WO2009017412A1

WO2009017412A1 - Sugar proces-derived aroma composition and its preparation and use

Info

Publication number: WO2009017412A1
Application number: PCT/NL2008/050528
Authority: WO
Inventors: Johanna Anna Maria Catharina Vermulst; Johan Willem Kuiper; Erik De Been; Judith Maria Stefanie Van Den Berg; Margaretha Petronella Maria Leegwater; Margaretha Johanna Mannaerts- De Wit; Joannes Gerardus Maria Van Nispen; Gerardus Henricus De Raaff; Henricus Wilhelmus Carolina Raaijmakers; Rob Sikking
Original assignee: Koninklijke Coöperatie Cosun U.A.
Priority date: 2007-08-01
Filing date: 2008-08-01
Publication date: 2009-02-05

Abstract

The invention pertains to an aroma composition for use as sugar-flavour, comprising 2- alkyl substituted pyrazines, obtainable by a process comprising subjecting a liquid withdrawn from sugar beet or sugar cane in the sugar manufacturing process to organophilic pervaporation (O-PV), and collecting the aroma composition as the permeate. Alternatively or additionally, the invention pertains to an aroma composition comprising two or more 2 -alkyl substituted pyrazines selected from the group consisting of 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2,3-dimethylpyrazine, 2,3- diethylpyrazine, 2,3,5-trimethylpyrazine, 2-ethyl-5-methylpyrazine, 2-ethyl-6- methylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine and 2,3,5,6-tetramethylpyrazine. The invention also pertains to the use thereof for masking off flavours and/or sugar-boosting in sweetened foods and beverages.

Description

SUGAR PROCES-DERIVED AROMA COMPOSITION AND ITS PREPARATION

AND USE

FIELD OF THE INVENTION The present invention relates to the field of sugar manufacturing industry and flavouring industry. The invention especially pertains to a sugar-derived aroma composition, to its preparation, and use thereof for masking off flavours and/or sugar- boosting in sweetened foods and beverages.

BACKGROUND OF THE INVENTION

Sugar (sucrose) is the most commonly used sweetener. However, sugar also provides a considerable amount of calories, which is often not desired. Therefore, artificial low- calorie sweeteners have been developed over the years. However, a frequently observed problem of these artificial sweeteners is the perception, which makes the sensation of sweetness provided by the artificial sweeteners inferior to the sweetness provided by sugar.

In principle, this problem could be solved by adding components to the artificial sweetener that remove or mask the unpleasant aftertaste. Many attempts have been made to find suitable candidates among the sugar ingredients, as illustrated by the following publications.

In US-A-2004/0151815 membrane techniques and chromatography are applied to sugar juices in the sugar manufacturing processes, in order to obtain a sucrose extract suitable as a flavour enhancer. The flavour enhancer comprises an essentially nonvolatile mixture containing non-sucrose components of sugar beet extract, "essentially non- volatile" meaning components which remain in solution even after evaporative operations at about 60 - 70 °C. Its contents is herein incorporated by reference. Sensory tests provided in US-A-2004/0151815 reveal that the flavour enhancer thus obtained does not give optimum performance. Moreover, its brownish colour makes it an unattractive food ingredient from a consumer's perspective and limits its application flexibility.

Alternatively, US 6,379,735 discloses a sugar-like flavouring component from molasses by using a spinning cone column at 40 - 60 °C. Temperatures exceeding 60 °C are avoided, allegedly causing an offensive smell. The flavouring component is used in sweetened beverages in excessive amounts of 0.01 - 5 wt%, to achieve a natural mellow feeling and sweet to it. The high amounts indicate the less intense effectiveness of the flavour enhancer. Its contents is herein incorporated by reference.

US 6,245,376 concerns a process for removing the bitter aftertaste and enhancing the sweetness of a cola beverage containing aspartame, by using about 1 - 20 ppb damascenone and at least one of the alcohols cis-3-hexenol, l-octen-3-ol or beta- phenylethyl alcohol. Its contents is herein incorporated by reference.

WO-A-2007/071729 discloses a process for the recovery of a brown food-grade sugar product from a sugar beet, subjecting the sugar beet solution to electrodialysis, thus removing (part of) malodorous volatiles. Its contents is herein incorporated by reference. Sugar aroma sensory analysis has also drawn attention to the need of identifying the compounds responsible for perceived off-odours and off- flavours in sugar. There are many different sources of volatile compounds that appear in the process of beet sugar manufacture. Volatile compounds often give rise to odours and flavours, and if allowed to remain in the final product, they limit its application. Gas chromatography allowed Philsgard et al. in ""Chemical and sensory properties of liquid beet sugar" J. Agric. Food Chem. 47 (1999) 4346-4352 to distinguish between various types of odour originating from sugar beet. Its contents is herein incorporated by reference. Recently, organophilic or hydrophobic pervaporation has been discussed in

Lipnizki et al. "Scale-up of pervaporation for the recovery of natural aroma compounds in the food industry Part 2: optimisation and integration" J. Food Eng. 54 (2002) 197-205 as a promising tool in aroma isolation on an industrial level, thus forming a commercially attractive alternative to thermally driven methods for isolating highly concentrated natural aroma extracts. The potential of the technique is demonstrated for recovery of natural apple aroma. WO-A-91/14497 also discloses a pervarporation process for selective removal of volatile substances from liquids. Both are silent on the use of this technique in sugar processing. Their contents is herein incorporated by reference. US 3,579,353 discusses the use of commercially available alkyl-substituted pyrazines, preferably those having a molecular weight less than 140, for enhancing the flavour of a food product. Similarly, GB 1,156,484 describes pyrazine flavouring agents. Both are silent on masking off flavours and/or sugar-boosting in sweetened foods and beverages; their contents is herein incorporated by reference.

Thus, a need exists for sugar-based flavour enhancer capable of masking off flavours in foods and beverages containing "non-sucrose" sweeteners, and/or enhancing the effect of sugar ("sugar boosting") in sugar-containing foods and beverages, thus requiring lesser amounts of sugar.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a sugar process-derived aroma composition which masks the disadvantageous aftertaste often associated with "non-sucrose" sweeteners, such as earthy, metallic and bitter taste. It is also an object of the invention to provide a method for enhancing or improving the flavour of sweetened foodstuffs, and especially beverages sweetened with sweeteners other than sugar. A third object of the invention is to increase the sweetness of sugar-reduced foods and drinks. It is now found that a well-suitable aroma composition can be extracted from sugar process streams comprising an organophilic pervaporation step. Organophilic pervaporation, or O-PV in short, is a process in which an aqueous feed, containing a (small) fraction of volatile compounds, is contacted with a hydrophobic, non-porous polymeric membrane. A vacuum is established on the permeate side to provide the driving force for selective mass transport from the feed through the membrane. The vaporous permeate is subsequently condensed to obtain a (liquid) product. It is the inventors' findings that the O-PV step is an essential step in selecting and concentrating the flavourant ingredients of the invention, and cannot be replaced by mere vacuum distillation. A more detailed description is given further below. The volatile aroma composition thus obtained improves the (after)taste and /or mouthfeel of all kinds of non-sucrose sweeteners, even when used in small amounts. In being volatile, the composition is quite distinct from the non-volatile sugar-derived flavourants such as that of US-A-2004/0151815. The performance of the present aroma composition surpasses the results obtained for existing formulae. Gas chromatographic analysis revealed that the sugar-derived aroma composition according to the invention is characterized by a large content of 2-alkyl substituted pyrazines. With "2-alkyl" it is understood that at least the 2 -position of the molecule is alkyl-substituted. The composition preferably contains two or more of 2,5- dimethylpyrazine, 2,6-dimethylpyrazine, 2,3- dimethylpyrazine, 2,3-diethylpyrazine,

2,3,5-trimethylpyrazine, 2-ethyl-5-methylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-

3, 5 -dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine and 2,3,5,6-tetramethylpyrazine.

The actual combination is largely dependent on the kind and source of the sugar feed.

DETAILED DESCRIPTION OF THE INVENTION

Aroma composition

The invention thus pertains to an aroma composition containing 2-alkyl substituted pyrazines, obtainable by a process comprising subjecting a liquid withdrawn from sugar beet or sugar cane in the sugar manufacturing process to organophilic pervaporation (O-PV), and collecting the aroma composition as the permeate.

Alternatively or additionally, the invention also pertains to an aroma composition comprising two or more 2-alkyl substituted pyrazines, preferably selected from the aforementioned list of 2,5 -dimethylpyrazine, 2,6-dimethylpyrazine, 2,3- dimethylpyrazine, 2,3-diethylpyrazine, 2,3,5-trimethylpyrazine, 2-ethyl-5- methylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-3, 5 -dimethylpyrazine, 2-ethyl-3,6- dimethylpyrazine and 2,3,5,6-tetramethylpyrazine.

It is preferred that the aroma composition contains two or more 2-alkyl substituted pyrazines. Where reference is made herein to '2-alkyl-substituted pyrazines', alkyl is selected from C1-C5 alkyl, preferably from C1-C4 alkyl. Particularly included are 2-methyl- and 2-ethyl substituted di-, tri- and tetra-alkyl pyrazines, wherein the additional alkyl substituent(s), especially methyl and ethyl, are located at the 3, 5 and/or 6 position.

In other words, the 2-alkyl substituted pyrazines of the invention are preferably represented by the formula

(I) in which

Ri is CH₃ or C₂H₅, and

R₂, R₃ and R4 are, independently, H, CH₃ or C2H5.

In one embodiment, one of the pyrazines present in the composition is 2,6- dimethylpyrazine. However, it is especially preferred if the composition comprises at least three of the pyrazines according to formula (I), including 2,6-dimethylpyrazine; more preferably also 2,3,5-trimethylpyrazine is present. 2,6-Dimethylpyrazine is preferably present in the aroma composition relative to other 2-alkyl substituted pyrazines in a weight ratio of 3:1 - 1:15, more preferably 2:1 - 1:10. It preferably contributes in an amount of 30 - 80 wt%, more preferably 35 - 70 wt% to the total weight of all pyrazines present in the composition.

For practical purposes, the numbers in the preceding and next paragraph are calculated on the sum of 2,6-dimethylpyrazine, 2,3-diethylpyrazine, 2,3,5- trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine and 2-ethyl-3,6-dimethylpyrazine, all or not present, and for which standards are available.

In a preferred embodiment, one of the pyrazines present in the composition is 2,3,5-trimethylpyrazine. It preferably contributes in an amount of 15 - 45 wt%, more preferably 20 - 40 wt% to the total weight of all pyrazines present in the composition. In view of the above, it is preferred that the composition also comprises 2,6- dimethylpyrazine. It is especially preferred if the composition comprises at least three of the pyrazines according to formula (I), including 2,3,5-trimethylpyrazine. It is more preferred that the composition comprises 2,3,5-trimethylpyrazine, 2,6-dimethylpyrazine and at least two 2-alkyl substituted pyrazines from the group consisting of 2-ethyl-3,5- dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine and 2,3-diethylpyrazine. It is preferred that the amount of 2,6-dimethylpyrazine and 2,3,5- trimethylpyrazine, individually, exceeds that of the other individual 2-alkyl substituted pyrazines present; the weight ratio of the sum of 2,6-dimethylpyrazine and 2,3,5- trimethylpyrazine over the sum of 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6- dimethylpyrazine and 2,3-diethylpyrazine is preferably higher than 1.5, more preferably higher than 4. It is preferred that the weight ratio of 2,3,5-trimethylpyrazine over the sum of 2-ethyl-3,5-dimethylpyrazine and 2-ethyl-3,6-dimethylpyrazine is in the range of 0.6 - 10; it is preferred that the weight ratio of 2,3,5-trimethylpyrazine over the sum of 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine and 2,3- diethylpyrazine is in the range of 0.5 - 10; it is preferred that the weight ratio of 2,3,5- trimethylpyrazine over the sum of 2,6-dimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine and 2,3-diethylpyrazine is in the range of 0.2 - 1.0, more preferably 0.2 - 0.8. The composition preferably also comprises guaiacol.

The aroma composition, for instance as derived from sugar cane, preferably comprises at least 0.1 ppm of the 2-alkyl substituted pyrazines of the invention, based on the total weight of the aroma composition. In a preferred embodiment, a sugar beet- derived aroma composition comprises at least 2 ppm, more preferably at least 4 ppm, most preferably at least 5 ppm of the 2-alkyl substituted pyrazines of the invention, based on the total weight of the aroma composition. Obviously, if the aroma composition is subjected to a (further) concentration step, the actual concentrations may be higher. In one embodiment, in a sugar-beet derived aroma composition, 2,6- dimethylpyrazine is preferably present in an amount of at least 0.5 ppm, more preferably at least 0.7 ppm, most preferably at least 1 ppm, based on the total weight of the aroma composition. In one embodiment, in a sugar-beet derived aroma composition, 2,3,5-trimethylpyrazine is preferably present in an amount of at least 0.5 ppm, more preferably at least 0.7 ppm, most preferably at least 1 ppm, particularly at least 2 ppm, based on the total weight of the aroma composition. The aroma composition of the invention may be addressed as a volatile composition, meaning that it is rich in volatile organic compounds (VOC). This is closely related to the involvement of an organophilic pervaporation step in the isolation procedure. Based thereon, the skilled person will recognize the term "volatile organic compounds" in the context of the invention. It typically involves components having a molecular weight of less than 250 g/mol. Alternatively or additionally, the VOCs may be characterized having a vapour pressure typically of at least 1 mmHg at 20 °C. Unless purposively added afterwards, the aroma composition as derived from organophilic pervaporation is an aqueous composition free from any components having a vapour pressure lower than the above-indicated value. Given the incorporation of a pervaporation step in the preparation route, the aroma composition is further characterized in that it is rich in volatile ingredients, especially oxo compounds such as alcohols, aldehydes and ketones. A non-limiting list of these other compounds is: dimethylsulfide, acetone, diacetone, isobutyraldehyde, 2- methyl-valeraldehyde, methanol, 2-butanone, 2-methyl-butyraldehyde, isovaleraldehyde, ethanol, 2-penten-3-ol-acetate, acetonitril, 2-methyl-3-buten-2-ol, isobutyl alcohol, isovaleronitril, methyl isoamylketone, methyl amyl ketone, iso-amyl alcohol, 2-methyl-l-butanol, trimethyloxazole, 2-methyl-tetrahydrofuran-3-one, 2- methyl- 1-heptanol, 2-acetyl furan, arras aldehyde, octyl alcohol, furfuryl alcohol, ethyl benzoate, methylsalicylate, butylated hydroxytoluene, phenylethanol, 2-cyclohexen-l- one, 2-cyclopenten-l-one, 3,4 dimethoxy acetophenone. Preferably, the aroma composition of the present invention comprises at least 2, 3, 4, 5 of the aforementioned components. In a preferred embodiment, the composition of the present invention comprises guaiacol or 2-methoxyphenol.

Inherent to its preparation route, the aroma composition is regarded as "desugarized". Obviously, no detectable amount of sucrose is present. In the context of the invention, "sugar" and "sucrose" refer to commercial crystalline saccharose manufactured either from sugar beet or sugar cane.

The aroma composition may further be characterized in that it is preferably free from damascenone and β-damascone.

As will be discussed further below, the preferred origin for obtaining the present aroma composition from is sugar beet. Where the aroma composition is derived from sugar beet, it preferably comprises the aforementioned 2,6-dimethylpyrazine, and further two or more of 2,3-dimethylpyrazine, 2,5-dimethylpyrazine 2,3,5- trimethylpyrazine, 2-ethyl-5-methylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-3,5- dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine and 2,3,5,6-tetramethylpyrazine. Most preferably, all are present in the sugar beet-derived aroma composition. Especially 2,3- dimethylpyrazine, 2,3,5-triethylpyrazine and 2,3,5,6-tetramethylpyrazine are characteristic for sugar beet. The weight ratio of 2,3-dimethylpyrazine and 2,3,5,6- tetramethylpyrazine is preferably between 1 : 1 and 1:10, more preferably in the range of 1:3 - 1:8.

If the aroma composition of the invention is obtained from sugar beet, this may alternatively be recognized in the final aroma composition by the presence of isovaleronitril, although not present as an active ingredient in the aroma composition. If the aroma compostion is derived from cane this can be recognized by the presence of dimethyl sulfide. Sugar-cane derived aroma compositions according to the invention may be recognized by the presence of 2,5- and 2,6-dimethylpyrazine.

Organophilic pervaporation (Q-PV) The invention also pertains to a process for isolating the above-described aroma composition from a sugar process stream, comprising subjecting a liquid withdrawn from sugar beet or sugar cane in the sugar manufacturing process to an organophilic pervaporation step, wherein the aroma composition is collected as the permeate. As already explained in the background description, the principle of O-PV involves selecting volatile compounds over a hydrophobic, non-porous polymeric membrane, using a vacuum on the permeate side. The separation across the membrane is based on the components exhibiting differing rates of diffusion through a thin polymer and an evaporative phase change comparable to a simple flash step. The vaporous permeate is subsequently condensed to obtain a (liquid) product, in this case the aforementioned aroma composition. Hence, the keywords of the technique are

"permeation" and "evaporation". For more details for the otherwise approved method the skilled person is referred to Lipnizki et al. ""Scale-up of pervaporation for the recovery of natural aroma compounds in the food industry Part 2: optimisation and integration'" J. Food Eng. 54 (2002) 197-205. Since pervaporation is applied in the present case to selectively separate volatile components of a liquid mixture, a high selectivity through the membrane is essential. The membrane suitable in organophilic pervaporation is hydrophobic, and typically made up from elastomer materials (polymers with glass transition temperatures below room temperature). The flexible nature of these polymers makes them ideal for allowing the aroma composition to pass through. Non-limiting examples include polyvinylalcohol, cellulose acetate, polyacrylonitrile, butadiene rubber, styrene butadiene rubber, poly dime thylsiloxane. The membrane configuration may be plate- and-frame, spiral-wound and hollow-fibre.

The feed temperature should be as high as possible to reduce the membrane area required. However, the maximum temperature will be determined by the temperature sensitivity of the aroma compounds, and limitations in the operating conditions of the membrane. In practice, good results are obtained at inlet temperatures in the range of 20 - 70 °C. The permeate pressure should be as low as possible, to maximize the aroma recovery and minimize the membrane area required. However, the minimum permeate pressure in the system will be limited by economical and technical limitations. In practice good results are obtained at 20 - 60 mbar. In principle, the pervaporation may be performed continuously or batch- wise.

The O-PV may be preceded by a pre-treatment, for example vacuum distillation, wherein the distillate is subjected to O-PV.

The aroma composition of the invention typically originates from a liquid withdrawn from sugar beet or sugar cane in the sugar manufacturing process. The liquid may be any stream or fraction withdrawn from any stage of the sugar processing, in particular a stream which has been subjected to heat treatment. However, it is not part of the invention to extract the aroma composition from sugar cane leaves. It is especially preferred to use sugar beet as the feed material, because of its abundant presence. In a typical embodiment of the invention, the sugar-derived liquid is selected from raw juice, thick juice and molasses. It may also be for instance an intermediary fraction withdrawn from the crystallization of sugar. Mixtures of said liquids may also be used. Good results are also obtained starting from bagasses, and even for vinasses, wherein the sugar processing involves a fermentation step prior to O-PV. In the preferred embodiment of the invention molasses is used as the starting liquid. Molasses is a liquid which is obtained as the residue after the crystallization of sucrose. It is abundantly available and is commonly used as feed for animals or as feedstock for the fermentation industry. Molasses having a Brix (the content of soluble solids) of 10 - 75 may be utilized.

Use of the aroma composition

In one aspect of the invention, the aroma composition may be used as a flavour enhancer or flavour-improver in foodstuffs sweetened with a non-sucrose sweetener to promote a sugar-like flavour and/or mouthfeel therein, and for diminishing or even eliminating off-flavours often associated with non-sucrose sweeteners.

In another aspect of the invention, the aroma composition may serve as a sugar- booster, i.e. enhancing the sugar perception, especially in terms of sugar-like flavour and/or mouthfeel, in a foodstuff. Hence, sugar-containing foodstuffs may be developed using lesser amounts of sugar (or sucrose) applying the aroma composition of the invention, thus lowering the caloric content of the product, and without the cost of incorporating non-sucrose sweeteners into the product to make up for the difference with the conventional "full sugar" counterpart. In general, the foodstuffs which are subject of the present invention may be described as reduced-sugar or reduced calorie foodstuffs, wherein the term "reduced- sugar" includes applications in which all sugar is replaced by non-sucrose sweeteners. In general terms, the invention thus pertains to a reduced-sugar foodstuff containing the aroma composition according of the present invention. Throughout the text, the terms "flavour enhancer" and "flavour improver" relate to the ability of the aroma composition to mask bitterness, earthy, and/or the "metallic" taste or aftertaste associated with many non-sucrose sweeteners, and the ability to promote the sugar-like flavour and/or mouthfeel of sugar-containing foodstuffs (in short, "sugar boosting"). "Non-sucrose" sweeteners are sweeteners which contain other sweeteners than sucrose and are generally not derived from sugar feed, including fructose, glucose, high fructose corn syrups, and especially artificial sweeteners, for example saccharin, aspartame, acesulfame-K, sucralose, neotame, alitame, cyclamate, and polyols, e.g. xylitol, sorbitol, lactitol, maltitol, mannitol and erythritol. The group of non-sucrose sweeteners with which the aroma composition may suitably be combined also includes stevia.

Hence, in one aspect the invention pertains to the use of the aroma composition of the present invention for diminishing or eliminating off flavours of non-sucrose sweeteners in food products. The aroma composition of the invention is typically used in diet and low-calorie foodstuffs sweetened with one or more of the aforementioned non-sucrose sweeteners.

The flavour improver of the invention may also be used in products sweetened with sugar. Especially products having a reduced amount of sugar, e.g. for low calorie purposes, may have their sweetness and/or mouthfeel enhanced by the product of the present invention. Hence, in another aspect the invention pertains to the use of the aroma composition for sugar -boosting in reduced-sugar food applications.

The "foodstuff or food product preferably comprises beverages, bakery products, confectionary, fruit fillings, sweet spreads and dairy products, e.g. ice-cream. The flavour improvers of the invention are also advantageous in diabetic foods, which are typically sweetened with reduced amounts of sugar or with fructose or artificial sweeteners.

The invention also relates to reduced-calorie foodstuffs containing a non-sucrose sweetener and the aroma composition according to the invention, wherein the non- sucrose sweetener preferably is an artificial sweetener, and reduced-sugar foodstuffs containing the aroma composition according to the invention, and reduced amounts of sugar (in particular sucrose) compared to its "full sugar" counterpart . An especially important field of use of the aroma composition of the present invention consists of beverages and concentrates and syrups thereof. Said beverages are typically selected from soft drink beverages, especially flavoured soft drink beverages, such as cola drinks.

Sensory tests revealed that the aroma composition may be added to foodstuffs in an amount of between 0.1 and 10 ppb, preferably between 0.2 and 5.0 ppb, more preferably between 0.4 and 3.0 ppb, in particular up to 1.4 ppb, of pyrazines in the foodstuff, in order to impart the desired flavouring effect to the foodstuff. The actual amount of aroma composition required to reach these levels can be easily calculated by the skilled person.

EXAMPLES

Example 1 - preparation of VD and Q-PV treated sugar beet molasses

Sugar beet molasses as obtained from Suiker Unie Specialiteiten Fabriek in Roosendaal

(The Netherlands) was diluted to 25 Brix% with demineralised water. The molasses were then subjected to vacuum distillation (VD). Thereto, 1 liter diluted molasses at 25 Brix was heated to 62 °C. The condenser was set at 2 °C. A vacuum pump was started and pressure was adapted to a value at which the molasses boiled steadily. The pressure varied between 140 to 100 mbar. The temperature of the cooling water at the condenser inlet varied between 2.1 - 3.1 °C. In 2 hours 320 gram distillate was collected. Water was added continuously to maintain the Brix value at a constant level. The above procedure was repeated three times - each time with new molasses - until 960 gram distillate was collected. The samples were cooled at 4 °C until pervaporation.

Thereto, 809 g of the distillate was heated to 60 °C and circulated over a membrane, wherein the absolute pressure difference over the circulation pump was maintained at 1233 mbar. Use was made of a membrane module with capillary pervaporation membranes based on PDMS (polydimethylsiloxane), supplied by X- flow. Its specific surface area was about 0.056 m² per module.

After 20 minutes of circulation, a vacuum pump down-stream from the membrane was switched on, resulting in a pressure drop to 39 mbar. The effluent vapour was collected in a condenser which was cooled at an inlet temperature was of 20 - 22 °C. The membrane flux varied between 4.4 - 5 1/m² hour. In 51 minutes 239 g condensate was produced.

Example 2 - preparation of Q-PV treated sugar beet molasses

Sugar beet molasses as obtained from Suiker Unie Specialiteiten Fabriek in Roosendaal (The Netherlands) was diluted to 24.6 Brix% with demineralised water, and then subjected to lab-scale pervaporation.

Thereto, 1000 g sugar beet molasses was heated to 40 °C and circulated over a membrane, wherein the absolute pressure difference over the circulation pump was maintained at 1274 mbar. Use was made of a membrane module with capillary pervaporation membranes based on PDMS (polydimethylsiloxane), supplied by X- flow (the Netherlands). Its specific surface area was about 0.056 m per module. After 20 minutes of circulation, a vacuum pump down-stream from the membrane was switched on, resulting in a pressure drop to 29 mbar. The effluent vapour was collected in a condenser which was cooled at an inlet temperature of 20 °C. The membrane flux varied between 0.8 - 0.9 kg/m² hour. In 210 minutes 167 g condensate was produced.

Example 3 - sensory test

The effect of the aroma composition obtained according to the recipe given in example 2 was studied for its contribution to diminish or eliminate off flavours of non-sucrose sweeteners in a number of soft drinks. Thereto, an amount of aroma composition corresponding to 0.8 ppb pyrazines was added to a number of low-calorie soft drinks containing artificial sweeteners. The soft drinks were subjected to a sensory evaluation test using professional panel members. The soft drinks were evaluated for differences in taste with respect to their low-caloric non-aroma composition-containing counterparts, using the sugar-containing soft drink ("regular") as a reference. The test was based on a scale from 2 to 6, in which 2 is the low-calorie reference, and 6 is the highest score for the regular soft drink.

The results for Coca-cola light, Orangina light, Hero Cassis light and "Dubbelfris witte druiven & citroen light" are summarized in table 1. The list of sweeteners present in these commercially available soft drinks is given in table 2. The results were averaged over 20 measurements, obtaining an accuracy of 0.05.

Table 1 - Sensory evaluation soft drinks

Coca-cola light Orangina light Hero Cassis light Dubbelfris witte druiven & citroen >ht

3.70 4.03 3.13 3.96

Table 2 - artificial sweeteners in soft drinks

The sensoric evaluation revealed that the taste of reduced-calorie soft drinks containing the aroma composition of the present invention shifted significantly towards the taste of their conventional sugar-containing counterparts. Comparative example I - Effect of Q-PV

The effect of the aroma composition given by the recipe of example 2 was compared to taste effects of flavouring compositions derived from sugar streams as these are commercially available or as obtained using conventional vacuum distillation. For the present case, the sugar stream was sugar beet molasses obtained from Suiker Unie Specialiteiten Fabriek in Roosendaal, The Netherlands.

The investigation also involved a sugar beet molasses which was derived from subsequent vacuum distillation and O-PV. The conditions for O-PV were as laid down in example 1.

Vacuum distillation (VD) conditions were similar to those reported in example 1 ; in this particular case VD involved a feed temperature of 60 °C and a condenser pressure of 20 mbar.

The comparison comprised a panel test in accordance with that of example 3. The flavouring compositions were added to a Hero Cassis light and evaluated for difference with the sugar-containing counterpart.

The O-PV-treated sugar beet molasses were added in amounts corresponding to a level of 20 ppm total pyrazines. The remaining samples were used in amounts recommended by the supplier. All evaluations took place at 7 °C, regular consumption temperature for soft drinks. The results are summarized in table 3, together with the amounts used. The evaluation is subdivided in +/++ if the taste was considered improved, while -/-- stands for deteriorating.

Table 3 - Sensory evaluation results

* : All these amounts correspond with 0.8 ppb total pyrazines.

The table shows that pervaporation has a positive effect on the taste profile of the soft drink.

Example 4 - Aroma production at pilot scale

(The Netherlands) was diluted to 30 Brix% with demineralised water, and then subjected to pilot-scale pervaporation.

Thereto, 300 kg of the sugar beet molasses was heated to 40.4 °C and circulated over a membrane, wherein the absolute pressure difference over the circulation pump varied during the process between 1430 to 1520 mbar. The circulation flow was maintained at levels of 3 m³/hr. Use was made of a membrane module with capillary pervaporation membranes based on PDMS (polydimethylsiloxane), supplied by X- flow.

After 20 minutes, the effluent vapour was collected in a condenser which was cooled at an inlet temperature was of 20 °C. A vacuum pump was used for that purpose, with a set point of 10 mbar. To discharge non-condensing gases a plate with a hole of 2 mm therein was placed between vacuum pump and condensate collector. Pressure dropped from 33 mbar to 27 mbar, and the temperature of the outflow of cooling water dropped from 23 to 21 °C. The membrane flux varied between 1.4 kg/m hour at start, to 1.1 kg/m² hour at the end. In about 6 hours 61.4 kg condensate was produced.

Claims

1. An aroma composition comprising 2-alkyl substituted pyrazines, obtainable by a process comprising subjecting a liquid withdrawn from sugar beet or sugar cane in the sugar manufacturing process to organophilic pervaporation (O-PV), and collecting the aroma composition as the permeate.

2. The aroma composition according to claim 1, comprising two or more 2-alkyl substituted pyrazines represented by the formula

in which

Ri is CH₃ or C₂H₅, and

R₂, R₃ and R4 are, independently, H, CH₃ or C₂H₅.

3. The aroma composition according to claim 1 or 2, comprising at least three of said 2-alkyl substituted pyrazines, including 2,6-dimethylpyrazine.

4. The aroma composition according to claim 1 or 2, comprising at least three of said 2-alkyl substituted pyrazines, including 2,3,5-trimethylpyrazine.

5. The aroma composition according to any one of the preceding claims, wherein said liquid is withdrawn from sugar beet, preferably from sugar beet molasses.

6. The aroma composition according to any one of the preceding claims, wherein O- PV is preceded by vacuum distillation, wherein the distillate is subjected to O-PV.

7. An aroma composition comprises 2,3,5-trimethylpyrazine, 2,6-dimethylpyrazine and at least two 2-alkyl substituted pyrazines from the group consisting of 2-ethyl- 3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine and 2,3-diethylpyrazine, said composition further comprising guaiacol, wherein 2,6-dimethylpyrazine and 2,3,5-trimethylpyrazine are each present in an amount that exceeds that of the other individual 2-alkyl substituted pyrazines present, and wherein the weight ratio of the sum of 2,6-dimethylpyrazine and 2,3,5- trimethylpyrazine over the sum of 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6- dimethylpyrazine and 2,3-diethylpyrazine is higher than 1.5.

8. The aroma composition according to claim 7, further comprising at least two components selected from the group consisting of dimethylsulfide, acetone, diacetone, isobutyraldehyde, 2-methyl-valeraldehyde, methanol, 2-butanone, 2- methyl-butyraldehyde, isovaleraldehyde, ethanol, 2-penten-3-ol-acetate, acetonitril, 2-methyl-3-buten-2-ol, isobutyl alcohol, isovaleronitril, methyl isoamylketone, methyl amyl ketone, iso-amyl alcohol, 2-methyl-l-butanol, trimethyloxazole, 2- methyl-tetrahydrofuran-3-one, 2-methyl-l-heptanol, 2-acetyl furan, arras aldehyde, octyl alcohol, furfuryl alcohol, ethyl benzoate, methylsalicylate, butylated hydroxytoluene, phenylethanol, 2-cyclohexen-l-one, 2-cyclopenten-l-one, and 3,4 dimethoxy acetophenone.

9. Use of the aroma composition according to any one of the preceding claims for diminishing or eliminating off flavours of non-sucrose sweeteners and/or promoting the sugar-like flavour and/or mouthfeel in reduced-sugar food products.

10. Use according to claim 9, said food products comprising beverages, bakery products, confectionary, fruit fillings, sweet spreads and dairy products, e.g. ice- cream.

11. A foodstuff, preferably a reduced-sugar foodstuff, containing the aroma composition according to any one of claims 1 - 8.

12. The foodstuff according to claim 11, containing between 0.1 and 10 ppb of pyrazines, based on the total weight of the foodstuff.

13. The foodstuff according to claim 11 or 12, being a beverage, a bakery product, a confectionary, a fruit filling, a sweet spread or a dairy product, e.g. ice-cream.

14. A process for isolating an aroma composition comprising 2-alkyl substituted pyrazines, comprising subjecting a liquid withdrawn from sugar beet or sugar cane in the sugar manufacturing process to organophilic pervaporation (O-PV), wherein the aroma composition is collected as the permeate.

15. The process according to claim 14, wherein O-PV is preceded by vacuum distillation, wherein the distillate is subjected to O-PV.

16. The process according to claim 14 or 15, wherein said liquid is molasses, preferably sugar beet molasses.