CA1057769A - Flavoring agents - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Flavoring agents, a method of imparting to foodstuffs a pleasant buttery caramel flavor and aroma by adding thereto a lower alkyl enol ester such as an acetate ester of aliphatic and alicyclic .alpha.-diketones.

Description

10577~9 The present invention relates to flavoring agents.
Numerous reports have been made concerning keto-enol tautomerism. In one particular study by J. Gerbier, Comptes Rendus dus Congres des Societes Savantes Dept., Section des Sciences, 87, 301 (1972), a comparison was made concerning the enolization of 2,4-pentanedione. Gerbier reported that enolization occurred or 2,4-pentanedione but that only one C-O group was enolized in each molecule, concluding that the hydrogen atom participating in enolization came from a CH2 group ~ituated between the two C=O groups.
Contrary to the Gerbier studies, it has been found that alicyclic and aliphatic ~-diketones ~uch as 2,3-pentanedione which are devoid of CH2 groups between the C=O group~ can be enolized under specific conditions. The resulting enol forms have a buttery caramel flavor and aroma but due to their instability are limited as to their use as flavoring agents. However, when these compounds are stabilized by silylation or acetylation, stable flavoring and aromatizing agents are derived.
According to one aspect of the invention there is provided a stable buttery caramel flavoring composition having as a principal flavoring component a lower alkyl ester of the enol form of an alicyclic or aliphatic ~-diketone selected from the formula:
~ CH2)n ~ H
H-(CH2)m - ~ ~ C = ~

~ R

wherein:
a) R represents a lower alkyl; and b) m and n are integers from 0 to 5 provided that where the ~-diketone is alicyclic, m is 1 and n i8 1.
According to another aspect of the invention there is provided an artificially buttery caramel flavored foodstuff lV5~7tj5~
comprising a foodstuff and lower alkyl ester of the enol form o an aliphatic or alicyclic ~-diketone selected from the formula:
~ CH2)n H
H-(CH2) - ~ - C ~ ~
_ ~ - R

wherein:
a) R represents a lower alkyls and b) m and n are integers from 0 to 5, provided that where the -diketone is alicyclic, m is 1 and n is 1, the ester flavoring composition being present in an amount effective to impart a buttery caramel flavor to the foodstuff.
According to a further aspect of the invention there i~
provided a method of flavoring a foodstuff which comprise~ adding to the foodstuff lower alkyl ester of the enol form o an aliphatic or alicyclic a-diketone selected from the formula:
~ CH2)n H
H-(CH2)m ~ ~ ~ C = ~

- ~ - R

wherein:
a) R represents a lower alkyl; and b) m and n represent integers from 0 to 5 provided that where the ~-diketone is alicyclic, m is 1 and n is 1, the ester beinq added to the foodstuff in an amount effective to impart a buttery caramel flavor to the foodstuff.
According to a further aspect of the invention there i8 provided a silyl ether of an aliphatic or alicyclic ~-diketone selected from the formula:
~ CH2)n ~ H
H-(CH2)m ~ ~ --``ff _ ~ - R

_~_ wherein:
a) R represents a lower alkyl; and b) m and n represent integers from 0 to 5 provided that where the ~-diketone is alicyclic, m is 1 and n is 1.
According to a further aspect of the invention, there is provided a method of enolizing aliphatic and alicyclic ~-diketones which comprises injecting the ~-diketone into a gas chromatograph having an injection port temperature of at least 300C. and maintaining the injection port temperature at least 300C. until the pure enol elutes therefrom.
According to a further aspect of the invention, there is provided a method of enolizing aliphatic and alicyclic ~-diketones which comprises combining the ~-diketone with an acid to form a mixture, heating the mixture to derive the resultant enol and extracting the enol from the mixture with a non-polar solvent to form an enol extract.
The pleasant, buttery caramel flavor and aroma of these compounds was first discovered when the enol form of

2,3-pentanedione, i.e., 3-hydroxy-3-penten-2-one was isolated from a coffee aroma concentrate. When converted to its stable trimethyl silyl ether or acetate ester, 3-penten-2-one, 3-hydroxy acetate, two new compounds which demonstrate the desirable buttery caramel flavor and aroma of the unmodified enol are derived. The acetate esters are preferred where the compounds of this invention are to be employed in foodstuffs.
Therefore, reference will henceforth be made principally to the use of the acetate esters when speaking in terms of incorporat-ing the compounds of this invention into foodstuffs.

~ _3_ ~0577~9 Due to the fact that the acetate esters of these alicyclic and aliphatic ~-diketones are stable as pure liquids or in non-polar solutions, the flavoring agents of this inven-tion find application as flavoring agents incorporated into liquid or non-polar solvent carriers for use in dry, and liquid foodstuffs in -3a-1(~577~9 which a natural buttery caramel or butterscotch flavor is desired. The amount to be added depends both on the system and the degree of flavor and aroma desired.
The acetate esters of the present invention are described in the formula:
(&H2)n H
H-(CH2)m - f f = ~
b I , ~ R
~ I
wherein n is an integer from 0 to S; m is an integer from 0 to 5 and R is a lower alkyl provided that where the ~-diketone is alicyclic, n is 1 and m is 1.
Representative of these compounds are l-buten-3-one, 2-hydroxyacetate; 3-hexen-4-one, 3-hydroxy acetate; 3-penten-2-one, 3-hydroxy acetate; cyclohex-1-en-2-one, 1-hydroxy acetate, 3-hexen-4-one, 3-hydroxy butyrate; 3-penten-2-one,

3-hydroxy butyrate; cyclohex-1-en-2-one, l-hydroxy butyrate;
3-hexen-4-one, 3-hydroxy propionate; 3-penten-2-one, 3-hydroxy propionate; cyclohex-1-en-2-one, and l-hydroxy propionate. In the interest of succinctness and clarity, reference will hence-forth be made principally to the preparation and use of 3-penten-2-one, 3-hydroxy acetate a new compound, but it is not wished to restrict this invention to this compound.
Generally, the enol form of an aliphatic or alicyclic a-diketone devoid of CH2 groups may be prepared by three methods. The ~-diketone preferably having been redistilled, may be injected directly into a gas chromatograph having an injection port temperature of at least about 300C., the higher ~ _4_ ~( lOS7769 temperature helping actually to form the enol. Although this method is the most direct in terms of obtaining the pure enol, the amount of enol derived is necessarily small due to injec-tion of the pure ~-diketone and such method may not therefore be preferred where large amounts of the enol are desired.
Secondly, the ~-diketone may be -4a-1~S'~'769 enolized at lower temperatures by combining the same with an acid such as hydrochloric acid or sulfuric acid, heating the mixture to about 100C. to 125C. and extracting the enol from the cooled mixture by means of a non-polar solvent. The pure enol may subsequently be isolated from the extract by distilla-tion or gas chromatography. The injection port temperature need not be as high as 300C. in this instance since the enol is already formed and therefore conventional methods of gas chromatography may be employed. The third method is the direct obtention of the enol ester of the a-diketone by the acid cat-alyzed reaction of the a-diketone and an acetylating agent.
Some of the acids which may be employed are for example, tri-fluoroacetic acid, methyl sulfonic acid, p-toluenesulfonic acid, boron trifluoride etherate and the like. Similarly, exemplary of the acetylating agents are isopropenyl acetate and acetic anhydride. This method is preferred over the previously mentioned methods since it affords a means of deriving the acetate esters of the present invention by the concurrent enolization and acetylation of the a-diketones. As mentioned previously, the enols of this invention are unstable and there-fore require subsequent or concurrent conversion to their stable acetate ester or trimethyl silyl ether forms, the acet-ate ester being preferred where the stabilized enol is to be employed in a food or beverage system.
A detailed explanation of the preparation of the enol form of a-diketones, methods totally new to the art, and the subsequent stabilization of the same to the silyl ether and acetate ester follows. Although methods of purification are also discussed, purification of the reaction product is not ~ _5_ ~57769 necessary in order that the buttery notes of these compounds be demonstrated. However, where the acetate esters are to be in-corporated into foodstuffs, purification is preferred. It should be apparent to those skilled in the art that obvious variations in both the concentrations of the reactant materials and the operating con--5a-ditions employed in the methods of preparing the silyl ether and acetate ester from the enol may be made without appreciably affecting the final product or the inherent qualities of the same.
EXAMPLE I
100 Mg portions of redistilled 2, 3-pentanedione are injected into a Perkin-Elmer Model 800 (Trademark) gas chromato-graph with a flame-ionization detector and effluent splitter, and dual stainless steel columns (1/8" x 6') packed with 15%
OV-101 on Anakrom ABS (Trademark), 80/90 mesh size.
The operating conditions are as follows:
a) Injection port temperature is maintained at 300C. to 350C.
b) the column temperature is 4 minutes at 70C., then programmed to 300C. at 5/minute;
c) the detector temperature is 300C.;
d) helium flow rate, 30 ml/minute;
e) hydrogen, 30 psi;
f) air flow rate, 360 ml/minute.
g) The component elutes at 3.5 minutes and contains mainly enol form and has a caramel-buttery aroma. It is collected into a melting point tube cooled with dry ice. The collected material is dissolved in a small amount of Freon 113 (Trademark) and the enol form is purified by rechromatography of the Freon solution on a Perkin-Elmer Model 900 gas chromato-graph, with a flame ionization detector and effluent splitter, and dual stainless steel columns (1/8" x 6') packed with 15%
stabilized DEGS on Anakrom ABS, 80/90 mesh size. The operating conditions of the second purification process are as follows:

~ -6-l~)S'~7~i9 Injection port temperature, 180C.; column temperature, 50 to 175C. at 2.5/minute; detector temperature, 180C., helium flow rate, 17 ml/minute; hydrogen, 22 psi; air flow rate, 54 psi. The injection port temperature is kept at 175-180C. in order to prevent thermal degradation of the enol form at higher temperatures. The pure enol (Rt of 12.9 minutes) is trapped into a melting point tube as described above.

-6a-lOS'7~7f~
The un-enolized 2,3-pentanedione elutes at 5.8 minutes.
EXAMPLE II
2,3-Pèntanedione is enolized to 3-hydroxy-3-penten-2-one by mixing with hydrochloric acid in a ratio of 2:1 by weight of the ~-diketone to HCl in a closed container. The mixture is heated at about 110C. for about an hour. After being cooled to room temperature, the mixture is extracted with Freon 113. The enol form in the extract is then isolated by GC
having an injection port temperature maintained at between about 300C. and 350C.
EXAMPLE III
3-Penten-2-one, 3-hydroxy acetate is prepared by combining 2,3-pentanedione with acetic anhydride and p-toluensulfonic acid, the amount of anhydride being about 1-1/2 to 4 times the concentration of acid on a molar basis. The mixture is cooled for about 1/2 hour. The reaction mixture is allowed to stand at room temperature after the initial cooling for a moderately long period, usually about 16 hours. The mix-ture is thereupon cooled for a second time and water is added.
The cooling source is removed after about one hour and after about 3 hours, the reaction mixture is diluted with ether. The ether layer is washed with water, 5% sodium bicarbonate and water. The ether extract is dried over sodium sulfate and is then concentrated and distilled. The product is subsequently purified by gas chromatography on a 15% SP-2100 column 1/8" x 12', programmed between 80C. and 175C.
EXAMPLE IV
The pure 3-hydroxy-3-penten-2-one of Example II is converted to its stable silyl ether form with hexamethyl-~ 7_ 1()5'77~

disilazane and trimethylchlorosilane immediately after GCisolation. The silyl ether is then separated from the excess reagents by chromatographing on the P-E 900 with 15% DEGS
column. It has a retention time of 10.7 minutes under the con-ditions previously described.

-7a-

Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A compound selected from the group consisting of the acetate ester of the enol form of 2,3-pentanedione and the trimethyl silyl ether of the enol form of 2,3-pentanedione.

2. A compound according to Claim 1, wherein the acetate ester is 3-penten-2-one, 3-hydroxy acetate.

3. A compound according to Claim 1, wherein the silyl ether is the trimethyl silyl ether of the enol of pentane-2,3-dione.