WO2008129457A1

WO2008129457A1 - Process for preparing sweet juice extract

Info

Publication number: WO2008129457A1
Application number: PCT/IB2008/051430
Authority: WO
Inventors: Eric Frerot
Original assignee: Firmenich Sa
Priority date: 2007-04-18
Filing date: 2008-04-15
Publication date: 2008-10-30

Abstract

Asweet juice extract is manufactured by (a) preparing a liquid comprising the extract of the fruit of one or more plants in the Cucurbitaceaefamily, (b) passing the liquidextract through a first filter having a molecular weight cut offequal to or greater than 1 500 Da to obtain a first permeateand first retentate, (c) passing the first permeate through a second filter having a molecular weight cut offequal to or less than 1 000 Da to obtain a second permeate and second retentate, and (d) optionally drying the second retentate to obtain a solid, preferably powdered sweet extract.

Description

PROCESS FOR PREPARING SWEET JUICE EXTRACT

Technical Field

The present invention relates to a process for preparing a very sweet extract from the juice of one or more plants in the Cucurbitaceae family and to an extract prepared according to this process.

Background and Prior Art

The plants of certain members of the Cucurbitaceae family are known to produce intensely sweet fruits due to the presence of terpene glycosides, or mogrosides. Terpene glycosides are natural materials, which provide a level of sweetness often many times more powerful than that of natural sugar but with the added distinction of negligible calories. A further advantage is that they are natural and so avoid the need for artificial sweeteners. Of the terpene glycosides or mogrosides present in the fruits derived from such plants, mogrosides IV and V, 11-oxo-mogroside V, and siamenoside I have been identified and characterized chemically as the very sweet components. See for example, Matsumoto, et al, Chem. Pharm. Bull, 38 (7), 2030-2032 (1990).

The best known, and most common fruit from the Cucurbitaceae family is Luo Han Guo, which is produced by the plant S. grosvenorii found in southern China.

The fresh fruit can be used for sweetening many kinds of foodstuffs and beverages but it is prone to decomposition if stored. To address this, it is typically treated by being slowly dried in an oven prior to be added to the product to be sweetened. Even so, the dried fruit still has an earthy, beany, vegetable flavour and a tendency to form off flavours, particularly bitter, astringent and browned flavours. The undesirable flavours have often been described as liquorice, vegetal and/or caramelic. Such flavours restrict the use of the dried fruits and dried fruit extracts to the preparation of dilute teas and soups and products to which sugar, honey and the like are added.

Alternatively, if the product is to be used in products which are not intended to be stored for long periods, the juices can simply be extracted from the fruit and used as such. However, such juice has a slightly acidic pH and contains sugars, which can brown and ferment creating an aesthetically displeasing product. For this reason, the juice is often concentrated by evaporation processes which involve heating the juice, usually under vacuum. Nevertheless, this creates the same off- flavours as when the fruit itself is dried. Furthermore, in the drying or evaporating processes, the loss of certain desirable components, and, in particular, certain mogrosides, is also inevitable. It would be desirable to provide an extract that avoids some or all of these disadvantages.

US 5,433,965 (Procter and Gamble) relates to beverages that are sweetened using Luo Han Guo juice and discloses, in example 5, a process for preparing the juice. The steps include mashing the pulp by hand, passing through a strainer, acidifying the permeate, passing through a 20 mesh screen and evaporating the juice. The last step is performed in order to remove volatile off-flavour precursors. In the general description the section relating to removal of off- flavour precursors states that evaporation; addition of a fining agent, adsorbent or precipitating agent to the juice fo llowed by removal of the resulting agent/precipitate preferably by filtration or centrifugation; and use of activated charcoal are all to be used to remove off- flavour materials and precursors thereof.

US 5,411,755 (Procter and Gamble) similarly relates to a process wherein the Luo Han Guo juice is treated by removal of pulp solids and use of ion exchange resins, fining agents, adsorbents, enzymes and precipitating agents to remove off-note precursors. The process is complicated in that it requires volatilisation of certain ingredients using expensive vacuum evaporation technology. In both of these documents, mechanical filtration is used to remove the agents which have been previously added in order to remove off-flavours and their precursors. Mechanical filtration is not considered as the means directly to remove the off-flavours and their precursors. It would be desirable to provide an effective process which avoids the very complicated systems disclosed in these documents.

US 6,124,442 (Zhou et al) relates to a multiple step process for extracting triterpene glycosides from juices in general, using macroporous resins combined with washing with ethanol.

WO-A-94/18855 (Procter and Gamble) relates to the use of Luo Han Guo (and some other species) as sweetening agents.

It would be desirable to address one or more of the abovementioned problems and/or to provide one or more of the benefits mentioned herein. Surprisingly, it has been found that a process that is much less complicated than many of the conventional processes disclosed in the prior art provides an effective way of addressing one or more of the problems and/or solutions referred to herein.

Summary of the Invention

Accordingly, the present invention provides a process for preparing a sweet juice extract comprising the steps of: (a) preparing a liquid comprising the extract of the fruit of one or more plants from the

Cucurbitaceae family, (b) passing the liquid extract through a first filter having a molecular weight cut off equal to or greater than 1 '5OO Da, and optionally repeating step (b) to obtain a first permeate and a first retentate,

(c) passing the first permeate through a second filter having a molecular weight cut off equal to or less than 1 '0OO Da to obtain a second retentate and a second permeate, and

(d) optionally drying the second retentate to obtain a solid, preferably powdered extract. The invention further provides a liquid or solid, preferably powdered extract prepared according to the process above.

The invention also provides a food or beverage product comprising a liquid or solid, preferably powdered extract prepared according to the process.

Detailed Description of the Invention

Molecular weight cut off is referred to herein as "MWCO". Daltons are referred to herein by the abbreviation "Da". In the process according to the invention, steps (a) to (d) as well as their order relative to each other are essential.

Step (a)

In the first step, a liquid is prepared comprising the extract of the fruit of one or more plants in the Cucurbitaceae family.

In particular, the process is carried out on the extract of the fruit of one or more plants in the Cucurbitaceae family, tribe Jollifieae, subtribe Thladianthinae, genus Siraitia. Especially preferred are the genus/species S. grosvenorii, S. siamensis, S. silomaradjae, S. sikkimensis, S. africana, S. borneensis, and S. taiwaniana. The most preferred fruit is derived from the genus/species S. grosvenorii, which is often called Luo Hah Guo fruit. Although the following description of the process of this invention is described with particular reference to making a Luo Han Guo extract, it will be understood that the process is not limited thereto.

The process is applicable to other sweet fruit juices of Cucurbitaceae family which contain at least 0.01% sweet triterpene glycosides or mogrosides. Preferably the juices will contain from 0.1% to about 15% mogrosides, preferably mogroside V, mogroside IV, (11-oxo-mogroside V) siamenoside and mixtures thereof.

The structures of mogrosides are described in "High-Performance Liquid Chromatographic Analysis of the Major Sweet Principle of Lo Han Kuo Fruits", Helena C. Makapugay, N. P. Dhammika Nanayakkara, Djaja D. Soejarto, and A. Douglas Kinghorn* J.Agric.Food Chem. 1985, 33, 348-350. Mogroside V is the key active ingredient for providing the sweet flavour and has the formula:

The juice upon which the process of the invention is applied can be obtained by any suitable method, many of which are well known to the person skilled in the art. For instance, a common method is given in US 5,411,755 in the section titled "Processing of the Fruit".

Alternatively, it can be obtained as a powdered extract. For instance, powdered instant Luo Han Guo is commercially available from suppliers such as Guilin Layn or the Yongfu Company, both of which are based in China. In this case, the liquid extract is simply prepared by addition of a suitable solvent, typically a water/ethanol mixture in a 5:1 to 15:1 ratio, followed by stirring until the powder has dissolved.

Once the liquid is prepared, it undergoes treatment steps (b) and (c). The order of these steps is critical for reasons given below.

Step (b)

A first filtration is carried out using a filter that has an MWCO point equal to or greater 1 '5OO Da, more preferably equal to or greater than 2'500 Da, most preferably equal to or greater than 3'00O Da. That is, materials having a molecular weight of 1 '500 Da or more, more preferably 2'500 or more, most preferably 3'00O or more will be retained as retentate and particles having a molecular weight inferior thereto will pass into the permeate.

The filter is preferably a membrane filter, also known as assize exclusion membrane filter.

The first filtration removes various proteinacious and high molecular weight materials. Most importantly, this simple yet surprisingly effective step removes a significant proportion of the off-flavours and colours without substantially reducing the level of mogrosides. The proteinacious and high molecular weight materials are also responsible for generating further off-odours during any subsequent drying process.

Without wishing to be bound by theory, it is believed that the proteinacious materials bind to smaller volatile components and it is the latter that are the cause of most off-notes. By performing this filtration step first, the removal of the undesirable compounds is optimised. Step (b) may be performed more than once. In this case, additional aliquots of solvent are passed through the filter to collect more permeate and to allow a greater proportion of desirable mogrosides to pass through the filter. In particular, step (b) can be repeated from 2 to 20 times, more preferably from 3 to 10 times, most preferably from 4 to 9 times in order to obtain the first permeate and first retentate. It has been found that step (b) gives improved yields when performed under diafiltration conditions. It is particularly preferred that a certain quantity of fresh water is added. In particular, the diafiltration conditions improve the yield of permeate, which notably increases the level of mogrosides in the final extract. Typically step (b) is performed at elevated pressure, so that the liquid to be filtered passes more readily through the filter. For instance, a pressure of 1.2 to 8 bar, more preferably 1.3 to 6 bar, most preferably 1.8 to 3 bar is applied during this step.

Most preferably, step (b) comprises ultrafiltration. Ultrafiltration (UF) comprises membrane filtration in which hydrostatic pressure forces a liquid against a semipermeable membrane and advantageously allows for a very precise separation of desirable materials from undesirable materials based on their respective molecular weights.

Whilst the first filtration preferably removes substantially all of the proteinacious materials, it allows a significant amount of mogrosides to pass into the permeate. Thus, it is preferred that at least 85%, more preferably 90% of the mogrosides pass through the filter into the permeate.

The use of a first filter having a cut-off below 1 '5OO Da is not suitable for use in step (b) of the present invention since it has been found that the loss of mogrosides into the retentate is increased dramatically, thereby reducing unacceptably the sweetening effect of the final product.

Step (c)

Following the first filtration step, or steps if repeated, a second different filtration step is required. This step is performed on the permeate obtained in step (b). In the second filtration step, the filter has an MWCO equal to or less than 1 '0OO Da. That is, materials having a molecular weight of greater than 1 OOO Da will be retained as retentate and particles having a molecular weight inferior thereto will pass into the permeate.

The filter is preferably a membrane filter. The small molecular weight components, and in particular, the free volatile components, are not retained by the filter but pass through into the permeate. It has been found that with an MWCO of 1 OOO Da, the components that are significantly responsible for the off-odour are not retained with the mogrosides, which are held in the retentate.

The second filtration step preferably removes at least 90% by weight of sotolone, methyl mercaptan, dimethyl sulphide and dimethyl disulphide that was present in the extract obtained in step (a).

Thus, the retentate comprises the concentrated mogrosides but is substantially free of components which adversely affect flavour and storage stability. Step (c) has been found to increase the level of total mogrosides in the final retentate to 30% or more, more preferably 35% or more, even more preferably 50% or more, most preferably 60% or more, based on the total dry weight of the extract.

The level of mogroside V in the final retentate is preferably 20% or more, more preferably 25% or more, even more preferably 30% or more, most preferably 40% or more, based on the total dry weight of the extract.

The mogroside V content in the retentate is preferably more than 50%, more preferably more than 60%, most preferably more than 70% by weight, based on the total weight of all mogrosides present in the retentate. By increasing the mogroside level, the sweetness intensity is dramatically improved and yet the generation of undesirable off-odours typically associated with extracts based on these fruits is avoided since the unwanted components are removed by this two-stage filtration.

In particular, the liquorice off- flavour usually associated with this type of extract is substantially avoided.

Typically step (c) is performed at elevated pressure, so that the liquid to be filtered passes more readily through the filter. For instance, a pressure of 1.2 to 8 bar, more preferably 1.3 to 6 bar, most preferably 1.8 to 3 bar is applied during this step.

Most preferably, step (c) comprises ultrafiltration Whilst, in theory, step (c) could be performed prior to step (b), it has surprisingly been found that this is not suitable in the context of the present invention since the removal of sufficient off-note compounds from the extract is not achieved and the end product has an unacceptable aroma profile.

Step (d)

The extract, in the form of the second retentate obtained according to step (c) can be used without additional treatment. In this case, it is limited in its use to the sweetening of final products that are liquid or pasty. Nevertheless, it is typically desirable to dry the retentate so that it can be stored and transported more easily. Additionally, it can then be used to sweeten foods which require ingredients in a solid form. The drying step preferably provides a solid product, more preferably a powdered product.

It is essential to perform the drying step after the filtration steps, since undesirable components particularly responsible for generation of off-odours must already have been removed in the filtration steps. Thus, according to the present invention, the drying step does not generate the off-odours typically associated with prior art drying processes that are carried out on the extract directly obtained from the plant without the intervening steps.

Any suitable process for drying can be used such as heating gently subjecting the retentate to reduced pressure (e.g. a vacuum), spray-drying and the like. A particularly preferred process involves the step of freeze-drying.

Juice or solid extract

The sweet juice extract prepared according to the process of the present invention, especially when concentrated or dried, can be used to provide natural sweetness for many purposes. Examples of such uses to provide sweetness are in beverages, such as tea, coffee, fruit juice and fruit- flavoured beverages; foods, such as jams and jellies, peanut butter, pies, puddings, cereals, candies, ice creams, yogurts, bakery products; health care products, such as toothpastes, mouthwashes, cough drops, cough syrups; chewing gums; and sugar substitutes.

Due to the highly effective sweetening capacity of the extract, it can be used at very low levels in foods. For instance, the extract may be present in an amount of from 0.0001% to 0.1%, more preferably from 0.001 to 0.05%, most preferably from 0.003 to 0.03%, e.g. from 0.004 to 0.015%, by weight of dry extract based on the total weight of the food.

Examples

The invention will now be illustrated with reference to the following examples. All amounts are % by weight unless otherwise indicated.

Example 1

Preparation of sweetness-enhancing extracts 5O g of powdered Luo Han Guo extract (ex Guilin Layn Natural Ingredients Corporation, China), herein referred to as "sample 1", were dissolved in 270 ml of deionized water and 30 ml of ethanol. The solution was poured into a 400 ml Amicon filtration cell containing a YM-3 modified cellulose filter with an MWCO of 3'00O Da. Ultrafiltration was performed under 2.5 bar of nitrogen. After 300ml of the solution had passed through the filter, a further 300 ml of solvent (water and ethanol at a 9:1 ratio) was added and ultrafiltration under nitrogen carried out. The batchwise filtration process was repeated until 2.1 litres of permeate had been recovered. In order to assess the quantity of dissolved material present in the permeate, The permeate was freeze-dried to yield 38.4 g (77%) of solid product (referred to herein as "sample 2").

20 g of sample 2 were dissolved in 180 ml of deionised water and 20 ml of ethanol. The solution was poured into a 400 ml Amicon filtration cell containing a YM-I modified cellulose filter having an MWCO of 1 '0OO Da. Ultrafiltration was performed under 2.5 bar of nitrogen. In this step, 2 litres of solvent (1800ml deionised water and 200ml ethanol) was transferred in a continuous process from a reservoir into the filtration cell and through the filter. The transfer rate was monitored to ensure that a constant volume was present in the cell. After the 2 litres of solution had passed through the filter, the retentate remaining in the cell was collected and freeze-dried to yield a light brown powder (7.7 g, 38.6%), herein referred to as "sample 3".

The total yield from sample 1 to sample 3 was 29.7% yield w/w.

Example 2

Comparison of sweetness in a neutral medium

Samples 1 to 3 were each dissolved in warm propylene glycol (45°C) to provide a l%w/w solution. Separately, a 5%w/w sucrose solution was prepared by dissolving sucrose crystals in water (Arkina mineral water purchased in Switzerland). The solutions were then diluted to the various concentrations given in the table below. Each sample was then stored at 20⁰C for 2 hours prior to evaluation by a panel of 3 expert flavourists. Table 1

Trial 7 had a round sweetness and strongest off-notes described as mushroom, nutty, woody and slightly liquorice. Trial 8 was found sweeter than trial 7 but still with significant detectable off-notes. Trial 9 was found to deliver the most significant sweetness both in terms of intensity and "clean" sucrose-like sweet taste.

Example 3

Preparation of a low fat yoghurt

Sample 3 and sucrose were each dissolved in warm propylene glycol (45°C) to provide l%w/w solutions. Separately, a sweetened yoghurt base was prepared by stirring sucrose into an unflavoured yoghurt (3.8wt% fat) to provide a sucrose level of 7wt%. The base was kept at 5°C overnight. The various solutions were then incorporated into the yoghurt base with stirring in the amounts given in the table below. The yoghurt products were kept at 5°C for 5 days prior to evaluation by a panel of 3 expert flavourists.

Table 2

No detectable off-notes were perceived when using between 50 ppm (trial 11) and 100 ppm (trial 13) of the extract in the low fat yoghurt products. The flavourists also found that trial 13 was very close to the target sample (trial 14) in terms of sweetness level achieved.

Example 4

Preparation of a low- fat dairy drink

Samples 1 and 3 were each dissolved in warm propylene glycol (45°C) to provide a l%w/w solution. Separately, a low- fat (0.5wt% fat) UHT milk mixture was prepared by mixing fat-free UHT milk with semi-skimmed milk and 3.5wt% sucrose in a weight ratio of7:13:l.

Sweetening compounds, as indicated in the table below, were then mixed into the low-fat dairy drink in the amounts shown to provide sweetened drinks. Each drink was divided into a first sample, which was stored at 5°C and a second sample, which underwent a pasteurisation step. Pasteurisation was carried out using a pilot scale UHT indirect 4 section plate exchanger at constant flow-rate (20 litre/hour with following parameters: preheating 70⁰C; UHT temperature 135°C; precooling 70⁰C; cooling 5°C). The pasteurised product was then filled into sterile PET bottles and stored at 5°C. All drinks were evaluated at room temperature by a panel of 4 expert flavourists.

Table 3

For all of these trials no noticeable difference was found for the perceived sweetness before and after UHT treatment.

The results demonstrate that the extract can be used as very low levels to replace sucrose without generating an undesirable (liquorice) off-taste. Example 5

Preparation of a Regular Cola

A regular Cola syrup was prepared by admixing the following ingredients: Table 4

(1) commercially available high fructose corn syrup, 77% solids, 23% water

(2) Sethness DS400

The syrup was then divided into two portions. Into one portion, lOOppm of sample 3 was added with stirring. The other portion was left unchanged. Carbonated water was then added with mixing to each portion in a weight ratio of 1 part syrup to 5 parts carbonated water.

It was found that the portion containing sample 3 had significantly increased sweetness.

Example 6

Preparation of a Diet Cola

A diet Cola syrup was prepared by admixing the following ingredients:

Table 5

(1) Sethness DS400

The syrup was then divided into two portions. Into one portion, lOOppm of sample 3 was added with mixing. The other portion was left unchanged. Carbonated water was then added with mixing to each portion in a weight ratio of 1 part syrup to 5 parts carbonated water.

The Cola portions were then evaluated by a panel of 3 expert flavourists. It was found that the portion containing sample 3 reduced the lingering and metallic aftertaste of the high intensity sweeteners and increased the natural sweetness perception of the beverage.

Claims

1. A process for preparing a sweet juice extract comprising the steps of:

(a) preparing a liquid comprising the extract of the fruit of one or more plants from the Cucurbitaceae family,

(b) passing the liquid extract through a first filter having a molecular weight cut off equal to or greater than 1 '5OO Da, and optionally repeating step (b), to obtain a first permeate and a first retentate,

(c) passing the first permeate through a second filter having a molecular weight cut off equal to or less than 1 '0OO Da to obtain a second permeate and second retentate, and

(d) optionally drying the second retentate to obtain a solid, preferably powdered extract.

2. A process as claimed in claim 1 wherein the first filter has a molecular weight cut off equal to or greater than 3'00O Da.

3. A process as claimed in either claim 1 or claim 2 wherein the second filter has a molecular weight cut off equal to or less than 750 Da.

4. A process as claimed in any one of the preceding claims wherein step (b) is performed under diafiltration conditions.

5. A process as claimed in any one of the preceding claims wherein step (b) is repeated from 2 to 20 times.

6. A process as claimed in any one of the preceding claims wherein step (b) is repeated from 4 to 9 times.

7. A process as claimed in any one of the preceding claims wherein step (c) is continuous.

8. A process as claimed in any one of the preceding claims wherein, after step (c), the concentration of mogroside V is at least 30% by weight based on the total weight of the extract.

9. A process as claimed in any one of the preceding claims wherein after step (c), the amount of sotolone, methyl mercaptan, dimethyl sulphide and dimethyl disulphide is reduced by at least 90% by weight compared to the content in the extract prior to step (b).

10. A food or beverage comprising a sweet extract prepared according to the process as defined in any one of claims 1 to 9.