GB2123672A - Sweetening compositions - Google Patents

Abstract

Sweet proteins such as thaumatin and monellin are protected from degradation by dyestuffs by forming a co-solution of the protein with a weakly acidic polysaccharide gum, e.g. gum arabic, gum karaya or gum tragacanth, and drying the solution. The solid product retains the sweetness properties and may be incorporated, optionally together with a food acid or bulking agent, in various beverages, mouth washes or in a pharmaceutical base.

Description

SPECIFICATION Sweetening compositions The present invention relates to sweetening compositions containing protein sweeteners.

Protein sweeteners are naturally occurring, high molecular weight proteins exhibiting an intense sweetness. They are generally obtained from various species of tropical fruiting plants. One example is the sweet principle known as thaumatin which occurs in the fruit of the tropical Thaumatococcus danielili Benth. of the family Marantaceae. This plant is grown in various parts of tropical Africa and is called Katemfe in Sierre Leone. The fruit is tetrahedral, approximately 4 cm in diameter and contains up to three large black seeds surrounded by a transparent jelly each having a white or light yellow aril at its apex. The arils are intensely sweet. Thaumatin can be extracted by the procedures described by van der Wel and Loeve, Eur J.Biochem 31 221-5, (1972), optionally with the modification that an aluminium salt solution is used as extractant, as is described in our British Patent No.1 501 409, or preferably with the modification that powdered dry aril is extracted with acid as described in our British Patent No. 2,01 5,533B.

Another example of a protein sweetener is the sweet principle known as monellin which is found in the fruit of the tropical plant Dioscoreophyllum cumminsii Diels., of the family Menispermaceae.

The plant and berries have become known as "Guinea Potato" or "Serendipity Berry". The plant is native to the forest of tropical West Africa and bears grape-like clusters of red berries about 10 mm in diameter. The berries have a tough outer skin enclosing a white sweet-tasting mucilaginous material surrounding the seed. The sweet principle can be extracted from the mucilaginous material using the procedure described, for example, in the paper of J. A. Morris et al. J. Biol. Chem. 248 (2), 534-9 (1973) or van der Wel, F.E.B.S. Letters 21(1), 88-90 (1973), and is the subject of our British Patent Specification No. 1337086.

Protein sweeteners, particularly thaumatin, are characterised by a large molecule carrying a number of widely separated ions giving them the character of a polyelectrolyte. This polyionic character can cause problems in a number of formulations in which protein sweeteners are included. Interaction with other ionic species can cause flocculation and precipitation of the protein. This is undesirable because the sweetness level in the composition is markedly decreased and the clarity of solutions is spoiled by clouding. A particular problem arises when a sweet protein is brought into contact with a colourant, e.g. the permitted food colours such as Tartrazine (E102), Sunset Yellow (elm 0) Ponceau 4R (E124), Green S (E142) and Brilliant Blue.

Clear aqueous solutions sweetened with thaumatin containing these colourants, in particular soft drink formulations, mouthwashes and the like, are prone to clouding and sweetness reduction on storage.

The problem cannot simply be overcome by neutralizing the ionic content of the protein as this tends to have the same effect as the interaction with colourants: the sweetness is removed and the protein is rendered insoluble.

It is has now been found that a particular formulation of the sweet protein is resistant to precipitation with colourants while remaining fully sweet and soluble. This formulation is also resistant to precipitation and loss of sweetness when used to sweeten beverages such as tea or coffee.

According to the present invention there is provided a composition, especially a sweetening composition, comprising a sweet protein, especially thaumatin, together with a weakly acidic carboxylic polysaccharide gum in a ratio of sweetener to gum, by weight, of from 1:5 to 1:30, formed by drying a solution containing the gum and the sweetener.

It is important to note that although reference is made throughout this specification to sweetening compositions, the compositions containing thaumatin can also be used at levels below the sweetness threshold to provide flavour enhancement as described and claimed in our British patent specification No. 1604218.

The gum of use according to the present invention must be a weakly acidic gum, that is to say a polysaccharide containing a small proportion of free carboxyl groups. The gum of choice is gum arabic (acacia), but also of interest are gum tragacanth and gum karaya and semi-synthetic gum derivatives.

The gum may comprise a single gum or be a mixture of two or more such gums. Strongly acidic gums are unsuitable for the purpose as they bind too securely to the protein-and so remove its sweetness and also its solubility in some cases. For example, carrageenan which is a sulphated gum, forms a stable complex with thaumatin which is unsuitable for sweetening purposes. In general the gum should have an acid value of about 2-25, especially about 2-10. A pKA value of about 4-6 is also desirable. It is also highly desirable that the gum is stable under acid conditions, e.g. at a pH of 2.8 to 3.5. This is especially important when the composition is used in soft drinks such as iemonade and cola. For this use, gum arabic and tragacanth are preferred.

The ratio of sweetener to gum should, as stated above, be from 1:5 to 1:30, preferably 1:6 to 1:20 by weight. A particularly preferred ratio is 1:8 to 1:9. If less gum is added the protection is incomplete and clouding with loss of sweetness can still occur. Amounts of gum greater than the maximum stated cause a decrease in the sweetness of the product. The decrease in sweetness is noticed at a ratio of more than 20 parts by weight of gum per part of protein sweetener and is unacceptable at a ratio of more than 30 parts of gum per part of sweetener.

It is essential that the composition is obtained by drying a co-solution of the two ingredients. A simple admixture of the dry ingredients, even when very finely divided and intimately mixed, is ineffective. Aqueous solutions containing the gum and the protein sweetener can be dried by any desired method, although freeze drying and spray drying are the most effective. Spray drying may be effected at a nozzle temperature of, say, about 200 to 3500C although it will be appreciated that care should be taken in order to avoid heat denaturation of the protein. It is found that the presence of the gum helps to protect against such denaturation. In general a solution concentration of at least 20% solids by weight is preferred and a suitably high concentration may be obtained by raising the temperature of the solvent.It will be seen that the viscosity of the gum should not be too great or else the solution to be dried may have to be made unacceptably dilute. Gum arabic and gum tragacanth do not suffer from this problem.

The composition according to the present invention thus comprises a bulked form of protein sweetener. At a preferred ratio of gum to sweetener of 9:1 by weight, the composition contains 10% of sweet protein. The composition is thus convenient to handle and to measure. It can be obtained as a fine, free-flowing particulate solid which is stable and is easily stored.

It will be appreciated that when the sweetening composition according to this invention is added to a liquid formulation such as a soft drink, the levels used to obtain a palatable degree of sweetness are very low, typically 250 mg of the composition per litre. At this level, the gum component of the composition provides no noticeable effect on the viscosity, mouthfeel and flavour. It is important to note that the gum is not being used at the levels applicable for a mouthfeel additive and that use at those levels could, as explained above, lead to an unacceptabie loss of sweetness.

As a minor modification of the composition according to the invention, it is possible, if desired, to incorporate as a third ingredient in the co-dried composition a food acid such as citric acid, malic acid or ascorbic acid or a mixture thereof. Such compositions are stable and easy to handle and represent a convenient way of adding the food acid to a soft drink or mouthwash formulation. The addition of the acid is also a convenient way to adjust the pH of the cosolution to be dried, e.g. to a value of 2.5 to 4. In general, the weight ratio of the food acid to gum may be about 1:6 to 1:3.

The sweetening composition according to the invention comprises the gum/sweet protein combination, optionaliy together with one or more food acids. At its simplest, the composition consists of these ingredients and nothing else. However, it is often desirable to bulk a protein sweetener even further than to a 1 0% sweetener content, for ease of handling, for example as a tabletop sweetener for tea or coffee. Accordingly the composition may be further extended with an inert bulking agent such as maltodextrins or sugars e.g. glucose or lactose. This extending component may be dry mixed with the co-dried sweetener/gum composition or, alternatively all the components may be co-dried at once from a single solution.

The following non-limiting examples illustrate the invention further.

EXAMPLE 1 Thaumatin Composition An aqueous solution was prepared containing thaumatin and gum arabic in a weight ratio of 1:9, to a total solids content of a little over 20%. Warming the solution above ambient temperature aided dissolution at the required concentration.

The solution was then spray dried at a nozzle temperature of about 2500 C. In an alternative method, the solution was freeze dried in vacuo.

EXAMPLE 2 Composition Containing Ascorbic Acid The procedure of Example 1 was repeated, but dissolving ascorbic acid (0.5 g), thaumatin (0.75 g) and gum arabic (6.25 g) in about 28 ml water. The solution at 20% solids content (based on thaumatin and gum) has a pH of 3.7.

EXAMPLE 3 Composition Containing Citric Acid The procedure of Example 1 was repeated, but dissolving citric acid (0.9 g), thaumatin (0.75 g) and gum arabic (6.25 g) in about 28 ml water. The solution had a pH of 2.5.

EXAMPLE 4 Demonstration of the Protective Effect of the Gum Model soft drink formulations were prepared using synthetic colours at 0.0005% w/v in distilled water adjusted to pH 3.0 with citric acid. For each colour, three samples were prepared containing respectively thaumatin 2 mg; the 9:1 gum arabic/thaumatin composition of Example 1,20 mg; and no thaumatin or gum arabic. Aliquots of 120 ml were bottied, capped and pasteurised at 80 C for 15 minutes. Samples were then stored at ambient temperature (about 200 C) and at about 300 C. The colours used in the tests were Tartrazine (El 02), Sunset Yellow (El 10), Ponceau 4R (El 24), Green S (El 42) and Brilliant Blue.In all cases the examples containing thaumatin were cloudy immediately after pasteurisation while the controls and the examples containing the composition remained clear. After 7 weeks storage the samples containing thaumatin alone showed settled precipitates and a loss of dissolved colour. The bottles stored at 300C were opened after 7 weeks and tasted and the optical density measured spectrophotometrically in 1 cm cells (Unicam SP 1800) in the visible region. Samples were diluted 1 :1 with water for the test. Results are given in the following table.

Optical Colour Sweetener* Taste Density Wavelength Tartrazine 1 - 1.04 430 nm Tartrazine 2 Slightly sweet 0.90 430 nm Tartrazine 3 Very sweet 1.04 430 nm Sunset Yellow 1 - 1.13 483 nm Sunset Yellow 2 Very slightly sweet 1.00 483 nm Sunset Yellow , 3 Very sweet 1.11 483 nm Ponceau 4R 1 - 0.77 508 nm Ponceau 4R 2 Very slightly sweet 0.66 508 nm Ponceau 4R 3 Very sweet 0.76 508 nm Green S 1 - 1.51 600 nm Green S 2 Slightly sweet 1.35 600 nm Green S 3 Very sweet 1.60 600 nm Brilliant Blue 1 - 1.45 600 nm Brilliant Blue 2 Slightly sweet 1.18 600 nm Brilliant Blue 3 Very sweet 1.38 600 nm * 1 - no thaumatin or gum 2 -- thaumatin 3 -thaumatin/gum arabic (1 ::9), composition of invention A quantitative estimate by a taste panel indicated that the samples containing thaumatin simplex lost about 80% of their sweetness. In these samples the colour loss was about 14%. The samples containing the composition according to the invention lost no sweetness, had no visible precipitate and an average colour loss of less than 1%.

EXAMPLE 5 Blackcurrant Cordial (reduced calorie) Blackcurrant concentrate 11.2 ml Sucrose 100.4 g Citric acid 1.1 g 9:1 gumarabic:thaumatin 250 mg Water to 1 litre Final pH: 3 Pasteurise 700C at least 1 5 min., store cool in the dark.

EXAMPLE 6 Cola (a) Reduced Calorie Cola flavour 1 ml Cola extract 4.8 g Sucrose 82.5 g Sodium benzoate 1 54 mg 10% Phosphoric acid 0.7 ml 9:1 gum arabic:thaumatin 250 mg Carbonated water to 1 litre Final pH: 2.9 (b) Low Calorie As above but with 0.26 g Na saccharin (or equivalent other high intensity sweetener) replacing the sucrose and the addition of 450 mg sodium citrate dihydrate.

EXAMPLE 7 Lemonade (a) Reduced Calorie Lemon flavour 0.4 ml Sucrose 68 g Na benzoate 154 mg Citric acid 220 mg 9:1 gum arabic:thaumatin 100 mg Carbonated Water to 1 litre (b) Low Calorie As above with 0.26 g Na saccharin replacing the sucrose.

(c) Saccharin Sweetening Only As (a) but with saccharin (0.32 g) plus only 11 mg 9 :1 gum arabic thaumatin to mask after taste of the saccharin.

EXAMPLE 8 Orange Squash (Reduced Calorie) Orange concentrate 9.2 ml Sucrose 74g Citric acid 2.4 9 Na benzoate 154 mg Colour: E102 13 mg plus Eel 02/124 7 mg 9:1 gum arabic :thaumatin 200 mg Water to 1 litre Pasteurise (940C 30 sec.) and store cool and dark.

EXAMPLE 9 Sweetened Fruit Juices (Nectars) Increased flavour and sweetness with a reduction in bitterness can be imparted to fruit juices by the addition of low levels of gum arabic/thaumatin. For example at 5 ppm, flavour enhancement and bitterness masking is observed while at 50 ppm sweetness is contributed.

EXAMPLE 10 Basic Mouthwash Ethanol 15 ml Glycerol 10 ml Cinnamon/peppermint oil (50:50 mixture) 0.066 ml Brilliant Blue q.v.

Tartrazine (El 02) 9:1 gum arabic :thaumatin 150 mg Water to 100 ml EXAMPLE 11 Heavy Syrup (Pharmaceutical Base) Ethanol 18% by weight Maltodextrin 5% Dextran 500 5% Sorbitol 3% Glycerol 5% Propylene glycol 3% Citric acid to pH 4.8 Brilliant Blue plus Ponceau 4R (E142) q.v Na benzoate 0.1% Peppermint oil 0.05% 9:1 gum arabic:thaumatin 0.8% Water to 100% In each of the above Examples, the 9:1 gum arabic:thaumatin mixture may be replaced by an equivalent quantity of a 9 :1 gum arabic: monellin mixture to give equal sweetness or by the same quantity of a 9:11 tragacanth :thaumatin mixture.

Claims (10)

1. A composition comprising a sweet protein together with a weakly acidic carboxylic polysaccharide gum in a ratio of sweet protein to gum, by weight, of from 1:5 to 1:30, and formed by drying a solution containing the gum and the sweetener.

2. A composition according to claim 1, in which the gum has an acid value of from 2 to 25.

3. A composition according to claim 1 , in which the gum has an acid value of from 2 to 10.

4. A composition according to claim 3, in which the gum has a pH value of 4 to 6.

5. A composition according to any of claims 1 to 4, in which the ratio of sweetener to gum by weight is from 1:6 to 1 :20.

6. A composition according to claim 5, in which the said ratio is from 1:8 to 1:9.

7. A composition comprising the gum/sweet protein composition according to any of claims 1 to 6, together with a food acid.

8. A composition according to claim 7, in which the weight ratio of food acid to gum is 1:6 to 1:3.

9. A composition comprising the gum/sweet protein composition according to any of claims 1 to 8, together with an inert bulking agent.

10. A method of producing a composition as defined in any of claims 1 to 9, in which a sweet protein and a weakly acidic polysaccharide gum are dissolved in a common solvent in a weight ratio of sweet protein to gum of from 1:5 to 1:30 and the co-solution so formed is dried.

10. A method of producing a composition as defined in claims 1, in which a sweet protein and a weakly acidic polysaccharide gum are dissolved in a common solvent in a weight ratio of sweet protein to gum of from 1:5 to 1:30 and the co-solution so formed is dried.

1 A method according to claim 10, in which the co-solution has a solids concentration of at least 20% by weight.

12. A method according to claim 10, or claim 11, in which the solvent comprises water.

13. A method according to any of claims 10 to 12, in which a food acid is also dissolved in the cosolution.

14. A method according to claim 13, in which the solution has a pH of 2.5 to 4.

New claims or amendments to claims filed on 30 Sept. 83.

Superseded claims 4 and 10.

New or amended claims.

4. A composition according to claim 3, in which the gum has a PKA value of 4 to 6.