Patent Description:
Stevia extract extracted from leaves of stevia is used as a natural sweetener instead of sugar. Steviol glycosides in stevia extract include stevioside, rebaudioside A, rebaudioside D, rebaudioside M and the like. Rebaudioside D, in particular, has a natural sweet flavor and is suitable for drinks and the like, but is difficult to be dissolved in water at room temperature (<NUM>) at high concentration (<NUM> ppm or more).

Patent Literature <NUM> discloses a technique for dissolving rebaudioside D in water at high concentration by adding, to water, rebaudioside D and a stevioside composition (a mixture of stevioside and another steviol glycoside such as Reb. A) in an amount equal to or more than that of rebaudioside D at a high temperature of <NUM> and mixing the solution with stirring. Patent Literature <NUM> discloses a method of preparing a supersaturated solution of rebaudioside D by mixing rebaudioside D in an aqueous liquid at an elevated temperature. Patent Literature <NUM> discloses a sweetened beverage comprising rebaudioside D and citric acid.

A solution prepared by dissolving rebaudioside D in water at high concentration at high temperature has the problem of reprecipitation of rebaudioside D over time after production. In such circumstances improvement of solution stability of rebaudioside D dissolved in water at high concentration is desired.

The present invention includes a method for producing a rebaudioside D-containing aqueous composition comprising rebaudioside D at a concentration of <NUM> ppm by weight or more,
the method comprising: a step of stirring for dispersing a steviol glycoside component comprising rebaudioside D and water in a temperature range of <NUM> to <NUM> under high shear at a tip speed (peripheral speed) of a rotor of <NUM>/s or more, wherein the steviol glycoside component comprises more than <NUM>% by weight of rebaudioside D based on a total weight of the steviol glycoside component.

In some embodiments, in the step of stirring for dispersing, the steviol glycoside component and water are stirred in the presence of a defoaming agent.

In some embodiments, the defoaming agent is selected from the group consisting of citric acid, L-ascorbic acid, DL-malic acid, hydrochloric acid, a citrate, an L-ascorbate, a DL-malate, potassium chloride, sodium chloride, magnesium chloride, calcium chloride, calcium sulfate, a phosphate, a fumarate, a gluconate, a succinate, a lactate, and a mixture of two or more thereof.

In some embodiments, the defoaming agent is selected from the group consisting of citric acid, L-ascorbic acid, DL-malic acid, hydrochloric acid, a citrate, an L-ascorbate, a DL-malate, potassium chloride, sodium chloride, magnesium chloride, calcium chloride, and a mixture of two or more thereof.

In some embodiments, a ratio of a weight of the defoaming agent (Wdef) to a weight of rebaudioside D (Wreb) (Wdef/Wreb) is <NUM> or more.

In some embodiments, a concentration of rebaudioside D in the rebaudioside D-containing aqueous composition is <NUM> to <NUM> ppm by weight.

In some embodiments, when the rebaudioside D-containing aqueous composition is stored in an environment of atmospheric pressure and a temperature of <NUM> after production, a ratio of a concentration of rebaudioside D in the rebaudioside D-containing aqueous composition on day <NUM> after the production (C<NUM>) to a concentration of rebaudioside D in the rebaudioside D-containing aqueous composition on day <NUM> of the production (C<NUM>) (C<NUM>/C<NUM>) is <NUM> or more.

In some embodiments, the rebaudioside D-containing aqueous composition is a concentrated liquid for a drink.

An embodiment of the present invention improves solution stability of rebaudioside D dissolved in water at high concentration. Furthermore, an embodiment of the present invention can eliminate or reduce foam generated by stirring for dispersing under high shear. Moreover, in an embodiment of the present invention, rebaudioside D can be dissolved in water in a stable manner without using stevioside which is bitter and leaves a bad aftertaste.

Hereinafter the present invention will be described in more detail. The following embodiments only illustrate the present invention, and do not limit the present invention. The present invention may be practiced in various modes as long as the modes do not deviate from the gist of the present invention.

In the present description, both "rebaudioside" and "Reb. " mean "rebaudioside. " For example, rebaudioside D is also referred to as Reb.

The "steviol glycoside component" includes at least rebaudioside D. When the steviol glycoside component includes a steviol glycoside component other than rebaudioside D, the steviol glycoside component also includes one or more selected from the group consisting of stevioside, rebaudioside A, rebaudioside B, rebaudioside C, rebaudioside E, rebaudioside F, rebaudioside G, rebaudioside H, rebaudioside I, rebaudioside J, rebaudioside K, rebaudioside L, rebaudioside M, rebaudioside N, rebaudioside O, rebaudioside Q, rebaudioside R, dulcoside A, rubusoside, steviolmonoside, and steviolbioside.

The "defoaming agent" is a compound or a composition which acts to eliminate or reduce foam generated when a solution containing rebaudioside D is stirred for dispersing. Furthermore, the defoaming agent may act to reduce generation of foam itself caused by stirring for dispersing a solution containing rebaudioside D. When a rebaudioside D-containing aqueous composition is used for a drink, the rebaudioside D-containing aqueous composition (or the drink) contains the defoaming agent in such an amount that causes no safety problem even when the defoaming agent remains in the drink.

The "rebaudioside D-containing aqueous composition" may also be used as a sweetening composition for drinks and the like.

"ppm" means "ppm by weight" (mg/ kg) unless otherwise specified. "ppm by weight" may be the same as "mg/ L" for an aqueous composition, a sweetening composition or a drink which mainly contains water and has a specific gravity of about <NUM>.

The content (ppm) of rebaudioside D, the steviol glycoside component, the defoaming agent and the like in rebaudioside D-containing aqueous composition (or sweetening composition) may be calculated based on the amount of raw materials added, or measured by a known method of analysis such as liquid chromatography.

The rebaudioside D-containing aqueous composition produced by the method of the invention is a solution containing rebaudioside D at a concentration of <NUM> ppm or more, and contains a steviol glycoside component including rebaudioside D, and water. The steviol glycoside components include more than <NUM>% by weight of rebaudioside D based on the total weight of the steviol glycoside components.

Rebaudioside D is not particularly limited, and may be derived from plant, may be those chemically synthesized and those biosynthesized. For example, while rebaudioside D may be isolated and purified from a plant body containing a large amount of rebaudioside D, it may be prepared by chemical synthesis or biosynthesis. In an embodiment of the present invention, rebaudioside D may be prepared by purifying stevia extract, or decomposing rebaudioside M.

Water is tap water, natural water, pure water (<NUM> to <NUM>/m), or a mixture of two or more of them.

In an embodiment of the present invention, the rebaudioside D-containing aqueous composition is a solution containing rebaudioside D at a concentration of <NUM> ppm or more, and contains a steviol glycoside component, water and a defoaming agent. The steviol glycoside components include more than <NUM>% by weight of rebaudioside D based on the total weight of the steviol glycoside components.

In an embodiment of the present invention, the concentration of rebaudioside D in the rebaudioside D-containing aqueous composition at atmospheric pressure at low temperature (<NUM>) to room temperature (<NUM>) is <NUM> ppm or more. In an embodiment of the present invention, the concentration of rebaudioside D in the rebaudioside D-containing aqueous composition (weight of rebaudioside D/ weight of rebaudioside D-containing aqueous composition) at room temperature (<NUM>) is in the range of <NUM> ppm to <NUM>,<NUM> ppm, <NUM> ppm to <NUM>,<NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, or <NUM> ppm to <NUM> ppm.

In an embodiment of the present invention, the lower limit of the concentration of rebaudioside D in the rebaudioside D-containing aqueous composition at atmospheric pressure at low temperature (<NUM>) to room temperature (<NUM>) is <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, or <NUM> ppm.

In an embodiment of the present invention, the upper limit of the concentration of rebaudioside D in the rebaudioside D-containing aqueous composition at atmospheric pressure at low temperature (<NUM>) to room temperature (<NUM>) is <NUM>,<NUM> ppm, <NUM>,<NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, <NUM> ppm, or <NUM> ppm.

In an embodiment of the present invention, the steviol glycoside component in the rebaudioside D-containing aqueous composition comprises more than <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, more than <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, <NUM>% by weight to <NUM>% by weight, or <NUM>% by weight to <NUM>% by weight of rebaudioside D based on the total weight of the steviol glycoside component.

In an embodiment of the present invention, the steviol glycoside component in the rebaudioside D-containing aqueous composition comprises <NUM>% by weight or more of rebaudioside D based on the total weight of the steviol glycoside component. In an embodiment of the present invention, the steviol glycoside component does not comprise one or more of stevioside, rebaudioside A, rebaudioside B, rebaudioside C, rebaudioside E, rebaudioside F, rebaudioside G, rebaudioside H, rebaudioside I, rebaudioside J, rebaudioside K, rebaudioside L, rebaudioside M, rebaudioside N, rebaudioside O, rebaudioside Q, rebaudioside R, dulcoside A, rubusoside, steviolmonoside, and steviolbioside. In an embodiment of the present invention, the steviol glycoside component does not comprise stevioside. In an embodiment of the present invention, the steviol glycoside component comprises more than <NUM>% by weight of rebaudioside D and less than <NUM>% by weight of rebaudioside M based on the total weight of the steviol glycoside component. In an embodiment of the present invention, the steviol glycoside component only consists of more than <NUM>% by weight of rebaudioside D and rebaudioside M based on the total weight of the steviol glycoside component.

In an embodiment of the present invention, the rebaudioside D-containing aqueous composition does not comprise one or more of polyol such as erythritol and a hydrophilic polymer.

In an embodiment of the present invention, the defoaming agent included in the rebaudioside D-containing aqueous composition is selected from the group consisting of citric acid, L-ascorbic acid, DL-malic acid, hydrochloric acid, a citrate, an L-ascorbate, a DL-malate, potassium chloride, sodium chloride, magnesium chloride, calcium chloride, calcium sulfate, a phosphate, a fumarate, a gluconate, a succinate, a lactate, and a mixture of two or more thereof. In an embodiment of the present invention, the defoaming agent is citric acid, L-ascorbic acid, DL-malic acid, hydrochloric acid, a citrate, an L-ascorbate, a DL-malate, potassium chloride, sodium chloride, magnesium chloride, calcium chloride or a mixture of two or more of them. In an embodiment of the present invention, the defoaming agent is sodium citrate, sodium L-ascorbate, sodium DL-malate, sodium chloride, or a mixture of two or more thereof. In an embodiment of the present invention, the defoaming agent is citric acid, L-ascorbic acid, DL-malic acid, hydrochloric acid, sodium chloride or trisodium citrate.

In an embodiment of the present invention, the ratio of the weight of the defoaming agent (Wdef) to the weight of rebaudioside D (Wreb) (Wdef/Wreb) in rebaudioside D-containing aqueous composition is <NUM> or more. In an embodiment of the present invention, the lower limit of the ratio (Wdef/ Wreb) is <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In an embodiment of the present invention, the upper limit of the ratio (Wdef/ Wreb) is <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> or more. In an embodiment of the present invention, the upper limit of the ratio (Wdef/ Wreb) is <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In an embodiment of the present invention, when the rebaudioside D-containing aqueous composition is used for a drink, the upper limit of the ratio (Wdef/Wreb) may be <NUM>, preferably <NUM> so that the drink is not too tart. In an embodiment of the present invention, the ratio (Wdef/Wreb) may be in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, in the range of <NUM> to <NUM>, or in the range of <NUM> to <NUM>.

In an embodiment of the present invention, when the rebaudioside D-containing aqueous composition is stored airtight in an environment of atmospheric pressure and a temperature of <NUM> after production, the ratio of the concentration of rebaudioside D in the rebaudioside D-containing aqueous composition on day <NUM> (i.e. <NUM> days) after the production (C<NUM>) to the concentration of rebaudioside D in the rebaudioside D-containing aqueous composition on day <NUM> of the production (C<NUM>) (C<NUM>/C<NUM>) is <NUM> or more. In an embodiment of the present invention, the ratio (C<NUM>/C<NUM>) is <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, or <NUM> or more. The ratio (C<NUM>/C<NUM>) does not exceed <NUM>.

In an embodiment of the present invention, the rebaudioside D-containing aqueous composition is a concentrated liquid for a drink. The concentrated liquid for a drink comprises a supersaturated solution of rebaudioside D.

In an embodiment of the present invention, the rebaudioside D-containing aqueous composition is a drink comprising water for dilution and a rebaudioside D-containing aqueous composition as a sweetening composition. In an embodiment of the present invention, the drink comprises a sweetener selected from the group consisting of rebaudioside A, rebaudioside B, rebaudioside E, rebaudioside F, rebaudioside M, rebaudioside N, stevia extract, a steviol glycoside having a structure to which rhamnose is bonded, stevioside, mogroside V, sucrose, high fructose corn syrup, erythritol, corn syrup, aspartame, sucralose, acesulfame potassium, saccharin and xylitol.

In an embodiment of the present invention, the rebaudioside D-containing aqueous composition is a drink and the drink is a carbonated drink. Examples of carbonated drinks include a soft drink, a non-alcoholic drink and an alcoholic drink, and are more specifically a sparkling drink, cola, diet cola, ginger ale, a soda pop, a fruit-flavored carbonated drink and fruit-flavored carbonated water, but the drink is not limited thereto.

In an embodiment of the present invention, the rebaudioside D-containing aqueous composition is a drink and the drink may contain a sweetener other than the steviol glycoside component. The sweetener is not particularly limited, and the drink may also contain, for example, one or more sweeteners selected from the group consisting of sucrose, high fructose corn syrup, erythritol, mogroside V, corn syrup, aspartame (also referred to as a L-phenylalanine compound), sucralose, acesulfame potassium, saccharin and xylitol. It is preferable to use a natural sweetener, and it is particularly preferable to use sucrose, high fructose corn syrup and corn syrup, in order to provide freshness, smoothness, a natural flavor and a moderate rich taste. One of the sweetening components may be used, or a plurality of them may be used. In an embodiment of the present invention, the rebaudioside D-containing aqueous composition is a drink and the drink may be an alcoholic drink containing alcohol. Alcohol means ethyl alcohol (ethanol) unless otherwise specified. The type of the alcoholic drink according to the present invention is not particularly limited as long as it contains alcohol. The alcoholic drink may be beer, low-molt beer, shochu highball or cocktail, or may be non-alcoholic beer, shochu highball-taste drink or a soft drink.

An embodiment of the present invention relates to a method for producing a rebaudioside D-containing aqueous composition comprising rebaudioside D at a concentration of <NUM> ppm by weight or more. The production method comprises a step of stirring for dispersing a steviol glycoside component comprising rebaudioside D and water in a temperature range of <NUM> to <NUM> under high shear at a tip speed (peripheral speed) of a rotor of <NUM>/s or more. The steviol glycoside component comprises more than <NUM>% by weight of rebaudioside D based on the total weight of the steviol glycoside component. Details of water and the steviol glycoside component are as described above.

The step of stirring for dispersing comprises adding a powdery (or liquid) steviol glycoside component to a container containing water and increasing the temperature of the solution in the container to a temperature range of <NUM> to <NUM> with mixing (or without mixing) the solution in the container. The temperature of the solution may be increased by a heating means such as a heater, or may be increased using kinetic energy caused by stirring for dispersing, or they may be combined. The temperature range may be <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. The lower limit of the temperature range may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. The upper limit of the temperature range may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. The temperature of water may be increased to the above temperature range and then the steviol glycoside component may be added.

The step of stirring for dispersing comprises stirring for dispersing the solution in the container under high shear while maintaining the temperature of the solution at the above temperature range. "Under high shear" means that the tip speed (peripheral speed) of the rotor of the stirrer used for stirring for dispersing is <NUM>/s or more. The tip speed of the rotor may be <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, <NUM>/s or more, or <NUM>/s or more. The tip speed of the rotor may be in the range of <NUM>/s to <NUM>/s <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, <NUM>/s to <NUM>/s, or <NUM>/s to <NUM>/s.

The peripheral speed (tip speed) of the rotor is affected by the diameter of the rotor (the length from the axis of rotation to the tip of the rotor and the like) and the rotational speed (rotation per minute (rpm)). The stirrer and the shape of the rotor used in the step of stirring for dispersing under high shear and the rotational speed are optional as long as the above tip speed of the rotor is obtained. A higher tip speed may be selected when the concentration of rebaudioside D dissolved in the rebaudioside D-containing aqueous composition is high. For example, when the concentration of rebaudioside D is <NUM>,<NUM> ppm, the tip speed of the rotor may be <NUM>/s or more, and when the concentration of rebaudioside D is <NUM>,<NUM> ppm, the tip speed may be <NUM>/s or more, and when the concentration of rebaudioside D is <NUM>,<NUM> ppm, the tip speed may be <NUM>/s or more, although the tip speed is not limited thereto.

The step of stirring for dispersing comprises stirring for dispersing a steviol glycoside component comprising rebaudioside D and water in the presence of a defoaming agent. Details of the defoaming agent are as described above.

An embodiment of the present invention relates to a method for producing a rebaudioside D-containing aqueous composition comprising rebaudioside D at a concentration of <NUM> ppm by weight or more. The production method comprises a step of stirring for dispersing a steviol glycoside component comprising rebaudioside D and water in the presence of a defoaming agent. Details of water, the steviol glycoside component and the defoaming agent are as described above.

In the following the present invention will be described in detail with reference to Examples. The present invention is not limited to these Examples.

<NUM> of rebaudioside D powder (purity of Reb. D: <NUM>%; the same in the following Examples) and <NUM> of anhydrous citric acid (purity of citric acid: <NUM>%; the same in the following Examples) were added to a container containing <NUM> liters of pure water (<NUM> to <NUM>/m; the same in the following Examples) at room temperature (<NUM>). The temperature of the solution in the container was increased to about <NUM> with a heater, and then the solution was stirred for dispersing under high shear (the tip speed (peripheral speed) of the rotor: <NUM>/s, the rotational speed: <NUM>,<NUM> rpm) until rebaudioside D was dissolved in water. The temperature of the solution naturally increased by stirring for dispersing and the temperature of the solution in which rebaudioside D was dissolved finally reached <NUM>. In-Line Ultra Sanitary Mixers (Model No.: FMX50) made by Silverson was used in the step of stirring for dispersing. Whether or not rebaudioside D was dissolved in water was determined by measuring turbidity (NTU) of the solution by using a turbidity meter (made by Thermo Fisher Scientific, Model No.: TN100IR). When visually observed, the solution was almost transparent when the solution had a turbidity of about <NUM> NTU, but the stirring for dispersing was continued under high shear until the solution finally had a turbidity of <NUM> to <NUM> NTU so that rebaudioside D was sufficiently dissolved in water. The solution after the stirring for dispersing was transparent, suggesting that rebaudioside D was sufficiently dissolved in water. The solution was cooled to room temperature to give a solution (rebaudioside D-containing aqueous composition) which contained rebaudioside D dissolved at high concentration (about <NUM>,<NUM> ppm in terms of the amount added) in water.

After production of the solution, the solution was sealed and stored in a refrigerator (in an environment of atmospheric pressure and temperature of <NUM>) (the lid of the container containing the solution was tightly sealed so that no water evaporated). A predetermined amount of the solution (<NUM>) was taken out of the refrigerator and filtrated through a filter having a pore size of <NUM> to measure the concentration (ppm) of rebaudioside D in the solution after filtration by liquid chromatography mass spectrometry (LC/MS) to determine the concentration of rebaudioside D. A predetermined amount of the solution (<NUM>) was taken out of the refrigerator every predetermined number of days and the concentration of rebaudioside D was measured after filtration with a filter having a pore size of <NUM> to determine the change in the concentration of rebaudioside D in the solution over time to evaluate solution stability of rebaudioside D. The results are shown in Table <NUM> and <FIG> is a plot of the values of Table <NUM> with the concentration (ppm) after filtration through the filter having a pore size of <NUM> on the vertical axis and the number of days after production on the horizontal axis.

As shown in Table <NUM> and <FIG>, the concentration of rebaudioside D0 day after production of the solution is <NUM> ppm, showing that rebaudioside D is dissolved in the solution at high concentration. The concentration of rebaudioside D <NUM> to <NUM> days after production of the solution is in the range of <NUM> ppm to <NUM> ppm, showing that solution stability of rebaudioside D dissolved at high concentration is maintained. The concentration of rebaudioside D <NUM> to <NUM> days after production of the solution is also in the range of <NUM> ppm to <NUM> ppm, showing that solution stability of rebaudioside D dissolved at a high concentration of <NUM> ppm or more is maintained.

A solution containing rebaudioside D at high concentration was prepared by usual stirring for dispersing as a comparative example. <NUM> of rebaudioside D powder (purity of Reb. D: <NUM>%) and <NUM> of anhydrous citric acid (purity of citric acid: <NUM>%) were added to a container containing <NUM> of pure water (<NUM> to <NUM>/m) at room temperature (<NUM>). The temperature of the solution in the container was increased to about <NUM> with a heater, and then the solution was stirred for dispersing using a magnetic stirrer (rotational speed <NUM> rpm) while gradually increasing the temperature of the solution to <NUM> with a heater so that the temperature history was the same as that in Example <NUM>. The turbidity of the solution was measured by the above turbidity meter in the same manner as in Example <NUM> and stirring for dispersing was continued until the turbidity of the solution was <NUM> to <NUM> NTU. The solution was then cooled to room temperature to give a solution in which rebaudioside D was dissolved at high concentration in water.

The solution of Comparative Example <NUM> was stored and cooled in a refrigerator (<NUM>) (under atmospheric pressure) so that moisture does not evaporate in the same manner as in Example <NUM>. A predetermined amount of the solution (<NUM>) was taken out of the refrigerator and filtrated through a filter having a pore size of <NUM> to measure the concentration (ppm) of rebaudioside D in the solution after filtration by liquid chromatography mass spectrometry (LC/MS) in the same manner as in Example <NUM>. A predetermined amount of the solution (<NUM>) was taken out of the refrigerator every predetermined number of days and the concentration of rebaudioside D was measured after filtration with a filter having a pore size of <NUM> to determine the change in the concentration of rebaudioside D in the solution over time to evaluate solution stability of rebaudioside D.

For each of the solution of Example <NUM> and the solution of Comparative Example <NUM>, the ratio (C/C<NUM>) of concentration C of rebaudioside D a predetermined number of days after the production of the solution to concentration C<NUM> (ppm) of rebaudioside D <NUM> day after the production of the solution was calculated to evaluate solution stability of rebaudioside D. The results are shown in Table <NUM> and <FIG>.

<FIG> is a plot of the values of Table <NUM> with the ratio (C/C<NUM>) of the concentration of rebaudioside D in the solution on the vertical axis and the number of days after production (days) on the horizontal axis. <FIG> also shows a linear approximation by the least-squares method.

Both the solution of Example <NUM> and the solution of Comparative Example <NUM> have a ratio of the concentration of rebaudioside D (C/C<NUM>) of <NUM> or more, <NUM> to <NUM> days after production, showing that the solution stability is maintained. However, while the ratio of the concentration of rebaudioside D (C/C<NUM>) was as high as <NUM>, <NUM> days after the production in the solution of Example <NUM>, the ratio of the concentration of rebaudioside D (C/C<NUM>) was significantly reduced to <NUM> in the solution of Comparative Example <NUM>.

Furthermore, the ratio of the concentration (C/C<NUM>) was reduced to <NUM> in the solution of Comparative Example <NUM><NUM> days after the production. The ratio of the concentration (C/C<NUM>) was kept relatively high at <NUM> in the solution of Example <NUM> even <NUM> days after the production. The ratio of the concentration (C/C<NUM>) in the solution of Example <NUM><NUM> days after the production was about the same as the ratio of the concentration (C/C<NUM>) <NUM> days after the production in Comparative Example <NUM>.

The above shows that the solution of Example <NUM> (rebaudioside D-containing aqueous composition) prepared by performing the step of stirring for dispersing under high shear has excellent solution stability for a longer time (about two-fold period) compared with the solution of Comparative Example <NUM> prepared by performing a usual step of stirring for dispersing using a magnetic stirrer.

When water containing rebaudioside D at high concentration is stirred for dispersing under high shear, a relatively large amount of foam is generated, and thus it is necessary to eliminate the foam or reduce the amount of the foam generated (collectively referred to as "defoam") to the extent that there is no practical impact. In Example <NUM>, the action of defoaming of the defoaming agent on the rebaudioside D-containing solution was investigated.

Pure water and rebaudioside D were added to a container and citric acid (anhydrous citric acid) was added thereto as a defoaming agent (excluding sample <NUM>). The solution in the container was stirred for dispersing at a pre-determined temperature of dissolution under high shear (the tip speed (peripheral speed) of the rotor of <NUM>/s, the rotational speed of <NUM>,<NUM> rpm) until rebaudioside D was completely dissolved in water (the turbidity was <NUM> to <NUM> NTU) and the solution was cooled to room temperature to give three types of samples <NUM> to <NUM>. "In-Line Ultra Sanitary Mixers" made by Silverson was used in the step of stirring for dispersing as in Example <NUM>. Details of samples <NUM> to <NUM> are shown in Table <NUM>.

The solution of sample <NUM> contains rebaudioside D at a concentration of about <NUM>,<NUM> ppm but no citric acid. The solution of sample <NUM> contains rebaudioside D at a concentration of about <NUM>,<NUM> ppm and citric acid at a concentration of about <NUM>,<NUM> ppm. The solution of sample <NUM> contains rebaudioside D at a concentration of about <NUM>,<NUM> ppm and a citric acid at a concentration of about <NUM>,<NUM> ppm.

A large amount of foam was generated in all of the samples <NUM> to <NUM> immediately after the step of stirring for dispersing. About <NUM> minute after the step of stirring for dispersing, however, the amount of foam did not still change in sample <NUM> not containing citric acid, but the amount of foam significantly reduced in sample <NUM> containing citric acid, and foam almost disappeared in sample <NUM> (<FIG>).

The above shows that citric acid has the action of defoaming for foam generated by stirring for dispersing of a solution containing rebaudioside D at high concentration under high shear. Furthermore, when the concentration of citric acid in the solutions is the same, the action of defoaming in sample <NUM> in which the concentration of rebaudioside D is about <NUM>,<NUM> ppm is larger than that in sample <NUM> in which the concentration of rebaudioside D is about <NUM>,<NUM> ppm.

In Reference Example <NUM>, how the concentration of the defoaming agent and the concentration of rebaudioside D in the solution affect the action of defoaming (and the action of suppressing generation of foam) was investigated.

Rebaudioside D was added to a container containing pure water and anhydrous citric acid was also added thereto as a defoaming agent (excluding samples <NUM> to <NUM>). The solution was stirred for dispersing using a magnetic stirrer at a predetermined temperature of dissolution to give <NUM> samples <NUM> to <NUM>. Details of samples <NUM> to <NUM> are shown in Table <NUM>.

<NUM> of the solution of samples <NUM> to <NUM> was put in a <NUM> tube and a hand shaking test was performed to measure foaming (height in mm of the portion of foam) and the time of defoaming (time until there is no visual change in defoaming for <NUM> seconds). The results are shown in Table <NUM>. For example, for sample <NUM>, the tube was shaken by hand for <NUM> minute in the hand shaking test, and then the tube was left to stand; since there was no change in defoaming for <NUM> seconds <NUM> seconds after leaving standing, the time of defoaming is <NUM> seconds.

Hand shaking test: <NUM> of the solution was put in a <NUM> tube and the tube was continued to be shaken by hand for <NUM> minute with substantially the same strength, the tube was left to stand, and then foaming (height in mm of the portion of foam) of the solution in the tube and the time of defoaming (seconds) were measured.

The time of defoaming of samples <NUM> to <NUM> containing citric acid was significantly reduced compared with samples <NUM> to <NUM> not containing citric acid. For example, a comparison between samples <NUM> to <NUM> and samples <NUM> to <NUM>, respectively, shows that the time of defoaming was reduced by a factor of about <NUM> to <NUM>. Furthermore, a comparison between samples <NUM> to <NUM> and samples <NUM> to <NUM> in Table <NUM> shows that citric acid also contributes to reduction of foamability. For example, while conditions of sample <NUM> and sample <NUM> were the same except for the presence of citric acid, foaming (height <NUM>) of sample <NUM> to which citric acid was added was reduced by about <NUM>% based on foaming (height <NUM>) of sample <NUM> to which citric acid was not added; this shows that citric acid not only has action of defoaming for foam generated but also contributes to suppress generation of foam itself.

In Reference Example <NUM>, how the ratio of the weight of the defoaming agent to the weight of rebaudioside D in the solution affects the action of defoaming was investigated.

Rebaudioside D was added to a container containing pure water and citric acid was added thereto as a defoaming agent (excluding sample <NUM>, sample <NUM>). The solution was stirred for dispersing using a magnetic stirrer at a predetermined temperature of dissolution to give <NUM> samples <NUM> to <NUM>. Details of samples <NUM> to <NUM> are shown in Table <NUM>. The concentration of Reb. D in the solution of samples <NUM> to <NUM> was different from that in samples <NUM> to <NUM>.

The above hand shaking test was performed for the solutions of samples <NUM> to <NUM> to measure foaming (height in mm of the portion of foam) and the time of defoaming (seconds). The results are shown in Table <NUM>.

<FIG> is a graph with the ratio of citric acid/Reb. D (mg/mg) on the horizontal axis and the time of defoaming (seconds) on the vertical axis for samples <NUM> to <NUM>. As <FIG> shows, when the ratio of citric acid/Reb. D (mg/mg) in the solution was <NUM> or more, the time of defoaming was more significantly reduced (about <NUM>/<NUM> or less) compared with the case where the ratio of citric acid/Reb. D (mg/mg) is <NUM>. Furthermore, when the ratio of citric acid/Reb. D (mg/mg) was <NUM> or more, the time of defoaming was more significantly reduced (about <NUM>/<NUM> or less). A sufficient action of defoaming can be obtained at a ratio of citric acid/ Reb. D (mg/ mg) in the solution of <NUM> or more, more preferably <NUM> or more, and further preferably <NUM> or more.

Furthermore, a comparison between samples <NUM> and <NUM> shows that the time of defoaming was significantly reduced (about <NUM>/<NUM>) due to the presence of citric acid and the action of defoaming of citric acid was found in both cases of a concentration of Reb. D in the solution of <NUM> ppm and <NUM> ppm.

In Reference Example <NUM>, defoaming agents other than citric acid were investigated.

Rebaudioside D was added to a container containing pure water, and anhydrous citric acid, L-ascorbic acid, DL-malic acid, hydrochloric acid, sodium chloride or trisodium citrate was also added thereto as a defoaming agent (excluding sample <NUM>). The solution was stirred for dispersing using a magnetic stirrer at <NUM> to give <NUM> samples <NUM> to <NUM>. Details of samples <NUM> to <NUM> are shown in Table <NUM>.

Claim 1:
A method for producing a rebaudioside D-containing aqueous composition comprising rebaudioside D at a concentration of <NUM> ppm by weight or more,
the method comprising: a step of stirring for dispersing a steviol glycoside component comprising rebaudioside D and water in a temperature range of <NUM> to <NUM> under high shear at a peripheral speed of a rotor of <NUM>/s or more, wherein the steviol glycoside component comprises more than <NUM>% by weight of rebaudioside D based on a total weight of the steviol glycoside component.