NOVEL SWEETENER COMPOSITIONS

Abstract: Novel sweetener compositions having improved solubility, characterized by containing as the active ingredients N-[(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester and Aspartame at a ratio of Aspartame to the sum of these two components of 10 to 99.5 % by weight.

Description: TECHNICAL FIELD The present invention relates to a powdery sweetener composition excellent in dissolution rate (solubility), comprising powdery N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester (Neotame, abbreviated hereinafter to "NM") and powdery Aspartame (abbreviated hereinafter to "APM") as active ingredients. BACKGROUND ART It is reported that the sweetness strength (sweetening potency) of a synthetic high-potency sweetener NM is about 10,000 times that of sucrose by weight ratio (Japanese patent Kohyou Publication JP-A-8-503206). The characteristics of its sweetness (properties in quality of sweetness) are not reported in detail, but according to the present applicant's findings, its early taste (sweet taste felt as quickly as sucrose when put in the mouth) is extremely weak, while its later taste (sweet taste felt later than sucrose when put in the mouth) is extremely strong. Further, its astringent taste is strong. Accordingly, the balance among the properties in quality of sweetness is poor as compared with sucrose regarded generally as a standard for evaluation of the properties (characteristics) in quality of sweetness. It is also reported that the sweetness strength of an amino acid type synthetic sweetener APM is about 200 times that of sucrose in weight ratio (See Japanese Patent Kokoku Publication JP-B-47-31031.). The quality of sweetness for APM are that the early taste is weak and the later taste is strong as compared with sucrose regarded as a standard for evaluation of quality of the sweetness. Various proposals have been made for the improvement in quality of the sweetness of NM and APM, particularly for the improvement in quality of the sweetness of the latter, thus achieving considerable effects. However, NM and APM have a further problem with dissolution characteristics; that is, NM and APM powders (crystalline raw powders) have poor dissolution characteristics in water (that is, they are not readily dissolved due to their easy formation of agglomerates, or their dissolution rate is low, etc.). Poor dissolution characteristics resulting from formation of agglomerates or the like is significantly disadvantageous to industrial production, since it causes a reduction in the production yield of foods and drinks such as soft drinks having NM or APM incorporated into it to confer sweetness. For improvement of the dissolution rate of APM, some proposals using pelletizing methods (granulations) have been made. However, these methods are not satisfactory in that these require further improvement of dissolution rate (See Japanese Patent Kokai Publication JP-A-4-346769 etc.) and requires simultaneous use of a relatively large amount of excipients (See Japanese Patent Kokai Publications JP-A-49-126855, JP-A-50-19965, JP-A-57-150361 etc.). Under the background of the prior art described above, the object of (problem to be solved by) the present invention is to provide an excellent method for improving the dissolution rate of NM and APM. DISCLOSURE OF INVENTION As a result of their eager study to achieve the above-described object, the present inventors have unexpectedly found that the dissolution rate of NM, particularly of a specific crystal of NM (which may be also called "C-type crystal") is improved by APM in a certain range, and vice versa, and further that the dissolution rate of a mixture of both of them at a specific mixing range is higher than not only that of NM alone but also that of APM alone, and particularly this phenomenon is remarkable and significant when NM is in the form of C-type crystal, and on the basis of these findings, the present invention has been completed. The crystalline form of powdery NM that is one of the active ingredients in the novel sweetener composition of the present invention is not particularly limited. For example, it may be either the known crystals (which may be also called "A-type crystal(s)") or the C-type crystal(s), but for the object of the present invention, the latter is significantly superior to the former. In an additional remark, the crystal structure of known NM as disclosed in WO95/30689 is described as IR I spectrum data therein. Further, the present inventors i analyzed the structure of its single crystal, and as a result, they confirmed that this crystal is a monohydrate, and when measured by powder X-ray diffractometry, the crystal shows characteristic peaks in diffractive X-ray (X-ray diffraction pattern) at diffraction angles of at least 6.0°, 24.8°, 8.2°, and 16.5° (2 , CuKα radiation (ray; line)). For the sake of convenience, the present inventors referred to this crystal as "A-type crystal". As a result of their further study, the present inventors have found that the water content of dry A-type crystal is usually in the range of 3 to 6 % by weight (including crystal water), but if this A-type crystal is further dried until its water content is reduced to less than 3 %, a novel crystal of N-(3,3-dimethylbutyl) -APM with improved dissolution rate wherein the crystal water has been eliminated, is obtained, and this novel crystal was referred to as "C-type crystal". When measured by powder X-ray diffractometry using CuKα radiation), this C-type crystal shows characteristic peaks in diffractive X-ray (X-ray diffraction pattern) at diffraction angles different from those of the A-type crystal, that is, at diffraction angles (2) of at least 7.1°, 19.8°, 17.3°, and 17.7°. Reference is made to Reference Examples 1 to 3 below. powdery APM that is the other active ingredient in the novel powdery sweetener composition of the present invention can be used in the form of e.g. the hydrated crystals, to which it is not particularly limited. The mixing ratio of NM and APM used in the novel sweetener composition of the present invention is in the range of 10 to 99.5 % by weight in terms of the ratio of APM to both of them. If the ratio of APM used therein is less than 10 % by weight, the effect of APM on the promotion of NM dissolution is decreased, whereas with the ratio of more than 99.5 % by weight, the effect of APM on the promotion of NM dissolution is hardly observed. C-type crystals when mixed with APM in this range have significant promoting effect on dissolution rate and are thus superior to A type crystals, as can be seen from Tables 1 and 2 below. If C-type crystals are used as powdery NM, the ratio of APM to the total amount of NM and APM used therein is preferably in the range of 10 to 97 % by weight. The dissolution rate of a mixture of NM C-type crystals and APM in the range of 10 to 90 % by weight of APM thereto is higher than that of NM A-type crystals alone, and the dissolution rate of a mixture of NM C-type crystals and APM in the range of 50 to 97 % by weight of APM thereto is higher than the dissolution rate of not only that of NM C-type crystals alone but also that of APM alone. If powdery NM and powdery APM are separately and at the same time added to water (separate addition) without previously mixing both of them at the predetermined ratio (that is, without using the sweetener composition of the present invention) , both of them do not affect their mutual dissolution rate, and in this case, the dissolution rate as a whole is low but identical to the dissolution rate of one of them which has a lower dissolution rate when used alone (Experimental Example 3 below). For the purpose of easy application or improvement in quality of sweetness, the novel sweetener composition of the present invention, similar to the case of conventional high-potency sweetener compositions, can incorporate diluents (thinners) and excipients such as sugar alcohols, oligosaccharide, food fibers (dietary fibers) and the like, or other synthetic high-potency sweeteners such as Alitame, saccharin, Acesulfame K etc. as necessary in an amount within such a range as not to spoil the NM and APM dissolution rate (solubilities) improved by the present invention. The diluents and excipients in this case include low-potency sweeteners such as sucrose, glucose or the like. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention is explained in more detail by reference to Reference Examples and Experimental Examples. Reference Example 1: Preparation of NM The followings were introduced successively under stirring to a reactor equipped with an agitating blade for ensuring very efficient transfer of gaseous hydrogen to a liquid layer. That is, 700 ml ion exchanged water, 4.21 ml of acetic acid, 20 g of 10 % palladium carbon, 1,300 ml of methanol, 56 g of Aspartame and 25 ml of 3,3-dimethylbutylaldehyde were introduced. The reactor was filled with a nitrogen gas stream, and then the reaction mixture was hydrogenated at a H 2 gas flow rate of 200 ml/min. at room temperature. The progress of this reaction was monitored by sampling the reaction mixture and analyzing the product in high performance liquid chromatography (HPLC). After the hydrogenation reaction for 6 hours, this reaction was terminated by filling the reactor with a nitrogen gas and filtering the reaction mixture through a fine pore filter (0.45 µm) to remove the catalyst. As a result of the analysis of the resulting filtrate (1, 494 g), the yield was 81%. Subsequently, this filtrate was concentrated to 281 g to remove the methanol, and crystals were precipitated under stirring at 10 °C overnight. Finally, 87 g white wet crystals of NM (yield: 77 %) were obtained at a high purity (99 % or more, HPLC). Reference Example 2: Production of A-type crystals A part of NM prepared in Reference Example 1 was used to prepare 100 g aqueous solution of NM at a concentration of 3 % by weight (dissolved at 60 °C). Then, the solution was cooled from 60 °C to 30 °C for 5 minutes under stirring. When the liquid temperature was reached to 30 °C, crystallization of white crystals was initiated. After overnight aging under the liquid temperature kept at 30 °C, the crystals were collected on a filter paper. (a) The diffractive X-ray (X-ray diffraction pattern) of the wet crystals obtained above was measured by powder X-ray diffractometry (diffractometer) using CuKα ray(radiation). The obtained powder X-ray diffraction pattern is shown in Fig. 1. As is evident from the pattern of the figure, the wet crystals showed characteristic diffraction peaks at least 6.0°, 24.8°, 8.2° and 16.5°, and they were A-type crystals. Further, (b) the wet crystals were placed in a vacuum dryer set at 50 °C, and dried until their water content was reduced to 5 % by weight. The dried crystals thus obtained were measured by powder X-ray diffractometer using CuKα Radiation (ray) , indicating that the crystals were A-type crystals as well. Further, as a result of IR spectrum (KBr) measurement, its values agreed with those described in WO95/30689. Reference Example 3: Production of C-type crystals The dried A-type crystals with a water content of 5 % by weight described above were continued to be dried in the vacuum dryer until their water content was reduced to 0.8 % by weight. The X-ray diffraction pattern of the dried crystals was measured by powder X-ray diffractometry (diffractometer) using CuKα ray. The thus obtained powder X-ray diffraction pattern is shown in Fig. 2. As is evident from the pattern of the figure, the dried crystals showed characteristic diffraction peaks at least at 7.1°, 19.8°, 17.3°, and 17.7°. As described above, the crystals are C-type crystals. Experimental Example 1 (Dissolution rate of raw (original) powders each from NM C-type crystals and APM, and a mixture thereof) A predetermined amount of the sample was introduced into 900 ml water (20 °C) in a 1-L elution tester (the Japanese Pharmacopoeia, Paddle method, 100 rpm) and its dissolution time was measured (end point was visually confirmed). Specifically, 1 g of sample taken from each mixture consisting of NM C-type crystal raw powder (average particle size of about 100 µm) and APM raw powder (average particle size of about 15 µm, IB-type bundled crystals) at the predetermined various ratios (APM content (% by weight)) shown in Table 1 below, was weighed, and then measured for its dissolution time. For comparison, 1.00 g, 0.90 g, 0.50 g, 0.10 g, 0.03 g, and 0.005 g samples were taken from said NM raw powder, and then their dissolution times were determined in the same manner as above. For the same purpose, 1.00 g, 0.97 g, 0.90 g, 0.50 g, and 0.10 g samples were taken from said APM raw powder, and then their dissolution times were determined in the same manner. The dissolution time (min) (time needed for the dissolution) of each sample is shown in Table 1 below. Dissolution times of NM C-type crystals, APM raw (original) powder, and mixture thereof NM C-type crystals alone (original powder) APM alone (original powder) Weight of NM C-type crystals Dissolution time Weight of APM Dissolution time 1.00 g 62 min 0.10 g 10 min 0.90 60 0.50 20 0.50 55 0.90 27 0.10 40 0.97 29 0.03 30 1.00 30 0.005 4 - - Mixture (1 g) Content of APM original powder Weight of APM Weight of NM Dissolution time 10 weight-% 0.10 g 0.90 g 25 min 50 0.50 0.50 15 90 0.90 0.10 8 97 0.97 0.03 18 99.5 0.995 0.005 25 As can be seen from this table, the dissolution rate (solubility) of the mixture thereof (the sweetener composition of the present invention) is always remarkably and significantly improved as compared with not only those of the NM C-type raw (original) crystals alone but also those of the APM alone. The degrees of sweetness of NM and APM are respectively about 10,000 and about 200 times that of sucrose, as described above. From this viewpoint, the dissolution time of 1 g mixture should be compared with the dissolution time of an amount of NM necessary to achieve the same degree of sweetness, but even in such comparison, there is the promoting action of APM on the dissolution of NM, as follows. That is, the sweetness of 1 g mixture containing 50 % APM raw (original) powder is equal to the sweetness of 0.51 g of NM alone, and the dissolution time of the former is 15 minutes, while the dissolution time of the latter is about 55 minutes, so there is a significant difference therebetween. Experimental Example 2 (Dissolution rate of raw (original) powders each from NM A-type crystals and APM, and a mixture thereof) The same experiment as that in Experimental Example 1 was conducted except that NM A-type crystal original powder (average particle size of 100 µm) was used in place of NM C-type crystal original powder. The dissolution time (min) of each sample is shown in Table 2. Dissolution times of NM A-type crystals, APM original powder, and mixture thereof NM A-type crystal alone (original powder) APM alone (original powder) Weight of NM A-type crystals Dissolution time Weight of APM Dissolution time 1.00 g 42 min 0.10 g 10 min 0.90 40 0.50 20 0.50 35 0.90 27 0.10 16 0.97 29 0.03 10 1.00 30 0.005 - - - Mixture (1 g) Content of APM original powder Weight of APM Weight of NM Dissolution time 10 weight-% 0.10 g 0.90 g 35 min 50 0.50 0.50 25 90 0.90 0.10 23 97 0.97 0.03 29 99.5 0.995 0.005 30 As can be seen from this table, the dissolution rate of the mixture (the sweetener composition of the present invention) is improved remarkably and significantly as compared with NM A-type crystals original powder alone. It can also be seen that the dissolution rate of the mixture at a range of the certain mixing ratios (50 to 97 % by weight of APM) is superior to that of APM powder alone (original powder). In a similar comparison to that in Experimental Example 1, there is the promoting action of APM on the dissolution of NM, for example, as follows. That is, the sweetness of 1 g mixture containing 50 % APM original powder is equal to the sweetness of 0.51 g of NM alone, and the dissolution time of the former is 25 minutes, while the dissolution time of the latter is about 35 minutes, so there is a significant difference therebetween. Experimental Example 3 (Separate addition of NM original powder and APM original powder) The same NM and APM as in Experimental Example 1 were used, and the dissolution time was determined in the same manner as that in Experimental Example 1. That is, 0.5 g each of both of them was weighed (1.0 g in total) and introduced simultaneously without being previously mixed, into the elution tester (separate addition). The results are shown in Table 3 below. For reference, the dissolution time of 0.5 g NM original powder alone (Experimental Example 1) is also shown together in the table. Dissolution time of NM and APM when separately added NM C-type crystals alone (0.5 g) Separate addition (1 g in total) (0.5 g NM C-type crystals/0.5 g APM original powder) 55 minutes 55 minutes From this table, the improvement of NM dissolution rate (solubility) by APM is not observed when NM and APM are separately added without being previously mixed. According to the present invention, Aspartame (APM) is mixed with Neotame (NM) whereby poor dissolution characteristics of NM can be significantly improved, and further, the dissolution rate of APM can also be improved depending on the mixing ratio. BRIEF DESCRIPTION OF DRAWINGS FIG. 1: A powder X-ray diffraction pattern of A-type crystals. FIG. 2: A powder X-ray diffraction pattern of C-type crystals. INDUSTRIAL APPLICABILITY According to the present invention, Aspartame (APM) is mixed with Neotame (NM) whereby the poor dissolution characteristics (solubility) of NM can be significantly improved, and simultaneously a sweetener excellent in quality of sweetness can be easily obtained. Accordingly, the present invention is advantageous particularly for use in drinks where a sweetener is dissolved in industrial production, but the present invention is not limited thereto and can be used as an improved sweetener composition in any uses.

Claims: Sweetener composition comprising powdery N-[N-(3,3-dimethyl butyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester and powdery Aspartame as active ingredients, wherein the ratio of Aspartame to the total amount of both of them is in the range of 10 to 99.5 % by weight. The sweetener composition according to claim 1, wherein the crystalline form of said powdery N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester is C-type crystal. The sweetener composition according to claim 2, wherein said ratio of Aspartame to the total amount of N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester and Aspartame is in the range of 10 to 97 % by weight. The sweetener composition according to claim 2, wherein said ratio of Aspartame to the total amount of N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester and Aspartame is in the range of 50 to 97 % by weight.

Inventors: HIRANO ATSUHIKO, ISHIDA HIROTOSHI, KISHISHITA AKIHIRO, NAGAI TAKESHI, NAGASHIMA KAZUTAKA, HIRANO, ATSUHIKO, ISHIDA, HIROTOSHI, KISHISHITA, AKIHIRO, NAGAI, TAKESHI, NAGASHIMA, KAZUTAKA, HIRANO, Atsuhiko Ajinomoto Co., Inc., ISHIDA, Hirotoshi Ajinomoto Co., Inc., KISHISHITA, Akihiro Ajinomoto Co., Inc., NAGAI, Takeshi Ajinomoto Co., Inc., NAGASHIMA, Kazutaka Ajinomoto Co., Inc.
Applicants: AJINOMOTO KK, AJINOMOTO CO., INC.
Application year: 1999
Main classification: A23L1
IPC codes: C07K5, A23L1