JPH047251B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for desalting a plant extract. More specifically, the present invention relates to a method for removing membrane contaminants and low molecular weight substances from a plant extract containing oligosaccharides. (Prior Art) Conventionally, as a method for desalting cheese whey, JP-A-58-175438 discloses a method for concentrating and desalting cheese whey that combines a reverse osmosis method and an electrodialysis method. There are many other known methods for desalting cheese whey using an electrodialyzer (for example, JP-A No. 49-54568 Method for Desalting Whey;
49-116257 Method for desalting milk, JP-A-51-51547 Method for desalting milk or whey, JP-A-52-117445 Process for producing purified lactose, JP-A-53-79057, JP-A-53-
79060, JP-A-56-65242, etc.). In addition, as a method for purifying various sugar solutions, (a) JP-A-52-
82737 uses ultrafiltration method (molecular weight cutoff 200~
100,000) and an electrodialysis method is disclosed. Other sugar solution purification methods include JP-A-51-79737, JP-A-52-108035, JP-A-53-69841, JP-A-54-23137, JP-A-57-
129700, JP-A-57-159500, JP-A-57-174100, etc. are known. However, although various methods for purifying liquids containing various monosaccharides and disaccharides such as lactose and sugar as mentioned above are known, the method of the present invention for desalting plant extracts mainly containing oligosaccharides is unknown. (Purpose) The present inventors aimed to desalinate a plant extract containing oligosaccharides. (Progress) While attempting to remove the ash content of soybean whey, which is one of the oligosaccharide-containing plant extracts and is rich in stachyose and raffinose, using an electrodialysis device, the present inventors discovered that soybean whey (its production The content of salts, nitrogen compounds, polysaccharides, organic acids, coloring substances, flavors, etc. differs depending on the process), but unlike cheese whey, which is animal-based, we encountered the problem that it could not be easily desalted using an electrodialysis machine. In other words, it becomes difficult for current to flow and the electrical conductivity does not decrease, resulting in extremely poor desalination efficiency. In order to solve this problem, as a result of intensive research into the causes and solutions, we found that, unlike in the case of cheese whey, plant extracts contain various fouling substances (membranes) such as organic acids such as phytic acid and water-soluble polysaccharides. pollutants)
It was found that these substances inhibit electrodialysis. In the step before electrodialysis, a membrane that is an electrodialysis inhibitor is filtered using an ultrafiltration membrane with a molecular weight cutoff of 1500 to 17500, preferably an ultrafiltration membrane with a molecular weight cutoff 2500 to 12500. The present invention was completed by discovering that pollutants can be removed and desalination can be carried out efficiently. (Structure) The present invention is characterized in that (1) in the step before desalting the plant extract using an electrodialysis membrane,
This is a method for desalting a plant extract, characterized by including a step of filtering using a 17500 (preferably 2500 to 12500) ultrafiltration membrane. The plant extract used in the present invention is a plant extract of grains, beans, etc., and is rich in oligosaccharides of at least tricarbonate or higher (usually tricarbonate to pentose) (at least 30% of the oligosaccharides are % by weight or more, preferably 50% by weight or more), such as soybean extract, extracts of other legumes, etc., but it is easy to obtain, economical, effective use of industrial by-products, etc. From this viewpoint, it is preferable that the soybean extract contains abundant oligosaccharides such as raffinose, stachyose, and verbascose (70 to 90% by weight or more based on the total oligosaccharides). For example, soybean extract refers to an extract containing sugar derived from soybeans, such as (a) soybean whey obtained in the soybean protein manufacturing process, (b) soybean broth, tofu soup, soybean soaking liquid, soybean steaming liquid, or From these, one or more of water-soluble proteins (soybean albumin, β-amylase, trypsin inhibitor, etc.), water-soluble polymer substances such as saponin (at least substances with a higher molecular weight than the oligosaccharide referred to in the present invention), etc. Examples include a soybean extract that has been removed. To give a more specific example, regarding (a), soybean raw materials (defatted soybeans, etc.) are extracted in an aqueous system, and soybean whey and soybean raw materials obtained after removing soybean protein and okara components are extracted with a polar organic solvent (such as alcohol). polar organic solvent-soluble components obtained by extraction with organic solvents, etc.). Regarding (b), examples include the broth from steaming soybeans in the manufacturing process of natto, miso, etc., the residual liquid that does not coagulate tofu in the tofu manufacturing process, and the soaking liquid when soybeans are soaked in water, etc. As the electrodialysis device used in the present invention, a known device can be used. The membrane used in the electrodialysis device is preferably an ion exchange membrane such as an anion membrane or a cation membrane, and specific examples include (a) Selemion (manufactured by Asahi Glass Co., Ltd.), (b) Neoceptor (manufactured by Tokuyama Soda Co., Ltd.),
(c) Ionics membrane (manufactured by Ionics, USA), (d)
Membranes from other manufacturers (such as those manufactured by Asahi Kasei Corporation) can be mentioned. In the present invention, in the step before desalting the plant extract using an electrodialysis membrane,
It is important to include a filtration step using a ~17500 ultrafiltration membrane. Preferably a molecular weight cutoff of 2500
~12500 ultrafiltration membranes are suitable. Molecular weight cutoff
If it is less than 1500, the recovery rate of the target sugar component will decrease, which is not preferable. If the molecular weight cutoff exceeds 17,500, the effect of removing membrane contaminants will be low and electrodialysis will be inhibited, resulting in a decrease in desalting efficiency, which is undesirable. Furthermore, if desired, in the present invention, before the step of desalting the plant extract using an electrodialysis membrane, that is,
Before or after the step of filtration using an ultrafiltration membrane with a molecular weight cutoff of 1500 to 17500, perform reverse osmosis filtration using a reverse osmosis membrane with a sodium chloride rejection rate of 80% or less (preferably 10 to 70%). can include steps. Here, the sodium chloride rejection rate (%) is expressed by the following formula. (1-Sodium chloride concentration in permeate solution/Sodium chloride concentration in stock solution) x 100 This reverse osmotic filtration allows the concentration of plant extracts and the removal of low-molecular substances (amino acids, organic acids, , salts, etc.) and the effect of concentrating oligosaccharides, and are preferable in the process of processing plant extracts. Not only can salts and the like be removed to some extent, reducing the load on electrodialysis, but also browning reactants such as amino acids can be removed, which has the effect of whitening the color tone of the resulting oligosaccharide mixture. When the sodium chloride rejection rate exceeds 80%, the electrodialysis load of the plant extract containing concentrated oligosaccharides increases (specifically, the initial electrical conductivity increases).
I don't like it very much. In addition, a reverse osmosis membrane with a sodium chloride rejection rate of less than 10% reduces the electrodialysis load and is preferable for electrodialysis, but on the other hand, it is undesirable because the recovery rate of plant extracts containing oligosaccharides decreases. Furthermore, if desired, in the present invention, the molecular weight cut-off
Before the filtration process using an ultrafiltration membrane of 1500 to 17500, the plant extract (generally highly acidic) is
The method may include a step of adjusting the pH to 7.0 to 8.3, heating if necessary, and removing sludge that is formed.
Known separation means such as filtration and centrifugation can be used to remove the dregs. It has the effect of further increasing the efficiency of electrodialysis. Furthermore, a sterilizing effect can be added by heating. In addition, in the present invention, depending on the plant extract,
If desired, a step of filtration using an ultrafiltration membrane having a molecular weight cutoff of 20000 to 100000 may be included before the step of filtration using an ultrafiltration membrane having a molecular weight cutoff 1500 to 17500. By removing high molecular substances such as proteins in advance, the molecular weight cutoff is 1500~
It has the effect of extending the life of the 17500 ultrafiltration membrane. In addition, as a method of protein removal other than using such an ultrafiltration membrane, a thermal history equivalent to 10 minutes or more is applied at 100°C or higher (preferably in the presence of calcium ions).
Alternatively, the protein can be made insolubilized and removed using known means. Plant extracts containing oligosaccharides desalted by such a method can be widely used industrially, depending on the type of oligosaccharides. For example, soybean whey in soybean extract generally has a dry solid content of less than 10% (usually 2 to 5%), and the sugar component in the dry solid content is approximately
It contains about 50% crude protein, about 21% crude protein, and about 25% ash, and by desalting it using the method of the present invention,
Sugar content in dry solids is at least 80% (usually
95% or more), ash content is approximately 8% or less (usually 5% or less)
stachyose is usually 45% or more, raffinose is usually 10% or more, that is, oligosaccharides are at least 30% (usually
55% or more) soybean extract (oligosaccharide mixture). (Example) Embodiments of the present invention will be described below with reference to Examples. Example 1 Extract 10 kg of defatted soybeans with 150 kg of warm water (50°C),
The okara was removed by centrifugation to obtain 130 kg of soy milk.
Then, the pH was adjusted to 4.5 and the curd was separated to obtain soybean whey 100 (referred to as A). This soy whey has a dry solid content of 2.4Kg (sugar 1.3Kg, protein 0.5Kg,
The ash content was 0.6 kg). Next, protein was removed using an ultrafiltration membrane with a molecular weight cutoff of 20,000 (DUY-M, manufactured by Daicel Corporation) to obtain Permeate (filtrate) 90 (referred to as B). Next, a reverse osmosis membrane (DRS-10 manufactured by Daicel) with a sodium chloride rejection rate of 15% (molecular weight cutoff approximately 200) was used.
The mixture was concentrated 5 times at a pressure of 15 kg/cm ² and 10° C. to obtain 18 concentrated liquids (referred to as C). Then adjust the pH to 7.8 using 5N NaOH.
After heating at 120°C for 10 minutes, centrifuge (2000g) to remove the resulting sludge, and remove the supernatant of 16 (referred to as D).
I got it. Next, using an ultrafiltration membrane with a molecular weight cutoff of 5000 (DUY-HH manufactured by Daicel), the membrane was removed at the same time as contaminants and concentrated at 20°C and a pressure of 7 kg/cm ² to obtain 13 permeates (referred to as E). Obtained. Next, using an electrodialysis device (Stack Pack manufactured by Yuasa Ionics), the flow rate was 1.4 m/sec.
Using 20 pairs of electrodialysis membranes consisting of an anion membrane and a cation membrane of 2.2 dm ² per 10, the electrical conductivity of the liquid decreased to an initial electrical conductivity of 13200 μS/cm ² in 90 minutes at a voltage of 30 V.
The mixture was treated until the concentration was 1020 μS/cm ² or less, and desalted to obtain an oligosaccharide mixture (referred to as F). The relationship between electrical conductivity and electrodialysis treatment time at this time is shown in FIG. The obtained liquid F had a dry solid content of 5.1% by weight, a sugar content of 97% by weight, and an ash content of 3% by weight in the dry solid content,
Of the sugars, sucrose was 38% by weight, stachyose was 49% by weight, raffinose was 13% by weight, and verbascose was in a trace amount. Comparative Example 1 Sixteen supernatants D obtained in the same manner as in Example 1 were electrodialyzed without being treated with an ultrafiltration membrane having a molecular weight cut off of 5000. It took 270 minutes for the liquid conductivity to reach 1300 μS/cm ² , which is less than one-tenth of the initial electrical conductivity of 13800 μS/cm ² . However, it was clear that the anion membrane was contaminated and subsequent electrodialysis would significantly prolong the electrodialysis treatment time. The relationship between electrical conductivity and electrodialysis treatment time at this time is shown in FIG. Example 2 Soybean whey 100 (referred to as A) was obtained from 10 kg of defatted soybeans in the same manner as in Example 1, and then an ultrafiltration membrane with a molecular weight cutoff of 20,000 (HFA-20 manufactured by Abcor) was obtained.
Perform protein removal using permeate (filtrate) 90
(referred to as B) was obtained, and then using a reverse osmosis membrane (DRS-10 manufactured by Daicel Corporation) with a sodium chloride rejection rate of 15% (molecular weight cut off 200), a pressure of 15 Kg/cm ² and 10 ° C.
Concentrate 5 times to obtain a concentrated solution of 18 (referred to as C).
Thirteen permeates (referred to as E) were obtained by removing the pollutants and concentrating them simultaneously using a PBIL membrane (TL-215). Next, using an electrodialysis membrane (Celemion manufactured by Asahi Glass Co., Ltd.) without PH treatment, at a flow rate of 1.4 m/sec, using 20 pairs of electrodialysis membranes consisting of an anion membrane and a cation membrane of 2.2 dm ² per 10, the voltage was increased. 30V, 150
Initial electrical conductivity is 13,500 μS/cm ² at 10 min.
An oligosaccharide mixture (referred to as F) was obtained by desalting to 1200 μS/cm ² , which is less than one-fold. The relationship between electrical conductivity and electrodialysis treatment time at this time is shown in FIG. The obtained liquid F had a dry solid content of 5.3% by weight, a sugar content of 93% by weight, and an ash content of 5% by weight in the dry solid content,
Of the sugars, sucrose was 40% by weight, stachyose was 47% by weight, raffinose was 13% by weight, and verbascose was in a trace amount. Comparative Example 2 18 Concentrated Solution C obtained in the same manner as in Example 2 was subjected to electrodialysis treatment without treatment with an ultrafiltration membrane having a molecular weight cut off of 4000. It took 400 minutes for the liquid conductivity to reach 1300μS/cm ² , which is less than one-tenth of the initial electrical conductivity of 13500μS/cm ² .
In addition, the anion membrane was so contaminated that it was difficult to continue electrodialysis treatment. The relationship between electrical conductivity and electrodialysis treatment time at this time is shown in FIG. Example 3 Soak 20 kg of whole soybeans in 200 kg of water overnight, then drain the water.
200 kg of water was added again and the mixture was ground to obtain Go. then 90
The mixture was heated at ℃ for 5 minutes and filtered through a No. 3 filter cloth (140 mesh) to obtain 160 kg of soy milk. Then, the so-called Yu120 obtained when producing tofu by adding calcium sulfate
Using a reverse osmosis membrane (Teijin TL-230) with a sodium chloride rejection rate of 15%, the mixture was concentrated 5 times at a pressure of 15 kg/cm ² at 10°C to obtain 24 concentrated liquids. Next, using an ultrafiltration membrane with a molecular weight cutoff of 5000 (DUY-HH, manufactured by Daicel), the membrane-removed contaminants and concentration were simultaneously performed to obtain 19 permeates. Next, using an electrodialysis device (Stack Pack manufactured by Yuasa Ionics) at a flow rate of 1.4 m/sec, using 20 pairs of electrodialysis membranes of 2.2 dm ² per 10,
The liquid conductivity becomes the initial electrical conductivity at a voltage of 30V and 250 minutes.
An oligosaccharide mixture was obtained by desalting to a concentration of 1,600 μS/cm ² , which is less than one-tenth of 28,000 μS/cm ² . The resulting liquid had a sugar content of 83% by weight and an ash content of 5% by weight in the dry solid content. Example 4 Add 150 kg of 70% ethanol to 10 kg of defatted soybeans,
Soybean whey 120 was obtained by stirring and extraction. Ethanol was removed using an evaporator to obtain soybean whey 45 (dry solid content: 2.8 Kg, sugar content: 1.9 Kg). Next, remove contaminants using an ultrafiltration membrane with a molecular weight cutoff of 5000 (DUY-HH manufactured by Daicel).
Got 38 permeates. Next, desalination was performed in the same manner as in Example 1 using an electrodialysis device (Stack Pack manufactured by Yuasa Ionics), and freeze-dried to obtain a powdered oligosaccharide mixture (1.7 kg). The sugar content was 91% and the ash content was 7%. Example 5

[Table] Soybean whey A obtained in the same manner as in Example 1
Permeate B obtained by ultrafiltration was treated with a reverse osmosis membrane to obtain a concentrated solution C, and the pH was adjusted to 7.8 to remove the resulting sludge. The time (minutes) required for the sugar recovery rate and electrical conductivity to become one-tenth of the initial electrical conductivity when electrodialyzing permeate obtained by changing
(time*) was shown. As is clear from the table, when the molecular weight cutoff of the ultrafiltration membrane is less than 1500, the electrical conductivity is lower than the initial electrical conductivity.
Although the time required to reduce the amount to 1/10 is short (in other words, the electrodialysis efficiency is good), the sugar recovery rate decreases, which is not desirable. In addition, when the molecular weight cutoff of the ultrafiltration membrane exceeds 17,500, the sugar recovery rate improves, but the time required for the electrical conductivity to become one-tenth of the initial electrical conductivity increases (in other words, This is undesirable because electrodialysis efficiency deteriorates), membrane contamination becomes severe, and electrodialysis becomes difficult. Here, the sugar recovery rate is expressed by the following formula. Sugar recovery rate = sugar concentration of permeate / liquid sugar concentration before ultrafiltration x 100% Experimental example 1 Permeate (B) obtained by ultrafiltrating soybean whey (A) obtained in the same manner as in Example 1. Sugar recovery rate of 5-fold concentrated solution C obtained by reverse osmosis pressure filtration with the sodium chloride rejection rate of the reverse osmosis membrane changed as shown in the following table The following table shows the initial electrical conductivity (μS/cm ² ) when this solution was applied to an electrodialyzer under the same conditions as in Example 1.

[Table] However, 100% sodium chloride rejection was obtained by concentrating 5 times using an evaporator. Also, the same blocking rate is 3~
10% is Teijin YBIL membrane TL-215, same rejection rate 5 ~
20% is Teijin YBIL membrane-230, rejection rate 50-70
% was Nitto Denko NTR-7250, and the same rejection rate was 95% using Daicel DRS-95. From this result, when the sodium chloride rejection rate of the reverse osmosis membrane increases (in other words, it becomes difficult for low-molecular substances to permeate), the initial electrical conductivity in the electrodialysis treatment of 5 times concentrated liquid C increases, and the electrodialysis Because the processing is burdensome and the electrodialysis processing time is prolonged,
It is appropriate that the sodium chloride rejection rate is not large, preferably within 80%. Furthermore, if the sodium chloride rejection rate of the reverse osmosis membrane is less than 10%, the recovery rate of the sugar content of the 5-fold concentrated solution C will decrease, which is undesirable because the yield of the oligosaccharide mixture after the subsequent electrodialysis treatment will decrease. Furthermore, the color tone of the dried oligosaccharide mixture obtained tended to become whiter as the sodium chloride rejection rate decreased. Experimental Example 2 In the same manner as in Example 1, soybean whey A was obtained, and permeate B obtained by ultrafiltration was treated with a reverse osmosis membrane to obtain a 5-fold concentrated solution C. This solution was purified by PH using 5N NaOH. was adjusted to 6.0 to 8.6 and heated at 120°C for 10 minutes, and the resulting sludge was removed by centrifugation (2000 g), and the obtained supernatant (referred to as D) was electrodialyzed in the same manner as in Example 1. FIG. 2 shows the relationship between electrical conductivity and treatment time. This figure shows that electrodialysis can be performed more efficiently by adjusting the pH. It can be seen that a pH of 7.0 to 8.3 is suitable. (Effects) As detailed above, the present invention (that is, in the step before electrodialysis, an ultrafiltration membrane with a molecular weight cutoff of 1500 to 17500, preferably a molecular weight cutoff of 2500 to 12500
By filtration using an ultrafiltration membrane, membrane contaminants that inhibit electrodialysis can be removed and desalination can be carried out efficiently). It is something that has become easier. Furthermore, the method of the present invention can be applied to, for example, microbial extracts, as long as the oligosaccharide solution contains membrane contaminants such as electrodialysis membranes.
The resulting low-ash, high-purity oligosaccharide mixture can be widely applied in the food field as a sweetener with suppressed sweetness, and can also be widely used industrially as a microbial growth promoter, etc., and the present invention will contribute to the development of industry. This will contribute greatly.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between electrical conductivity and electrodialysis treatment time in electrodialysis treatment of plant extracts. 1...Example 1, 2...Example 2, 3...Comparative example 1, 4...Comparative example 2, Figure 2 shows the electrical conductivity and electrodialysis treatment in electrodialysis treatment of PH-treated plant extract FIG. 3 is a diagram showing a time relationship. 1...PH
7.7, 2...PH7.2, 3...PH8.6, 4...PH6.0.

Claims (1)

[Claims] 1. A step of filtering the plant extract using an ultrafiltration membrane with a molecular weight cutoff of 1,500 to 17,500 (preferably 2,500 to 12,500) before desalting the plant extract using an electrodialysis membrane; and a method for desalting a plant extract, comprising the step of performing reverse osmosis filtration using a reverse osmosis membrane with a sodium chloride rejection rate of 80% or less before or after the filtration step. 2. The desalination method according to claim 1, further comprising the steps of adjusting the pH to 7.0 to 8.3 and removing sludge. 3. Claims 1 or 2, wherein the desalted plant extract contains 80% by weight or more of sugars in the dry solid content, and 30% by weight or more of oligosaccharides of three or more monosaccharides. Desalination method as described. 4. The desalting method according to claim 3, wherein the oligosaccharide is mainly composed of raffinose and stachyose. 5. The desalting method according to any one of claims 1 to 4, wherein the plant extract is a soybean extract.