NO138714B - TASTE PREPARATION FOR IMPROVING THE MEAT TASTE OF FOODS - Google Patents

Description

The present invention relates to a flavor preparation

for improving the meat flavor of foodstuffs, and containing sulfur-containing furan derivatives.

Artificial flavoring agents for foods have in recent times

gained greater and greater application. In many ways, such artificial flavoring agents are preferred over natural flavoring agents,

at least partly because you then achieve a far smoother and better taste. It can e.g. mention that natural flavoring agents such as extracts, essences, concentrates, etc., are often under-

threw very wide variation due to changes with regard to the quality and type of the raw materials and the method of processing. Such a variation is reflected in the final product, and usually results in very uneven taste characteristics, which is undesirable both on the manufacturer's side and on the consumer's side. Furthermore, the presence of natural products in the food may be undesirable, because these natural products have an increased tendency to be destroyed during storage. This is a serious problem, particularly in connection with products, such as soups, chips, ready-made dinners, canned foods, sauces, syrups, and the like, which are often stored for a certain time before they are consumed.

The fundamental problem in the production of artificial flavors is to achieve the best possible natural flavor quality.

This has generally proven to be very difficult, because one

do not have knowledge of the mechanism that produces taste

the substances in the food. This is particularly pronounced in products where you want a meat flavor and/or roast flavor.

A reproduction of roast taste and meat taste of different

type has long been an area of particular interest in food

the industry. The lack of foodstuffs, and especially protein-containing foodstuffs, in many parts of the world has created a need to use non-meat-containing foodstuffs for the production of proteins and then to make these proteins as edible and as meat-like as possible. There is consequently a very strong growing need for substances or compounds that will very closely simulate or very exactly reproduce the taste and aroma found in fried products and meat products. The previously used meat flavoring substances are generally based on protein hydrolyzate or sulphur-containing amino acids. In this context, reference should be made to US patent no. 3,395,016, in which it is stated that a composition with a meat-like taste and aroma is obtained by heating a mixture of a hydrolysed vegetable protein, L-cysteine hydrochloride, thiamine hydrochloride and water.

In modern society, large quantities of meat-containing or meat-based foods are constantly sold in preserved form, and examples include canned soups, dry soup mixes, dried meat, freeze-dried or lyophilized meat, prepackaged meat mince, etc. While these products contain meat or meat extracts, then the flavourings, aroma, etc., have very often been reduced due to the processing technique, and it is in many cases very desirable to supplement or improve the taste of these preserved meat-containing foods, which is achieved according to the present invention.

According to the present invention, a flavoring preparation is provided for improving the meat taste in foodstuffs, and this preparation is characterized by the fact that it contains as an active ingredient a furan derivative with the general formula:

wherein the symbols are defined according to one of the following alternatives: (1) n is 1, R-^ is hydrogen, R 2 is methyl, R^ is hydrogen or methyl and the dashed line is a single or a double bond; (2) n is 2 or 3, R-^and R ? is methyl, R^ is hydrogen or methyl, and the dashed line is a double bond;

(3) n is 1,2,3 or 4, R is

B^ and R^ are methyl, R^ and R^- are hydrogen or methyl and the dashed line is a single or double bond.

With such a preparation, the taste of pure meat or roasted or fried meat can be achieved. Preferably the preparation contains

from 0.0001 to 10% of at least one of the above-defined furan derivatives.

It has been found that when the ring in the above formula is a furyl ring, the compounds have a very desirable and distinct meat flavor and aroma, and when the ring is a dihydrofuryl ring, the roast flavor or aroma will be more dominant.

The new furan derivatives used are oily liquids or crystalline solids, and are usually characterized by a very distinct and pleasant meat flavor or the flavor of roasted or fried Icjøtt. The dominant taste is one that can be compared to roasted protein, while at the same time there is a total absence of unpleasant taste factors.

It is understood that certain of the novel compounds may exist in various isomeric forms, and the formulas set forth herein include such isomeric forms. As an example, it can be mentioned that 2-methyl-[2,3H]-dihydrofuran-3-thiols can exist as geometric isomers and as optical isomers. An example of one of the isomers of this compound is the following:

Another isomer is:

It is understood that the derivatives of dihydrofuran can be 2,3H or 4,5H. Thus, 2-methyldihydrofuran-3-thiol includes both 2-methyl-[4,5H]-dihydrofuran-3-thiol and 2-methyl-[2,3H]-dihydrofuran-3-thiol, while bis(5-ethyl-2 -methyl-3-dihydrofuran)-disulfide includes both bis[5-ethyl-2-methyl-3-([4,5H]-dihydrofury])]-disulfide and bis[-5-ethyl-2-methyl-3- ([2,3H]-dihydrofuryl)]-disulfide.

The present preparation can produce a definitive taste

or aroma in a relatively aromaless and tasteless foodstuff,

and is able to enhance one or more already present taste qualities. The preparation can thus be used to improve the taste of a canned meat product, e.g. where the taste may be reduced or undesirably changed during canning.

It is therefore understood that the defined sulphur-containing compounds can be mixed with other flavoring ingredients, carriers, diluents or the like, in order to thereby produce preparations that can give flavor qualities to foodstuffs, improve already present flavor qualities or change present flavor qualities. The furyl monosulphides, disulphides and mercaptans generally impart a meaty flavor or aroma. The dihydrofuryl sulphides, disulphides and mercaptans, on the other hand, give frying qualities and taste qualities which in some cases can be compared to the taste of roasted sesame seeds. The taste characteristics of the compounds are thus prominent and so persistent that a desired taste or smell or aroma can be produced by simply using one or more compounds in undiluted form, e.g. by adding an undiluted compound to a processed fish product.

The defined sulfur compounds can be combined with organic acids such as fatty acids, saturated or unsaturated acids as well as amino acids, alcohols, including primary and secondary alcohols, esters, carbonyl compounds, including aldehydes, and ketones, lactones, cyclic organic compounds such as benzene derivatives, ali -cyclic compounds, heterocyclic compounds such as furans, pyridines, pyrazines and the like, sulfur-containing compounds such as thiols, sulphides, disulphides and the like, proteins, lipids, carbohydrates and so-called taste enhancing substances such as monosodium glutamate, guanylates, inosinates, natural flavoring substances such as vanillin , and similar substances to improve existing taste or to give food products new taste characteristics. It is obvious that the choice and amount of the substances mentioned above will depend on the special taste character that you want to give the final product, and especially in connection with flavor preparations that are used to improve or enhance other taste characteristics, will vary greatly strongly dependent on the material in which the taste or aroma is to be improved. In addition, inorganic substances such as sodium chloride or freshness preservatives such as butylated hydroxyanisole, butylated hydroxytoluene and propyl gallate can be used for preservative purposes.

As mentioned above, it may also be desirable to use carriers or diluents such as gum arabic, carrageenan or ethyl alcohol, water, propylene glycol, etc. When the carrier is an emulsion, the flavor preparation can also contain emulsifying

agents such as mono- and di-glycerides of fatty acids and similar compounds. With the help of these carriers or diluents, the composition can be worked up into any desired physical form. It is understood that the furan derivatives can be used in liquid, encapsulated, emulsified, solid or spray-dried form and then added to foodstuffs. Said derivatives can be used alone or in combination

tion with other constituents. In connection with foodstuffs where a combination of ingredients is used, the preparation can

one of the ingredients is added in advance, after which it is all incorporated into the food itself.

The furan derivatives should be used in sufficient amounts to

that the foods to which they are added acquire a distinct meaty flavor possess an aroma or a distinct taste or aroma of fried or roasted meat. Said derivatives are very effective and thus only need to be used in very small quantities. The amount will, however, depend on the type of food that is to be improved in taste, and one must e.g. use larger amounts to produce meat flavor in totally tasteless material while smaller amounts are needed when the compounds are used to enhance an already present meat flavor.

It is obvious that the amount of furfuryl sulfur derivs

can be varied within a very wide range to produce the desired taste or aroma. The required amount will be very easily determined in practice, and it is obvious that the use of too small amounts will give too bad a taste, while the use of large amounts usually does not give any further benefits.

It is therefore preferred that the final product contains at least approx. 1.0 parts of said sulfur derivatives per one million parts of the food, based on the weight of the total composition,

and it is usually not desirable to use more than approx. 500 parts per million (ppm) in the final product. The desirable range for use in practice is therefore from 0.001 to approx. 500 ppm of said furfuryl sulfur compounds. When said compounds are added to foodstuffs in the form of a meat flavor composition, the amount should be sufficient to obtain a suitable taste and aroma in the final food product. A flavor preparation according to the present invention thus contains from 0.0001% to .10% sulfur derivatives based on the total weight of said preparation. Unless otherwise stated, all parts, percentages and ratios are by weight.

Flavor preparations according to the present invention can be added to the food products by conventional techniques. The flavourings, together with other liquids, if this is desired, can be mixed with a carrier, e.g. gum arabic, tragacanth, carrageenan,

etc, and then spray-dried to thereby obtain a particle-shaped, solid flavouring. When you want a powdered solid

flavor mixture, then the solids of the flavor composition or the pure furyl-sulfur derivatives can be mixed well in a mixer to achieve homogeneity.

When liquid substances are included in the production of food products, the present preparation can either be combined with the liquid to be used in the final product, or alternatively it can be added together with a liquid carrier

substance in which they are dissolved, emulsified, or otherwise dispersed.

It has been found that the bis(2,5-dimethyl-3-furyl)sulfide can be readily prepared by reacting 2,5-dimethylfuran with an appropriate sulfur chloride in the presence of a catalyst. Thus, bis-(2,5-dimethyl-3-furyl)-sulfide can be prepared by a reaction between 2,5-dimethylfuran and sulfur dichloride, "SC12, and bis(2,5-dimethyl-3-furyl)-sulfide is prepared by a reaction between 2,5-dimethylfuran and sulfur monochloride, i.e. S2C12.

Although the reaction can be carried out in the absence of catalysts, it is however preferred to use these, such as Lewis acids, e.g. metal salts such as stannous chloride, ferric chloride, ferric bromide, zinc chloride, boron trifluoride and boron trifluoride complexes such as boron trifluoride diethyl etherate and similar compounds.

It has further been found that the most suitable reaction time is between 15 minutes and 2 hours, and that the most desirable temperature range is between -30° and +50°C, and that it is advantageous to use a reaction medium to regulate the reaction, and said medium can e.g. be a hydrocarbon solvent such as hexane, cyclohexane and the like, or dimethylfuran used in large excess. The ratio between the reactants should be such that the dimethylfuran compound is used in large, molar excess in relation to the sulfur chloride. The reaction should preferably be carried out at atmospheric pressure.

It has further been discovered that furan-3-thiols and methyl-substituted furan-3-thiols can be prepared by a reaction between a suitable dihydrofuranone-3 or tetrahydrofuranone-3 and hydrogen sulfide in the presence of anhydrous hydrogen chloride at temperatures from -60° to -100 °C. This reaction gives furan-3-thiols, dihydrofuran-3-thiols and tetrahydrofuran-3-thiones as well as methyl-substituted derivatives of these compounds.

The reaction between di- or tetrahydrofuranone-3- or methylated compounds with hydrogen sulphide in the presence of gaseous hydrogen chloride will take place over a period of from 5 to ■ 25 hours at temperatures from -60° to -100°C. The reaction medium can be any polar solvent with a melting point below approx. -100 C and a viscosity which means that the reaction mass can be turbulently mixed at said temperature. Desirable polar solvents with the above properties are dimethyl ether of diethylene glycol, tetrahydrofuran, methanol, ethanol and similar compounds. The hydrogen sulfide reactant is preferably used in amounts corresponding to 5 to 10 times the amount of said furanone-3.

It is further obvious that the thione can be easily converted to the corresponding thiol with a reducing agent such as lithium aluminum hydride, diethoxy aluminum hydride, ethoxy aluminum hydride and similar compounds. The medium for this reduction can be an oxygenated solvent such as diethyl ether, tetrahydrofuran, dimethyl ether of diethylene glycol (diglym) and the like. The temperature can vary from 0°C to the boiling temperature of the reaction medium. Although the reaction can be carried out in a number of varying pressure ranges, it is preferred that atmospheric pressure is used. The reducing agent is preferably used in a molar excess in relation to the thione.

It is also obvious that the corresponding bis(3-furyl), bis(3-dihydrofuryl) and bis(3-tetrahydrofuryl) disulfides can be prepared by oxidizing the corresponding thiols under slightly oxidizing conditions. Thus, the thiols can be oxidized in an air stream bubbled through said thiols at approx. 20°C and 760 mm Hg pressure for 8 hours. The reaction mass is stirred to maintain proper contact between the reactants. Other suitable weak oxidizing agents include ferric chloride, iodine-potassium iodide, dimethyl disulfide, dimethyl sulfoxide and the like.

The time span for this weak oxidation reaction will vary from approximately instantaneous oxidation and up to 20 hours at temperatures from 10° to 50°C and atmospheric pressure. The pH of the reaction mass depends on the nature of the oxidizing agent, and the reaction time is a function of the reactants' net oxidation-reduction potential and the concentrations in which they are used. It is preferred to use stoichiometric amounts of the thiol and the oxidizing agent if -

easily removable oxidizing agents such as dimethylsulfoxide, dimethylsulfide and the like are not used, because then the oxidizing agent can be used in excess.

Another method which is a reaction where 2-methyl-5-furoic acid, 2-methyl-5-cyanofuran or 2-methyl-5-halo-furan is treated with oleum (fuming sulfuric acid), whereby the 3-sulpho derivative is produced. When using the 5-furoic acid, the barium salts of the resulting acid can be easily obtained by treating the acid with barium carbonate, which is used in excess to thereby eliminate

lower any unreacted sulfuric acid. The barium salt can then be converted to the sodium salt which is then decarboxylated with an equivalent amount or an excess of mercuric chloride in a boiling aqueous solution. The resulting sodium sulphonate is reacted with a very large excess of thionyl chloride, and the excess thionyl chloride is used as a solvent to which traces of dimethylformamide have been added. Instead of an excess of thionyl chloride, other inert solvents can be used, e.g. benzene, hexene or diethyl ether. The resulting 3-chlorosulfo group can then be reduced to the thiol (-SH) group by reaction with a reducing agent used in excess to ensure total reduction. Suitable reducing agents are lithium aluminum hydride, mono-alkoxy-aluminum dihydride, di-alkoxy-aluminum hydride or zinc in hydrochloric acid, and if desired these reducing agents can be used in a common solvent. The reduction can be carried out at room temperature or up to boiling temperature under atmospheric pressure. Said dissolution medium can be oxygenated compounds such as diethyl ether, tetrahydrofuran, diglyme and the like.

Saturated furan-3-thiols can also be prepared by treating methyl-3-halotetrahydrofurans with sodium hydrosulfide under reflux conditions in the presence of ethanol, methanol or similar compounds. The mercaptans used in the present preparation can,

if desired, reacted with various chlorosulphur compounds

claims to thereby produce di-, tri- or tetra-sulphides. Thus a thiol such as 2-methyl-3-furanthiol can be reacted with an equimolar amount of methyldisulfur chloride, CH^Cl, at temperatures from

-60°C up to Q°C, whereby methyl (2-methyl->furyl)-trisulfide is produced. This reaction can be carried out in a solvent such as diethyl ether, cyclohexane, hexane, carbon tetrachloride, benzene and

the like. In a similar way, a thiol such as 2-methyl-3-furanthiol can be reacted with an equimolar amount of methanesulfenyl chloride, CH SCI, whereby methyl (2-methyl-3-furyl)-disulfide is produced. This reaction can also be carried out in a solvent such as diethyl ether, cyclohexane, hexane, carbon tetrachloride, benzene and the like. The reaction temperature is preferably from -60°C and up to 0°C at atmospheric pressure.

The di- and tetra-hydro compounds according to the present invention can also conveniently be prepared directly from suitable alkyl or dialkyl di- or tetra-hydrofurans, and then under reaction conditions of the type explained above in connection with analogous reactions.

The bis(2-methyl-3-furyl)-disulfide and the 2-methyl-3-furan-thiol according to the present invention can also be prepared by: (a) forming a mixture of thiamine, cysteine, hydrolysed vegetable protein and water and heating the mixture under reflux for a period from approx. 2 to approx. 10 hours, as specified in the U.S. patent no. 3 39^ 016, (b) by removing the distillate at regular intervals, (c) treating the distillate in an extraction process where a low-boiling solvent such as methylene chloride or the like is used as the extractant, whereby bis(2-methyl-3 -furyl)-disulfide and the 2-methyl-3-furanthiol of the present invention is obtained, and (d) separates the furyl-sulfur compounds from the mixture, e.g. by a gas-liquid chromatographic column or conventional column chromatography.

Due to their advantageous taste qualities, the following compounds are preferably used in the present taste preparations:

bis(2-methyl-3-furyl)-disulfide,

2-methylfuran-3-thiolJ

bis-(2,5-dimethyl-3-furyl)-disulfide,

2-methyl-[4,5H]-dihydrofuran-3-thiol, and

methyl (2-methyl-3-furyl)-disulfide.

The following examples illustrate the production of the new compounds used in the present flavor preparations.

Example I

Preparation of bis(2,5-dimethyl-3-furyl)-sulphide

and bis(2>5-dimethyl-3-furyl)-disulfide.

A 1-liter three-necked flask equipped with an addition funnel and magnetic stirrer was charged with 175 g of 2,5-dimethylfuran and 0.4 g of stannous chloride. After cooling to -20°C, 75.3 g of sulfur dichloride, SC12, was added during 33 minutes while the temperature was constantly maintained at -20°C. The reaction mixture was stirred for 1 hour 40 minutes and then heated to +34°C. The mixture was then dissolved in 1 liter of ice water, and an extraction with hexane gives, after drying over sodium sulfate and removal of the solvent, 64.8 g of residue. Column chromatography of this residue on 1625 g of silicic acid with 5% diethyl ether in hexane as eluent gives 14.4 g of a mixture of mono- and dis-sulphides. Distillation of 11.0 g of this mixture gives 3.8 g of bis(2,5-dimethyl-3-furyl)-sulfide, boiling point 81° - 85°C at 0.15 mm Hg, as well as 5.1 g of bis(2,5-dimethyl-3- furyl)-disulfide, boiling point 112° - 116°C at 0.45 mm Hg.

By repeating the above experiment, but using 98.5 g of sulfur monochloride, S2C12, instead of the aforementioned sulfur dichloride, 54.2 g of residue is obtained. Chromatography of 1355 g of silicic acid with 5% ether in hexane as eluent gives 13.9 g of mono- and di-sulphide. Distillation of 11.0 g of this mixture gives 1.96 g of the 40/60 mixture, as this could be determined by proton magnetic resonance spectrum (PMR) of mono- and di-sulphide, as well as 6.6 g of bis(2,5-dimethyl -3-furyl)-disulfide, boiling point 115°C at 0.45 mm Hg.

Data with regard to said bis(2,5-dimethyl-3-furyl)-sulphide are the following:

Proton magnetic resonance

In carbon tetrachloride:

2.2 (singlet, 6 protons)

2.3 (singlet, 6 protons) and

5.78 (singlet, 2 protons) ppm.

Infrared spectrum:

Mass spectrum

Both compounds give a soup mix a distinct meat flavor at a concentration of 0.2 ppm. Said bis(2,5-dimethyl-3-furyl)-disulfide is preferred, and both 3-furyl sulfides are preferred over bis(5-methyl-2-furyl)-disulfide, which was only found to have a rubbery chemical smell and taste under the same conditions.

Example II

Production of bis(2,5-dimethyl-3-furyl)-monosulphides

To a 25 mL three-necked flask, equipped with an addition funnel, magnetic stirrer, and ice bath, was added 9.6 g of 2,5-dimethylfuran and 1.104 g of stannous chloride. Then 2 g of sulfur dichloride, SC12, was added over 33 minutes at 0°C. The reaction mixture was then poured into 50 cm 3 of ice water, and the reaction mass extracted twice with 20 cm 3 of isopentane and once with 40 cm 3 of diethyl ether. After removing the solvent, fiddle approx. 3 g of a brown oil.

This brown oil tasted like roasted meat. Column chromatography on 50 g of silica with 5% ether in hexane as eluent gave 0.6 g of a substance with a distinct aroma of roasted or fried meat. Rechromatography of this material on 25 g of silica using hexane and then 1% ether in hexane as eluent gave 0.22 g of a mixture of 2,5-dimethyl-3-furyl monosulfide and 2,5-dimethyl-3 -furyl disulfide.

The resulting mixture of bis(2,5-dimethyl-3~furyl)-

sulfide and -disulfide were recovered after the combined solvents had evaporated. The sulfide and disulfide had a meaty aroma and a taste like that of cooked meat.

Example III

Preparation of bis(2,5~ dimethyl-3-furyl)-disulphide

A 500 cm^ wooden-necked flask equipped with a thermometer and addition funnel and cooled in an ice bath of acetone and dry ice was added 78.6 g of 2,5-dimethylfuran, 0.1 g of anhydrous stannous chloride and

3 3

100 cm hexane. Over 1 hour, 27 cm of sulfur monochloride, S 2 Cl 2 , was added while maintaining the temperature between -22°C and 0°C.

During the last 20 minutes a vacuum was applied to remove evolved hydrogen chloride gas.

After the reaction was finished, the reaction mass was completely

into 200 cm^ of ice water. Hexane-insoluble substances were filtered off, and the aqueous layer separated from the hexane layer. The hexane layer was washed with a volume of a 10% aqueous sodium bicarbonate solution and then with 100 cc of water. This was followed by washing with 200 cc of water, 5% aqueous sodium carbonate solution and 200 cc of water. The hexane solution was then dried over anhydrous sodium sulfate and filtered, after which the hexane was evaporated to give 21.9 g of a dark oil. On standing, a solid substance was precipitated from the aforementioned dark oil. The remaining oil was

dissolved in 50 cm^ of hexane and the hexane solution washed twice with 50 cm 3 of water and once with 100 cm 3 of water. After drying over sodium sulfate and removal of the solvent, 11.4 g of an oil were recovered.

10 g of this crude oil was dissolved in 5% diethyl ether i

hexane and subjected to column chromatography using a

column with a diameter of 5.5 cm and a length of 78 cm, packed with 200 g of silicon dioxide and where a mixture of diethyl ether and hexane was used as eluent. Analysis of 5.3 g of a product recovered from the column using proton magnetic resonance and infrared spectrum and mass spectroscopy confirms that bis(2,5-dimethyl-3-furyl)-disulfide had been produced. This substance had a distinct aroma of roasted meat and a taste of cooked meat.

Analytical data are the following:

Infrared:

Proton magnetic resonance: f

In carbon tetrachloride:

2.1 (singlet, 6 protons),

2.27 (singlet, 6 protons), and

6.0 ppm (singlet, 2 protons).

Mass spectrum:

Main peak 43,, molecular peak 254, other peaks in descending order: 127, 128 and 85.

Example IV

Production of furan-3-thiol derivatives

A 250 ml flask equipped with a mechanical stirrer, gas supply tube, calcium chloride, drying tube, thermocouple and Y-tube was added with 50 ml of distilled diglyme, and the diglyme was then saturated with gaseous hydrogen chloride at temperatures from 0-5°C below constant stirring.

The flask was then immersed in a dry ice-isopropanol bath at -80°C. It was then added 14.0 g (0.14 mol) of 2-methyl-3-tetrahydrofuranone, as well as 28.5 g (0.84 mol) of hydrogen sulphide which had been cooled to -80°C and which was slowly heated and boiled over in the reaction flask.

About. 1.5 hours after the hydrogen sulphide addition, got

a reddish color in the reaction mixture. After 2.5 hours, which was necessary to add all the hydrogen sulfide, the reaction mixture was orange. The stirring was then stopped and

the reaction mixture set aside for 16 hours.

A one-liter Erlenmeyer flask to which was added sufficient sodium bicarbonate to cover the bottom of the flask was then placed in a dry ice-isopropanol bath. The reaction mixture was then slowly poured over the sodium bicarbonate to reduce foaming. Additional sodium bicarbonate was added until all foaming stopped. The neutralized mixture was treated with 200 ml of water and quickly extracted with 100 ml of methylene chloride. The organic solution was dried and concentrated to give 39.5 g

of an oil. This was distilled under vacuum, whereby a first distillate was obtained at 73-80°C and 57 mm Hg, and a second distillate at 80-83°C at the same pressure. 25 ml of second distillate was dissolved in 100 ml of ethyl ether and extracted four times with 5 ml of a 5% aqueous sodium hydroxide solution to remove the red color. The basic fraction obtained was acidified with 11.2 cm 3 hydrochloric acid and extracted twice with 10 ml of ethyl ether, dried over sodium sulfate and concentrated.

This concentrate was then chromatographed to separate 2-methylfuran-3-thiol and 2-methyl-[4,5H]-dihydrofuran-3-thiol.

These thiols had a distinct aroma of roasted meat, and the taste and smell of furan-3-thiol was very similar to that found in the disulfide prepared in Example III.

Analytical data with regard to said 2-methylfuran-3-thiol are the following:

Infrared:

Proton magnetic resonance:

In carbon tetrachloride:

2.12 (doublet, 3 protons),

2.23 (doublet, 1 proton),

G,08 (doublet, 1 proton), and

7.04 ppm (doublet, 1 proton.

Mass spectrum:

Main peak: 43, molecular peak: 114, other peaks in descending order: 41, 45, 85, 47, 113, 71, 75, 74.

Example V

Preparation of bis(2-methyl-1-3-furyl)-disulphide

The thiols prepared as indicated in Example III were oxidized under mild conditions by dissolving 5 g of the thiol in 100 cm 3 hexane. The solution was placed in a 250 cm 2 flask equipped with a tube connected to an air source, a stirrer, and a heating device. Air was bubbled in at room temperature at a rate of 20 ml/min for 20 hours. The solvent was replaced as needed to maintain the original solution volume. At the end of the reaction, the solvent was evaporated and the resulting mixture was purified by column chromatography to give 3 g of bis(2-methyl-3-furyl)-disulfide.

This purified bis(2-methyl-3-furyl)-disulfide had a meat-like flavor of a cooked meat aroma when used in a soup concentrate at a concentration of 0.2 ppm. By way of comparison, it can be stated that 5-methyl-2-furyl disulphide at a concentration of 0.2 ppm in the same soup concentrate had only a rubbery taste and aroma.

Analytical data for said 3-furyl disulfide are the following:

Infrared:

Proton Magnetic Resonance:

In carbon tetrachloride:

7.14 (doublet, 2 protons),

6.25 (doublet, 2 protons) and

2.07 ppm (singlet, 6 protons)

Mass spectrum:

Main peak: 113, molecular peak: 226, other peaks in descending order: 43, 45, 51, 114, and 85.

Example VI

The following ingredients were homogeneously mixed at 25°C:

This mixture had an excellent flavor of roasted or fried meat when used in a soup concentrate at a ratio of 10 ppm.

Example VII

The monosulphide which was prepared as indicated in example I was dissolved in propylene glycol, whereby a 0.1% solution was obtained. This solution was used in an amount of 0.966 g and added to 7.3 g of a soup concentrate consisting of the following:

The resulting mixture was added approx. 250 cm^ of water, whereby a soup with an excellent meat flavor was obtained.

The preparation from example VI (0.005 g) also gives a soup with a good taste of roasted meat.

Example VIII

Half a gram of the soup concentrate from Example VII was emulsified in a solution containing 100 g of gum arabic and 300 g of water. The resulting emulsion was spray dried using a Bowen Lab Model dryer using 250 cubic feet of air with an inlet temperature of 260°C, an outlet temperature of 93°C and a rotation speed of 50,000 rpm. 12 g of the spray-dried material was mixed with 29.2 g of the soup concentrate from Example VII. The resulting mixture was then added approx. 250 cm^ of boiling water, and an excellent meat-flavored soup was obtained.

Example IX

The following ingredients were mixed as described in example VI, whereby a preparation with an excellent meat taste was obtained:

Example X

Isolation of bis(furyl) disulphides from a reaction mixture

A 1800 kg portion had the following composition:

and this was heated under reflux for 4 hours. After the first 45 minutes, a total of 160 liters of condensate was removed during the next three hours and 15 minutes. Each four liter portion of the condensate was extracted with 400 ml of methylene chloride. -After removing the methylene chloride under a very weak vacuum, a 50 ml residue was obtained which had a very strong flavor of roasted meat.

Thin layer chromatography (8 x 8 x 1.25 mm, silica gel G, 200 X/plate) of approx. 2.4 g, yielded 0.066 g of a pure compound with a very good roasted meat taste on suitable dilution. This compound had the following mass spectrum:

m/e (relative intensity):

225 (9.6), 227 (1.9), 228 (1.7), 113 (10.0), 43 (4.7), 114 (4.4), f 45 (3.6), 85 (3.1), 51 (2.9), 69 (17.6).

Proton magnetic resonance in carbon tetrachloride shows:

207 (singlet, 2-CCH,),

6.25 (doublet, 2-furyl protons), and

7.14 ppm (doublet, 2-furyl protons).

The above data are in very good agreement with the proposed structure for bis(2-methyl-3-furyl)-disulfide, which is as follows:

When the crude extract was analyzed by gas/liquid chromatography, a compound with a very intense smell of roasted meat was obtained. This compound was identified as 2-methylfuran-3-thiol.

Example XI

Preparation of 2-methyl-3~ furanthiol

A 500 cm^ wooden-necked flask equipped with a Y-tube, thermometer and stirrer was added with 32 g of fuming sulfuric acid (oleum) containing 20% SO^. The temperature was maintained at 24-28°C, after which 40 g (0.318 mol) of 5-methyl-2-furoic acid was slowly added over 45 minutes. After the addition was complete, the reaction mixture was stirred for an additional 2 hours and 15 minutes, and then allowed to stand for 16 hours.

The mixture was then poured over 600 cc of ice water and neutralized to pH 5 with 430 g of barium carbonate, and during this neutralization a thick paste formed. After adding 500 cc of water, the paste was boiled and vacuum filtered in a hot state. The barium sulfate-containing solids remaining after filtration were boiled with 700 cc of water and the mixture was vacuum filtered while hot. Both filtrates were combined and cooled for 2

day, whereby a number of crystals were obtained. The filtrate was evaporated to a volume of approx. 500 cm^ and cooled in ice, for recovery of additional crystals. The remaining filtrate was evaporated to a volume of 500 cc, after which 100 cc of methanol was added and the liquid cooled to produce crystals. The total yield of solid crystals (barium-2-methyl-3-sulfo-5-furoic acid) was 93.5 g.

Barium-2-methyl-3-sulfo-5-furoic acid in an amount of

98.2 g and 1800 cm of distilled water were added to a flask and this

was heated in a steam bath to 70°C until all solids were dissolved. Then 116 g of a 20% aqueous sulfuric acid was gradually added to precipitate the barium sulfate. The decanted liquid was cooled in ice and then filtered. Water was evaporated from the filtrate and the residue evaporated under high vacuum at room temperature, whereby 35.1 g of a yellow oil was obtained which crystallized after standing in a drying room overnight.

The sodium salt of the sulfofuroic acid was prepared by dissolving 33.1 g of the crystallized oil (sulfofuroic acid) in 100 cc of water and slowly adding 6.75 g of sodium bicarbonate.

After drying in a steam bath and then in a vacuum drying cabinet,

37.4 g of the sodium salt containing water of crystallization was obtained.

The sodium salt was decarboxylated by adding 13.2 g of mercuric chloride (-HgCl^) in 60 cm^ water to a 500 cm^ three-necked flask equipped with a condenser and a gas outlet tube, as well as a Y-tube, a nitrogen supply tube, a stirrer, and a heating jacket. Next, 11.1 g of the sodium salt of the sulfofuroic acid in 80 cc of water was added to the flask, followed by 1.95 g of sodium hydroxide in 20 cc of water. The mixture was boiled under reflux for 2 hours and 40 minutes, while the pH was maintained at 4-5 by adding aqueous sodium hydroxide or hydrochloric acid, as needed, and a strong evolution of carbon dioxide was obtained. The mixture was then cooled to room temperature and filtered. The filtrate was adjusted to pH 7-8 with 10% aqueous sodium bicarbonate solution, and hydrogen sulfide was bubbled through the mixture to precipitate mercury sulfide. This was separated by filtration, and the filtrate concentrated in a rotary evaporator. About. 30 cm 3 of water was added to dissolve all solids after concentration, and the mixture was cooled, whereby 4.93 g of 2-methylfuran-3-sulfonic acid was crystallized. The crystals were filtered off liquid and then dried.

The sulfonic acid derivative was converted to the sulfonyl chloride derivative by treating 1.3 g of the sulfonic acid with 33 g of thionyl chloride and two drops of dimethylformamide for 75 minutes at 25°C. The excess thionyl chloride was removed in a rotary evaporator,

and the residue washed with benzene, the benzene evaporated, yielding 0.88 g of an amber oil with a sharp, meaty taste.

The amber oil was then reacted with 0.8 g of lithium aluminum hydride in 30 cc of diethyl ether. The reaction was carried out by adding the hydride to 20 cm 3 ether, filtering, and then adding the oil to 10 cm 3 ether at reflux over 8 minutes. The reflux continued for another 75 minutes. The remaining hydride in the mixture was reacted with methanol in ether, and the product was poured into ice water, acidified to pH 1 with hydrochloric acid and then extracted with ether to give an oil. This oil was dried, filtered and purified from ether, whereby 0.27 g of a yellow oil with a good meaty aroma was obtained.

Proton magnetic resonance of the main peak obtained from this oil by gas-liquid chromatography shows a thiol. Mass spectroscopy of the compound shows peaks at 113 and 113-

These results confirm the production of 2-methyl-3-furanthiol.

Example XII

Preparation of bis-(2-methyl-3-furyl)-tetrasulphide

A flask containing a solution of 2-methyl-3-furanthiol (1.65 g) in ethyl ether (10 ml) and solid sodium bicarbonate (3.0 g) cooled to -30°C was added dropwise a solution of sulfur monochloride (1 .01 g) in ethyl ether (10 mL). After standing for 45 minutes, the reaction mixture was poured into 75 ml of water,

and the upper layer separated and washed with 25 ml of water. After extraction of the aqueous washing solutions with 25 ml of ether, the ether solutions were combined and washed twice with 30 ml of water until the pH of the wax solutions was approx. 5. The ether solution was dried over anhydrous sodium sulfate followed by removal of the solvent in vacuo to give 1.6 g of bis-(2-methyl-3-furyl)-tetrasulfide.

Column chromatography of the amber oil on 60 g of silica packed in hexane followed by elution with hexane,

gave 1.1 g of analytically pure bis(2-methyl-3-furyl)-tetrasulfide as a light yellow oil. This purified bis(2-methyl-3-furyl)-tetrasulfide

had a nice, meaty flavor when used in a soup-

concentrate at a concentration of 0.2 ppm.

Infrared:

X max.

3100

2900

1570

1510

1435

1380

122.5

1122

1086

938

887

730

645 cm ^.

Proton magnetic resonance in carbon tetrachloride:

2.37 (singlet, 6 protons),

6.38 (doublet, J=2Hz, 2 protons),

7.20 (doublet, J=2Hz, 2 protons).

Mass spectrum:

Main peak 43j molecular peak 290, other peaks in descending

order: 113, 45, 226, 114, 51, 85 and 69.

Elemental analysis: calculated for C^qH^qC^S^:

C 41.35, H 3.47, S 44.16

Found: C 41.52, H 3.38, S 43.77.

Claims (5)

1. Flavoring preparation for improving the meat flavor in foodstuffs, characterized in that it contains as active ingredient a furan derivative with the general formula: wherein the symbols are defined according to one of the following alternatives: (1) n is 1, R^ is hydrogen, B^ is methyl, R^ is hydrogen or methyl and the dashed line is a single or a double bond; (2) n is 2 or 3, R₂ and R₂ are methyl, R₂ is hydrogen or methyl, and the dashed line is a double bond; (3) n is 1,2,3 or 4, R is R2 and R^ are methyl, R^ and R^ are hydrogen or methyl and the dashed line is a single or double bond. 2. Preparation according to claim 1, characterized in that the furan derivative is bis(2-methyl-3~furyl)disulfide with Amaxved 3>22>6>32>6>60>7>22'llj28 and 13>6 p 1 infrar^ d spectrometry. 3. Preparation according to claim 1, characterized in that the furan derivative is 2-methylfuran-3~thiol with ^malcs at 3.92, 6.60, 7.26, 7.40 and 13.8 y in infrared spectrometry. 4. Preparation according to claim 1, characterized in that the furan derivative is bis(2,5-dimethyl-3-furyl)disulfide. 5. Preparation according to claim 1, characterized in that the furan derivative is methyl (2-methyl-3-furyl) disulfide.