WO2018195267A1

WO2018195267A1 - Fast hydratable konjac flour

Info

Publication number: WO2018195267A1
Application number: PCT/US2018/028289
Authority: WO
Inventors: Jing Guo
Original assignee: Dow Global Technologies Llc
Priority date: 2017-04-20
Filing date: 2018-04-19
Publication date: 2018-10-25

Abstract

A fast hydratable konjac flour has a glucomannan content of at least 70 weight percent, based on the total weight of the konjac flour, a median particle Equivalent Projected Circle Diameter, EQPC 50,3, of at least 110 micrometers, and a surface ratio S/Stot of not more than 0.08, wherein S is the surface of the konjac flour particles having a particle length LEFI of less than 40 micrometers and Stot is the total surface of the konjac flour particles.

Description

FAST HYDRATABLE KONJAC FLOUR

FIELD

The present invention relates to konjac flour that is fast hydratable in water and a process for preparing it.

INTRODUCTION

Konjac (Amorphophallus konjac) is a plant, the tuber of which is the source of a well- known foodstuff in China and Japan, namely konjac flour. This flour, which contains a variety of insoluble materials described below as well as a major amount of desirable water- soluble substances, comprises a highly viscous sol of glucomannan and soluble starches when reconstituted in water. The principal soluble constituent is glucomannan, a polysaccharide comprised of D-glucose and D-mannose, which is useful as an ingredient in various foodstuffs, cosmetic, medicinal and dietary supplement compositions as well as in industrial applications such as films, oil drilling fluids, and paints.

There are numerous impurities in crude native konjac flour, including insoluble starches, cellulose, and nitrogen-containing materials, including proteins, many of which impurities constitute the "sacs" which encapsulate the konjac flour in the tuber. On average, dried crude Konjac flour contains between 49% to 60% glucomannan fiber as the main carbohydrate. The remaining carbohydrate includes 10% to 30% starch, 2% to 5% insoluble fiber, 5% to 14% crude protein, 3% to 5% sugars and 3% to 5.3 ash (mineral content). The flour sacs from various Amorphophallus species ranges from about 100 to 500 micrometers in size. Because of its relatively large sacs, native konjac flour has excellent dispersibility in water, but it takes a long time for the maximum viscosity of an aqueous sol to be reached, usually requiring heating and agitation. Stated in another way, the hydration rate of native konjac flour in room temperature or cool water is relatively slow. This slow hydration is a problem for many uses of crude native konjac flour, particularly those which employ continuous flow production.

To make the most effective use of the glucomannan comprised in konjac, konjac is typically purified and comminuted in dry form to produce konjac flour. A Chinese professional standard sets minimum 70 % glucomannan content for top grade common konjac flour while the European community requests 75 % glucomannan for konjac gum (Commission Directive 2001/30/EC: Amending Directive 96/77/EC laying down specific purity criteria on food additives other than colours and sweeteners, Official Journal of the European Communities, 31.5.2001, L 146/1, 2001).

However, dry konjac glucomannan is often very difficult to dissolve in cold water and often even in warm water. U.S. Patent No. 8,003,152 discloses that it often takes 2 to 6 hours to dissolve regular konjac powder in water. Even at relatively high temperatures of 80° C or higher, rigorous agitation is required to ensure full dissolution, resulting in high energy costs. Without rigorous agitation, the outside particles of the konjac flour are hydrated before the inside of the particles when added to water. When purified,

glucomannans like konjac glucomannan often take up water so quickly that a gelatinous membrane of hydrated outside particles is thus formed around the inside particles, shielding the inside particles from complete hydration. The first particles that come into contact with water immediately swell and stick to each other, forming a gel-like barrier that shields the remaining particles from hydration. The gel blocking behavior is visible as the formation of "lumps" which require a long time for complete dissolution. The lumps take excessive periods of time to hydrate or in some situations fully fail to hydrate for practical application.

Accordingly, the skilled artisans have intensely searched for ways of improving the hydration rate and for decreasing lump formation of konjac glucomannan in cold water, i.e., water below, at or only slightly above room temperature. The buildup of the viscosity of the aqueous glucomannan is an indication of the hydration of the glucomannan.

To speed up the hydration rate generally requires a reduction in particle size.

However, even in a conventional cold mill (which would be the mill of choice to those skilled in the art), grinding causes the konjac flour to degrade as evidenced by its turning brown and smelling burnt, and importantly, also causes a large reduction in attainable viscosity.

To produce rapidly hydratable konjac flour, U.S. Patent No. 5,733,593 relates to two mechanical processes that provide konjac flour that hydrates more rapidly than native (unprocessed) konjac flour. According to the first mechanical process native konjac flour is cryogenically cooled (deep-frozen) using liquid nitrogen to make crude konjac flour particles sufficiently brittle to fracture easily, followed or accompanied by grinding until the particle size of the flour is 149 micrometers or less. However, this procedure is capital intensive and has high production cost. The second mechanical process is a multi-step process wherein the steps have to be used in combination. The second mechanical process includes [a] moistening native konjac flour to plasticize it and then milling several times between two rolls to form flaked konjac flour particles, spreading the flaked konjac flour particles on trays, drying them, allowing them to stand for hours, collecting them and grinding them. The second mechanical process is very time intensive, which results in high production costs.

U.S. Patent No. 5,486,364 discloses the use of readily available konjac glucomannan as sustained release excipient. The readily available konjac glucomannan is produced as described in U.S. Patent No. 5,733,593. Cryogenically ground konjac has a particle size distribution that 11% of the particles have a size of 105 - 150 micrometers, 24% of the particles have a size of 75 - 105 micrometers, and 60% of the particles have a size of less than 75 micrometers. Sustained release tablets could be produced. However, when the crude konjac flour was used, of which 27% of the particles had a size of 150 - 250 micrometers and 50% of the particles had a size of 250 - 420 micrometers, the produced tables fell apart.

U.S. Patent No. 8,003,152 discloses a fast-hydratable, phosphate-modified konjac composition. The fast hydration is attributable to the combination of finer konjac particles and the presence of supporting agents. The konjac particles have a size of 100 to 200 mesh (149 to 74 micrometers). The konjac composition is produced by suspending konjac flour in an aqueous solution of phosphate salts and ethanol, recovering the phosphate-modified konjac from the suspension and grinding the phosphate-modified konjac to an average particle size of less than 150 micrometers, preferably to an ultra-fine particle size of 80 - 100 micrometers. Just before drying the ground phosphate-modified konjac particles, they are mixed with carrageenan gum, Jerusalem artichoke, psyllium husk or xanthan gum as a first supporting agent and optionally agar, alginate, carboxymethylcellulose, casein, guar gum, gellan gum, gelatin, gum Arabic, locust bean gum, or pectin as a second supporting agent. The amount of the konjac particles is 30 to 90 percent by weight of the fast- hydratable, phosphate-modified konjac composition. The amount of the first supporting agent is 10 to 80 percent by weight of the composition. The amount of the second supporting agent is up to 50 percent by weight of the composition. However, the use of an aqueous solution of phosphate salts and ethanol is often not desired for konjac flour that is intended for consumption. Moreover, the process for preparing the fast-hydratable, phosphate-modified konjac composition is expensive due to the large amount of ethanol used as a suspending agent. Furthermore, the need to combine the phosphate-modified konjac particles with one or more supporting agents adds to the complexity of the process and the resulting phosphate-modified konjac composition. Accordingly, it would be desirable to provide new konjac flour which has a high glucomannan content, such as at least 70 weight percent, but which is still fast hydratable. It would be particularly desirable to provide new konjac flour which has a high glucomannan content, can be produced by a simpler process than those disclosed in U.S. Patent Nos. 5,486,364 and 8,003,152 and which does not require phosphate modification of the konjac.

SUMMARY

One aspect of the present invention is Konjac flour having a glucomannan content of at least 70 weight percent, based on the total weight of the konjac flour, having a median particle Equivalent Projected Circle Diameter, EQPC 50,3, of at least 110 micrometers, and having a surface ratio S/Stot of not more than 0.08, wherein S is the surface of the konjac flour particles having a particle length LEFI of less than 40 micrometers and Stot is the total surface of the konjac flour particles.

Another aspect of the present invention is a method for processing konjac flour, which comprises the steps of A) mixing konjac flour having a glucomannan content of at least 70 weight percent, based on the total weight of the konjac flour, with an aqueous liquid to prepare moist konjac having a moisture content of from 35 to 97 percent, based on the total weight of the moist konjac, and B) drying and grinding the moist konjac such that the median particle Equivalent Projected Circle Diameter, EQPC 50,3, of the dried and ground konjac flour is at least 110 micrometers and the surface ratio S/Stot is not more than 0.08, wherein S is the surface of the konjac flour particles having a particle length LEFI of less than 40 micrometers and Stot is the total surface of the konjac flour particles.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 illustrates the hydration rate of two konjac flours of the present invention, of a comparative konjac flour and of a fast-hydratable, phosphate-modified konjac composition of the prior art.

DESCRIPTION OF EMBODIMENTS

Surprisingly, it has been found that the novel konjac flour is fast hydratable in water and can be produced by a simpler procedure than those disclosed in the prior art.

The konjac flour of the present invention has a glucomannan content of at least 70 percent, preferably least 75 percent, more preferably least 80 percent, even more preferably least 85 percent, and most preferably at least 90 percent, based on the total weight of the konjac flour.

Konjac flour having such glucomannan content can be produced by purifying crude konjac flour. As mentioned above, crude konjac flour typically contains between 49% and 60% glucomannan fiber as the main carbohydrate; the remaining carbohydrate includes 10% to 30% starch, 2% to 5% insoluble fiber, 5% to 14% crude protein, 3% to 5% sugars and 3% to 5.3 ash (mineral content). Processes for purifying crude konjac flour are known in the art. To separate the light konjac starch from the heavy glucomannan fiber, air can be blown over the dried crude konjac flour to separate the two carbohydrates. The

glucomannan fiber can then be purified using alcohol to remove additional starch, alkaloids and other materials. Konjac flour having a glucomannan content of at least 70 percent is also designated herein as "konjac glucomannan" or "konjac glucomannan fiber". Konjac flour having a glucomannan content of more than 90 percent, based on the total weight of the konjac flour, is commercially available under the designation konjac glucomannan powder from the company Konjac foods. It passes through a sieve of 120 mesh (125 micrometers). Such purified konjac flour having a glucomannan content of at least 70 percent is a preferred starting material for producing the konjac flour of the present invention that has a median particle Equivalent Projected Circle Diameter, EQPC 50,3, of at least 110 micrometers and a surface ratio S/Stot of not more than 0.08, wherein S is the surface of the konjac flour particles having a particle length LEFI of less than 40 micrometers and Stot is the total surface of the konjac flour particles.

The konjac flour of the present invention is described in more details further below. It is producible by a method for processing konjac flour having a glucomannan content of at least 70 weight percent, which comprises the steps of A) mixing the konjac flour with an aqueous liquid to prepare moist konjac flour having a moisture content of from 35 to 97 percent, based on the total weight of the moist konjac flour, and B) drying and grinding the moist konjac such that the median particle Equivalent Projected Circle Diameter, EQPC 50,3, of the dried and ground konjac flour is at least 110 micrometers.

In step A) of the method of the present invention konjac flour that has a glucomannan content of at least 70 percent, preferably least 75 percent, more preferably least 80 percent, even more preferably least 85 percent, and most preferably at least 90 percent, based on the total weight of the konjac flour, is mixed with an aqueous liquid to prepare moist konjac having a moisture content of from 35 to 97 percent, based on the total weight of the moist konjac. The particle size of the konjac flour that is used as a starting material in step A) is not very critical. It can be even smaller than the particle size of the konjac flour of the present invention. In one aspect of the invention the particle size of the konjac flour that is used as a starting material in step A) has an EQPC 50,3 of less than 110 micrometers. Preferred lower limits of the moisture content are 40, 55, 65, and 70 percent, respectively. Preferred upper limits of the moisture content are 95, 92, 90 and 85 percent respectively. Most preferably the moisture content is from 65 to 90 percent, based on the total weight of the moist konjac. The aqueous liquid used in step A) may comprise a minor amount of an organic liquid diluent; however, the aqueous liquid should comprise at least 55, preferably at least 65, more preferably at least 75, most preferably at least 90, and particularly at least 95 weight percent of water, based on the total weight of the aqueous liquid. Preferably the aqueous liquid is water.

The mixing in step A) is typically conducted in a compounder that allows thorough and intense mixing. Useful compounders are, for example, granulators, kneaders, extruders, or roller mills, wherein the mixture of the konjac flour and aqueous liquid is homogenized by applying shear forces and compounding, such as a twin-screw compounder. Co-rotating as well as counter-rotating machines are suitable. So-called divided trough kneaders with two horizontally arranged agitator blades that engage deeply with one another and that perform a mutual stripping action, as in the case of twin-screw compounders are particularly suitable. Suitable single-shaft, continuous kneaders include the so-called Reflector® compounders, which are high performance mixers of modular construction, consisting of a multi-part, heatable and coolable mixing cylinder and a unilaterally mounted blade mixer. Double arm heavy-duty mixers and sigma blade heavy-duty mixers are preferred. A stirred vessel with a vertically arranged mixer shaft is also suitable if suitable flow baffles are mounted on the vessel wall in order to prevent the kneaded mass rotating together with the stirrer shaft, and in this way an intensive mixing action is imparted to the kneaded material. Also suitable are double-walled mixing vessels with a planetary stirrer and inline homogenizer.

In the mixing step A) the konjac flour and the aqueous liquid are generally mixed at a temperature of from 2 to 90 °C, preferably from 2 to 65 °C, and more preferably from 2 to 50 °C. It has surprisingly been found that the konjac flour of the present invention is more readily hydratable in water when the temperature in the mixing step A) is from 2 to 50 °C, more preferably from 5 to 40 °C, most preferably from 8 to 30 °C, and particularly from 8 to 20 °C, than when the temperature in the mixing step A) is higher than 65°C. The temperature in the mixing step A) is preferably controlled by controlling and optionally varying or adjusting the temperature of the added aqueous liquid and/or the jacket temperature of the compounder.

In the mixing step A) a mixture of konjac and aqueous liquid is obtained that is usually in the shape of moist granules, moist lumps, a moist paste and/or a moist dough.

In step B) the moist konjac is subjected to drying and grinding such that the median particle Equivalent Projected Circle Diameter, EQPC 50,3, of the dried and ground konjac flour is at least 110 micrometers, preferably at least 120 micrometers, more preferably at least 130 micrometers, and most preferably at least 135 micrometers and the surface ratio S/Stot is not more than 0.08, preferably not more than 0.07, more preferably not more than 0.06, most preferably not more than 0.05, and particularly not more than 0.045, wherein S is the surface of the konjac flour particles having a particle length LEFI of less than 40 micrometers and Stot is the total surface of the konjac flour particles. In step B) the moist konjac is subjected to drying and grinding such that the EQPC 50,3 of the dried and ground konjac flour is generally up to 250 micrometers, preferably up to 220 micrometers, more preferably up to 200 micrometers, and most preferably up to 170 micrometers. How to determine the EQPC 50,3 is described further below.

Drying and grinding can be conducted in sequence or simultaneously, provided that the dried and ground konjac flour has the above-mentioned particle size. In one aspect of the present invention the moist konjac is first partially or fully dried, for example in an oven, and then subjected to grinding. Useful grinding devices are known in the art, for example Hosokawa Alpine Mills. In another aspect of the present invention the moist konjac is subjected simultaneously to grinding and at least partial drying. Combined grinding and at least partial drying can be conducted in a known combined grinding and drying device, such as a gas-swept impact mill, preferably an air-swept or nitrogen-swept impact mill, wherein moist konjac is subjected to an impacting and/or shearing stress. Preferred gas-swept impact mills are Ultra Rotor mills (Altenburger Maschinen Jaeckering, Germany), Turbofiner PLM mills (PALLMANN Maschinenfabrik GmbH & Co. KG, Germany) or a Hosokawa Alpine Mill. Gas classifier mills are also useful gas-swept impact mills, for example, the Hosokawa Alpine Air Classifier mill - ZPS Circoplex Hosokawa Micron Ltd., Cheshire, England. The circumferential speed of the grinding and drying device is preferably controlled and optionally varied or adjusted in a range of 100 to 120 m/s. Drying is typically accomplished with a combination of gas and mechanical energy. Drying is optionally completed after the grinding.

The above described method is useful for producing konjac flour having particles of a certain size and shape. After the above-mentioned processing steps the konjac flour of the present invention can be obtained. Surprisingly, it has been found that konjac flour of the present invention and konjac flour that is obtained by the method of the present invention is faster hydratable in water than known comparable konjac flour that has not been processed by the method of the present invention. Hence, the method of the present invention increases the hydration rate of the konjac flour in water at room temperature. The hydration rate can be assessed by the viscosity increase when blending konjac flour and water at room temperature. More details on how to assess the hydratability, i.e., the hydration rate of the konjac flour in water at room temperature are provided in the Examples section.

Particle size and shape of the konjac flour can be determined by a high speed image analysis method which combines particle size and shape analysis of sample images. All particles of a given sample in a video stream are identified and their size and shape parameters are calculated. An image analysis method for complex powders is described in: W. Witt, U. Kohler, J. List, Current Limits of Particle Size and Shape Analysis with High Speed Image Analysis, PARTEC 2007. A high speed image analysis system is

commercially available from Sympatec GmbH, Clausthal- Zellerfeld, Germany as dynamic image analysis (DIA) system QICPIC™. The high speed image analysis system is useful for measuring among others the following dimensional parameters of particles:

LEFI (Length of Fiber): The particle length LEFI is defined as the longest direct path that connects the ends of the particle within the contour of the particle. "Direct" means without loops or branches.

EQPC (Equivalent Projected Circle Diameter): EQPC of a particle is defined as the diameter of a circle that has the same area as the projection area of the particle.

All particle size distributions, e.g., the LEFI or the EQPC, can be displayed and applied as number (0), length (1), area (2) and volume (3) distribution. The volume distribution is designated by the number 3 after the comma in the terms "LEFI 50,3" or "EQPC 50,3". The designation 50 reflects the median value. In a given sample of konjac flour, the median LEFI 50,3 means that 50% of all particles in the volume distribution have a LEFI that is smaller than the given value in μιη and 50% of all particles in the volume distribution have a LEFI that is larger. In a given sample of konjac flour, the median EQPC 50,3 means that 50% of all particles in the volume distribution have an EQPC that is smaller than the given value in μιη and 50% of all particles in the volume distribution have an EQPC that is larger.

Fine Particles:

For the purpose of the present invention fine particles have a particle length LEFI of less than 40 micrometers and generally a particle length LEFI of at least 10 micrometers. The detection limit of the Dynamic Image Analysis DIA system QICPIC™ with a M7 optical system is 10 micrometers.

The volume of the fine particles in a given sample of konjac flour is calculated according to Equation 1

π (EQPC)³

V = n (Equation 1),

6

wherein V is the volume of fine particles, n is the number of fine particles in the sample and EQPC here is the median EQPC 50,0 determined from the number particle size distribution of the fine particles.

The volume fraction of the fine particles is V/V_tot, wherein V is the volume of the fine particles, as calculated above, and V_tot is the total volume of the given sample of konjac flour. Vtot can be calculated using Equation 1 above, except that for calculating Vtot n is the number of all particles and EQPC is the median EQPC 50,0 determined from the number particle size distribution of all particles.

The surface of the fine particles in a given sample of konjac flour is calculated according to Equation 2

S = π [EQPC)² n (Equation 2),

wherein S is the surface of fine particles, n is the number of fine particles in the sample and EQPC here is the median EQPC 50,0 determined from the number particle size distribution of the fine particles.

The surface fraction of the fine particles is S/Stot, wherein S is the surface of the fine particles, as calculated above, and Stot is the total surface of the given sample of konjac flour. Stot can be calculated using Equation 2 above, except that for calculating Stot n is the number of all particles and EQPC is the median EQPC 50,0 determined from the number particle size distribution of all particles.

The konjac flour of the present invention has a median particle Equivalent Projected

Circle Diameter, EQPC 50,3, of at least 110 micrometers, preferably at least 120 micrometers, more preferably at least 130 micrometers, and most preferably at least 135 micrometers. The konjac flour of the present invention generally has an EQPC 50,3 of up to 250 micrometers, preferably up to 220 micrometers, more preferably up to 200

micrometers, and most preferably up to 170 micrometers.

The konjac flour of the present invention has a surface ratio S/Stot of not more than

0.08, preferably not more than 0.07, more preferably not more than 0.06, most preferably not more than 0.05, and particularly not more than 0.045. S is the surface of the fine konjac flour particles, i.e., of konjac flour particles having a particle length LEFI of less than 40 micrometers. Stot is the total surface of the konjac flour particles. It is to be understood that a representative sample is drawn from the konjac flour and the surface ratio S/Stot of this sample is measured to determine the surface ratio S/Stot of the konjac flour.

The konjac flour of the present invention preferably has a median particle length, LEFI 50,3, of at least 170 micrometers, more preferably at least 180 micrometers, most preferably at least 190 micrometers, and particularly at least 200 micrometers. The konjac flour of the present invention preferably has a LEFI 50,3 of up to 350 micrometers, more preferably up to 300 micrometers, most preferably up to 270 micrometers, and particularly up to 250 micrometers.

The konjac flour of the present invention preferably has a volume ratio V/V_tot of not more than 0.025, preferably not more than 0.020, more preferably not more than 0.015 and most preferably not more than 0.013. V is the volume of the fine konjac flour particles, i.e., of konjac flour particles having a particle length LEFI of less than 40 micrometers. V_tot is the total volume of the konjac flour particles. It is to be understood that a representative sample is drawn from the konjac flour and the volume ratio V/Vtot of this sample is measured to determine the volume ratio V/Vtot of the konjac flour.

Without wanting to be bound by the theory, the inventors of the present invention believe that the method of the present invention not only has an impact on the shape of the konjac flour particles but that the konjac flour of the present invention preferably comprises agglomerated particles which can also be provided by the method of the present invention. The inventors believe that coarser and granular konjac flour particles are produced by the method of the present invention. Contrary to the teaching in the prior art that a reduction in particle size is generally required to speed up the hydration rate of konjac flour, the inventors have surprisingly found that konjac flour that is processed by the method of the present invention exhibits an increased hydration rate. This is highly surprising because the method of the present invention increases the Projected Circle Diameter, EQPC 50,3, and typically also the median particle length, LEFI 50,3.

The konjac flour of the present invention has a glucomannan content of at least 70 percent, preferably least 75 percent, more preferably least 80 percent, even more preferably least 85 percent, and most preferably at least 90 percent, based on the total weight of the konjac flour. The glucomannan content in the konjac flour can be up to 100 percent, based on the total weight of the konjac flour. More typically it is up to 98 percent or up to 95 percent, based on the total weight of the konjac flour.

The konjac flour of the present invention typically reaches at least 50 percent of its peak viscosity in water at 25 °C within 15 minutes, preferably within 12 minutes after addition of the konjac flour to water. The konjac flour of the present invention typically reaches at least 80 percent of its peak viscosity in water at 25 °C within 25 minutes, preferably within 22 minutes after addition of the konjac flour to water.

The konjac flour may be used in combination with one or more other gelling agents, for example those listed in U.S. Patent No. 8,003,152 as first or second supporting agents, i.e., carrageenan gum, Jerusalem artichoke, psyllium husk, xanthan gum, agar, alginate, carboxymethylcellulose, casein, guar gum, gellan gum, gelatin, gum Arabic, locust bean gum, or pectin. However, the amount of additional gelling agents preferably is only from 0 to 5 weight percent, more preferably from 0 to 2 weight percent, and most preferably only from 0 to 1 weight percent, based on the weight of the Konjac flour. Most preferably the konjac flour is not combined with another gelling agent to provide a fast hydratable konjac flour composition.

Some embodiments of the invention will now be described in detail in the following Examples.

EXAMPLES

Unless otherwise mentioned, all parts and percentages are by weight. In the

Examples the following test procedures are used. Determination of the LEFI 50,3, the EQPC 50,3, the volume fraction of fine particles

V/Vtot and the surface fraction of fine particles S/Stot

The konjac flour particles were analyzed as received or after treatment according to the Examples below with a high speed image analyzer sensor QICPIC, Sympatec, Germany, with a dry disperser RODOS/L with an inner diameter of 4 mm and a dry feeder VIBRI/L and Software WINDOX5, Vers. 5.3.0 and M7 lens. The terms LEFI 50,3, EQPC 50,3, volume fraction of fine particles V/V_tot and surface fraction of fine particles S/Stot have the meanings as defined further above.

Hydration Rate of Konjac Flour

1 weight part of konjac flour (or konjac flour composition) and 99 weight parts of deionized water were mixed at 25 °C in a Rheometer from ATS RheoSystems using 25 ml cup and CC25 wing-impeller at room temperature. The shear rate was 200 s ¹ for 60 s, and then 100 s ¹ for 120 min. Each measurement was done in duplicate. The viscosity of the aqueous mixture was plotted against time. The viscosity build-up of the aqueous mixture over time is an indication of the hydratability of the konjac flour (or konjac flour composition). Comparative Example A

The konjac flour of Comparative Example A was acquired from Konjac Foods under the designation Konjac glucomannan powder. It has a glucomannan content (dried) of more than 90 percent, based on the total weight of the konjac flour and a viscosity of more than 35,000 mPa- s, measured as a 1 weight percent solution at 25 °C. It passes through a sieve of 120 mesh (125 micrometers).

Example 1

80 g of konjac flour of Comparative Example A was fed into a jacketed laboratory heavy-duty Linden LK II 1 kneader. The kneader was equipped with dual Sigma (Z-form) blades running at 60 rpm. Heated water circulated in the jacket. The temperature of the heated water circulating in the jacket was set to 90 °C. A total of 300 ml water was added to the konjac flour in the kneader over a time period of one hour and kneading was continued to process the mixture of water and konjac flour to a dough. The temperature in the kneader increased from about 35 °C to about 80 °C within this hour of adding water and kneading the dough. Kneading of the dough continued for additional 10 minutes without addition of water. The dough was then removed from the kneader, broken up into smaller portions and dried in an oven at a temperature of 55 °C. The dried dough was then ground using a Hosokawa Alpine Mill Model 160-UPZ with a 0.2mm screen, which is a gas-swept impact mill. Nitrogen was used in the gas-swept impact mill. A hot gas stream, i.e. nitrogen was fed with 1400 m³/h into the bottom of the mill. The circumferential speed of the rotor was 110 m/s. A cyclone was used to separate the dried product from the nitrogen. Example 2

80 g of konjac flour of Comparative Example A was fed into the same jacketed laboratory heavy-duty Linden LK II 1 kneader as in Example 1. The temperature of the water circulating in the jacket was set to 5 °C. 60 ml of water was added to the konjac flour in the kneader over a time period of 25 minutes while the kneader was running at 40 rpm. The temperature in the kneader decreased from 15 °C to 13.5 °C. Then the speed of the kneader was increased to 60 rpm and kneading was continued for additional 30 minutes. During these 30 minutes an additional amount of water (223 ml) was added to the konjac flour in the kneader. The temperature in the kneader decreased to 10 °C. Kneading of the dough continued for additional 5 minutes without addition of water. The dough was then removed from the kneader, broken up into smaller portions, dried and ground as in Example 1.

Comparative Example B

Comparative Example B is a fast-hydratable konjac composition as described in U.S. Patent No. 8,003,152. It is commercially available from Vitalico LLC, San Mateo, California (USA) under the designation Exquina™. U.S. Patent No. 8,003,152 discloses that the fast-hydratable konjac composition is made from 30 to 90 percent by weight of phosphate-modified ground konjac of an average particle size of less than 150 micrometers, 10 to 80 percent by weight of a first supporting agent selected from carrageenan gum, Jerusalem artichoke, psyllium husk and xanthan gum and optionally up to 50 percent by weight of a second supporting agent selected from agar, alginate, carboxymethylcellulose, casein, guar gum, gellan gum, gelatin, gum Arabic, locust bean gum, and pectin.

Dimensional Parameters of Konjak Particles

The dimensional parameters of all particles in samples of the Konjac flour of Comparative Example A and of Examples 1 and 2 and in a sample of the Konjac flour composition of Comparative Example B were determined using a high speed image analyzer as described further above. The results are listed in Table 1 below. Table 1

Hydration Rate

The hydration rates of the konjac flour of Examples 1 and 2 and of Comparative Example A and of the konjac flour composition of Comparative Example B at a concentration of 1 wt.-% in water at 25 °C are measured as described further above. The results are illustrated in Fig. 1.

Fig. 1 illustrates that the konjac flour of Comparative Example A is not able to build up viscosity to a significant degree at a concentration of 1 wt.-% konjac flour in water at 25 °C. The viscosity build-up of the konjac flour of Example 1 in water is improved over that of Comparative Example A.

The konjac flour of Example 2 is able to build up a very high viscosity in water within a very short time period, as illustrated in Fig. 1. The konjac flour of Example 2 reaches 50 percent of its peak viscosity in water at 25 °C within 12 minutes after addition of the konjac flour to water. The konjac flour of of Example 2 reaches 80 percent of its peak viscosity in water at 25 °C within 22 minutes after addition of the konjac flour to water.

Fig. 1 also illustrates that the konjac flour of Example 2 achieves a substantially higher viscosity than the fast-hydratable konjac composition of Comparative Example B in about the same time period, although the concentration of the konjac flour of Example 2 is the same as that of the fast-hydratable konjac composition of Comparative Example B. The slope of the hydration curve (viscosity increase curve) in Example 2 is steeper than that of Comparative Example B. This means that the konjac flour of Example 2 hydrates faster than the fast-hydratable konjac composition of Comparative Example B. Also the peak viscosity of the konjac flour of Example 2 is significantly higher than that of the fast-hydratable konjac composition of Comparative Example B. Note that the y-axis (viscosity) in Fig. 1 is logarithmic.

The viscosity build-up of the konjac flour of Example 1 is lower than that of the fast-hydratable konjac composition of Comparative Example B. However, the use of the phosphate-modified konjac composition of Comparative Example B as disclosed in U.S. Patent No. 8,003,152 may not be acceptable to many consumers.

Visual Inspection

In another experiment, 2 weight parts of the konjac flour of Examples 1 and 2 and of

Comparative Example A, respectively, and 98 weight parts of deionized water were mixed at room temperature while stirring using an overhead mixer at 600 rpm.

The konjac flour of Comparative Example A formed a large amount of lumps. The fine particles of the konjac flour of Comparative Example A took up water so quickly at their surfaces that lumps were formed without achieving a thorough hydration that is necessary to achieve a significant viscosity increase. The lumps would take a long time to hydrate or in some practical end-uses may even fail to hydrate.

In contrast thereto, the konjac flours of Example 1 and 2 did not form lumps.

Claims

1. Konjac flour

having a glucomannan content of at least 70 weight percent, based on the total weight of the konjac flour,

having a median particle Equivalent Projected Circle Diameter, EQPC 50,3, of at least 110 micrometers, and

having a surface ratio S/Stot of not more than 0.08, wherein S is the surface of the konjac flour particles having a particle length LEFI of less than 40 micrometers and Stot is the total surface of the konjac flour particles.

2. The konjac flour of claim 1 having a glucomannan content of at least 75 weight percent.

3. The konjac flour of claim 1 or claim 2 comprising agglomerated particles.

4. The konjac flour of any one of claims 1 to 3 having an EQPC 50,3 of at least 120 micrometers.

5. The konjac flour of claim 4 having an EQPC 50,3 of at least 135 micrometers.

6. The konjac flour of any one of claims 1 to 5 having an EQPC 50,3 of up to 250 micrometers.

7. The konjac flour of any one of claims 1 to 6 wherein the surface ratio S/Stot is not more than 0.06.

8. The konjac flour of claim 7 wherein the surface ratio S/Stot is not more than 0.045.

9. The konjac flour of any one of claims 1 to 8 having a median particle length, LEFI 50,3, of at least 170 micrometers.

10. The konjac flour of any one of claims 1 to 9 having a LEFI 50,3 of up to 300 micrometers.

11. A method for processing konj ac flour, comprising the steps of

A) mixing konjac flour having a glucomannan content of at least 70 weight percent, based on the total weight of the konjac flour, with an aqueous liquid to prepare moist konjac having a moisture content of from 35 to 97 percent, based on the total weight of the moist konjac, and

B) drying and grinding the moist konjac such that the median particle Equivalent Projected Circle Diameter, EQPC 50,3, of the dried and ground konjac flour is at least 110 micrometers and the surface ratio S/Stot is not more than 0.08, wherein S is the surface of the konjac flour particles having a particle length LEFI of less than 40 micrometers and Stot is the total surface of the konjac flour particles.

12. The method of claim 11 wherein the konjac flour is mixed with water in a granulator, kneader, extruder, or roller mill.

13. The method of claim 11 or 12, wherein the konjac flour is mixed with water at a temperature of from 2 to 50 °C.

14. The method of any one of claims 11 to 13 wherein the method increases the hydration rate of the konjac flour in water at room temperature.

15. The method of any one of claims 11 to 14 wherein the konjac flour of any one of claims 1 to 10 is obtained after the processing steps.