Producing method of microcapsule and microcapsule produced by the producing method

Abstract

To provide a producing method of a simple microcapsule in which strength and sealing property of a microcapsule having a wall film derived from plants are improved and a microcapsule produced by the method.SOLUTION: In a producing method of a microcapsule using a simple coacervation method with a liquid or solid hydrophobic substance as a core substance, and with a mixture in which methylcellulose or hydroxypropyl methylcellulose or a mixture in which they are used in an arbitrary proportion as a wall membrane, glucomannan is added to methylcellulose or hydroxypropyl methylcellulose or a mixture in which they are used in an arbitrary proportion.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing microcapsules having a wall membrane derived from a plant, and to microcapsules produced by this method. [Background technology]

[0002] Gelatin, a protein derived from animals, is widely used as the wall of microcapsules, but since the problems of BSE and hog cholera became widely known, there has been an increasing demand for microcapsules with walls derived from plants.

[0003] There is also an increasing demand for allergen-free microcapsule walls used in products that may be ingested by the human body, such as food and cosmetic products.

[0004] As a method for producing microcapsules having a plant-derived wall, there is a method for producing microcapsules using a simple coacervation method in which methylcellulose or hydroxypropylmethylcellulose is used as the wall, and a method for producing microcapsules is known in which dextrin is used as a coacervate inducer and the dextrose equivalent of the dextrin is selected depending on the particle size and shape of the microcapsules to be produced, thereby adjusting the viscosity of the coacervate to a viscosity corresponding to the particle size and shape of the microcapsules (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-176907 A Summary of the Invention [Problem to be solved by the invention]

[0006] The microcapsule manufacturing method and the microcapsules described in Patent Document 1 are advantageous in that they have a plant-derived wall membrane that corresponds to the particle size and shape of the microcapsule.

[0007] The microcapsules described in Patent Document 1 are sustained-release microcapsules. The advantage of sustained-release is that the core substance can be released without the need for a switch for releasing the core substance in the capsule, but on the other hand, there is a disadvantage that if the release speed is fast, the remaining time of the core substance in the capsule will be short.

[0008] Patent Document 1 also describes a method for thickening the wall of a microcapsule by adding an aqueous solution of methylcellulose or hydroxypropylmethylcellulose and dextrin, thereby improving its strength and sealing properties. However, the method for thickening the wall of the microcapsule requires a troublesome process of repeatedly heating a gelled coacervate twice, which makes the microcapsule manufacturing process and temperature control complicated.

[0009] In order to solve the above problems, the present inventors focused on glucomannan (konjac) and conducted extensive testing and research, which resulted in the completion of the present invention.

[0010] An object of the present invention is to provide a simple method for producing microcapsules having a plant-derived wall membrane which improves the strength and sealing property of the microcapsules, and to provide microcapsules produced by this method. [Means for solving the problem]

[0011] In order to achieve the above object, the invention described in claim 1 is a method for producing microcapsules using a simple coacervation method in which a liquid or solid hydrophobic substance is used as a core material and methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any proportion is used as a wall membrane, the method being characterized in that glucomannan is added to methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any proportion.

[0012] The invention described in claim 2 is characterized in that both the methylcellulose or hydroxypropylmethylcellulose or a mixture of these in any ratio and the glucomannan described in claim 1 are reacted with tannic acid.

[0013] The invention described in claim 3 is characterized in that the methylcellulose or hydroxypropylmethylcellulose or a mixture of these in any ratio as described in claim 2 is used in combination with a sugar cane extract or molasses flavor as a part of the polyphenols that are the main components of the gelling agent that gels the glucomannan.

[0014] The invention described in claim 4 is a microcapsule produced by the production method described in any one of claims 1 to 3. Effect of the Invention

[0015] According to the method for producing microcapsules described in claim 1, in a method for producing microcapsules using a simple coacervation method in which a liquid or solid hydrophobic substance is used as a core material and methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any proportion is used as a wall membrane, by adding glucomannan to methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any proportion, it is possible to produce microcapsules with improved wall membrane strength and sealing properties compared to the invention described in Patent Document 1. Furthermore, compared to the invention described in Patent Document 1, the microcapsule production process is shorter and temperature control is simpler, making it possible to easily produce microcapsules.

[0016] According to the method for producing a microcapsule as described in claim 2, by reacting the methylcellulose or hydroxypropylmethylcellulose or a mixture of these in any ratio as described in claim 1 with the glucomannan by adding tannic acid, it is possible to produce a microcapsule having a hardened wall membrane and improved wall strength and sealing property.

[0017] According to the microcapsule production method of claim 3, by using the methylcellulose or hydroxypropylmethylcellulose or a mixture of these in any ratio as described in claim 2 and a sugar cane extract or molasses flavor as a part of the polyphenols that are the main components of the gelling agent that gels the glucomannan, it is possible to produce microcapsules that have reduced unpleasant flavors such as astringency and bitterness that occur when tannic acid is used as a hardening agent for the microcapsule wall membrane.

[0018] According to the microcapsules described in claim 4, since they are produced by the production method described in any one of claims 1 to 3, it is possible to obtain stable microcapsules, as well as microcapsules having high strength and excellent sealing properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the method for producing microcapsules according to the present invention and the microcapsules produced by this method will be described in detail.

[0020] The method for producing microcapsules according to the present invention is carried out by a simple coacervation method. The core material of the microcapsules is a liquid or solid hydrophobic material, and the material forming the wall of the microcapsule is selected from methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any ratio, and glucomannan is used in combination with this.

[0021] Although it is possible to produce microcapsules using glucomannan alone by the simple coacervation method, this is not practical because the range of microcapsule particle sizes that can be produced is narrow and it is extremely difficult to thicken the microcapsule walls.

[0022] In addition, the strength and sealing properties of microcapsules can be improved by using glucomannan in combination with gelatin wall microcapsules, but there are very few cases where such performance is required.

[0023] In the invention described in Patent Document 1, the microcapsule wall is thickened to impart high wall strength and high sealing ability to the microcapsule wall, and a process of heating a gelled coacervate twice is required as a means of thickening the wall. However, in the present invention, by using glucomannan in combination with methylcellulose or hydroxypropylmethylcellulose or a mixture of these in any ratio for the microcapsule wall, it is possible to obtain sufficient wall strength and high sealing ability with a thin wall, and a wall with sufficient wall strength and high sealing ability can be obtained with a single heating.

[0024] The amount of glucomannan added to methylcellulose or hydroxypropylmethylcellulose or a mixture of these in any ratio is preferably 1 to 10% by weight. If the amount of glucomannan added is less than 1% by weight, the effect of improving the strength and sealing property of the microcapsule wall is weak. If the amount of glucomannan added is more than 10% by weight, some glucomannan will remain as it is and the glucomannan that does not become the wall of the microcapsule may cause thickening of the aqueous solution during the microcapsule production process, making it difficult to produce the microcapsules.

[0025] As the coacervate inducer, dextrin including maltodextrin and powdered candy, the dextrose equivalent of which is selected according to the particle size and shape of the microcapsules to be produced, is suitable.

[0026] Tannic acid may also be used as a hardener for the wall membrane formed from methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any ratio, and glucomannan. Tannic acid has excellent properties as a hardener, but may leave behind unpleasant tastes such as astringency and bitterness.

[0027] In the gelation process of the coacervate to form the microcapsule wall, in addition to raising the temperature to 58°C or higher, it is preferable to add polyphenols as a gelling agent to suppress the fluidity of the coacervate, and the addition of a tea extract containing catechins is even more preferable. When the microcapsules are used for food, the astringency, bitterness, and other unpleasant flavors caused by the use of tannic acid can be reduced by combining a sugar cane extract or molasses flavor with part of the polyphenols used as a gelling agent.

[0028] It is desirable to turn the coacervate into a microcapsule wall membrane through a process of gelling the coacervate, and then harden the microcapsule wall membrane with a hardener. A commonly known method for hardening glucomannan is to heat it with an alkali such as calcium hydroxide to 80°C or higher. Through repeated testing and research, the inventors discovered that glucomannan also hardens when tannic acid is added, and that it hardens at temperatures equivalent to those at which methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any ratio is hardened, without the need for the addition of alkali or heating to 80°C or higher. In the present invention, the addition of tannic acid enabled glucomannan, together with methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any ratio, to harden at a temperature at which methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any ratio was hardened.

[0029] According to the above-mentioned microcapsule manufacturing method, sufficient wall strength and high sealing properties can be obtained with a thin wall, and this wall can be obtained by a single heating process, so that the microcapsule manufacturing process is shorter than that of the invention described in Patent Document 1. Furthermore, since the microcapsule wall can be hardened at approximately the same temperature as that of the invention described in Patent Document 1, temperature control is simplified and microcapsules can be manufactured easily. EXAMPLES

[0030] EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0031] [Example 1] 15.6g of water and 97.2g of 3% aqueous solution of hydroxypropyl methylcellulose (Metolose 60SH50: Shin-Etsu Chemical Co., Ltd.) were added to 13.5g of 1% aqueous solution of glucomannan (Reolex RS: Shimizu Chemical Co., Ltd.), and 40.5ml of fragrance (lavender oil: Nagakodo Co., Ltd.) was added to this mixed aqueous solution and dispersed into droplets of 20μm diameter to prepare an O / W type emulsion. 19.4g of water was added to the emulsion, and 48.6g of 25% aqueous solution of dextrin (Sandek #180: Sanwa Starch Co., Ltd.) was added, and the mixture was heated to 60°C and stirred for 20 minutes. 6.5g of 14% aqueous solution of tea extract (Sunphenon 90S: Taiyo Kagaku Co., Ltd.) was slowly dripped as a gelling agent, followed by 13g of 5% aqueous solution of tannic acid to harden the wall membrane. The mixture was stirred at 60° C. for 1 hour, then the heating was stopped and stirring was continued overnight to obtain a microcapsule slurry.

[0032] [Example 2] 9.7g of water and 92.4g of 3% aqueous solution of hydroxypropylmethylcellulose (Metolose SE-50: Shin-Etsu Chemical Co., Ltd.) were added to 18g of 1% aqueous solution of glucomannan (Reolex RS: Shimizu Chemical Co., Ltd.), and 42ml of olive oil was added to this mixed aqueous solution and dispersed into droplets of 20μm diameter to prepare an O / W type emulsion. 18.5g of water was added to the emulsion, and 46.2g of 25% aqueous solution of dextrin (Sandek #30: Sanwa Starch Co., Ltd.) was added, and the mixture was heated to 60℃ and stirred at low speed for 20 minutes. 4.7g of sugar cane extract (MSX-100(J): Mitsui Sugar Co., Ltd.) was added, and 6.2g of 14% aqueous solution of tea extract (Sunphenon 90S: Taiyo Kagaku Co., Ltd.) was slowly dripped in, followed by 13.9g of 5% aqueous solution of tannic acid to harden the wall membrane. The mixture was stirred at 60° C. for 1 hour, then the heating was stopped and stirring was continued overnight to obtain a microcapsule slurry. This microcapsule slurry was dehydrated, silica fine powder (AEROSIL200FAD: manufactured by Nippon Aerosil Co., Ltd.) was added as a drying aid, the mixture was kneaded, and then dried to obtain a polynuclear microcapsule powder for food use.

[0033] [Comparative Example 1] This is a reproduction of Example 1 of Patent Document 1, and 25 ml of fragrance (lavender oil: Nagakodo Co., Ltd.) was added to 90 g of a 2% aqueous solution of hydroxypropylmethylcellulose (Metolose 60SH50: Shin-Etsu Chemical Co., Ltd.), and dispersed to form droplets with a diameter of 20 μm to prepare an O / W type emulsion. While keeping the emulsion at 40°C, 30 g of a 25% aqueous solution of dextrin (Sandec #180: Sanwa Starch Co., Ltd., dextrose equivalent 18-21) was added, and the mixture was heated to 60°C and stirred for 20 minutes. 4 g of a 25% aqueous solution of tea extract (Sunfood 100: Mitsubishi Chemical Foods Co., Ltd.) was slowly dripped as a gelling agent, followed by 8 g of a 5% aqueous solution of tannic acid to harden the wall membrane. The mixture was stirred for 1 hour at 60°C, the heating was stopped, and stirring was continued overnight to obtain a microcapsule slurry.

[0034] [Comparative Example 2] This is a reproduction of Example 2 of Patent Document 1, in which 25 ml of fragrance (lavender oil: manufactured by Nagakodo Co., Ltd.) was added to 90 g of a 2% aqueous solution of hydroxypropylmethylcellulose (Metolose 60SH50: manufactured by Shin-Etsu Chemical Co., Ltd.) and dispersed to form droplets with a diameter of 20 μm to prepare an O / W type emulsion. While keeping the emulsion at 40°C, 30 g of a 25% aqueous solution of dextrin (Sandec #180: manufactured by Sanwa Starch Co., Ltd., dextrose equivalent 18-21) was added, and the emulsion was then heated to 60°C and stirred for 20 minutes. 1.2g of 25% aqueous solution of tea extract (Sunfood 100: manufactured by Mitsubishi Chemical Foods Co., Ltd.) was slowly dripped, and a mixture of 22.5g of 2% aqueous solution of hydroxypropyl methylcellulose, 7.2g of 25% aqueous solution of dextrin (Sandec #180: manufactured by Sanwa Starch Co., Ltd., dextrose equivalent 18-21), and 4.8g of 25% aqueous solution of dextrin (Sandec #30: manufactured by Sanwa Starch Co., Ltd., dextrose equivalent 2-5) was added after stopping heating, and the mixture was heated again to 60°C and stirred for 20 minutes. 3.8g of 25% aqueous solution of tea extract was slowly dripped, followed by 10g of 5% aqueous solution of tannic acid to harden the wall membrane. The mixture was stirred for 1 hour at 60°C, and the heating was stopped and stirring was continued overnight to obtain a microcapsule slurry.

[0035] The microcapsules prepared in Example 1 and Comparative Examples 1 and 2 were tested and evaluated for the following items. The microcapsule slurries obtained in Example 1 and Comparative Examples 1 and 2 were filtered, dehydrated, and concentrated to 70% volume, and the same amount of 17% polyvinyl alcohol (Gohsenol N-300: manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.) aqueous solution as the amount dehydrated was added to prepare a microcapsule ink. This was screen-printed on paper and dried for 10 minutes in a constant temperature dryer set at 70°C to prepare a sample. The sample was stored in different environments, and a sensory evaluation was conducted to test the period during which the odor could be continuously detected. The results are shown in Table 1.

[0036] [Table 1]

[0037] When a small amount of the food microcapsule powder obtained in Example 2 was eaten, the astringency and bitterness of tannic acid was not felt, and the taste and aroma of the core substance was felt. These microcapsule powders were stored for 6 months and subjected to the same confirmation test, but no change was found. In addition, each microcapsule powder was redispersed in water and observed under a microscope, but no change was found. Industrial Applicability

[0038] According to the present invention, there is provided a method for easily and stably producing microcapsules having a plant-derived wall membrane with improved strength and sealing properties. The microcapsules are widely used in foods, food additives, cosmetics, industrial consumer products, etc.

Claims

1. A method for producing microcapsules using a simple coacervation method in which a liquid or solid hydrophobic substance is used as a core material and methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any proportion is used as a wall membrane, the method being characterized in that glucomannan is added to methylcellulose, hydroxypropylmethylcellulose, or a mixture of these in any proportion.

2. The method for producing microcapsules according to claim 1, characterized in that both the methylcellulose or hydroxypropylmethylcellulose or a mixture of these in any ratio and the glucomannan are reacted with each other by adding tannic acid.

3. The method for producing microcapsules according to claim 2, characterized in that the methylcellulose or hydroxypropylmethylcellulose or a mixture of these in any ratio is used in combination with a sugar cane extract or molasses flavor as a part of the polyphenols that are the main components of the gelling agent that gels the glucomannan.

4. A microcapsule produced by the method according to any one of claims 1 to 3.

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