JP4446126B2 - Method for producing fast-dissolving konjac mannan - Google Patents

Description

  The present invention relates to a method for producing konjac mannan having a fast solubility, that is, a time required to reach a peak viscosity when swollen (dissolved) in water.

  Glucomannan, the main component of konjac mannan, has unique chemical and physical properties such as the formation of elastic irreversible elastic gels by adding alkali to the aqueous solution and heating it. It has been used as a raw material for konjac production. For the production of konjac, konjac fine powder obtained by slicing tubers of a plant of the taro family called konjac koji, drying, pulverizing, and removing impurities such as starch and fiber by wind sorting is used.

  Glucomannan has high thickening, gelling, binding, etc. at low concentrations, and has physiological effects as low-calorie dietary fiber, so it is used to improve the quality of foods other than konjac . However, the average particle diameter of konjac fine powder is as large as about 300 μm or more, and since the surface is covered with a hard sack, it takes a long time to swell (dissolve) in water, and requires about 3 to 4 hours or more at room temperature. For this reason, attempts have been made to shorten the swelling (dissolution) time with respect to water by making konjac fine powder fine particles to increase the specific surface area. However, konjac mannan having a glucomannan content of 50% or more, which is represented by konjac fine powder, contains about 10% of water and is elastic like rubber, so that it is difficult to pulverize by mere mechanical grinding. For this reason, there is a method of pulverizing in a state of being brittle after cooling to ultra-low temperature with liquid nitrogen or the like, but it is not suitable for production on an industrial scale.

  As another method, there is a method disclosed in Japanese Patent Publication No. 6-97960 of the present applicant. This method consists in adding 3 to 20 times the dry weight of water to a konjac flour to swell it to form a sol, and adding the ethanol to the sol to wet-grind and dry. The sack is broken by swelling to a sol, and pulverization is facilitated by precipitation with ethanol.

  By this method, it is possible to finely pulverize to an average particle size of about 100 μm, and the swelling (dissolution) time for water at which the viscosity reaches a peak is shortened to about 2 hours. However, it is desirable to further reduce the swelling (dissolution) time in water, for example, so that the viscosity peak time can be shortened to within 1 hour, more preferably to about 30 minutes.

  Many impurities such as trimethylamine and sulfite remain in the konjac fine powder and have a unique irritating odor. Therefore, it is desirable to remove these impurities in the process of making fine particles.

  These needs are met by the present invention. The present invention does not swell the konjac mannan having a glucomannan content of 50% or more, typically konjac flour, with water, but conversely, the water contained in the raw material is brought into contact with a dehydrating organic solvent for dehydration. The principle is to make fine particles in a state where elasticity is lost. For this reason, konjac mannan can be made into fine particles by stirring in a high-speed stirrer in the form of a slurry of a dehydrating solvent.

  Therefore, in the present invention, the average particle size is reduced to 50 μm or less in a stirrer equipped with a stirring blade rotating at high speed in a slurry state in which konjac mannan having a glucomannan content of 50% or more is dispersed in water-containing ethanol having a content of 50% or more and 95% or less. Provided is a method for producing a readily soluble konjac mannan characterized by stirring and drying after solid-liquid separation.

  Preferably, the dehydration treatment with hydrous ethanol can be performed repeatedly. For this reason, the raw material konjac mannan is dispersed in the water-containing ethanol, slowly stirred and then solid-liquid separated, and then dispersed again in water-containing ethanol to form a slurry, which is stirred in a high-speed stirrer to form fine particles.

  Repeated contact with hydrous ethanol increases the degree of dehydration uniformly and facilitates the formation of fine particles.

  In the present invention, ethanol, which is a dispersion medium, is recovered by solid-liquid separation, so that impurities with an irritating odor are eluted in hydrous ethanol and can be used for general foods. The recovered water-containing ethanol can be reused by re-distilling.

  The konjac mannan particles swell with water, and the sac is broken and forms a sol or colloidal solution. However, it does not swell at all in absolute alcohol, and does not swell in ethanol containing water as the ethanol content increases. Rather, water contained in konjac mannan diffuses to the ethanol side and is dehydrated. Other solvents having dehydration performance include hexane and acetone, but water-containing ethanol of 50% to 95%, preferably 70% to 95% is suitable for food applications.

  The degree of dehydration depends on the ratio of water-containing ethanol to konjac mannan and the contact time. In the case of 50% or more hydrous ethanol, the ratio of konjac mannan to hydrous ethanol (wt / vol) is at least 1: 5, preferably 1:10, and the total contact time with hydrous ethanol is 30 minutes or more. It is. This contact time includes pretreatment in water-containing ethanol and high-speed stirring time in a stirrer. Therefore, using a different or the same stirrer, the raw material konjac mannan is first brought into contact with water-containing ethanol while stirring slowly, and after solid-liquid separation, the cake may be dispersed again in water-containing ethanol and stirred at high speed, or the first water-containing Contact with ethanol may be omitted, and necessary contact time may be secured simultaneously with high-speed stirring. It is preferable to contact konjac mannan without pulverization and hydrous ethanol, then re-disperse the solid-liquid separated cake in hydrous ethanol and subject to high-speed stirring accompanied by pulverization. Uniform dehydration and elution removal of impurities are achieved at the same time.

  High-speed agitation accompanied by atomization is performed using a stirrer equipped with a stirring blade that rotates at high speed. This type of stirrer is an apparatus for mixing solids and liquids or liquids that do not mix with each other. Depending on the direction of the liquid flow in the machine, it may be classified into a radial flow type and an axial flow type, and either of them may be used. The specific number of rotations varies depending on the particular stirrer employed. For example, in the case of HOMOMIXER MARK II manufactured by Tokushu Kika Co., Ltd. used in the examples, it was performed at 10,000 RPM.

  The duration of the high-speed stirring should be sufficient for the atomized konjac mannan to reach an average particle size after drying of 50 μm or less, preferably 30 μm or less. The specific stirring time varies depending on the presence / absence of pretreatment with water-containing ethanol, the model to be used, the rotational speed, etc., but generally 20 minutes will be sufficient.

  After micronization by high-speed stirring, the slurry is filtered for solid-liquid separation, and the wet cake is dried at a temperature of 100 ° C. or less and pulverized. The resulting finely divided konjac mannan is less than half the average particle size compared to conventional readily soluble glucomannan, shortened to about 1/4 in the time to reach the viscosity peak, and about 95% of the viscosity peak is expressed in about 15 minutes. The

  In the following examples, parts by weight and parts by volume are in a relationship of g: ml.

Example 1
10 parts by weight of konjac mannan (konjac fine powder) having a glucomannan content of 75% was added to 100 parts by volume of 95% water-containing ethanol, and slowly stirred for 30 minutes so as to be uniformly dispersed. Thereafter, the dispersion was once filtered, and the filter cake was redispersed in 100 parts by volume of 80% water-containing ethanol. K. The mixture was stirred for 20 minutes in a HOMOMIXER MARK II at a rotation speed of 10,000 RPM.

  After the stirring, the dispersion was filtered to separate into solid and liquid, and the cake was dried at 90 ° C. for 24 hours and pulverized.

Example 2
10 parts by weight of konjac mannan (konjac fine powder) having a glucomannan content of 80% was added to 100 parts by volume of 70% hydrous ethanol, and the mixture was slowly stirred for about 60 minutes so as to disperse uniformly. Thereafter, the dispersion was filtered once, and the filter cake was redispersed in 100 parts by volume of 80% water-containing ethanol, and stirred at a rotational speed of 10,000 RPM for 20 minutes using the high-speed stirrer used in Example 1. Thereafter, the dispersion was filtered for solid-liquid separation, and the cake was stirred and pulverized at 90 ° C. for 24 hours.

1. Particle size distribution of micronized konjac mannan The particle size distribution of micronized konjac mannan produced in Example 1 and Examples was measured by a laser diffraction particle size distribution measuring apparatus, model SALD-3000S, manufactured by Shimadzu Corporation. For comparison, the particle size distributions of the raw material konjac mannan (konnyaku fine powder) used and the conventional readily soluble glucomannan (Shimizu Chemical Co., Ltd., ROLEX RS) were also measured.

  FIG. 1 is a particle size distribution curve of the finely divided konjac mannan produced in Example 1, and FIG. 2 is a particle size distribution curve of the finely divided konjac mannan produced in Example 2. The graphs of FIGS. 1 and 2 show that the average diameter of the raw material konjac mannan is 323 μm and 315 μm, and the average particle diameter of the conventional readily soluble glucomannan is 91 μm, whereas the average particle of glucomannan produced by the method of the present invention The diameter is 26 μm.

2. Solubility of micronized konjac mannan As a representative, micronized konjac mannan produced in Example 1 was selected, and the change over time in the viscosity of a 1% aqueous solution was measured at 25 ° C. ± 1 ° C. using a B-type viscometer. For comparison, the same time-dependent changes in the viscosity of raw material konjac fine powder, conventional readily soluble glucomannan (Rolex RS manufactured by Shimizu Chemical Co., Ltd.), and high purity glucomannan (Propol A manufactured by Shimizu Chemical Co., Ltd.) are the same. Measured under conditions. The results are shown in the graph of FIG.

  The fast-dissolving konjac mannan produced by the method of the present invention reached a peak viscosity of about 35,000 mPa · s in about 30 minutes, and developed a viscosity of about 95% at the viscosity peak in about 15 minutes. On the other hand, in the conventional easily soluble glucomannan, it takes about 2 hours to reach the peak viscosity of about 35,000 Pa · s, and in about 15 minutes, only about 50% viscosity at the viscosity peak is developed. Of course, a short viscosity peak time of about 30 minutes cannot be obtained with raw material konjac refined powder and high-purity glucomannan.

2 is a graph of a particle size distribution curve of finely divided konjac mannan produced in Example 1. FIG. The particle size distribution curve graph of micronized konjac mannan manufactured in the Example. The graph of the viscosity change with time of micronized konjac mannan produced by the method of the present invention.

Claims (2)

Konjac mannan having a glucomannan content of 50% or more is dispersed in hydrous ethanol having a content of 70% or more and 95% or less at a ratio of konjac mannan to hydrous ethanol of at least 1: 5 (wt / vol), and is rotated at high speed in a slurry state. Stirring with a stirrer equipped with a stirring blade until the average particle size is 50 μm or less, including at this time the konjac mannan is brought into contact with water-containing ethanol for at least 30 minutes, solid-liquid separation and then drying. Manufacturing method of konjac mannan. Before stirring the konjac mannan in the slurry in the water-containing ethanol in the stirrer, the ratio of the konjac mannan to the water-containing ethanol of 70% to 95% water-containing ethanol at least 1: 5 (wt / vol) 2. A pretreatment step for maintaining a dispersed state in which the solid-liquid separation is performed, wherein the total contact time of konjac mannan and hydrous ethanol in the pretreatment step and the stirring step in the stirrer is kept at least 30 minutes or more. the method of.

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