.

[0022] Example 1 Defatted okara obtained in the soy protein isolate production process was added with water to a solids content of 6%. The pH was adjusted to 2.0 with hydrochloric acid and heated at 80°C for 90 minutes with stirring to extract the water-soluble soy polysaccharides, yielding a slurry containing the water-soluble soy polysaccharides. The pH of the slurry was adjusted to 5.0 with sodium hydroxide and centrifuged at 8000 rpm for 30 minutes in a centrifuge (CR20G II, Hitachi, Ltd.) to obtain a supernatant. The resulting supernatant was added with 8% sodium hydroxide (solids to liquid) to a pH of 12, and the mixture was incubated at 45°C for 45 minutes to deesterify the methyl ester of galacturonic acid. The pH was then adjusted again to 5.0 with hydrochloric acid. The pH-adjusted solution was then precipitated with 60% ethanol by weight, purified with 90% aqueous ethanol, and dried at 80°C for 3 hours to obtain the water-soluble soy polysaccharides of the present invention.

[0023] Example 2 After the same heat extraction procedure for water-soluble soybean polysaccharides as in Example 1, the pH was adjusted to 4.0 with sodium hydroxide, and centrifugal separation, deesterification, purification, and drying were carried out under the same conditions as in Example 1 to obtain water-soluble soybean polysaccharides.

[0024] Example 3 Water-soluble soybean polysaccharides were obtained in the same manner as in Example 1, except that the heat extraction conditions for the water-soluble soybean polysaccharides were pH 3.5, 80°C, and 90 minutes.

[0025] (Comparative Example 1) Water-soluble soybean polysaccharides were obtained in the same manner as in Example 1, except that the heat extraction conditions for the water-soluble soybean polysaccharides were pH 5.5, 124°C, and 90 minutes.

[0026] (Comparative Example 2) After the same heat extraction procedure for water-soluble soybean polysaccharides as in Example 1, the water-soluble soybean polysaccharides were obtained by centrifuging, deesterifying, purifying, and drying under the same conditions as in Example 1, without adjusting the pH with sodium hydroxide.

[0027] (Comparative Example 3) After the same heat extraction procedure for water-soluble soybean polysaccharides as in Example 1, the pH was adjusted to 3.5 with sodium hydroxide, and the mixture was centrifuged, deesterified, purified, and dried under the same conditions as in Example 1 to obtain water-soluble soybean polysaccharides.

[0028] The sugar compositions and arabinose / galactose values of the water-soluble soybean polysaccharides obtained in Example 1 and Comparative Examples 1 to 3 are shown in Table 1.

[0029] (Evaluation of Acidic Protein Drinks of Examples 1 to 3 and Comparative Examples 1 to 3) 200g of skim milk powder was added to 800g of room temperature water, stirred and dissolved at 70°C for 20 minutes, and cooled to obtain a 20% skim milk powder solution. 500g of sugar was added to 500g of room temperature water and stirred and dissolved to obtain a 50% sugar solution. 50g of each water-soluble soy polysaccharide was added to 950g of water, stirred and dissolved at 80°C for 20 minutes, and then cooled to 20°C to obtain a 5% water-soluble soy polysaccharide solution. 200 g of the 20% skim milk powder solution, 70 g of 50% sugar solution, 40 g of 5% water-soluble soybean polysaccharide solution, and 190 g of water were mixed, and the pH was adjusted to 4.2, 4.4, and 4.6 with 50% citric acid solution, followed by homogenization at 150 kg / cm2. The homogenized solution was sterilized at 90°C for 20 minutes, filled into containers, and cooled to obtain an acidic protein beverage. The prepared acidic protein beverage was stored at 4°C for 7 days, and the thickness of the syneresis from the liquid surface (top gap) was measured. The dispersed particle size of the milk protein in the beverage was measured using a laser diffraction particle size distribution analyzer, SALD-2300 (Shimadzu Corporation), and calculated as the median diameter. The pass criteria were a top gap of 4 mm or less and a median diameter of 3.3 μm or less. The viscosity was measured using a BM type viscometer (TV-20, manufactured by Toki Sangyo Co., Ltd.) under the conditions of 4°C, rotor No. 1, 60 rpm, and 1 minute.

[0030] (Table 1) TIFF2025118830000001.tif119168

[0031] In Comparative Example 1, which had a high arabinose / galactose ratio, the gaps and median diameter increased as the beverage pH increased, resulting in a deterioration in stability. In contrast, Examples 1 to 3 showed good stabilizing power with little change depending on the beverage pH. On the other hand, Comparative Examples 2 and 3, which had a low arabinose / galactose ratio, also showed inferior stability at a beverage pH of 4.2 compared to Comparative Example 1, confirming that a drastic decrease in arabinose actually worsened stability. Furthermore, the viscosities of the beverages of Examples 1 to 3 were low, ranging from 5.8 cP to 6.6 cP, and had a refreshing taste.

Claims

1. A water-soluble soybean polysaccharide in which the arabinose / galactose ratio among the constituent sugar components of the water-soluble soybean polysaccharide is in the range of 0.15≦arabinose / galactose≦0.40 and the degree of methyl esterification is 30% or less.

2. 2. The water-soluble soybean polysaccharide according to claim 1, wherein the arabinose / galactose ratio is 0.20≦arabinose / galactose≦0.

35.

3. A method for producing water-soluble soybean polysaccharides, in which the arabinose / galactose ratio is in the range of 0.15≦arabinose / galactose≦0.40 and the degree of methyl esterification is 30% or less, is characterized by heating a soybean raw material under conditions of pH 1.5 to 4.0, 40°C to less than 100°C, for 15 to 600 minutes to obtain a slurry containing water-soluble soybean polysaccharides, adjusting the pH to 4.0 to 7.0, and then performing solid-liquid separation. The resulting solution containing water-soluble soybean polysaccharides is deesterified and then purified.

4. 4. The method for producing water-soluble soybean polysaccharides according to claim 3, wherein the soybean raw material is heated under conditions of pH 1.5 to 3.5, 60°C to less than 100°C, for 30 to 150 minutes.

5. 4. The method for producing water-soluble soybean polysaccharides according to claim 3, wherein the arabinose / galactose ratio is 0.20≦arabinose / galactose≦0.

35.

6. 5. The method for producing water-soluble soybean polysaccharides according to claim 4, wherein the arabinose / galactose ratio is 0.20≦arabinose / galactose≦0.

35.

7. 3. A dispersion stabilizer for proteins, comprising the water-soluble soybean polysaccharide according to claim 1 or 2 as an active ingredient.

8. An acidic protein food or drink containing the protein dispersion stabilizer according to claim 7.

9. 9. The acidic protein food or drink according to claim 8, wherein the pH of the acidic protein food or drink is 4.2 to 4.

6.

10. 9. The acidic protein food or drink according to claim 8, which is an acidic protein drink.

11. 11. The acidic protein food or drink according to claim 10, wherein the pH of the acidic protein food or drink is 4.2 to 4.

6.

12. A method for producing an acidic protein food or drink, comprising adding the dispersion stabilizer according to claim 7 in an amount of 0.05 to 3.0% by weight, in terms of the amount of water-soluble soybean polysaccharide, to the acidic protein food or drink.

13. The method for producing an acidic protein food or drink according to claim 12, wherein the pH of the acidic protein food or drink is 4.2 to 4.

6.

14. A method for stabilizing the dispersion of protein in acidic protein foods and drinks, which comprises adding the dispersion stabilizer according to claim 7 in an amount of 0.05 to 3.0% by weight, in terms of the amount of water-soluble soybean polysaccharide, to the acidic protein foods and drinks.

15. 15. The method for stabilizing dispersion of protein in an acidic protein food or drink according to claim 14, wherein the pH of the acidic protein food or drink is 4.2 to 4.6.

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