Method for producing an oligosaccharide composition

Abstract

The present invention aims to provide a novel method for producing an oligosaccharide composition in which the proportion of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose is less than 20%. [Solution] The above problem can be solved by a method for producing an oligosaccharide composition, which includes an extraction step of suspending pea seeds in water with a pH of 7.5 or higher and extracting the oligosaccharides into a water-soluble fraction. By suspending pea seeds in water with a pH of 7.5 or higher and extracting the oligosaccharides into a water-soluble fraction, an oligosaccharide composition can be obtained in which the ratio of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose is less than 20%, without performing a purification step or fractionation step.

Description

Technical Field

[0001] The present invention relates to a method for producing an oligosaccharide composition. In particular, the present invention relates to a method for producing an oligosaccharide composition with a reduced sucrose content.

Background Art

[0002] Raffinose family oligosaccharides are a group of oligosaccharides containing α1-6 linked galactose, and include raffinose in which galactose is α1-6 linked to the 6-position of glucose, which is a constituent sugar of sucrose, stachyose in which galactose is α1-6 linked to the 6-position of galactose, which is a constituent sugar of raffinose, and verbascose in which galactose is α1-6 linked to the 6-position of the non-reducing terminal galactose of stachyose. Raffinose family oligosaccharides are safe oligosaccharides that humans routinely ingest through their daily diet.

[0003] Raffinose family oligosaccharides are hardly digested or absorbed in the human small intestine, reach the large intestine, and function as oligosaccharides that serve as growth factors for enterobacteria useful to humans such as bifidobacteria, thereby improving the intestinal environment. Raffinose and stachyose assimilated by enterobacteria are converted into short-chain fatty acids and organic acids, which suppress the proliferation of harmful bacteria and suppress excessive immune responses such as allergies. Verbascose has been reported to strongly activate immune cells.

[0004] Raffinose family oligosaccharides are contained in various plants, mainly legumes and root vegetables, and among them, soybeans and sugar beets are known as foods containing particularly large amounts thereof. Soy oligosaccharides, extracted and concentrated from soybeans, are recognized as Foods for Specified Health Uses (standard type). The standard for their composition is that they contain 20% or more stachyose and raffinose. However, since soybeans also contain a lot of sucrose, soy oligosaccharides tend to be high in sucrose. Sucrose is digested and absorbed in the small intestine and becomes an energy source, but excessive intake can lead to obesity. The World Health Organization recommends limiting daily sugar intake to less than 5% of total daily energy intake (equivalent to approximately 25g of sucrose). If you consume 5g of soy oligosaccharide syrup, which is the recommended daily intake, you will ingest approximately 2g of sucrose. However, considering that we also consume a lot of sucrose from our regular diet, it is preferable that the sucrose content derived from the oligosaccharide composition be less than 1g. In other words, for oligosaccharide compositions with a generally recommended daily intake of around 5g, it is preferable that the sucrose content be less than 20%. Therefore, for oligosaccharide compositions that contribute to health, oligosaccharide compositions with a sucrose content of less than 20% are desirable. Furthermore, molasses, a by-product of sugar production using sugar beets as a raw material, is also rich in raffinose. For this reason, molasses is used as sugar beet oligosaccharide syrup, but commercially available sugar beet oligosaccharide syrup contains a large amount of sucrose. Therefore, in order to produce an oligosaccharide composition with a high raffinose content by reducing the sucrose from commercially available sugar beet oligosaccharide syrup, a multi-stage purification process is required. A multi-stage purification process is complicated and increases manufacturing costs, so the price of the oligosaccharide composition product obtained in this way is very high.

[0005] Patent Document 1 discloses a method for producing soybean oligosaccharides, characterized by heating a soybean whey solution at 70-110°C, adjusting the pH to 3.0 or lower using phosphoric acid, and removing the resulting precipitate. This method allows for the purification of practical oligosaccharides with very little sugar breakdown and efficient protein removal. However, it is stated that the soybean oligosaccharides contained 58% carbohydrates, of which 40% were trisaccharides or more, 55% were sucrose, and 5% were monosaccharides.

[0006] Patent Document 2 describes a method for preparing galactooligosaccharides, characterized by using soybean seed hypocotyls as a raw material and mixing and stirring them in an acidic aqueous solution with a pH of 3 to 6 to extract oligosaccharides such as raffinose and stachyose. This method allows for the simple and inexpensive extraction of galactooligosaccharides with low levels of impurities such as crude protein and ash. However, Patent Document 2 does not describe the sucrose concentration in the extract.

[0007] Non-patent document 1 describes the results of measuring the sugar composition of commercially available soy oligosaccharide syrup, which showed that it contained 34.6% sucrose per solid unit. Non-patent document 2 describes the results of an investigation into the oligosaccharide composition of various varieties of garden peas (green peas), which revealed that they contain sucrose, raffinose, stachyose, and verbascose. It also states that in all varieties, sucrose accounted for more than 20% of the total oligosaccharides. Non-patent document 3 describes a multi-step treatment process, including ethanol precipitation, activated carbon treatment, and ion exchange resin treatment, performed on an oligosaccharide composition extracted from peas in order to increase the content of raffinose oligosaccharides and decrease the proportion of sucrose. The document states that they succeeded in preparing an oligosaccharide composition in which raffinose oligosaccharides accounted for 76.79% and sucrose accounted for 11.48%.

[0008] According to Non-Patent Literature 3, it is possible to reduce the proportion of sucrose to 20% or less and increase the proportion of raffinose oligosaccharides by subjecting the pea seed extract to a multi-stage purification process. However, as with the case of the beet oligosaccharide syrup mentioned above, the process, including ethanol precipitation, activated carbon treatment, and ion exchange resin treatment, is complicated and costly, making it difficult to provide an inexpensive oligosaccharide composition that consumers desire. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 4-187695 [Patent Document 2] Japanese Patent Application Publication No. 5-123200 [Non-patent literature]

[0010] [Non-Patent Document 1] Takano, Yutaka et al., Journal of the Japan Society for Food Science and Technology, 1991, Vol. 38, No. 8, 681-683. [Non-Patent Document 2] Ikuno et al., Journal of Horticultural Science, 1997, 66(3·4):637–640. [Non-Patent Document 3] Gulewicz Piotr et al.,Journal of Agricultural and Food Chemistry,2000,48,3120-3123 [Overview of the project] [Problems that the invention aims to solve]

[0011] The present invention aims to provide a novel method for producing an oligosaccharide composition in which the proportion of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose is less than 20%. [Means for solving the problem]

[0012] As a result of diligent research to solve the above problems, the present inventors have found that by suspending pea seeds in water with a pH of 7.5 or higher and extracting the oligosaccharides into a water-soluble fraction, an oligosaccharide composition in which the ratio of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose is less than 20% can be easily obtained without performing purification or fractionation steps, and have completed the present invention. That is, the present invention includes the following configuration. [1] A method for producing an oligosaccharide composition, comprising an extraction step of suspending pea seeds in water with a pH of 7.5 or higher and extracting oligosaccharides into a water-soluble fraction. [2] A method for producing an oligosaccharide composition according to [1], further comprising a separation step of separating pea seed whey from the suspension after the extraction step. [3] A method for producing the oligosaccharide composition according to [2], further comprising a concentration step of concentrating the pea seed whey. [4] A method for producing an oligosaccharide composition according to [2] or [3], wherein the separation step is a step of removing starch, dietary fiber and protein from the suspension after the extraction step. [5] A method for producing the oligosaccharide composition according to any one of [1] to [3], wherein the pea seeds are in the form of a powder. [6] A method for producing an oligosaccharide composition according to any one of [1] to [3], wherein in the extraction step, the content of pea seeds in the suspension is 5% by weight or more and 30% by weight or less. [7] A method for producing an oligosaccharide composition according to any one of [1] to [3], wherein the extraction step is a step of suspending pea seeds in water with a pH of 7.5 or higher and stirring the suspension at 15°C to 100°C for 30 minutes or more. [8] A method for producing the oligosaccharide composition according to any one of [1] to [3], wherein the ratio of the amount of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose in the oligosaccharide composition is less than 20%. An oligosaccharide composition prepared by a method for producing an oligosaccharide composition described in any one of items [9][1] to [3], wherein the ratio of the amount of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose is less than 20%.

[10] A method for reducing the amount of sucrose in an oligosaccharide composition extracted from pea seeds, characterized by comprising the step of suspending pea seeds in water with a pH of 7.5 or higher and extracting the oligosaccharide into a water-soluble fraction.

[11] The method according to

[10] , wherein the pea seeds are in the form of a powder. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a novel method for producing an oligosaccharide composition in which the ratio of the sucrose amount to the total amount of sucrose, raffinose, stachyose and verbascose is less than 20%. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0014] [Figure 1] These are a graph showing the relationship between the pH of water for suspending pea seeds and the sucrose concentration, and a graph showing the relationship between the pH of water for suspending pea seeds and the raffinose family oligosaccharide concentration (those marked with different alphabets indicate a statistically significant difference at a significance level of p<0.05 (Tukey-Kramer test)). [MODE FOR CARRYING OUT THE INVENTION]

[0015] Hereinafter, the present invention will be described in further detail.

[0016] In the present specification, the raffinose family oligosaccharides is a general term for raffinose, stachyose and verbascose.

[0017] The method for producing the oligosaccharide composition of the present invention includes an extraction step of suspending pea seeds in water having a pH of 7.5 or higher to extract the oligosaccharides into a water-soluble fraction.

[0018] (Extraction Step) This step is a step of suspending pea seeds in water having a pH of 7.5 or higher to extract oligosaccharides from the pea seeds into the water-soluble fraction. In the extraction process, the pH of the water can be adjusted to 7.5 or higher, either before or after suspending the pea seeds in the water. The pH of the water can be adjusted, for example, by adding hydrochloric acid, sodium hydroxide, etc. pH can be measured using equipment commonly used for measuring the pH of liquids, such as a LAQUA F72 (Horiba, Ltd.). In the extraction process, the pH of the water in which the pea seeds are suspended is preferably 7.5 or higher, more preferably 8.5 or higher, and even more preferably 9.5 or higher. The upper limit is pH 12 or lower. By setting the pH of the water in which the pea seeds are suspended to 7.5 or higher, the ratio of sucrose to the total amount of sucrose, raffinose, stachyose, and vervascose in the oligosaccharide composition becomes less than 20%.

[0019] In the extraction process, the pea seed suspension may be stirred to extract oligosaccharides, and the stirring time is preferably 15 minutes or more, more preferably 30 minutes or more, and even more preferably 60 minutes or more. There is no particular upper limit, but for example, it is 120 minutes or less. Also, in the extraction process, the temperature of the pea seed suspension is preferably 15°C to 100°C, more preferably 15°C to 80°C, and even more preferably 15°C to 60°C.

[0020] In the extraction process, the content of pea seeds in the suspension is preferably 5% by weight or more and 30% by weight or less, and more preferably 10% by weight or more and 20% by weight or less.

[0021] (Pea seeds) The pea seeds used in the method for producing the oligosaccharide composition of the present invention are not particularly limited, but may include green peas, yellow peas, red peas, white peas, etc. It is preferable that the pea seeds used in the method for producing the oligosaccharide composition of the present invention are not heat-treated. The pea seeds can be in the form of dried products, powder, etc., and powder is preferred.

[0022] The method for producing the oligosaccharide composition of the present invention may further include a separation step of separating pea seed whey from the suspension after the extraction step.

[0023] (separation process) This step involves removing insoluble substances such as starch, dietary fiber, and protein from the pea seed suspension after the extraction step, and separating the pea seed whey. In the separation process, the method for separating pea seed whey from the pea seed suspension only needs to remove insoluble substances such as starch, dietary fiber, and protein from the pea seed suspension after the extraction process. Examples include centrifugation, membrane treatment, and filtration. In particular, to remove protein from the pea seed suspension after the extraction process, the protein and oligosaccharides may be separated using an ultrafiltration membrane, or the suspension may be heated to a high temperature to coagulate the protein, and then centrifuged.

[0024] (Pea seed whey) In this invention, pea seed whey refers to the liquid obtained by removing insoluble substances from a pea seed suspension after the extraction process. Examples of insoluble substances include insoluble starch, dietary fiber, and protein. In this invention, pea seed whey contains dissolved sucrose, raffinose, stachyose, and velvasocose extracted from pea seeds.

[0025] The method for producing the oligosaccharide composition of the present invention may further include a concentration step of concentrating the pea seed whey obtained in the separation step.

[0026] (concentration process) This step involves concentrating the pea seed whey obtained in the separation step to concentrate the oligosaccharides in the pea seed whey. In the present invention, the concentration step may also be a step of drying the pea seed whey obtained in the separation step. Drying the pea seed whey may involve removing some of the water from the pea seed whey, or it may involve removing almost all of the water from the pea seed whey. In the concentration process, any method that can concentrate the pea seed whey is sufficient as long as it can concentrate the oligosaccharides extracted from the pea seeds. Examples include membrane treatment, spray drying, freeze-drying, and vacuum drying. The molecular weight cutoff of the ultrafiltration membrane used in membrane treatment is, for example, 10,000 Da or less.

[0027] The method for producing the oligosaccharide composition of the present invention preferably does not include any steps to reduce the amount of sucrose, such as a purification step or a fractionation step, in addition to the extraction step described above. This is because, according to the present invention, an oligosaccharide composition in which the ratio of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose is less than 20% can be easily prepared by performing the above extraction step on pea seeds without carrying out such complicated steps.

[0028] The oligosaccharide composition of the present invention is prepared by the manufacturing method described above. The ratio of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose in the oligosaccharide composition of the present invention is preferably less than 20%, more preferably less than 19%, and even more preferably less than 18%. The quantitative determination of sucrose, raffinose, stachyose, and verbascose in the oligosaccharide composition of the present invention can be carried out by known methods such as ion chromatography. The oligosaccharide composition of the present invention does not need to be the one after the separation or concentration steps described above; it may be used as is after the extraction step.

[0029] The oligosaccharide composition of the present invention can be used, for example, as an oligosaccharide syrup. Furthermore, by incorporating the oligosaccharide composition of the present invention into food, the oligosaccharide concentration of the food can be increased. Examples of foods to which the oligosaccharide composition of the present invention can be added include milk or dairy products, plant-based foods using plant-derived raw materials, and the like.

[0030] The form of the oligosaccharide composition of the present invention is not particularly limited, but examples include powder, liquid, gel, etc. [Examples]

[0031] The following describes in detail some embodiments of the present invention, but the present invention is not limited to these embodiments, and various improvements based on known methods can be made.

[0032] (Examples 1-3 and Comparative Examples 1-4) 10 g of pea seed powder was suspended in 90 g of water, and then sodium hydroxide solution or hydrochloric acid was added to adjust the pH to 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, and 9.5, respectively. Next, the suspension was stirred at room temperature (25°C) for 2 hours to obtain the oligosaccharide compositions of Examples 1-3 and Comparative Examples 1-4.

[0033] (Quantitative determination of sucrose, raffinose, stachyose, and vervascose) The following methods were used to quantify sucrose, raffinose, stachyose, and velvascose in Examples 1-3 and Comparative Examples 1-4. Examples 1-3 and Comparative Examples 1-4 were centrifuged at 10,000 × g for 10 minutes, and the supernatant was filtered through a 0.45 μm filter to obtain the samples. Subsequently, the samples were subjected to ion chromatography (HPAE-PAD) to quantify sucrose, raffinose, stachyose, and velvascose. The analytical conditions for ion chromatography were as follows. The elution times for sucrose, raffinose, stachyose, and velvascose were 17 minutes, 25 minutes, 27 minutes, and 31 minutes, respectively. <Ion chromatography analysis conditions> Column: CarboPac PA1 (Thermo Fisher Scientific) Manufactured by IC) Mobile phase A: 20mM NaOH Mobile phase B: 160mM NaOH Gradient conditions: 0 min ~ 17.5 min Mobile phase A 100% (Mobile phase B 0%) 17.5 minutes to 20 minutes Mobile phase A100% → Mobile phase A0% 20 minutes to 35 minutes Mobile phase A0% (Mobile phase B100%) Flow rate: 1 mL / min Temperature: 25℃ Detector: Electrochemical detector Sample: 10 uL Furthermore, from the quantitative values, the ratio of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose in Examples 1-3 and Comparative Examples 1-4, as well as the ratio of raffinose oligosaccharides to the total amount of sucrose, raffinose, stachyose, and verbascose, were determined. The results are shown in Table 1. Note that the amount of raffinose oligosaccharides is the sum of the amounts of raffinose, stachyose, and verbascose. Furthermore, the sucrose concentration and raffinose oligosaccharide concentration of Examples 1-3 and Comparative Examples 1-4 were determined from quantitative values. The results are shown in Table 2 and Figure 1. Note that the raffinose oligosaccharide concentration is the sum of the raffinose concentration, stachyose concentration, and verbascose concentration.

[0034] [Table 1]

[0035] As the pH of the water in which the pea seeds were suspended increased, the proportion of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose in the extract decreased. In particular, when oligosaccharides were extracted with water with a pH of 7.5 or higher, the proportion of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose became less than 20% (Examples 1-3). From the above, it was found that by extracting oligosaccharides from pea seeds with water at a pH of 7.5 or higher, an oligosaccharide composition can be produced in which the ratio of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose is less than 20%.

[0036] [Table 2]

[0037] As the pH of the water in which the pea seeds were suspended increased, the sucrose concentration in the oligosaccharide composition decreased, while the raffinose oligosaccharide concentration increased. In other words, by extracting oligosaccharides from pea seeds with water at a pH of 7.5 or higher, it was possible to reduce only the extraction efficiency of sucrose without significantly altering the extraction efficiency of raffinose oligosaccharides.

[0038] These results show that by extracting oligosaccharides from pea seeds with water at a pH of 7.5 or higher, it is possible to produce an oligosaccharide composition in which only the amount of sucrose among sucrose, raffinose, stachyose, and verbascose is reduced.

Claims

1. A method for producing an oligosaccharide composition, comprising an extraction step of suspending pea seeds in water with a pH of 7.5 or higher and extracting oligosaccharides into a water-soluble fraction.

2. Furthermore, the method for producing the oligosaccharide composition according to claim 1, comprising a separation step of separating pea seed whey from the suspension after the extraction step.

3. Furthermore, the method for producing the oligosaccharide composition according to claim 2, comprising a concentration step of concentrating the pea seed whey.

4. The method for producing an oligosaccharide composition according to claim 2 or 3, wherein the separation step is a step of removing starch, dietary fiber and protein from the suspension after the extraction step.

5. A method for producing an oligosaccharide composition according to any one of claims 1 to 3, wherein the pea seeds are in the form of a powder.

6. A method for producing an oligosaccharide composition according to any one of claims 1 to 3, wherein in the extraction step, the content of pea seeds in the suspension is 5% by weight or more and 30% by weight or less.

7. A method for producing an oligosaccharide composition according to any one of claims 1 to 3, wherein the extraction step is a step of suspending pea seeds in water with a pH of 7.5 or higher and stirring the suspension at 15°C to 100°C for 30 minutes or more.

8. A method for producing an oligosaccharide composition according to any one of claims 1 to 3, wherein the ratio of the amount of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose in the oligosaccharide composition is less than 20%.

9. An oligosaccharide composition prepared by a method for producing an oligosaccharide composition according to any one of claims 1 to 3, wherein the ratio of the amount of sucrose to the total amount of sucrose, raffinose, stachyose, and verbascose is less than 20%.

10. A method for reducing the amount of sucrose in an oligosaccharide composition extracted from pea seeds, characterized by comprising the step of suspending pea seeds in water with a pH of 7.5 or higher and extracting the oligosaccharides into a water-soluble fraction.

11. The method according to claim 10, wherein the pea seeds are in the form of a powder.

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