Activated carbon and method for removing riboflavin

Abstract

The objective is to provide activated carbon that exhibits high selective adsorption of riboflavin even in the presence of lactose, and further, to provide a method for removing riboflavin using said activated carbon. [Solution] Activated carbon in which, in the interval pore volume calculated by the CI method from the nitrogen adsorption isotherm at 77K, the ratio ((A) / (B)) of the pore volume (A) with a pore diameter greater than 2 nm and less than or equal to 5 nm (B) to the pore volume with a pore diameter of 2 nm or less is 0.2 or more and 3.5 or less, and the total amount of acidic functional groups measured by the Boehm method is 0.3 meq / g or more and 2.5 meq / g or less.

Description

[Technical Field]

[0001] The present invention relates to activated carbon and a method for removing riboflavin. [Background technology]

[0002] Riboflavin is an essential nutrient found in various foods such as milk, egg whites, and liver, and is also known as vitamin B2 or lactoflavin. Riboflavin is classified as a water-soluble vitamin and exists in the body as an essential component of the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN).

[0003] On the other hand, riboflavin is highly photosensitive, and when exposed to a certain amount of light, such as fluorescent lamps or sunlight, photo-oxidation of riboflavin generates radicals. It is known that these radicals oxidize lipids, resulting in off-flavors.

[0004] Technologies for reducing photo-induced off-odors from dairy products or skim milk have been disclosed to date. For example, Patent Document 1 discloses skim milk in which the expression of photo-oxidation-induced off-odors is reduced by the removal of riboflavin, and a method for producing the same. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-148618 [Overview of the project] [Problems that the invention aims to solve]

[0006] Conventional inventions, as shown in Patent Document 1, remove riboflavin by contacting skim milk, a water-soluble component, with a synthetic adsorbent resin, but this method has the problem of having a limited range of application.

[0007] Activated carbon is a possible adsorbent that can solve the above problems. However, with conventional activated carbon, when attempting to adsorb and remove riboflavin from a composition containing lactose along with riboflavin, such as dairy products, it tends to adsorb lactose as well.

[0008] This invention has been made in view of these circumstances, and aims to provide activated carbon that exhibits high selective adsorption of riboflavin even in the presence of lactose, and further aims to provide a method for removing riboflavin using said activated carbon. [Means for solving the problem]

[0009] Generally, milk is a food rich in various nutrients, with water, carbohydrates, proteins, lipids, vitamins, and minerals being its main components. Water accounts for approximately 80% of the total content of milk, followed by carbohydrates, particularly lactose. It is generally known that 100 mL of milk contains approximately 4.8 g of lactose.

[0010] On the other hand, riboflavin is one of the representative water-soluble vitamins found in milk, but its content is relatively small, amounting to only about 0.15 mg per 100 mL of milk.

[0011] Initially, the inventors' studies suggested that riboflavin, with a molecular weight of 376.36, would readily adsorb to micropore regions that contribute to the adsorption of low-molecular-weight substances. However, lactose, a major carbohydrate found in milk, is a disaccharide with a molecular weight of approximately 342.30, and its abundance is significantly greater than that of riboflavin. Furthermore, the molecular weights of the two are similar. Therefore, the inventors concluded that the influence of lactose cannot be ignored in separation operations to selectively remove or recover riboflavin, and that separation performance from lactose must be considered when removing or recovering riboflavin.

[0012] The inventors conducted diligent research and discovered that when the ratio ((A) / (B)) of the pore volume (A) between 2 nm and 5 nm in diameter to the pore volume (B) of activated carbon with a pore diameter of 2 nm or less is within a specific range, the ratio ((C) / (D)) of the riboflavin removal rate (C) to the lactose removal rate (D) increases, indicating that activated carbon has a high riboflavin removal capacity even in the presence of lactose. They also discovered that when the total amount of acidic functional groups in activated carbon is within a certain range, the above ratio (C) / (D) increases, indicating that activated carbon has a high riboflavin removal capacity even in the presence of lactose. This invention was completed based on these findings and further research.

[0013] In other words, we discovered activated carbon with high selective adsorption capacity for riboflavin even in the presence of lactose, using the following configuration, and arrived at the present invention. The present invention encompasses the following preferred embodiments.

[0014] [1] In the interval pore volume calculated by the CI method from the nitrogen adsorption isotherm at 77K, The ratio ((A) / (B)) of the pore volume of pores with a diameter of 2 nm or less (B) to the pore volume of pores with a diameter of 2 nm or less (A) with a diameter of 5 nm or less is between 0.2 and 3.5. Activated carbon in which the total amount of acidic functional groups, as measured by the Boehm method, is between 0.3 meq / g and 2.5 meq / g.

[0015] [2] The activated carbon according to [1], which is a riboflavin adsorbent for adsorbing riboflavin in a riboflavin-containing composition.

[0016] [3] The activated carbon according to [2], wherein the riboflavin-containing composition is a food, a pharmaceutical, a cosmetic, or a raw material thereof.

[0017] [4] The specific surface area calculated by the BET method from the nitrogen adsorption isotherm at 77K was 1100m 2 / g or more 2000m 2 Activated carbon described in any of [1] to [3], which is less than or equal to / g.

[0018] [5] The activated carbon according to any one of [1] to [4], having a bulk density of 0.20 g / mL or more and 0.50 g / mL or less.

[0019] [6] A riboflavin removal method having an adsorption step of adsorbing riboflavin in a riboflavin-containing composition onto the activated carbon according to any one of [1] to [5].

[0020] [7] The adsorption step is taken as the first adsorption step, A desorption step of desorbing the riboflavin from the activated carbon after the first adsorption step by washing with water or an alkali, And a second adsorption step of adsorbing riboflavin in a new riboflavin-containing composition onto the activated carbon after the desorption step. The riboflavin removal method according to [6].

Advantages of the Invention

[0021] According to the present invention, it is possible to provide an activated carbon having high selective adsorbability for riboflavin even in the coexistence of lactose, and a riboflavin removal method using the activated carbon.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention. A numerical range represented by "~" includes the numerical values before and after "~".

[0023] <Activated Carbon> [Ratio of Pore Volume in Intervals] The activated carbon of this embodiment has a ratio ((A) / (B)) of the pore volume (A) [mL / g] with a pore diameter exceeding 2 nm and not exceeding 5 nm to the pore volume (B) [mL / g] with a pore diameter of 2 nm or less, in the pore volume in intervals calculated by the CI (Cranston-Inkley) method from the nitrogen adsorption isotherm at 77K, being 0.2 or more and 3.5 or less.

[0024] The inventors have found that pores with a diameter greater than 2 nm and less than or equal to 5 nm readily adsorb riboflavin molecules, while micropores with a diameter of 2 nm or less readily adsorb lactose molecules. Therefore, the larger the ratio ((A) / (B)) of the pore volume of pores greater than 2 nm and less than or equal to 5 nm (A) to the pore volume of pores with a diameter of 2 nm or less (B), the higher the selective adsorption of riboflavin tends to be. Specifically, a ratio ((A) / (B)) of 0.2 or higher results in sufficiently high selective adsorption of riboflavin. Furthermore, a ratio ((A) / (B)) of 0.5 or higher tends to result in even higher selective adsorption of riboflavin. A ratio ((A) / (B)) of 1.0 or higher is more preferable.

[0025] On the other hand, if the ratio ((A) / (B)) is too large, the adsorption of riboflavin is likely to be inhibited due to competition with substances of similar size to riboflavin, if such substances are present. In this embodiment, the activated carbon has a ratio ((A) / (B)) of 3.5 or less, which reduces the possibility of inhibition of riboflavin adsorption. A ratio ((A) / (B)) of 3.2 or less is preferable.

[0026] [Total acidic functional group amount] The activated carbon of this embodiment has a total acidic functional group content of 0.3 meq / g or more and 2.5 meq / g or less, as measured by the Boehm method.

[0027] When the total amount of acidic functional groups is 0.3 meq / g or more, the activated carbon surface becomes hydrophilic, increasing its affinity for water, and thus the activated carbon surface is more easily covered by water molecules. This suppresses the movement of hydrophilic substances, especially lactose, to the activated carbon surface, making them less likely to be adsorbed. As a result, the selective adsorption of riboflavin is improved. Furthermore, when the total amount of acidic functional groups is 0.3 meq / g or more, the increased hydrophilicity of the activated carbon surface makes it easier for riboflavin to desorb from the activated carbon. As a result, the efficiency of repeated recycling is increased. The total amount of acidic functional groups in the activated carbon is more preferably 0.4 meq / g or more, and even more preferably 0.5 meq / g or more.

[0028] In addition, when the total amount of acidic functional groups is 2.5 meq / g or less, deterioration of the graphite structure on the activated carbon surface and the functional groups imparted by oxidation partially block the pore entrances, making it less likely for the specific surface area to decrease. As a result, it becomes less likely for the adsorptivity of riboflavin to decrease. The total amount of acidic functional groups of the activated carbon is more preferably 2.2 meq / g or less, and even more preferably 2.0 meq / g or less.

[0029] [Specific surface area] The activated carbon of this embodiment preferably has a specific surface area calculated by the BET (Brunauer - Emmett - Teller) method from the nitrogen adsorption isotherm at 77K of 1100 m 2 / g or more and 2000 m 2 / g or less.

[0030] When the specific surface area of the activated carbon is 1100 m 2 / g or more, sufficient adsorption performance can be ensured. The specific surface area of the activated carbon is more preferably 1200 m 2 / g or more, and even more preferably 1300 m 2 / g or more.

[0031] When the specific surface area of the activated carbon is 2000 m 2 / g or less, there is a tendency for fewer micropores that do not contribute to the adsorption of riboflavin, so the adsorptivity of riboflavin tends to be high. Also, when the specific surface area is 2000 m 2 / g or less, since the micropores do not predominate, the diffusion resistance does not become too large, and the adsorption rate tends to be less likely to decrease. Furthermore, when the specific surface area is 2000 m 2 / g or less, excessive activation to obtain a high specific surface area is not required, so the structure is less likely to be weakened and pulverized. The specific surface area of the activated carbon is more preferably 1950 m 2 / g or less, and even more preferably 1900 m 2 / g or less.

[0032] [Packing density] In this embodiment, the activated carbon preferably has a packing density of 0.20 g / mL or more and 0.50 g / mL or less. In this specification, the packing density of the activated carbon can be measured, for example, in accordance with JIS K 1474.

[0033] When the packing density of activated carbon is 0.20 g / mL or higher, the volume of riboflavin that can be adsorbed relative to the volume of activated carbon tends to be larger. Also, when the packing density is 0.20 g / mL or higher, the particle strength of the activated carbon tends to be higher, and as a result, the decrease in handling ease due to dust dispersion and the decrease in ease of filtration (solid-liquid separation) are less likely to occur. A packing density of 0.23 g / mL or higher is more preferable, and 0.26 g / mL or higher is even more preferable.

[0034] When the packing density is 0.50 g / mL or less, the pressure loss is reduced, and the contact efficiency between activated carbon and riboflavin increases, resulting in a faster adsorption rate and a tendency for a larger adsorption amount per unit time. The packing density of the activated carbon is more preferably 0.47 g / mL or less, and even more preferably 0.44 g / mL or less.

[0035] [Iodine adsorption performance] Iodine adsorption performance is an indicator of liquid-phase adsorption capacity. In this embodiment, the activated carbon preferably has an iodine adsorption performance of 500 mg / g or more and 1400 mg / g or less. In this specification, the iodine adsorption performance of activated carbon can be measured, for example, in accordance with JIS K 1474.

[0036] When the iodine adsorption capacity of activated carbon is 500 mg / g or higher, the adsorption capacity of riboflavin increases, and as a result, the selective adsorption capacity of riboflavin in the presence of lactose tends to increase. The iodine adsorption capacity of activated carbon is more preferably 600 mg / g or higher, and even more preferably 700 mg / g or higher.

[0037] Furthermore, if the iodine adsorption performance of the activated carbon is 1400 mg / g or less, the lactose adsorption performance is suppressed, and as a result, the selective adsorption of riboflavin in the presence of lactose tends to be higher. The iodine adsorption performance of the activated carbon is more preferably 1300 mg / g or less, and even more preferably 1200 mg / g or less.

[0038] [Ignition residue] In this embodiment, the activated carbon preferably has an ignition residue of 3.0% by mass or less. In this specification, the ignition residue of activated carbon can be measured, for example, in accordance with JIS K 1474.

[0039] The ignition residue serves as an indicator of the amount of metal ions contained in the activated carbon. When the amount of metal ions is low, the acidic functional groups are less likely to adsorb the metal ions, making the activated carbon surface more hydrophilic. As a result, the activated carbon surface is more easily covered with water molecules, suppressing the movement of hydrophilic lactose to the activated carbon surface, thus improving the selective adsorption of riboflavin. From this viewpoint, the activated carbon of this embodiment preferably has an ignition residue of 3.0% by mass or less. Furthermore, an ignition residue of 3.0% by mass or less makes it suitable for liquid-phase adsorption applications. The ignition residue of the activated carbon is more preferably 2.9% by mass or less, and even more preferably 2.8% by mass or less.

[0040] The lower limit of the ignition residue is not particularly limited, but is usually 0.0001% by mass or more, preferably 0.001% by mass or more, and more preferably 0.01% by mass or more.

[0041] [Shape of activated carbon] The shape of the activated carbon in this embodiment is not limited and can be particulate, pelletized, fibrous, or sheet-shaped, with particulate being preferred. Examples of particulate form include powder, spherical, and crushed chips.

[0042] Examples of powdered activated carbon include fine powder, powder, fine granules, and granules. Powdered activated carbon is suitably used, for example, as an adsorbent used batch by batch processing. Powdered activated carbon is also suitably used, for example, as a raw material for molded bodies. Pellet-shaped and crushed chip-shaped activated carbon is suitably used, for example, as an adsorbent used continuously in column processing and flow-through processing.

[0043] <Method for manufacturing activated carbon> A method for producing activated carbon may include a gas activation step in which the carbonized product obtained by carbonizing the raw material is gas-activated with an activated gas, and an adjustment step in which the total amount of acidic functional groups in the activated product obtained in the gas activation step is adjusted. It is preferable that the activated carbon is obtained through these steps.

[0044] Another method for producing activated carbon may include a chemical activation step in which a raw material is impregnated with an activator and heated, and an adjustment step in which the total amount of acidic functional groups in the activated product obtained in the chemical activation step is adjusted. It is also preferable that the activated carbon be obtained through these steps.

[0045] (raw materials) Examples of raw materials for activated carbon include plant-based materials (wood, bamboo, fruit shells (coconut shells, etc.), etc.), mineral-based materials (coal, lignite, petroleum or coal pitch, etc.), and polymer materials (phenolic resins, cellulose, polyacrylonitrile, etc.). Activated carbon can be obtained by carbonizing and / or activating these raw materials as needed. Among these activated carbon raw materials, plant-based materials are preferred from the viewpoint of addition to food and low impurity content, and wood, wood powder, and sawdust are more preferred from the viewpoint of easy adjustment of specific surface area and pore volume ratio.

[0046] (Gas activation process) After converting the aforementioned raw materials into carbonized material by steaming or other known methods, an activated product is obtained through a gas activation process.

[0047] The gas activation process can be carried out using known methods, such as treating the material in a gas containing an active gas like water vapor or carbon dioxide at a temperature of 700 to 1000°C. This forms pores on the surface of the carbide, making it easier to obtain activated carbon with the above ratio (A) / (B) being between 0.2 and 3.5. As a result, oxygen atoms contained in the active gas form acidic functional groups on the surface of the activated carbon, making it possible to suitably obtain activated carbon with a total acidic functional group content of 0.3 meq / g to 2.5 meq / g.

[0048] The gas activation time is not particularly limited, but is, for example, 30 minutes to 48 hours, preferably 40 minutes to 36 hours, and more preferably 50 minutes to 24 hours.

[0049] (Chemical activation process) The chemical activation process, which involves impregnating the raw material with an activator and heating it, is not particularly limited, and conventional methods can be used. Examples of activators include inorganic acids and inorganic bases such as zinc chloride, phosphoric acid, alkalis, and alkaline earth metal compounds. After mixing aqueous solutions of these with the raw material and impregnating it, the activated material is obtained by heat treatment at, for example, 300 to 800°C. The chemical activation process promotes carbonization and pore formation of the raw material, making it easier to obtain activated carbon in which the above ratio (A) / (B) is between 0.2 and 3.5.

[0050] The atmospheric gas in the chemical activation process is not particularly limited, but in the case of zinc chloride activation using zinc chloride as the activator, it is preferable that the atmospheric gas contains oxygen. In zinc chloride activation, by setting the oxygen concentration in the atmospheric gas to 0.1% by volume or higher, functional groups are imparted to the activated carbon by the oxygen in the atmospheric gas along with the dehydration condensation reaction of the raw materials during zinc chloride activation, making it easier to obtain activated carbon with a total acidic functional group content of 0.3 meq / g to 2.5 meq / g. In zinc chloride activation, the upper limit of the oxygen concentration in the atmospheric gas is not particularly limited, but by setting it to 50% by volume or lower, preferably 30% by volume or lower, consumption due to combustion of the activated carbon does not occur, and activated carbon with a total acidic functional group content of 0.3 meq / g to 2.5 meq / g is preferably obtained. There are no particular restrictions on the coexisting gas used to adjust the oxygen concentration in the atmospheric gas; for example, nitrogen, carbon dioxide, argon, or water vapor can be used.

[0051] The duration of drug activation is not particularly limited, but is, for example, 30 minutes to 48 hours, preferably 40 minutes to 36 hours, and more preferably 50 minutes to 24 hours.

[0052] (adjustment process) The activated material obtained in this manner is then subjected to a subsequent adjustment process to become activated carbon with an adjusted total amount of acidic functional groups. The adjustment process consists of either a washing process, an oxidation process, or a combination thereof. A preferred configuration of the adjustment process is a washing process, and it is also preferable to go through an oxidation process after the washing process. It is preferable that the activated carbon is obtained through these adjustment processes.

[0053] (Washing process) Activated materials typically have acidic functional groups such as carboxyl groups, lactone groups, and phenolic hydroxyl groups on their surface. In the case of gas activation, some or all of the acidic functional groups tend to become basic metal salts through ionic bonding with metal ions contained in the raw material. In the case of chemical activation, some or all of the acidic functional groups tend to become bonded (hydrogen bonded and / or esterified) or coordinate bonded with the activator. Through the washing process, metal ions or activators are removed, and some or all of the functional groups that were bonded to them are restored as acidic functional groups. For this reason, by going through the washing process, activated carbon in which the total amount of acidic functional groups is particularly suitable to be obtained, is 0.3 meq / g or more and 2.5 meq / g or less.

[0054] The amount of metal ions and activators contained in the filtrate obtained by washing the activated material is not particularly limited, as long as the total amount of acidic functional groups is between 0.3 meq / g and 2.5 meq / g. However, when activated carbon is used in contact with the riboflavin-containing composition, it is preferable that the activated carbon has high purity. From this viewpoint, it is preferable that the amount of metal ions and activators contained in the filtrate be 10% by mass or less relative to the dry weight of the filtrate.

[0055] The washing process involves contacting the activator with water or an aqueous solution containing an acid or base. The method of contact is not particularly limited; for example, the activator may be placed in a container containing neutral water or an aqueous solution containing an acid or base and immersed and / or stirred, or the activator may be filled into a cylinder and contacted by flowing neutral water or an aqueous solution containing an acid or base in an upward / downward flow through the cylinder. The ratio of the amount of neutral water or an aqueous solution containing an acid or base to be contacted with the activator is also not particularly limited, but sufficient removal of metal ions or activators can be achieved by using a ratio of 100 to 10,000 parts by mass of neutral water or an aqueous solution containing an acid or base per 100 parts by mass of the activator.

[0056] The amount of recovered acidic functional groups can be estimated by the pH of the filtrate, specifically the pH of the aqueous solution containing water, acid, or base that has been brought into contact with the activator or filter. The pH range of the filtrate is preferably 3 to 9, and more preferably 4 to 8. By having a filtrate pH in the range of 3 to 9, metal ions or activators are sufficiently removed, and activated carbon with a total acidic functional group content of 0.3 meq / g to 2.5 meq / g can be suitably obtained.

[0057] The washing process may involve a single contact with a large amount of aqueous solution containing water, acid, or base, or multiple contacts, so that the pH of the filtrate containing water, acid, or base after contact with the activator or filter material is in the range of 3 to 9. If multiple contacts are performed, the pH of the filtrate containing water, acid, or base after the final contact should be within the above range. Multiple contacts are preferable, as this allows for more efficient removal of metal ions or activators, and makes it particularly easy to obtain activated carbon with a total acidic functional group content of 0.3 meq / g to 2.5 meq / g. When multiple contacts are performed, the type and composition of the aqueous solution containing water, acid, or base can be arbitrarily changed each time.

[0058] The acid used is not particularly limited; mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid, or organic acids such as formic acid and acetic acid can be used. The acid is preferably a mineral acid such as hydrochloric acid, sulfuric acid, or nitric acid, and more preferably hydrochloric acid. These may be used individually, or two or more may be mixed and used depending on the type of metal ion or activator. The base is also not particularly limited; hydroxides such as sodium hydroxide and potassium hydroxide, carbonates such as sodium carbonate and potassium carbonate, bicarbonates such as sodium bicarbonate and potassium bicarbonate, ammonia, and ammonium salts exhibiting weak basicity such as ammonium carbonate and ammonium bicarbonate can be used. The base is preferably a carbonate, bicarbonate, or ammonium salt, and more preferably ammonium bicarbonate.

[0059] The water used may contain ions of alkali metals such as sodium, or alkaline earth metals such as magnesium and calcium. For example, according to the "Standard Tables of Food Composition in Japan (8th Revised Edition) Supplementary Edition 2023, Table 26" of the Ministry of Education, Culture, Sports, Science and Technology, tap water in Japan contains up to 10.40 mg / 100g of sodium, 1.57 mg / 100g of magnesium, and 6.66 mg / 100g of calcium, although this varies by region. If these ions are present in large quantities, they will affect the total amount of acidic functional groups by ion exchange with acidic functional groups during the washing process, but the effect is small if they are present in amounts found in tap water. Specifically, it is preferable that the ions contained in the water used in the washing process are such that sodium is 104.0 mg / L or less (10.40 mg / 100g or less), magnesium is 15.7 mg / L or less (1.57 mg / 100g or less), and calcium is 66.6 mg / L or less (6.66 mg / 100g or less). This is preferable because it allows for a sufficiently small amount of ions to exchange with acidic functional groups during the washing process, making it easier to obtain activated carbon with a total acidic functional group content of 0.3 meq / g or more and 2.5 meq / g or less.

[0060] If the total amount of acidic functional groups in the washed product obtained through the washing process is between 0.3 meq / g and 2.5 meq / g, the washed product can be used as is or dried and then used as an adsorbent.

[0061] (Oxidation process) If the total amount of acidic functional groups in the activated material or washing material is insufficient, an oxidation treatment step may be performed. By going through the oxidation treatment step, acidic functional groups are additionally imparted to the surface of the washing material, making it easier to obtain activated carbon with a total amount of acidic functional groups of 0.3 meq / g or more and 2.5 meq / g or less.

[0062] The oxidation treatment method is not particularly limited; it may involve contact with an oxidizing gas in the gas phase, or a chemical reaction with an oxidizing agent in the liquid phase. Examples of oxidizing gases in the gas phase include oxygen, ozone, nitrogen dioxide, sulfur dioxide, chlorine dioxide, and water at high temperatures. Examples of oxidizing agents in the liquid phase include the aforementioned oxidizing gases, as well as nitric acid, chloric acid, hydrogen peroxide, and organic / inorganic peroxides (such as peracetic acid and peroxodisulfate). If oxidation treatment is performed, it is preferable to obtain activated carbon after additional washing. The additional washing is more preferably carried out by the washing process described above.

[0063] <Uses of activated carbon> The activated carbon in this embodiment may be a riboflavin adsorbent for adsorbing riboflavin in a riboflavin-containing composition. The riboflavin-containing composition is not particularly limited as long as it contains riboflavin, and may be food, pharmaceuticals, cosmetics, quasi-drugs, pet food, veterinary drugs, feed, fertilizers, pesticides, reagents, etc., or may be raw materials thereof.

[0064] The activated carbon of this embodiment is suitably used as a riboflavin adsorbent for adsorbing riboflavin in foods, pharmaceuticals, cosmetics, or their raw materials. Furthermore, because the activated carbon of this embodiment exhibits high selective adsorption of riboflavin even in the presence of lactose, it is particularly suitable as a riboflavin adsorbent for adsorbing riboflavin in dairy products containing relatively high concentrations of lactose.

[0065] Furthermore, "food" refers to all food and beverages, including drinks and dairy products. "Dairy products" refers to milk and products containing milk. Examples of "dairy products" include raw milk, cow's milk, special milk, raw goat's milk, pasteurized goat's milk, raw sheep's milk, raw buffalo milk, adjusted milk, low-fat milk, non-fat milk, processed milk, cream, butter, butter oil, cheese, concentrated whey, ice cream, concentrated milk, skimmed concentrated milk, unsweetened condensed milk, unsweetened skimmed condensed milk, sweetened condensed milk, sweetened skimmed condensed milk, whole milk powder, skimmed milk powder, cream powder, whey powder, protein-concentrated whey powder, buttermilk powder, sweetened milk powder, prepared milk powder, prepared liquid milk, fermented milk, lactic acid bacteria beverages, and milk beverages. In addition, "food" may also be a nutritional functional food, a food for specified health uses, or a food with functional claims.

[0066] The activated carbon of this embodiment is a food additive compliant product if it meets all the standards for properties, confirmation tests, and purity tests of activated carbon as recorded in "D. Component Standards and Storage Standards" of the 10th edition of the Japanese Food Additives Compendium, which was established in 2024. Such food additive compliant activated carbon may be used as a food additive as is, or it can be suitably used in food manufacturing processes, for example, as a riboflavin adsorbent that comes into direct contact with food ingredients in a process to adsorb and remove trace amounts of riboflavin from beverage ingredients containing a large amount of lactose.

[0067] <Method for removing riboflavin> The riboflavin removal method of this embodiment includes an adsorption step in which riboflavin in a riboflavin-containing composition is adsorbed onto the activated carbon of this embodiment.

[0068] The method for adsorbing riboflavin in a riboflavin-containing composition onto activated carbon is not particularly limited and includes, for example, adding activated carbon to a liquid riboflavin-containing composition and stirring, or contacting a cartridge filled with activated carbon with the riboflavin-containing composition.

[0069] In the riboflavin removal method, the riboflavin-containing composition may be, for example, a food, a pharmaceutical, a cosmetic, or a raw material thereof. Furthermore, since the activated carbon of this embodiment exhibits high selective adsorption of riboflavin even in the presence of lactose, the riboflavin removal method of this embodiment is suitably used when removing riboflavin from dairy products or raw materials thereof that contain relatively high concentrations of lactose. Accordingly, in the riboflavin removal method, the riboflavin-containing composition may particularly be a dairy product or a raw material thereof.

[0070] The activated carbon in this practical form tends to have high riboflavin desorption properties because its total acidic functional group content is 0.3 meq / g or more. Therefore, it can be reused by desorbing riboflavin after the adsorption step. For this reason, the riboflavin removal method of this embodiment may include a first adsorption step of adsorbing riboflavin from a riboflavin-containing composition onto the activated carbon of this embodiment, a desorption step of desorbing riboflavin from the activated carbon after the first adsorption step by washing with water or alkali, and a second adsorption step of adsorbing riboflavin from a new riboflavin-containing composition onto the activated carbon after the desorption step.

[0071] For water or alkaline washing in the desorption process, distilled water, deionized water, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate aqueous solution, sodium bicarbonate aqueous solution, etc., can be used as washing solutions. The concentration of the aqueous solution is, for example, 0.1 to 1.0 mol / L.

[0072] <Composition from which riboflavin has been removed> By using the activated carbon of this embodiment to remove riboflavin as described above, a composition from which riboflavin has been removed can be obtained. The composition from which riboflavin has been removed can be used as food, pharmaceuticals, cosmetics, or raw materials for these products.

[0073] A composition from which riboflavin has been removed preferably contains 30 to 150 mg / 100g (= 0.03 to 0.15% by mass) of vitamins such as riboflavin, 1.0 to 20% by mass of carbohydrates such as lactose, and has had riboflavin removed by a removal rate of 50% or more. Since such a composition from which riboflavin has been removed has suppressed odors derived from vitamins, it can be more preferably used, for example, as a food, pharmaceutical, cosmetic, or as a raw material for these. The riboflavin removal rate is the ratio of the difference in riboflavin concentration (mg / L) before and after riboflavin removal to the riboflavin concentration (mg / L) before riboflavin removal, and can be calculated using the following formula. Riboflavin removal rate (%) = (Riboflavin concentration before removal (mg / L) - Riboflavin concentration after removal (mg / L)) / Riboflavin concentration before removal (mg / L) × 100 [Examples]

[0074] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0075] 1. Preparation of activated carbon [Example 1] To 100 parts by mass of Japanese wood flour, 280 parts by mass of a 60% zinc chloride aqueous solution (prepared by dissolving Wako Pure Chemical Industries, Ltd.'s solution in distilled water) was added and left at room temperature for 4 hours. This mixture was then placed in a magnetic crucible and activated with zinc chloride for 1 hour in a box furnace (electric furnace, JTEKT Thermo Systems Co., Ltd. KBF848N2 (product name)) preheated to 600°C under an air atmosphere (oxygen concentration 20% by volume, nitrogen concentration 80% by volume) to obtain the activated product.

[0076] After allowing the activator to cool to room temperature, it was added to 1000 parts by mass of 3.5% hydrochloric acid (Wako Pure Chemical Industries, Ltd., prepared from 35% hydrochloric acid) per 100 parts by mass of the activator, stirred at 60°C for 30 minutes, and then filtered. This process was repeated one more time to obtain the filtrate. The filtrate contained 2.7% by mass of zinc chloride, an activator, relative to its dry weight. The filtrate was added to 1000 parts by mass of distilled water per 100 parts by mass, heated to 60°C, stirred for 30 minutes, and then filtered. The pH of this filtrate was 1. This operation was repeated four more times to confirm that the pH of the filtrate was 6, and the resulting washed material was dried to obtain the activated carbon of Example 1 with an adjusted total amount of acidic functional groups.

[0077] [Example 2] The washed material obtained in the same manner as in Example 1 was subjected to oxidation treatment. Specifically, the washed material was placed in a reaction vessel equipped with a stirring blade, and water was added to 100 parts by mass of the washed material so that the solid-liquid ratio of the washed material to water was 0.128, and mixed to obtain a slurry. 65.8 parts by mass of 60% nitric acid was added to the slurry, and the mixture was reacted at 80°C for 90 minutes, after which it was filtered to obtain a cake. This cake was placed in 1000 parts by mass of distilled water per 100 parts by mass, stirred at room temperature for 1 hour, and then filtered. The pH of this filtrate was 1. This operation was repeated 10 more times, and it was confirmed that the pH of the filtrate became 4. The obtained washed material was dried to obtain the activated carbon of Example 2, in which the total amount of acidic functional groups was adjusted.

[0078] [Example 3] 100 parts by mass of Japanese wood flour were mixed with 100 parts by mass of crushed raw coconut shells from the Philippines and 360 parts by mass of 85% phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.). This mixture was placed in a magnetic crucible and dried in a box furnace (electric furnace, JTEKT Thermo Systems Co., Ltd. KBF848N2 (product name)) pre-set to 140°C until the volatile content in air at 140°C was 5%. An appropriate amount of water was added, and the mixture was molded into pellets approximately 3 mm in diameter and 10 mm in length using a pre-extrusion molding machine (Fuji Powder MG-55). The resulting molded material was transferred to a magnetic crucible and heated in a box furnace (electric furnace, JTEKT Thermo Systems Co., Ltd. KBF848N2 (product name)) under a nitrogen atmosphere from room temperature at a rate of 10°C / min to 450°C, and then heated at 450°C for a further 30 minutes to obtain char.

[0079] The carbide was washed five times with 60°C hot water and then placed into a rotary kiln preheated to 900°C. Then, while rotating the kiln at 3.0 rpm, gas (30.0% steam, 2.5% oxygen, and 67.5% nitrogen) was introduced into the kiln, and the kiln was activated for 60 minutes to obtain the activated material.

[0080] After allowing the activated material to cool, 12.5 parts of 36% hydrochloric acid and 410 parts of distilled water were added to 100 parts by mass of the activated material, and the mixture was stirred at room temperature for 1 hour to obtain a filtrate. The filtrate contained 3.7% by mass of ash relative to its dry weight. This filtrate was washed five times with 50°C warm water, and then 2 parts of ammonium bicarbonate (Wako Pure Chemical Industries, Ltd.) and 410 parts of distilled water were added, and the mixture was stirred at room temperature for 1 hour and filtered. The pH of this filtrate was 7. The filtrate was then washed five times with water heated to 50°C containing 16 mg / L sodium, 5 mg / L magnesium, and 10 mg / L calcium, and the pH of the filtrate was confirmed to be 5. The resulting washed material was dried to obtain the activated carbon of Example 3, in which the total amount of acidic functional groups was adjusted.

[0081] [Example 4] To 100 parts by mass of Japanese wood flour, 180 parts by mass of 85% phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added and mixed. Without drying, the mixture was placed in a magnetic crucible, and in a box furnace (electric furnace, KBF848N2 (product name) manufactured by JTEKT Thermo Systems Corporation), the temperature was raised from room temperature to 420°C at a rate of 10°C / min under a nitrogen atmosphere, and then heated to 450°C for 30 minutes to perform phosphoric acid activation and obtain the activated product.

[0082] The activator was added to water containing 16 mg / L sodium, 5 mg / L magnesium, and 10 mg / L calcium in an amount of 1000 parts by mass per 100 parts by mass of the activator, heated to a boil, and filtered after 10 minutes. This operation was repeated three times and filtered to obtain the filtrate. The filtrate contained 5.1% by mass of phosphoric acid, the activator, relative to its dry weight. Furthermore, this filtrate was added to 10 mM phosphate buffer (prepared from sodium dihydrogen phosphate (manufactured by Wako Pure Chemical Industries, Ltd.), disodium hydrogen phosphate (manufactured by Wako Pure Chemical Industries, Ltd.), and distilled water) in an amount of 1000 parts by mass per 100 parts by mass of the filtrate, heated to a boil, and filtered after 10 minutes. This operation was repeated six times, and it was confirmed that the pH of the filtrate was 5. The washed material was dried to obtain the activated carbon of Example 4, in which the total amount of acidic functional groups was adjusted.

[0083] [Comparative Example 1] To 100 parts by mass of Japanese wood flour, 280 parts by mass of a 60% zinc chloride aqueous solution (prepared by dissolving Wako Pure Chemical Industries, Ltd.'s solution in distilled water) was added and left at room temperature for 4 hours. This mixture was then placed in a magnetic crucible and activated with zinc chloride under a nitrogen atmosphere for 1 hour in a box furnace (electric furnace, JTEKT Thermo Systems Co., Ltd. KBF848N2 (product name)) preheated to 600°C to obtain the activated product.

[0084] After allowing the activator to cool to room temperature, it was added to 1000 parts by mass of 3.5% hydrochloric acid (Wako Pure Chemical Industries, Ltd., prepared from 35% hydrochloric acid) per 100 parts by mass of the activator, stirred at 60°C for 30 minutes, and then filtered. This process was repeated once more to obtain the filtrate. 100 parts by mass of this filtrate was added to 1000 parts by mass of distilled water, heated to 60°C, stirred for 30 minutes, and then filtered. The pH of this filtrate was 1. This operation was repeated four more times until the pH of the filtrate reached 6, and the washing material was obtained. After drying the washing material, 70 parts of sodium ligninsulfonate (manufactured by Nippon Paper Industries Co., Ltd.) were mixed with 100 parts by mass of the washing material, water was added, and the mixture was kneaded to obtain a mass. This mass was heat-treated in a box furnace (electric furnace, KBF848N2 (product name) manufactured by JTEKT Thermo Systems Co., Ltd.) preheated to 850°C for 1 hour under a nitrogen atmosphere, while thermally decomposing sodium ligninsulfonate. After the heat-treated product was allowed to cool to room temperature, it was added to 1000 parts by mass of distilled water per 100 parts by mass of the heat-treated product, stirred at room temperature for 1 hour, and then filtered. The pH of the filtrate was 11. This operation was repeated 5 times, and it was confirmed that the pH of the filtrate became 8. The washed material was dried to obtain the activated carbon of Comparative Example 1, in which the total amount of acidic functional groups was adjusted.

[0085] [Comparative Example 2] The washed material obtained in the same manner as in Example 3 was added to a 10% sodium hydroxide aqueous solution (prepared from Wako Pure Chemical Industries, Ltd.) at 60°C in an amount of 5000 parts by mass per 100 parts by mass of the washed material. After stirring for 30 minutes, the mixture was filtered. This process was repeated once more to obtain the filtrate. The pH of this filtrate was 14. The filtrate was added to a amount of distilled water in an amount of 1000 parts by mass per 100 parts by mass, heated to 60°C, stirred for 30 minutes, and filtered. This operation was repeated four times, and it was confirmed that the pH of the filtrate was 9. The water-washed material was dried to obtain the activated carbon of Comparative Example 2.

[0086] [Comparative Example 3] Carbonized coconut shells from the Philippines were carbonized at a temperature of 600°C for approximately 2 hours to obtain carbonized material. The obtained carbonized material was then placed in a rotary kiln equipped with stirring blades, heated to 850°C, within a rotary kiln volume of 1 m³. 3The amount added was approximately 0.06 times the original amount. Subsequently, while rotating the kiln at a rotation speed of 3.0 rpm, gas (50% water vapor, 10% oxygen, and 40% nitrogen) was introduced into the kiln, and the activation treatment was performed for 90 minutes to obtain the activated material.

[0087] The activated material was placed in 3.5% hydrochloric acid (prepared by Wako Pure Chemical Industries, Ltd.) at a ratio of 1000 parts by mass per 100 parts by mass of the activated material, immersed at room temperature for 1 hour, and then filtered. The filtered material was treated with distilled water at 60°C in the same manner as in Example 1 to obtain the activated carbon of Comparative Example 3.

[0088] [Comparative Example 4] Carbonized coconut shells from the Philippines were carbonized at a temperature of 550°C for approximately 2 hours to obtain carbonized material. The obtained carbonized material was placed in a rotary kiln equipped with stirring blades inside a furnace heated to 900°C, with a rotary kiln volume of 1 m³. 3 The amount added was approximately 0.06 times the original amount. Subsequently, while rotating the kiln at a rotation speed of 3.0 rpm, gas (30.0% by volume of water vapor, 2.5% by volume of oxygen, and 67.5% by volume of nitrogen) was introduced into the kiln, and the activation treatment was carried out for 140 minutes to obtain the activated material.

[0089] The activated material was placed in 3.5% hydrochloric acid (prepared by Wako Pure Chemical Industries, Ltd.) at a ratio of 1000 parts by mass per 100 parts by mass of the activated material, immersed at room temperature for 1 hour, and then filtered. The filtrate was treated with distilled water at 60°C in the same manner as in Example 1 to obtain the activated carbon of Comparative Example 4.

[0090] [Comparative Example 5] Carbonized wood powder from Japan and Malaysia was carbonized at a temperature of 550°C for approximately 8 hours to obtain carbonized material. The obtained carbonized material was then placed in a rotary kiln equipped with stirring blades, heated to 850°C, within a rotary kiln volume of 1 m³. 3 The material was introduced at approximately 0.06 times the original amount. Subsequently, while rotating the kiln at a rotation speed of 3.0 rpm, gas (50.0% by volume of water vapor, 10.0% by volume of oxygen, 35.0% by volume of nitrogen, and 5.0% by volume of carbon dioxide) was introduced into the kiln, and the activation treatment was carried out for 60 minutes to obtain the activated material.

[0091] The activated material was placed in 3.5% hydrochloric acid (prepared by Wako Pure Chemical Industries, Ltd.) at a ratio of 1000 parts by mass per 100 parts by mass of the activated material, immersed at room temperature for 1 hour, and then filtered. The filtered material was treated with distilled water at 60°C in the same manner as in Example 1 to obtain the activated carbon of Comparative Example 5.

[0092] [Comparative Example 6] Colombian bituminous coal is placed in a rotary kiln equipped with stirring blades inside a furnace heated to 900°C, with a rotary kiln volume of 1 m³. 3 The amount added was approximately 0.06 times the original amount. Subsequently, while rotating the kiln at a rotation speed of 3.0 rpm, gas (100.0 volume%) of water vapor was introduced into the kiln, and the activated material was obtained by performing the activation treatment for 100 minutes.

[0093] The activated material was placed in 3.5% hydrochloric acid (prepared by Wako Pure Chemical Industries, Ltd.) at a ratio of 1000 parts by mass per 100 parts by mass of the activated material, immersed at room temperature for 1 hour, and then filtered. The filtered material was treated with distilled water at 60°C in the same manner as in Example 1 to obtain the activated carbon of Comparative Example 6.

[0094] 2. Evaluation The physical properties of the activated carbon obtained in the examples and comparative examples were evaluated by the following methods.

[0095] [Nitrogen adsorption isotherm of activated carbon at 77K] Using a BELSORP-miniII manufactured by Microtrac-Bell Co., Ltd., the activated carbon obtained in the examples and comparative examples was heated under reduced pressure (vacuum level: 0.1 kPa or less) at 250°C for 3 hours. Subsequently, the nitrogen adsorption isotherm of the activated carbon at 77 K was measured.

[0096] [Pore volume of pores with a diameter greater than 2 nm and less than or equal to 5 nm (A)] The cumulative pore volume of pores with a diameter greater than 2 nm and less than or equal to 5 nm contained in 1 g of activated carbon (i.e., pore volume (A) with a diameter greater than 2 nm and less than or equal to 5 nm, unit: mL / g) was calculated from the nitrogen adsorption isotherm described above using the CI (Cranston-Inkley) method.

[0097] [Pore volume of pores with a diameter of 2 nm or less (B)] The cumulative pore volume of pores with a diameter of 2 nm or less contained in 1 g of activated carbon (i.e., pore volume of pores with a diameter of 2 nm or less (B), unit: mL / g) was calculated from the nitrogen adsorption isotherm using the CI method.

[0098] [Pore volume ratio ((A) / (B))] From the above pore volumes (A) and (B), the ratio of pore volume (A) with a pore diameter between 2 nm and 5 nm to pore volume (B) with a pore diameter of 2 nm or less (pore volume ratio (A) / (B)) was calculated.

[0099] [Total acidic functional group amount] The total amount of acidic functional groups in activated carbon was determined by acid-base titration (Boehm method) as follows. Approximately 1 g of activated carbon was taken and immersed in 50 mL of 0.1 M NaOH aqueous solution, and shaken at room temperature for 24 hours. This solution was filtered using a membrane filter (DISMIC® 25HP045AN (product name) manufactured by Advantec Toyo Co., Ltd.) to obtain the filtrate. 10 mL of this filtrate was accurately taken and back-titrated with 0.1 M HCl aqueous solution. An automatic neutralization titrator AT-510 (manufactured by Kyoto Electronics Manufacturing Co., Ltd., electrode: C-171 used) was used for the titration. A blank test without activated carbon was performed in the same manner, and the amount of phenolic hydroxyl groups was determined from the value obtained by subtracting the titration volume from the blank test.

[0100] Similarly, 1 g of activated carbon was immersed in 50 mL each of 0.05 M Na2CO3 solution and 0.1 M NaHCO3 solution, and shaken at room temperature for 24 hours. This solution was filtered, and 10 mL of the filtrate was accurately taken and back-titrated with 0.1 M HCl aqueous solution. A blank test without activated carbon was performed in the same manner, and the amount of lactone groups and carboxyl groups was determined from the values ​​obtained by subtracting the titration volume from the blank test.

[0101] The total amount of acidic functional groups (unit: meq / g) in activated carbon was calculated by summing the above amounts of phenolic hydroxyl groups, lactone groups, and carboxyl groups.

[0102] [BET specific surface area] Specific surface area of ​​activated carbon (unit: m²) 2 The specific surface area (P / g) was determined from the nitrogen adsorption isotherm at 77K using the BET method. Specifically, a straight line was obtained from the nitrogen adsorption isotherm at 77K using the multipoint method in the region where the relative pressure P / P0 = 0.01 to 0.10 using BET analysis, and the BET specific surface area was calculated from this straight line.

[0103] [Grinding and drying of evaluation samples, 50% particle size (D50)] Activated carbon was pulverized so that the 50% particle size (D50) of the volume-based cumulative distribution was between 10 μm and 50 μm. The pulverized activated carbon was then dried for 3 hours in a constant-temperature drying oven (Yamato Scientific Co., Ltd., DVS402 (product name)) at 115°C to obtain a dried product. After that, the activated carbon was left in a desiccator equipped with silica gel as a desiccant and allowed to cool to room temperature. The 50% particle size (D50) was measured as the volume-based median diameter using a laser diffraction light scattering particle size distribution analyzer.

[0104] [Filling density] For the pulverized activated carbon, the packing density (g / mL) was calculated using the following formula, based on the measurement method described in JIS K 1474, with a 50 mL graduated cylinder used as the packing density measurement container, and employing the powder packing method. Packing density (g / mL) = Mass of activated carbon (g) / Volume of activated carbon packed (mL)

[0105] [Iodine adsorption performance] The amount of iodine adsorbed was measured in accordance with JIS K 1474. Specifically, first, the activated carbon was pulverized in accordance with JIS Z 8801-1 until more than 90% of it passed through a 45 μm sieve, and then dried for 3 hours in a constant-temperature drying oven (DVS402 (product name) manufactured by Yamato Scientific Co., Ltd.) at 115°C. After that, it was cooled to room temperature in a desiccator using silica gel as a desiccant to obtain the activated carbon after cooling.

[0106] On the other hand, 25.0 g of potassium iodide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 13.0 g of iodine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were dissolved in approximately 1 L of distilled water to prepare an iodine solution. The iodine solution was titrated with a 0.1 mol / L sodium thiosulfate solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and distilled water was added to the iodine solution as needed to prepare a 0.05 mol / L iodine solution.

[0107] Next, an arbitrary amount of the activated carbon after cooling (an amount that results in a residual iodine concentration of approximately 2.5 g / L in the supernatant of the filtrate described below) was weighed and placed in a 100 mL Erlenmeyer flask with a stopper. Then, 50 mL of the 0.05 mol / L iodine solution described above was added using a volumetric pipette. At room temperature (20°C to 30°C), the mixture was shaken at 200 revolutions per minute for 15 minutes using a shaker (medium-sized reciprocating shaker NR-10 (product name) manufactured by Taitec Co., Ltd.) to adsorb the iodine onto the activated carbon and obtain a mixture. Subsequently, the mixture was filtered using a cellulose mixed ester membrane filter (A045A025A (product name) manufactured by Advantec Toyo Co., Ltd.) to obtain a filtrate. Ten mL of the supernatant of the filtrate was collected using a volumetric pipette and titrated with a 0.1 mol / L sodium thiosulfate solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., factor: 1.000). The residual iodine concentration was calculated using the following formula (VIII).

[0108] Iodine residual concentration (g / L) = Volume of 0.1 mol / L sodium thiosulfate solution used in titration (mL) × Factor of 0.1 mol / L sodium thiosulfate solution × 12.69 / 10···(VIII)

[0109] The amount of iodine adsorbed per gram of activated carbon was calculated using the following formula (IX).

[0110] Iodine adsorption capacity per gram of activated carbon = (Factor of 10 × 0.05 mol / L iodine solution - Volume of 0.1 mol / L sodium thiosulfate solution used for titration (mL) × Factor of 0.1 mol / L sodium thiosulfate solution) × 12.69 × 5 / Mass of activated carbon (g) ... (IX)

[0111] The factor for a 0.05 mol / L iodine solution was calculated using equation (X).

[0112] Factor of 0.05 mol / L iodine solution = (Amount of 0.1 mol / L sodium thiosulfate solution used in titration (mL) × Factor of 0.1 mol / L sodium thiosulfate solution) / 10 ... (X)

[0113] Using Freundlich's adsorption isotherm, an adsorption isotherm was created with the iodine residual concentration on the x-axis and the iodine adsorption amount per gram of activated carbon on the y-axis. The iodine adsorption amount (mg / g) per gram of activated carbon at an iodine residual concentration of 2.5 g / L was calculated. This iodine adsorption amount was defined as the iodine adsorption performance.

[0114] [Ignition residue] The ignition residue (mass%) was measured in accordance with JIS K 1474. The activated carbon used for measurement was dried before measurement. Specifically, the activated carbon was dried for 3 hours in a constant temperature drying oven (Yamato Scientific Co., Ltd. DVS402 (product name)) at 115±5℃, and then cooled to room temperature in a desiccator using silica gel as a desiccant. The cooled activated carbon was then strongly heated for 1 hour in an electric furnace (Yamato Scientific Co., Ltd. FO811 (model)) at 850±50℃. Next, the obtained ash was cooled to room temperature in a desiccator using silica gel as a desiccant, its mass (mass of ash) was measured, and the ignition residue was calculated using the following formula.

[0115] Ignition residue (mass %) = Mass of ash (g) / Mass of activated carbon before ashing (g) × 100

[0116] [Riboflavin removal rate (C)] A mixed test solution containing riboflavin and lactose was prepared using the following method. Specifically, riboflavin and lactose were dissolved separately in distilled water to prepare a mixed test solution with a riboflavin concentration of 50 mg / L and a lactose concentration of 50,000 mg / L (5%). 50 mL of the obtained mixed test solution was transferred to a 100 mL brown Erlenmeyer flask with a stopper, and approximately 0.008 w / v% of the pre-pulverized and dried activated carbon from the examples and comparative examples was added and shaken. More specifically, the activated carbon and test solution were shaken at a rate of 140 times / min for 24 hours in a 25°C water bath using a shaking thermostat (Tytec Water Bath Shaker MM-10 (product name)). After that, the filtrate was obtained by filtering using a membrane filter (Advantec Toyo Co., Ltd. DISMIC® 25HP045AN (product name)). Next, the absorbance of the mixed test solution and the absorbance of the filtrate were measured using a UV-Vis spectrophotometer (Hitachi High-Tech, Double Beam Spectrophotometer U-2910 (product name)). The absorbance was measured at a wavelength of 445 nm using a quartz cell with a path length of 10 mm.

[0117] The riboflavin concentration (measured value) of the filtrate obtained by the above measurement was defined as the "residual riboflavin concentration of the filtrate," and the riboflavin removal rate (C) (%) was calculated using the following formula.

[0118] Riboflavin removal rate (C) (%) = [(Initial riboflavin concentration in test solution (50 mg / L) - Residual riboflavin concentration in filtrate (mg / L))] / [Initial riboflavin concentration in test solution (50 mg / L)] × 100

[0119] [Lactose removal rate (D)] The lactose concentrations of the mixed test solution and filtrate obtained using the same procedure as described above were quantified using high-performance liquid chromatography (HPLC) (Vanquish Flex, Thermo Fisher Scientific Co., Ltd.) under the following conditions.

[0120] (HPLC analysis conditions) Column: Shodex Asahipak NH2P-50 4E (manufactured by Resonac Co., Ltd.) Column size: 4.6mm I.D. x 250mm Mobile phase: Acetonitrile (for LCMS, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and ultrapure water Detector: Charged particle detector (CAD)

[0121] The lactose concentration (measured value) of the filtrate obtained from the above measurements was defined as the "residual lactose concentration of the filtrate," and the lactose removal rate (D) (%) was calculated using the following formula.

[0122] Lactose removal rate (D) (%) = [(Initial lactose concentration of test solution (50000 mg / L) - Residual lactose concentration of filtrate (mg / L))] / [Initial lactose concentration of test solution (50000 mg / L)] × 100

[0123] [Selective adsorption of riboflavin] To evaluate the selective adsorption of riboflavin, the ratio of the riboflavin removal rate (C) to the lactose removal rate (D) ((C) / (D)) was calculated. A larger ratio ((C) / (D)) indicates higher selective adsorption of riboflavin in the presence of lactose.

[0124] [Riboflavin desorption rate] (Adsorption process) To evaluate the adsorption and desorption performance, a riboflavin adsorption and desorption test was conducted using the following procedure. First, a step was performed to sufficiently adsorb riboflavin onto activated carbon. Specifically, 10 mg of activated carbon was added to 100 mL of a riboflavin aqueous solution at a predetermined concentration (50 mg / L), and contact shaking was performed in a light-shielding Erlenmeyer flask with a stopper. More specifically, a shaking constant temperature bath (Tytec Water Bath Shaker MM-10 (product name)) was used to shake the mixture in a 25°C water bath at a rate of 140 times / min for 17 hours. After adsorption, solid-liquid separation was performed by filtration, and the residual riboflavin concentration in the filtrate was measured using a UV-Vis spectrophotometer (Hitachi High-Tech Double Beam Spectrophotometer U-2910 (product name)). Absorbance was measured at a wavelength of 445 nm using a quartz cell with a path length of 10 mm.

[0125] (Desorption process) Next, as a desorption step, the activated carbon after adsorption treatment was recovered, suspended in 100 mL of distilled water, and subjected to contact shaking in a light-shielding Erlenmeyer flask with a stopper. More specifically, it was shaken at a rate of 140 times / minute for 5 hours in a shaking bath at 70°C. After desorption, solid-liquid separation was performed again, and the riboflavin concentration in the solution was measured.

[0126] The concentrations after adsorption and desorption were calculated using the above procedure, and the riboflavin desorption rate was determined using the following formula. This allowed for evaluation of the reusability of the adsorbent and the reversibility of adsorption and desorption. In this specification, "high riboflavin desorption rate" means that the riboflavin desorption rate measured by this method is 7% or higher.

[0127] Riboflavin desorption rate (%) = Riboflavin concentration after desorption (mg / L) / [Initial riboflavin concentration before adsorption (mg / L) - Residual riboflavin concentration after adsorption (mg / L)] × 100

[0128] [Food additive compatibility] The suitability of activated carbon as a food additive was evaluated by determining whether it "conforms" if it met all the criteria for properties, confirmation tests, and purity tests for activated carbon as described in "D. Component Specifications and Storage Standards" of the 10th edition of the Official Compendium of Food Additives mentioned above, and whether it "fails" if it did not meet at least one of the criteria.

[0129] The results of the above evaluation are shown in Table 1.

[0130] [Table 1]

[0131] As shown in the table, the activated carbon of this embodiment (Examples 1-4), which has a ratio (A) / (B) of 0.2 to 3.5 and a total acidic functional group content of 0.3 meq / g to 2.5 meq / g, was found to have excellent selective adsorption of riboflavin from the presence of high-concentration lactose, as well as excellent riboflavin desorption, due to its high ratio (C) / (D) and riboflavin desorption rate.

[0132] Even when the ratio (A) / (B) was between 0.2 and 3.5, activated carbons in which the total amount of acidic functional groups was less than 0.3 meq / g due to a conditioning process consisting of a washing process, an oxidation process, a heat treatment process, or a combination thereof (Comparative Examples 1, 2, and 5) showed a relatively high degree of riboflavin desorption, but low selective adsorption of riboflavin.

[0133] Furthermore, even when the total amount of acidic functional groups was adjusted to 0.3 meq / g or more and 2.5 meq / g or less during the adjustment process, activated carbon with a ratio (A) / (B) of less than 0.2 (Comparative Example 6) showed no improvement in either selective adsorption or desorption of riboflavin.

Claims

1. In the pore volume of each section calculated by the CI method from the nitrogen adsorption isotherm at 77K, The ratio ((A) / (B)) of the pore volume of pores with a diameter of 2 nm or less (B) to the pore volume of pores with a diameter of 2 nm or less (A) with a diameter of 5 nm or less is between 0.2 and 3.

5. Activated carbon in which the total amount of acidic functional groups, as measured by the Boehm method, is between 0.3 meq / g and 2.5 meq / g.

2. The activated carbon according to claim 1, which is a riboflavin adsorbent for adsorbing riboflavin in a riboflavin-containing composition.

3. The activated carbon according to claim 2, wherein the riboflavin-containing composition is a food, a pharmaceutical, a cosmetic, or a raw material thereof.

4. The specific surface area calculated by the BET method from the nitrogen adsorption isotherm at 77K is 1100 m². 2 / g or more 2000m 2 The activated carbon according to claim 1, wherein the amount is less than or equal to / g.

5. The activated carbon according to claim 1, wherein the packing density is 0.20 g / mL or more and 0.50 g / mL or less.

6. A method for removing riboflavin, comprising an adsorption step of adsorbing riboflavin in a riboflavin-containing composition onto activated carbon as described in claim 1.

7. The adsorption step described above is designated as the first adsorption step. A desorption step in which the riboflavin is desorbed from the activated carbon after the first adsorption step by washing with water or alkaline water, The riboflavin removal method according to claim 6, further comprising a second adsorption step of adsorbing riboflavin from a new riboflavin-containing composition onto the activated carbon after the desorption step.

8. The riboflavin removal method according to claim 6 or 7, wherein the riboflavin-containing composition is a food, a pharmaceutical, a cosmetic, or a raw material thereof.

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