GB1595141A - Use of acetals as aldehydes generators for flavourings - Google Patents

Abstract

An aldehyde is added in the form of an aldehyde generator chosen from the class consisting of: a) the linear acetals of formula <IMAGE> n is an integer between 0 and 5, or b) the vinyl ethers of formula <IMAGE> The substituents R, R1, R2, R3, R4 and R5 in these formulae have the meanings defined in Claim 1. This aldehyde generator is capable of releasing the desired aldehyde under the conditions of use.

Description

(54) USE OF ACETALS AS ALDEHYDE GENERATORS FOR FLAVOURINGS (71) We, HERCULES INCORPORATED, a Corporation of the State of Delaware, United States of America, of 110 Market Street, Wilmington, Delaware 19899, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a novel method of fixing aliphatic aldehydes by means of certain acetals which act as generators responding to the conditions of use in a food product to yield the desired aldehyde. This invention also relates to their use in flavors to generate the desired aldehydes.

It is well known that both acetaldehyde and propionaldehyde occur in a wide variety of fresh and prepared foodstuffs, such as fruit, meat, dairy products, baked goods and vegetables. Acetaldehyde has been found particularly important in contributing to the flavor impact and "fresh" effect of certain foodstuffs, especially of the citrus fruit and red berry types. As such, it is indispensable in compounding artificial flavors where the "fresh effect" is needed. The same can be said of propionaldehyde, which also contributes to the flavor of a wide range of fruit and food types.

Other aliphatic aldehydes, such as butyraldehyde, octylaldehyde, and the like, varying in carbon number from C-4 to about C-12, are known for giving impact and special flavor effects in a wide variety of flavors corresponding to their occurrence in nature in a wide variety of foodstuffs. For example, butyraldehyde occurs in apple, strawberry, milk, fish, beef, pork, beer, banana, cranberry, grape, peach, onion, potato, ginger, bread and blue cheese; 2-methyl propanal is found in potato, tomato, bread, blue cheese, milk, cacao, egg, fish, beef, pork and sherry; 2-methyl butanal is found in cacao, egg, fish, beef, beer, currant and olive; 3-methyl butyraldehyde occurs in cacao, fish, chicken, beef, beer, peanut, currant, olive, peach and mushroom; valeraldehyde occurs in milk, tea, fish, chicken, beef, pork, beer, cranberry, currant, grape, olive, mushroom, onion and potato; 2-ethoxy propanal occurs in rum, as does 3-ethoxy propanal; 3-methyl pentanal occurs in beer; 2-methyl pentanal occurs in onion; 2-ethyl butanal occurs in citrus and bread; hexanal occurs in banana, citrus, soy beans, milk, fish, chicken, beef, lamb, tea, cranberry, grape, olive, melon, peach, cucumber, mushroom, onion, potato and tobacco; heptaldehyde is found in citrus, cranberry, currant, grape, olive, peach and bread. Octaldehyde is found in bread, carrot, olive and citrus; nonyl aldehyde is found in banana, citrus, cranberry, milk, fish, beef, beer, tea, chicken, currant, melon, olive, carrot, ginger and bread; decanal occurs in bread, ginger, milk, fish, cacao, beer, cucumber, grape and citrus; undecyl aldehyde is found in citrus, milk, fish, beef and cucumber; while dodecanal is found in milk, fish, beef, citrus, grape and cucumber; cis-6-nonenal is found in melon and cucumber; and phenyl acetaldehyde is found in peach, beans, mushroom, mint and blue cheese.

Much effort has been expended in the last two decades, as attested by patent literature on the subject, to provide a stable "fixed" form of acetaldehyde which would release only under the desired conditions of use and not before. The main reasons for this difficulty in "fixing" acetaldehyde lies in its physical characteristics of being a gas at room temperature (210C.) under normal ambient conditions, being miscible with water, and having a high degree of chemical reactivity and instability.

Its chemical instability is exemplified by its tendency to polymerize or form paraldehyde and metaldehyde, oxidized to acetic acid, or combine chemically with itself and other materials in the presence of acid or base.

To accomplish fixation of acetaldehyde, workers have sought to entrap it in crystal defect or clathrate inclusion complexes of a variety of types, including those based on oligosaccharides or monosaccharides. The inclusion complex would release acetaldehyde under the conditions of use, such as when a dry beverage powder is dissolved in water. The drawback to this method, in general, is that only a small amount of acetaldehyde is fixed in stable form by these methods giving a large ratio of inclusion matrix to aldehyde which makes it quites expensive to use the aldehyde in this form. For example, Dame et al in U.S. Patent No. 3,314,803 presents a method for encapsulating acetaldehyde in a mannitol matrix. An initial acetaldehyde entrapment of 2 to 10% is realized upon spray drying the mannitolacetaldehyde mixture. When exposed to ambient conditions in the open, however, acetaldehyde is rapidly lost to the atmosphere and, within a few days, is reduced to a maximum long-term stable fix of between 1 and 2.5%. This loss of acetaldehyde from the matrix is even observed upon incorporation of the encapsulate in a food base, such as a dry beverage powder contained in a package, especially in the presence of small amounts of water or water vapor, either of which may be present in the food product base. itself or entrained during the normal packaging operations.

Other examples of polysaccharide inclusion matrices in the patent literature include a carbohydrate complex in U.S. Patent No. 3,625,709 by Mitchell, the use of arabinogalactan by Glicksman and Schachat in U.S. Patent No. 3,264,114, and the use of lactose by Knapp in U.S. Patent No.3,736,149. All of the latter methods suffer from the disadvantages of a low degree of acetaldehyde fixation. Moreover, they exhibit instability in the presence of small amounts of water or water vapor, which would be incurred upon storage in a non-hermetically sealed package, which is sufficiently permeable to allow atmospheric moisture to enter, or to the exposure incurred during normal processing and packaging operations.

Earle, in U.S. Patent No. 3,767,430, describes a method of "fixing" acetaldehyde in a sucrose crystal matrix but the amount of acetaldehyde is less than 0.1% and generally about 0.001 to 0.05%.

The second method of "fixing" acetaldehyde is that of chemical derivatization, which must satisfy several, often conflicting requirements, including that of chemical inertness and stability under the usual storage conditions, quick release of aldehyde upon mixing or preparing the food product for use, and the property of not interfering with the aroma or taste of the desired flavor. To satisfy the latter requirement the derivative and its conversion products, other than the target aldehyde, should be relatively odorless and tasteless.

Many attempts to provide suitable chemical derivatives for generating acetaldehyde are evinced in the patent literature. A variety of aldehyde derivatives have been proposed for generating acetaldehyde, including carbamates, carbonates, ureides, ethylidene compounds (U.S. Patent No. 2,305,620) and certain acetals (U.S. No. 3,857,964). All the aforementioned derivatives suffer from at least some of the disadvantages of produciiig off-tastes, being toxic, or being too stable to release at an appropriate rate in the desired foodstuff.

Use of well-known acetals of acetaldehyde, propionaldehyde, and other aliphatic aldehydes, up to about dodecylaldehyde, derived from monohydric alcohols, such as dimethyl, diethyl and dihexyl acetals, is precluded by the taste of the acetal itself, which is usually unacceptably different from the parent aldehyde, and thus interferes with the balance of the desired flavor, especially in the case of C, to C8 aldehyde acetals. Moreover, use of alcohols to make such acetal is limited to those having 1 to 5 carbon atoms, since those from C6 and higher, up to about C2, lend their own flavor and also distort the intended flavor.

It is the object of this invention to provide aldehyde acetals derived from polyols or high molecular weight monoalcohols which fulfill the major requirements of stability and of "fixing" aldehydes in flavors and flavored food bases, and of providing a quick-release effect under the conditions of intended use.

These acetals also do not interfere with the desired flavor, are stable to moisture, heat, and oxidation under normal conditions of storage, are capable of being incorporated into a dry flavor and remaining stable, and provide a higher percentage of stable, fixed acetaldehyde in a dry flavor or flavor base than has heretofore been found possible.

The acetals of the invention have the chemical formula

wherein (1) R is a 2 to 6 carbon multivalent hydrocarbon radical (which may contain an ether linkage); (2) n is an integer equal to or less than the valence of R, but at least two, with the exception that n may be 1 when the radical R- is substituted by the divalent radical

and in the case wherein n is less than the valence of R, the remaining valences of R are satisfied by functional groups selected from the class consisting of phenoxy, alkoxy, hydroxyl, acyloxy, carbalkoxy, carboxyl, alkylaryl, acetal and ketal groups and hydrocarbon radicals containing such groups; (3) R, is a hydrocarbon radical having 1 to 12 carbon atoms and (4) R2 is a hydrocarbon radical of 1 to 7 carbon atoms.

The acetals of the invention can be synthetized by reaction of the appropriate vinyl alkyl ether with the desired polyol in the presence of an acid catalyst as exemplified by the reaction of propylene glycol (I) with propenyl ethyl ether (II) to form Compound III structure (1 ,2-di[( 1 '-ethoxy)propoxylpropane)

The polyols found useful include propylene glycol, 1,3-propane diol, glycerine, mannitol, sorbitol, neopentyl, glycol, pentaerythritol and hexamethylene glycol, or other relatively bland polyols capable of forming a linear acetal through reaction with a vinyl ether and yielding an acetal in accordance with the invention as hereinbefore defined.

The structures depicted in Fig. 3 are additional, but by no means limiting, types of polyols, which can be employed. The molecular weight of the polyol has a practical limit in the weight of the parent acetal derivative relative to the amount of aldehyde which can be released. (ald) and (alc) are as previously described for structures in Figs. 1 and 2.

U on searching the literature for methods for synthesizing 1,2,3-tris[(l'- ethoxygethoxy]propane, it was found that the compounds had not been made even though there had been several attempts to do so. Russian workers published several papers on the reaction of ethyl vinyl ether with glycerol and the reaction ot glycerol trivinyl ether with alcohols: (a) M. F. Shostakovsky et al, Bul Acad. Sci., U.S.S.R., Div. Chem. Sci., 137 40 (1954) (b) M. F. Shostakovsky et at, ibid., 583-7 (1954) (c) M. F. Shostakovsky et al, ibid., 313-6 (1955) (d) M. F. Shostakovsky et al, ibid., 317-20 (1955).

Thus, 1,2,3-tris-9fl'-ethoxy)ethoxy]propane XI does appear in the literature as a target compound, but attempts at its synthesis have failed. It was said to be unstable, decomposing to give the dioxolane XII when reacting ethyl vinyl ether with glycerol under acid catalysis or when reacting glycerol trivinyl ether XIII with ethanol:

011 --OH -t i h, --OH Ref. a-.e , all t 1 Ref . d Ref Ref d Eto 0, v + EtOH XI xm AI Xm In both the syntheses employing glycerol trivinyl ether and ethyl vinyl ether, the reaction mixtures were allowed to reach their natural temperature upon combining all reagents. the exothermic reaction raised the temperature in each case to between 75 and 95"C. It has been found that, surprisingly, when the reaction temperature is kept below about 120"C. and the vinyl ether reagent is always maintained at about an equivalent molar ratio in relation to the moles of alcohol reactant, by concurrent addition of alcohol and vinyl ether, the formation of cyclic products is suppressed. Thus, by concurrent dropwise addition of four moles of ethyl vinyl ether and one mole of glycerine into a reaction flask containing hydrochloric acid catalyst and a solubilizing mixture made up of the dimethyl ether of di-ethylene glycol and trimethyl hexadecyl ammonium chloride, one is able to form Compound XI, which has not previously been synthesized. It has also been found that the analogous reaction can be successfully performed on other polyhydroxy compounds, such as propylene glycol, mannitol, sorbitol and the like to give the corresponding multilinear acetals. Since materials such as mannitol and sorbitol are not soluble in ethyl vinyl ether, the reaction can be facilitated by use of a nonreactive cosolvent for the polyhydroxy compound, such as dimethylformamide, hexamethylphosphoric triamide, dimethyl sulfoxide, or Nmethyl-2-pyrrolidone. The multilinear acetals derived from polyols to our knowledge are a new class of compounds heretofore inaccessible by known synthetic techniques. The above-described synthetic method has been used on glycerine to give the tris-linear acefal XI in 31% yield admixed with acetal XII which was obtained in 36.4% yield, or on propylene glycol to give the dilinear acetal XIV in 67% yield, and on mannitol in n-methyl-2-pyrrolidone solvent to give acetal XV in approximately 70% yield.

Example 1 4-[(1 '-Ethoxy), Ethoxy Methyl]-2-Methyl-l ,3-Dioxolane and 1,2,3-[(1 '-Ethoxy)Ethoxy] Propane Into a 2000 ml. flask, equipped with mechanical stirrer, heating mantle, thermometer, condenser and twin addition funnels, was added 5 ml. of 36% hydrochloric acid and 1.6 ml. of 50% trimethyl hexadecyl ammonium chloride in isopropyl alcohol. Next, 294.4 g. of glycerine (3.16 m.) and 921.6 g. of ethyl vinyl ether (12.8 m.) were added concurrently dropwise at a proportional rate over a onehour period between 23 and 39 C. The reaction mixture was homogeneous at this point and had turned yellow. The mixture was then held at reflux with stirring for an additional hour at 40"C. with mild heating. After standing at room temperature for 14 hours, the reaction mixture was then quenched with 10 g. of sodium carbonate with stirring. After distilling off lights to a pot temperature of 110"C. and a head temperature of 56"C. at 760 mm. Hg, the products were flash-distilled under the following parameters to give 588 g. of yellow oil containing 51.4% 1,2,3-tris-[(1'- ethoxy)ethoxy]-propane (31% yield) and 37.3% 4-[(1'-ethoxy)ethoxy methyl]-2methyl-1,3-dioxolane (36.4% yield): Pot. Temp. Head Temp. Vacuum 60-212 C 40-144 C 10-0.1 mm. Hg.

The flash distillate was rectified as follows on a l"x 1' Goodloe column, rated at about seven plates: Linear Time Pot Head Vacuum Weight Acetal Dioxolane (hr.) ( C.) ( C.) (mm. Hg) Fraction (g.) (%) (%) Comments 0 24 23 1.8 R.R.2:1 2.75 124 48 0.10 1 52.2 96.3 3.25 129 48 0.08 2 50.6 99.7 3.83 155 51 0.09 3 50.4 99.9 4.61 163 49.5 0.08 4 40.7 96.6 R.R. 20:3 5.36 167 58 0.08 5 30.5 97.5 5.72 170 78 0.08 6 13.7 46.7 6.14 171 92 0.13 7 13.3 14.6 6.61 178 98 0.10 8 17.8 64.6 7.76 184 117 1.0 9 57.9 98.1 8.08 207 102 0.11 10 38.3 99.5 R.R. 10:20 8.24 210 105 0.13 11 48.2 99.8 8.5 210 108 0.11 12 56.2 99.9 8.67 211 102 0.11 13 58.1 99.9 The purity of the acetals was determined by gas chromatography. For the 1,2,3-tris-[(1'-ethoxy)ethoxy]-propane, a 6'x" stanless steel column was used with 20% SE30 on acid-washed Chromasorb W packing, programmed from 135 C. to 220 C at 4 /minute, He flow~60 ml./minute, and for the 4-[(1'-ethoxy)ethoxy methyl]-2-methyl-1,3-dioxolane, 20% Carbowax 20 m. column was used, with the remaining parameters the same. "Chromasorb" and "Carbowax are registered Trade Marks".

Spectral and Physical Data (A) 1,2,3-tris [(1 '-ethoxy)ethoxy]propane 25 d-0.9561 n2D 1.4222 25 B.P. 117 C. at 1.0 mm. Hg; 1020C. at 0.11 mm. Hg NMR Spectrum Methyl protons (18H)-uneven quartet having its center of gravity at l.15x; monoalkoxy protons (1 lH)-broad multiplet having its center of gravity at about 3.48a; dialkoxy methine protons (3H)-broad multiplet having its center of gravity at about 4.678.

IR Spectrum (CCI4 solution) Strong ether C-O-C stretch bands at 1054 cm-', 1080 cm-', 1095 cm-', 1105 cm-', and 1133 cm-' (maximum intensity band in the spectrum).

(B) 4-[(1 '-ethoxy)ethoxy methyli -2-methyl-i ,3-dioxolane 25 d-- 1.0073 n20 1.4243 25 B.P. at 0.09 mm. Hg, 51 C.

NMR Spectrum Multiplet of sharp peaks (~6) having its center of gravity at 1.2#, 3 methyl groups, 9 protons; broad multiplet extendinfg from 3.1# to 4.3#, alkoxy protons, 7 protons; quartet centered at 4.66, linear acetal methine, 1 proton; quartet centered at 5.01a, dioxolane acetal methine, 1 proton.

IR Spectrum (CCI4 solution) Strong ether C-O-C stretch bands between 980 cm-' and 1200 cm-'.

Example 2 1,2-Di-[(1'-Ethoxy) Ethoxy] Propane Into a 250 ml. flask, equipped with condenser, static nitrogen head, mechanical stirrer, and two addition funnels, was charged 8 drops of 36.5% hydrochloric acid, 7 ml. of bis-(2-methoxyethyl) ether and 1 drop of 50% trimethyl hexadecyl ammonium chloride in isopropanol. There was then added dropwise from separate addition funnels concurrently at a proportional rate 43.3 g. of ethyl vinyl ether and 15.2 g. of propylene glycolat at 40C. over 23 minutes. Reflux was continued for two more hours at 40 C., mixture cooled, and 0.4 g. of solid sodium hydroxide added. The product was distilled directly after first removing light under vacuum. Distillation performed in a 14"x+10 mm. concentric tube column under the following parameters: Time Pot Temp. Head Temp. Vacuum Weight Product (hr) ( C.) ( C) (mm. Hg) Fraction (%) (%) Comments 0 22 20 5 Removal of lights 1.55 82 28 0.03 3 ml. collected 1.62 85 28 0.12 1 3.1 0.2 1 98 92 46 0.09 2 0.54 26 2.20 94 49 0.08 3 6.1 97 Discontinued 2.53 67 20 0.04 Restart 3.21 94 44 0.02 4 7.3 99.7 3.34 95 43 0.06 5 5.5 99.9 4.79 98 46 0.04 6 4.3 99 4.92 112 47 0.04 7 4.4 98 5.05 126 43 0.08 8 1.3 99 5.34 142 45 0.07 9 0.14 98 5.61 165 50 0.1 10 0.42 93 5.76 165 55 0.09 11 0.34 75 Yield: 29.5 g, 67.1% molar yield.

Spectral and Physical Data 25 d- 0.9153 nD20 1.4112 25 B.P. 470 at 0.04 mm Hg NMR Spectrum Multiplet with center of gravity at 1.18a, 15 protons, methyl groups; broad multiplet with center of gravity at 3.57a, 7 protons, hydrogens adjacent to one oxygen; broad multiplet centered at about 4.71S, 2 protons, acetal methine protons.

IR Spectrum Strong ether C-O-C stretch absorptions between 1020 cm-t and 1200 cm-' with maxima at 1061 cm-', 1087 cm-', 1104 cm-' and 1140 cm-'.

Example 3 1,2-[(1'-Ethoxy) Propoxy] Propane Into a 50 ml. flask, equipped with addition funnel, magnetic stirrer, thermometer and static nitrogen head, was charged 15 g. of propenyl ethyl ether, 5.1 g. of propylene glycol, 6.2 g. of bis-(2-methoxy ethyl) ether and 1 drop of 50% trimethyl hexadecyl ammonium chloride in isopropanol. Three drops of concentrated hydrochloric acid was added and the mixture stirred at between 41 and 43 C. for hours, cooled, and allowed to stand at room temperature overnight.

After heating at 40 C. for an additional 3 hours, the mixture was quenched with 4.5 g. of KOH. After removal of lights under vacuum, the product was distilled under the following parameters on a short path still: Time Pot. Temp. Head Temp. Vacuum Weight Product (hr.) ( C.) ( C.) (mm. Hg) Fraction (g.) (%) 0 23 22 0.48 49 25 0.4 2.35 83 62 0.08 1 0.42 52.5 2.42 84 63 0.08 2 1.54 95.1 2.52 89 65 0.09 3 2.36 98.9 2.69 114 64 0.05 4 1.41 98.6 Fraction 3 exhibited the following spectral data: NMR Spectrum Multiplet wxtending from 0.7# to 1.9# for methyl hydrogens and ethyl CH2 hydrogens-19 protons; complex multiplet extending from 3.1# to 4#, having a center of gravity of about 3.5# for protons alpha to only one oxygen-4 protons; multiplet (broad quintet) extending from 4.2(3 to 4.6(3 for acetal methine hydrogens-2 protons.

IR Spectrum (neat oil) Strong ether C-O-C stretch bands between 950 cm-' and 1200 cm-' with maxima at 973 cm-', 1034 cm-', 1065 cm-' and 1132 cm-'.

Example 4 1,2,3,4,5-Hexa-[(1'-Ethoxy) Ethoxy] Hexane Into a 250 ml. flask, equipped with static nitrogen head and magnetic stirrer, was charged 18.6 g. of mannitol, 100 ml. of N-methyl pyrrolidinone and 64.8 g. of ethyl vinyl ether. There was then added 10 drops of concentrated HCI and the mixture stirred at between 22 and 28 for 4.5 hours and allowed to stand overhightJ The next day an infrared spectrum of an appropriately worked up sample. showed the virtual absence of hydroxyl absorption and strong ether C+C bands. 'The reaction mixture was poured, with stirring, into 750 ml. of water containing excess NaOH and extracted twice with 150 ml. portions of hexane. Each extract was washed consecutively with two 750 ml. portions of water. The combined organic phases were dried over solid sodium carbonate-sodium sulfate and vacuum evaporated at about 10 mm. Hg to give 59 g. of crude oil. Distillation was performed on a short path micro still under the following conditions: Charge: 19 g. of crude+0.2 g. of Na2CO3.

Time Pot. Temp. Head Temp. Vacuum Weight (hr.) ( C.) ("C.) (mm. Hg.) Fraction (g.) 0 55 22 0.5 0.35 185 170 0.5 1 - 1.35 182 175 0.6 2 0.2 1.62 184 176 0.6 3 0.4 1.65 185 176 0.6 4 2.3 1.70 186 176 0.6 5 0.7 1.77 187 178 0.6 6 4.4 1.80 180 174 0.6 7 1.5 1.83 182 174 0.5 8 0.8 1.89 186 176 0.5 9 3.1 1.75 184 175 0.5 10 1.9 1.78 182 178 0.5 11 0.6 IR Spectrum (CCI4 solution) Weak, broad band at 3500 cm-' indicating some free hydroxyl; strong C-O-C ether stretch bands extending between 990 cm-' and 1200 cm-' with maxima at 1044 cm-', 1082 cm-', and 1136 cm-'.

NMR Spectrum (CCI4 solution, TMS reference) Non-symmetrical quartet extending from 1.06 to 1.4(3 with center of gravity about 1.25, methyl protons- 34.5 protons (theory 36); broad multiplet extending between 3.28 and 4.0a having a center of gravity about 3.6a, hydrogens on monoalkoxy substituted carbons, 20 protons; broad complex multiplet extending between 4.45a and 5.1(3, having its center of gravity at about 4.75a, acetal methine protons, 5.5 protons (theory 6.0). A spectrum run in CDCI3 showed the methyl to alkoxy to acetal methine proton ratios to be 33.9/20/5.9. A d4-MeOD exchanged spectrum changed the ratio to 32.8/20/5.7 while a d6-DOAc exchanged spectrum showed the ratios to be 34.9/20/5.9. Oximation analysis of acetal hydrolyzed at pH 3.5 in the presence of hydroxylamine showed 96.4% of the theoretical acetaldehyde to be generated, indicating no more than 20% of the sixth hydroxyl in the molecule to be free OH.

Example 5 A citrus drink was prepared at about 23"C. by combining 8 drops of a 1% solution of orange flavor in 95% ethanol and 14 ml. of citric syrup and bringing to volume with water in a 4 oz. container (about 114 g. of water was used). The orange flavor was orange terpenes containing 5% by weight of acetaldehyde. The citrus syrup was made by adding to 1 gallon of 67.5% sucrose in water, 14 ml. of a 25% by weight solution of sodium benzoate in wafer and 44 ml. of 50% citric acid in water.

The pH of this syrup is normally about 3.1. A third drink was formulated using, as the orange flavor, orange terpenes containing 12% of 4-(1'-ethoxy)ethoxymethyl-2- methyl- I ,3-dioxolane.

Out of a panel of five professional flavorists four determined the flavor differences to be small between the drinks and the fifth judged the generatorfortified drink to be better on a blind selection basis. On a re-test the following day with freshly prepared drinks, tested within 20 minutes to 1/2 hour of mixing, only one flavorist out of five was able to identify the fortified drink on a blind selection basis.

Example 6 Test (a) Citrus drinks were prepared in the same manner as in Example 5 using in Drink No. 1 a non-fortified orange flavor, in Drink No. 2 the same orange flavor fortified with 7.7% of 4-(1'-ethoxy)ethoxymethyl-2-methyl-1,3-dioxolane, and in Drink No. 3, 7.7% 1,2,3-tris[(l'-ethoxy)ethoxy]propane. Four professional flavorists were asked to rate the drinks in order of "freshness" effect with the following results: Test Time* Rating Flavorist 1 1--2 minutes Drink 2 > Drink l; > Drink 3 Flavorist2 2minutes Drink 2 > Drink l, > Drink 3 Flavorist 3 About 2 min. Drink 3 > Drink 1, > Drink 2 Flavorist4 About lOmin. Drink 2 > Drink 3, > Drink 1 *Time interval between mixing and tasting This test showed a predominant preference for the generator-fortified beverages.

Test (b) Two orange drinks were prepared for the method described for Test (a) whereby an orange flavor fortified with 8% 1,2,3-tris-[(l'-ethoxy)ethoxy]propane was compared to one without acetaldehyde or generator present. As in Example 5 and Example 6(a), the drinks were made up at ambient temperature, approximately 230C. Within two minutes after the drinks were prepared, all 4 professional flavorists stated their preference to be the generator-fortified beverage because of its "fresh-juice" effect.

Test (c) Two orange-flavored drinks were prepared as in Test (b). One drink was an orange flavor fortified with 8% 1,2,3-tris[(l'-ethoxy)ethoxy]propane and the other without generator or acetaldehyde. The water used to make up the beverages was pre-chilled to 100C. and the flavor oil in alcohol at 1% was added to the beverage after the citric syrup was mixed in. Again all 4 professional flavorists found the generator-fortified beverage within 2 minutes after mixing to be preferred as having a "fresh-squeezed" juice effect. Two of the flavorists found the effect noticeable within I minute.

Example 7 Hydrolysis Study on Various Acetals Test (a) 4-1 '-ethoxy)ethoxymethyl-2-methyl- 1 ,3-dioxolane The title acetal (0.224 g.) was dissolved in 50 ml. of dilute sulfuric acid at pH 3.0. The solution absorbence was measured by ultraviolet spectroscopy at 275A giving the following data points relative to theoretical acetaldehyde generation.

This test showed that essentially only the linear acetal portion of the molecule released at this pH and temperature: %Acetaldehyde Absorbence Generated Time Run 1 Run2 (min.) (Theor. 0.197) (Theor. 0.175) Run 1 Run 2 2 0.050 0.012 25.4 6.9 4 0.072 0.04 36.5 22.9 10 0.116 0.1 58.9 57.1 20 0.164 0.14 83.2 81.1 30 0.193 0.15 98.0 85.7 Test (b) 1,2,3-tris[(1'-ethoxy)ethoxy]propane In a manner similar to that used in Test (a), except that acetal was solubilized by using 10% ethanol, the title acetal was subjected to hydrolysis under various pH conditions. The results are tabulated below: Absorbence Run 1 Run 2 Run 3 (pH 3) (pH 3.5) (pH 3) % Acetaldehyde Generated Time (Theor. (Theor. (Theor. Run 1 Run 2 Run 3 (min.) 0.297) 1.75) 0.35) (pH 3) (pH 3.5) (pH 3) 1 - - 0.058 - - 16.6 2 0.033 - 0.061 1

Claims (1)

1. (min.) 0.354) 0.347) 0.358) 0.35) 0.356) 0.366)

   1 0.03 0.03 0.03 - -

   2 0.07 0.07 0.055 0.017 - 0.005

   4 0.15 0.145 0.114 0.041 0.068 0.012

   10 0.33 0.327 0.274 0.128 0.125 0.034 20 - - - 0.252 0.209 0.076 30 - - - 0.030 0.255 0.119 40 - - - - - 0.155 % Acetaldehyde Generated

   1 8.5 8.6 8.4 -

   2 19.8 20.2 15.4 4.9 -

   4 42.4 41.8 31.8 11.7 - 3.3

   10 93.2 94.2 76.5 36.6 - 9.3 20 - - ~100 72.0 58.7 20.8 30 - - - 85.7 71.6 32.5 40 - - - - - 42.3 WHAT WE CLAIM IS: 1. An acetal having the chemical formula

   wherein (1) R is a 2 to 6 carbon multivalent hydrocarbon radical (which may contain an ether linkage); (2) n is an integer equal to or less than the valence of R, but at least two, with the-exception that n may be I when the radical R is substitued by the divalent radical

   and in the case wherein n is less than the valence of R, the remaining valences of R are satisfied by functional groups selected from the class consisting of phenoxy, alkoxy, hydroxyl, acyloxy, carbalkoxy, carboxyl, alkylaryl, acetal and ketal groups and hydrocarbon radicals containing such groups: (3) R, is a hydrocarbon radical having 1 to 12 carbon atoms and (4) R2 is a hydrocarbon radical of I to 7 carbon atoms.

   2. 1 ,2-dit( 1 '-ethoxy)ethoxylpropane.

   3. 1 ,2,3-tris[( 1 '-ethoxy)ethoxy]propane.

   4. 1,2,3,4,5,6-hexa[(1'-ethoxy)ethoxy]hexane.

   5. 1,2-di[(1'-ethoxy)propoxy]propane.

   6. 1,2-di[(l '-butoxy)ethoxy]propane.

   7. In the method of enhancing the flavor of a foodstuff by the incorporation of an aldehyde thereinto, the improvement that comprises adding to the said foodstuff an acetal as claimed in any one of Claims 1 to 6.

   8. An acetal as defined in Claim 1 substantially as described herein.

   9. A method of enhancing the flavor of a foodstuff according to Claim 7 substantially as described herein and exemplified.

   10. A foodstuff, the flavor of which has been enhanced by the method of Claim 7 or Claim 9.