Stevia composition

Stevia compositions are prepared from steviol glycosides of Stevia rebaudiana Bertoni. The compositions are able to provide a superior taste profile and can be used as sweetness enhancers, flavor enhancers and sweeteners in foods, beverages, cosmetics and pharmaceuticals.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a process for producing a highly purified food ingredient from the extract of theStevia rebaudianaBertoni plant and its use in various food products and beverages.

Description of the Related Art

Nowadays sugar alternatives are receiving increasing attention due to awareness of many diseases in conjunction with consumption of high-sugar foods and beverages. However many artificial sweeteners such as dulcin, sodium cyclamate and saccharin were banned or restricted in some countries due to concerns on their safety. Therefore non-caloric sweeteners of natural origin are becoming increasingly popular. The sweet herbStevia rebaudianaBertoni, produces a number of diterpene glycosides which feature high intensity sweetness and sensory properties superior to those of many other high potency sweeteners.

The above-mentioned sweet glycosides, have a common aglycon, steviol, and differ by the number and type of carbohydrate residues at the C13 and C19 positions. The leaves ofSteviaare able to accumulate up to 10-20% (on dry weight basis) steviol glycosides. The major glycosides found inStevialeaves are rebaudioside A (2-10%), stevioside (2-10%), and rebaudioside C (1-2%). Other glycosides such as rebaudioside B, D, E, and F, steviolbioside and rubusoside are found at much lower levels (approx. 0-0.2%).

Two major glycosides—stevioside and rebaudioside A (reb A), were extensively studied and characterized in terms of their suitability as commercial high intensity sweeteners. Stability studies in carbonated beverages confirmed their heat and pH stability (Chang S. S., Cook, J. M. (1983) Stability studies of stevioside and rebaudioside A in carbonated beverages. J. Agric. Food Chem. 31: 409-412.)

Steviol glycosides differ from each other not only by molecular structure, but also by their taste properties. Usually stevioside is found to be 110-270 times sweeter than sucrose, rebaudioside A between 150 and 320 times, and rebaudioside C between 40-60 times sweeter than sucrose. Dulcoside A is 30 times sweeter than sucrose. Rebaudioside A has the least astringent, the least bitter, and the least persistent aftertaste thus possessing the most favorable sensory attributes in major steviol glycosides (Tanaka O. (1987) Improvement of taste of natural sweetners.Pure Appl. Chem.69:675-683; Phillips K. C. (1989)Stevia: steps in developing a new sweetener. In: Grenby T. H. ed. Developments in sweeteners, vol. 3. Elsevier Applied Science, London. 1-43.) The chemical structure of rebaudioside A is shown inFIG. 1.

Methods for the extraction and purification of sweet glycosides from theStevia rebaudianaplant using water or organic solvents are described in, for example, U.S. Pat. Nos. 4,361,697; 4,082,858; 4,892,938; 5,972,120; 5,962,678; 7,838,044 and 7,862,845.

However, even in a highly purified state, steviol glycosides still possess undesirable taste attributes such as bitterness, sweet aftertaste, licorice flavor, etc. One of the main obstacles for the successful commercialization ofsteviasweeteners are these undesirable taste attributes. It was shown that these flavor notes become more prominent as the concentration of steviol glycosides increases (Prakash I., DuBois G. E., Clos J. F., Wilkens K. L., Fosdick L. E. (2008) Development of rebiana, a natural, non-caloric sweetener. Food Chem. Toxicol., 46, S75S82.).

Rebaudioside B (CAS No: 58543-17-2), or reb B, also known as stevioside A4(Kennelly E. J. (2002) Constituents ofStevia rebaudianaInStevia: The genusStevia, Kinghorn A. D. (Ed), Taylor & Francis, London, p. 71), is one of the sweet glycosides found inStevia rebaudiana. Sensory evaluations show that reb B was approximately 300-350 times sweeter than sucrose, while for reb A this value was approximately 350-450 (Crammer, B. and Ikan, R. (1986) Sweet glycosides from theSteviaplant. Chemistry in Britain 22, 915-916, and 918). The chemical structure of rebaudioside B is shown inFIG. 2.

It was believed that reb B forms from partial hydrolysis of rebaudioside A during the extraction process (Kobayashi, M., Horikawa, S., Degrandi, I. H., Ueno, J. and Mitsuhashi, H. (1977) Dulcosides A and B, new diterpene glycosides fromStevia rebaudiana. Phytochemistry 16, 1405-1408). However further research shows that reb B occurs naturally in the leaves ofStevia rebaudianaand currently it is one of nine steviol glycosides recognized by FAO/JECFA (United Nations' Food and Agriculture Organization/Joint Expert Committee on Food Additives) in calculating total steviol glycosides' content in commercial steviol glycosides preparations (FAO JECFA (2010) Steviol Glycosides, Compendium of Food Additive Specifications, FAO JECFA Monographs 10, 17-21).

Only a few methods are described in literature for preparing reb B.

Kohda et al., (1976) prepared reb B by hydrolysis of reb A with hesperidinase. Reb B was also prepared by alkaline saponification of reb A. The said saponification was conducted in 10% KOH-EtOH. The solution was acidified with AcOH, and extracted with n-BuOH. The BuOH-layer was washed with water and concentrated at low temperature in vacuo. The residue was crystallized from MeOH to give reb B. (Kohda, H., Kasai, R., Yamasaki, K., Murakami, K. and Tanaka, O. (1976) New sweet diterpene glucosides fromStevia rebaudiana. Phytochemistry 15, 981-983). The described processes might be suitable for laboratory scale preparation of reb B, but are hardly suitable for any large scale or commercial reb B preparation.

Ahmed et al., used mild alkaline hydrolysis of reb A to prepare reb B According to described procedure reb A was hydrolyzed to reb B, by refluxing with 10% aqueous KOH at 100° C. for 1 hr. After neutralization with glacial acetic acid, the precipitated substance was recrystallized twice from methanol (Ahmed M. S., Dobberstein R. H., and Farnsworth N. R. (1980)Stevia rebaudiana: I. Use of p-bromophenacyl bromide to enhance ultraviolet detection of water-soluble organic acids (steviolbioside and rebaudioside B) in high-performance liquid chromatographic analysis, J. Chromatogr., 192, 387-393). The use of methanol as recrystallization media will require its subsequent removal from the product. It is noted that handling of toxic substances such as methanol requires specialized manufacturing installations and, when applied in food processing, sophisticated food safety measures.

It is also noted that no significant work has been conducted to determine the potential of reb B as a sweetener or food ingredient. Moreover reb B is often viewed as process artifact and unnecessary impurity in commercial steviol glycosides preparations. No significant evaluation of reb B influence on overall taste profile of steviol glycosides preparations has been conducted.

On the other hand, the water solubility of reb B is reported to be about 0.1% (Kinghorn A. D. (2002) Constituents ofStevia rebaudianaInStevia: The genusStevia, Kinghorn A. D. (Ed), Taylor & Francis, London, p. 8). In many food processes where highly concentrated ingredients are used, a highly soluble form of reb B will be necessary.

Considering the facts mentioned above, it is necessary to evaluate reb B as a sweetener and food ingredient and develop a simple and efficient process for food grade reb B preparations suitable for food applications.

Within the description of this invention we will show that, when applied in specific manner, reb B may impact the taste profile and offer significant advantages forsteviasweeteners' use in various applications.

SUMMARY OF THE INVENTION

The present invention is aimed to overcome the disadvantages of existingSteviasweeteners. The invention describes a process for producing a high purity food ingredient from the extract of theStevia rebaudianaBertoni plant and use thereof in various food products and beverages as a sweetness and flavor modifier.

In the invention, rebaudioside A commercialized by PureCircle Sdn. Bhd. (Malaysia), containing, rebaudioside A (about 95-100%), stevioside (about 0-1%), rebaudioside C (about 0-1%), rebaudioside F (about 0-1%), rebaudioside B (about 0.1-0.8%), rebaudioside D (about 0-1%), and other glycosides amounting to total steviol glycosides' content of at least 95%, was used as a starting material. Alternativelysteviaextracts with different ratio of steviol glycosides may be used as starting materials.

The starting material was subjected to partial conversion into reb B under elevated pH conditions in aqueous media free of any co-solvents, including toxic alkanols. The obtained glycoside mixtures were used “as-is” as well as reb B was recovered and used as a pure ingredient.

The low solubility reb B and mixtures thereof were subjected to additional thermal treatment to increase solubility.

The obtained products were applied in various foods and beverages as sweeteners, sweetener enhancers and flavor modifiers, including soft drinks, ice cream, cookies, bread, fruit juices, milk products, baked goods and confectionary products.

DETAILED DESCRIPTION OF THE INVENTION

Rebaudioside A commercialized by PureCircle Sdn. Bhd. (Malaysia), containing, rebaudioside A (about 95-100%), stevioside (about 0-1%), rebaudioside C (about 0-1%), rebaudioside D (about 0-1%), rebaudioside F (about 0-1%), rebaudioside B (about 0.1-0.8%) and other glycosides amounting to total steviol glycosides' content of at least about 95%, was used as a starting material. Alternativelysteviaextracts with different ratio of steviol glycosides may be used as starting materials.

The HPLC analysis of the raw materials and products was performed on an Agilent Technologies 1200 Series (USA) liquid chromarograph, equipped with Phenomenex Prodigy ODS3, 5 μm (4.6×250 mm) column at 40° C. The mobile phase was 32:68 mixture of acetonitrile and 10 mmol/L sodium phosphate buffer (about pH 2.6) at 1 mL/min. A diode array detector set at 210 nm was used as the detector.

In one embodiment of the invention, reb A was dispersed in aqueous alkaline solution. The concentration of reb A is about 0-50% (w/v) preferably about 10-25%. The preferred alkaline agents include KOH and NaOH however other agents capable of increasing the pH of the media above about pH 7 may be used as well. The concentration of alkaline agents were about 0.05-2.0M, preferably about 0.1-1.0M. The mixture was incubated at about 10-150° C., preferably about 30-100° C., for a period of about 0.5-48 hrs, preferably about 1-24 hrs. As a result reb A is hydrolyzed to reb B. The molar yield of conversion of reb B is about 5-100%, preferably about 10-90%.

After the reaction, the alkaline agent is neutralized by an acid, preferably by sulfuric acid or ortho-phosphoric acid until a pH of about 3.0-5.0 is reached, preferably until a pH of about 3.0-4.0 is reached. Upon neutralization, a precipitate is formed. The precipitate is separated by any method known in the art such as filtration or centrifugation and washed with water until the water reaches a pH of about 4.0-5.0. The obtained crystalline material is dried under vacuum at about 60-105° C. to yield a mixture of reb A and reb B with ratio of about 5%:95% to about 95%:5%, preferably about 50%:50% to about 90%:10%.

In another embodiment, the separated precipitate is suspended in water and the mixture is subjected to continuous agitation over about 0.5-24 hrs, preferably about 1-3 hours, at about 50-100° C., preferably about 60-80° C. The ratio of precipitate to water (w/v) is about 1:5 to about 1:20, preferably about 1:10 to about 1:15. The washed crystals are separated and dried under vacuum at about 60-105° C. to yield reb B with about 99% purity.

In one embodiment the obtained compositions have a water solubility of less than about 0.2% (w/v). The compositions were combined with the water at ratio of about 1:1 (w/w) and the obtained mixture was further subjected to a gradient heat treatment which resulted in a high stability and high concentration solution. The gradient of about 1° C. per minute was used in heating the mixture. The mixture was heated to the temperature of about 110-140° C., preferably about 118-125° C. and was held at maximum temperature for about 0-120 min, preferably about 50-70 min. After the heat treatment, the solution was cooled down to room temperature at gradient of about 1° C. per minute. The solution was spray dried by a laboratory spray drier operating at about 175° C. inlet and about 100° C. outlet temperatures. An amorphous form of the composition was obtained with greater than about 20% solubility in water at room temperature.

Additionally the compositions can be used in drug or pharmaceutical preparations and cosmetics, including but not limited to toothpaste, mouthwash, cough syrup, chewable tablets, lozenges, vitamin preparations, and the like.

The compositions can be used “as-is” or in combination with other sweeteners, flavors and food ingredients.

The following examples illustrate various embodiments of the invention. It will be understood that the invention is not limited to the materials, proportions, conditions and procedures set forth in the examples, which are only illustrative.

100 g of rebaudioside A produced by PureCircle Sdn. Bhd. (Malaysia), containing, 98.1% rebaudioside A, 0.3% stevioside, 0.2 rebaudioside C, 0.2% rebaudioside F, 0.4% rebaudioside B and 0.6% rebaudioside D was dispersed in 1000 mL aqueous KOH (1M) and incubated at 50° C. for 2 hours. The mixture temperature was decreased to 20° C. and the pH was adjusted to pH 4.0 with sulfuric acid. The solution was held under moderate agitation conditions for 4 hours and a precipitate was formed. The precipitate was filtered and washed on the filter with 2000 mL of water. The washed crystals were dried under vacuum to yield 86 g material containing about 84% reb A and 16% reb B. The water solubility (at 25° C.) of obtained material was about 0.2% (w/v).

100 g of rebaudioside A produced by PureCircle Sdn. Bhd. (Malaysia), containing, 98.1% rebaudioside A, 0.3% stevioside, 0.2 rebaudioside C, 0.2% rebaudioside F, 0.4% rebaudioside B and 0.6% rebaudioside D was dispersed in 1000 mL aqueous KOH (1M) and incubated at 80° C. for 5 hours. The mixture temperature was decreased to 20° C. and the pH was adjusted to about pH 4.0 with sulfuric acid. The solution was held under moderate agitation conditions for 4 hours and a precipitate was formed. The precipitate was filtered and washed on the filter with 2000 mL of water. The washed crystals were dried under vacuum to yield about 75 g material containing about 9% reb A and about 91% reb B. The water solubility (at 25° C.) of obtained material was about 0.1% (w/v).

100 g of rebaudioside A produced by PureCircle Sdn. Bhd. (Malaysia), containing, 98.1% rebaudioside A, 0.3% stevioside, 0.2 rebaudioside C, 0.2% rebaudioside F, 0.4% rebaudioside B and 0.6% rebaudioside D was dispersed in 1000 mL aqueous KOH (1M) and incubated at 80° C. for 7 hours. The mixture temperature was decreased to 20° C. and the pH was adjusted to about pH 4.0 with sulfuric acid. The solution was held under moderate agitation conditions for 3-4 hours and a precipitate was formed. The precipitate was filtered and washed on the filter with 2000 mL of water. The washed crystals were dried under vacuum to yield about 71 g material containing about 99.1% reb B. The water solubility (at 25° C.) of obtained material was about 0.1% (w/v).

75 g of material prepared according to EXAMPLE 2 was suspended in 1000 mL water. The mixture temperature was increased to 70° C. The suspension was held under moderate agitation conditions for 4 hours. The crystals were filtered and dried under vacuum to yield about 65 g material containing about 99.0% reb B. The water solubility (at 25° C.) of obtained material was about 0.1% (w/v).

Preparation of SolubleSteviaComposition

50 g material prepared according to EXAMPLE 1 was mixed with 50 g of water and incubated in thermostatted oil bath. The temperature was increased at 1° C. per minute to 121° C. The mixture was maintained at 121° C. for 1 hour and then the temperature was decreased to room temperature (25° C.) at 1° C. per minute. The solution was dried using YC-015 laboratory spray drier (Shanghai Pilotech Instrument & Equipment Co. Ltd., China) operating at 175° C. inlet and 100° C. outlet temperature. About 47 g of an amorphous powder was obtained with about 25% (w/v) solubility in water (at 25° C.).

Preparation of SolubleSteviaComposition

42 g of reb A produced by PureCircle Sdn. Bhd. (Malaysia) with purity of 99.2% (dry basis) and 8 g of reb B prepared according to EXAMPLE 4 were mixed with 50 g of water and incubated in thermostatted oil bath. The temperature was increased at 1° C. per minute to 121° C. The mixture was maintained at 121° C. for 1 hour and then the temperature was decreased to room temperature (25° C.) at 1° C. per minute. The solution was dried using YC-015 laboratory spray drier (Shanghai Pilotech Instrument & Equipment Co. Ltd., China) operating at 175° C. inlet and 100° C. outlet temperature. About 48 g of an amorphous powder was obtained with about 1.5% (w/v) solubility in water (at 25° C.).

Low-Calorie Orange Juice Drink

Orange concentrate (35%), citric acid (0.35%), ascorbic acid (0.05%), orange red color (0.01%), orange flavor (0.20%), and 0.05%steviacomposition, were blended and dissolved completely in water (up to 100%) and pasteurized. Thesteviacomposition was selected from a commercialsteviaextract (containing stevioside 26%, rebaudioside A 55%, and 16% of other glycosides), a commercial rebaudioside A (containing 98.2% reb A) or material obtained according to EXAMPLE 5.

The sensory evaluations of the samples are summarized in Table 1. The data shows that the best results can be obtained by using the composition obtained according to EXAMPLE 5. Particularly the drinks prepared with said Composition exhibited a rounded and complete flavor profile and mouthfeel.

The same method can be used to prepare juices and juice drinks from other fruits, such as apples, lemons, apricots, cherries, pineapples, mangoes, etc.

A carbonated beverage according to formula presented below was prepared.

The sensory properties were evaluated by 20 panelists. The results are summarized in Table 2.

The above results show that the beverages prepared using the composition obtained according to EXAMPLE 5 possessed the best organoleptic characteristics.

Diet Cookies

Flour (50.0%), margarine (30.0%) fructose (10.0%), maltitol (8.0%), whole milk (1.0%), salt (0.2%), baking powder (0.15%), vanillin (0.1%) and differentsteviacompositions (0.03%) were kneaded well in dough-mixing machine. The obtained dough was molded and baked in oven at 200° C. for 15 minutes. Thesteviacompositions were selected from a commercialsteviaextract (containing stevioside 26%, rebaudioside A 55%, and 16% of other glycosides), a commercial rebaudioside A (containing 98.2% reb A) and material obtained according to EXAMPLE 5.

The sensory properties were evaluated by 20 panelists. The best results were obtained in samples containing the composition obtained according to EXAMPLE 5. The panelists noted a rounded and complete flavor profile and mouthfeel.

Differentsteviacompositions (0.03%) and sucrose (4%) were dissolved in low fat milk. Thesteviacompositions were selected from a commercialsteviaextract (containing stevioside 26%, rebaudioside A 55%, and 16% of other glycosides), a commercial rebaudioside A (containing 98.2% reb A) and the material obtained according to EXAMPLE 5. After pasteurizing at 82° C. for 20 minutes, the milk was cooled to 37° C. A starter culture (3%) was added and the mixture was incubated at 37° C. for 6 hours then at 5° C. for 12 hours.

The sensory properties were evaluated by 20 panelists. The best results were obtained in samples containing the composition obtained according to EXAMPLE 5. The panelists noted a rounded and complete flavor profile and mouthfeel.

It is to be understood that the foregoing descriptions and specific embodiments shown herein are merely illustrative of the best mode of the invention and the principles thereof, and that modifications and additions may be easily made by those skilled in the art without departing for the spirit and scope of the invention, which is therefore understood to be limited only by the scope of the appended claims.