Chocarom Pyrazine: A Remarkable Pyrazine for Flavors and

Chapter 13

Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: July 21, 2005 | doi: 10.1021/bk-2005-0908.ch013

Chocarom Pyrazine: A Remarkable Pyrazine for Flavors and Fragrances 1

1

2

Michael Zviely , Elias Abushqara , and Danny Hodrien 1

2

Frutarom Ltd., 25, HaShaish Street, Haifa 26110, Israel Flavors Division, Frutarom UK, 3 Henson Way, Kingsthorne Park, Kettering NN16 8PX, United Kingdom

Chocarom Pyrazine is a colorless transparent liquid consisting of an isomeric mixture of 3,5-dimethyl-2isobuty lpyrazine and 3,6-dimethy 1-2-isobuty lpyrazine. Chocarom Pyrazine isomers were isolated from several natural sources, e.g. skin and flesh of potato cultivars after baking. The odor threshold of 3,5-dimethyl-2isobutylpyrazine and 3,6-dimethyl-2-isobutyl-pyrazine indicates a relatively low φ value. The odor and flavor of Chocarom Pyrazine is reminiscent of the warmth of cocoa and hazelnut. It is slightly musky, animalic, with patchouli and vetiver tones and a mentholic note. The main uses of Chocarom Pyrazine for food are for chocolate, cocoa, baked goods, breakfast cereals, milk products, roasted and processed vegetables, soups, baked potatoes, sweet sauces and mint flavors. This unique pyrazine can be used fragrances. It has a very unique value in fragrance compositions. It imparts a strong and natural, original and long lasting effect. A beautiful tool for women's as well as men's fragrance creations, it boosts woody notes, chypre, oriental and fougere. It is also very useful in floral accords for providing depth and warmth.

© 2005 American Chemical Society

In Natural Flavors and Fragrances; Frey, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2005.

189


190 Pyrazines are materials obtained from Maillard reactions as byproducts of the browning reaction of sugars and proteins or amino acids. These reactions occur during roasting, cooking, baking, etc. of different food products. Pyrazines are among the most widely distributed heterocyclic compounds in nature, and often combined with other functional groups e.g. alkyl, acetyl, alkoxy and thioalkoxy. Pyrazines containing these chemical functionalities are present mainly in roasted products, generally thermally treated, including cocoa, coffee, barley, popcorn, peanuts, other nuts, bread, potato and beef. Over seventy pyrazines containing only alkyl groups have been identified in heated foods (/). Alkylpyrazines, which are important flavor contributors, among other flavor compounds in chocolate flavor, are formed via the Maillard reaction during the roasting process of cocoa production (2). Many of the pyrazines have a nutty aroma similar to that of peanuts (5). The importance of these materials motivated organic chemists to synthesize and use them in the flavor industry as ingredients in flavor formulations for roasted nuts, chocolate, meat flavors, etc. B y 1970, the first pyrazines obtained G R A S status in the U S , for use as flavoring substances, and today many pyrazines are commercially available for food applications.

Results and Discussion Chocarom Pyrazine is a colorless transparent liquid consisting of a 1:1 isomeric mixture of 3,5-dimethyl-2-isobutylpyrazine and 3,6dimethyl-2-isobutylpyrazine, as shown in Figure 1. Relevant C A S numbers are [38888-81-2] for dimethyl-isobutylpyrazine (positions not defined), and [70303-42-3] for 3,5-dimethyl-2-isobutyl-pyrazine.

3,5-dimethyl-2-isobutylpyrazine

3,6-dimethyl-2-isobutylpyrazine

Figure I. Chocarom Pyrazine isomers



191 Chocarom Pyrazine isomers were isolated from the skin and flesh of potato (Solanum tuberosum L.) cultivars after baking (4). 3,5[2,5-dimethyl-3-(2-methylpropyl)Dimethyl-2-isobutylpyrazine pyrazine] was isolated by Oruna-Concha, Craig, Duckham and Ames from the following potato cultivars - Cara, Nadine, Flanna and Marfona. 3,6-Dimethyl-2-isobutyl-pyrazine [3,5-dimethyl-2-(2methylpropyl)pyrazine], was found by the same team in Cara and Marfona potato cultivars. 2,5-Dimethyl-3-isobutylpyrazine was also detected by Welty, Marshall and Grun in chocolate ice cream prepared from cocoa flavor (5). Both pyrazines were also found as key odorant compounds in dark chocolate by Counet, Callemien, Ouwerx and Collin (6). The role of amino acids in alkyl-substituted pyrazines formation in model systems containing pyruvaldehyde was examined by Mea (7). 2,5-Dimethyl-3-isobutylpyrazine was formed in the model system with valine. Both isomers were prepared synthetically by Chen (8) by reacting acetol, isobutyraldehyde and ammonium acetate, with low yield of 22.3%. Subsequent proprietary work by the author has improved the yield to 65%. The odor threshold of 3,5-dimethyl-2-isobutylpyrazine and 3,6dimethyl-2-isobutyl-pyrazine was published by Wagner, Czerny, Bielohradski and Grosh, to be >2000 ng/1 air (9), which indicates a relatively low φ value (77), of only ca. 82,000. The odor and flavor of Chocarom Pyrazine is reminiscent of the warmth of cocoa and hazelnut. It is slightly musky animalic, with patchouli and vétiver tones and a mentholic note. The odor character is displayed graphically in Figure 2.

Chocoiate Woody

Patchouli

Figure 2. Radar organoleptic description of Chocarom Pyrazine


192 The main uses of Chocarom Pyrazine for food are for chocolate, cocoa, baked goods, breakfast cereals, milk products, roasted and processed vegetables, soups, baked potatoes, sweet sauces and mint flavors. Table I. Acceptable Daily Intake for Chocarom Pyrazine (10)


Food Category

Baked Goods Breakfast Cereals M i l k Products Processed Vegetables Seasonings & Flavors Soups Sweet Sauce

PADI Anticipated Anticipated Mean M a x i m u m mg/person/d Consumption Usual Use Use Level Level ** g/day* (ppm) (ppm) 137.2

1.5

2.0

0.21

20.0 39.5

1.5 2.0

2.0 3.0

0.03 0.08

85.0

0.5

1.5

0.04

0.01 31.7 6.8

5000 0.5 2.0

10000 1.5 3.0

0.05 0.02 0.01

* Based on MRCA mean frequency of eating and USDA mean portion size **PADI, mg/person/day calculated by: (Mean consumption, grams/day) χ (Anticipated Usual Use Level, ppm) χ 0.001 REFERENCE: Market Research Corporation of America (MRCA), in conjunction with the "Food intake and nutritive value of the diets of men, women, and children in the United States, Spring 1965", a preliminary report by the consumer and Food Economics Research Division, Agricultural Research Service, United States Department of Agriculture

Chocarom Pyrazine is a rich chocolate building-block for bakery, dairy products confectionery and ice-cream flavors. The recommended dosage is 500-3000 ppm in the final product, as described in Table I. Chocarom Pyrazine has a unique value in fragrance compositions; It imparts a strong and natural, original and long lasting effect. Chocarom Pyrazine is a beautiful tool for women's as well as men's fragrance creations. It boosts woody notes, chypre, oriental and fougère. It is also very useful in floral accords for providing depth and warmth. One of the most impressive perfumery creations using Chocarom Pyrazine is Tonkinarom, a fragrance base which has the following In Natural Flavors and Fragrances; Frey, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2005.

193 olfactive profile: animalic, macrocyclic, and polycyclic-free musk. It is very unique due to the utilization of Chocarom Pyrazine that provides a typical effect of the musk absolute from the pouches of the Musk Deer. Tonkinarom was formulated in 2 variations, the second being free either of animalic derived components or polycyclic musks.


φ Value of Chocarom Pyrazine The φ value of flavor and fragrance ingredients, provides a better appreciation of the odor intensity of a single molecule, taking into consideration its molecular mass (MM). It is analogous to ε value in UV/vis data of individual molecules. The φ value of a single molecule is defined as following: _ ψ

MM X l 0

3

Threshold ( p p m )

The subsequent table (Table II) lists the φ values for commercially important pyrazines.

some

Table II. φ Values for Some Commercially Important Pyrazines

SUBSTANCE 2-Methylpyrazine 2,3-Dimethylpyrazine 2,5-Dimethylpyrazine 2,6-Dimethylpyrazine 2-Ethylpyrazine 2-Ethy 1-5 -methylpyrazine 2-Ethyl-6-methylpyrazine 2,3,5-Trimethylpyrazine 2-Methoxy-3 -methylpyrazine 2-Methoxy-3-isobutylpyrazine 2-Acetylpyrazine 3,6-Dimethyl-2-isobutylpyrazine 3,5 -Dimethy 1-2-isobutylpyrazine

MOLECULAR MASS 94.11 108.14 108.14 108.14 108.14 122.16 122.16 122.16 124.14 166.22 122.13 164.25 164.25

φ VALUE 941 3,090 60,078 72,093 18,023 732,989 1,221,600 305,400 24,828,000 831,100,000 1,969,839 82,125 82,125

As seen in the table, both Chocarom Pyrazine isomers, i.e. 3,6dimethyl-2-isobutylpyrazine and 3,5-dimethyl-2-isobutyl-pyrazine, have φ values of ca. 82,000, thus belonging to the low φ value pyrazines group. This characteristic shows more clearly the pyrazines odor impact, as shown in the following graphs of low, medium and In Natural Flavors and Fragrances; Frey, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2005.

194


high φ value pyrazines. Low odor impact pyrazines are defined as having φ values up to 250,000) e.g. 2,5-dimethylpyrazine; medium odor impact pyrazines have φ values of 250,000 to 5,000,000, e.g. 2acetylpyrazine and high impact odor pyrazines, e.g. 2-methoxy-3isobutylpyrazine, having φ value of 24,828,000. This concept is shown also by Figures 3 - 6 .

200001800016000 14000η 12Ό00100008.0006-000Φ0000

2-Me

Pyrazine

2

,3-Me 2

2

-Et

Figure 3. Low φ value pyrazines

350000300000250000 200000 15000010000050000-

a

02-Et

2.5"Me2

2.6"Me2

3" i B u "2«5- 2- i B u "3»5- 2'3-5'Me3 Μβ2 Μβ2

Figure 4. Medium-Low φ value pyrazines


195

2-500000 2Ό00000 1.500000


1-000000 500000

—

ο -I—•

1 — ι — I

2~Et-5-Me

L — , — ι E

2" *"6"

Me

2"

Ac

FigureS. Medium-High φ value pyrazines

—

9000000001 800000000

1

700000000 600000000 500000000 400000000 300000000 200000000 100000000 ο

-I

•'·•" '· 2-MeO-3-Me

—•—.

•

1

2"MeO-3-iBu

Figure 6. High φ value pyrazines


196 Physical Data of Chocarom Pyrazine Chocarom Pyrazine is a colorless transparent liquid, insoluble in water. In ethyl alcohol 50% it is soluble from 1:1 to 1:10. Boiling Point: 73-75°C at 2 mmHg Flash Point: 75°C (cc) Specific Gravity D : 0.924 - 0.934 Refractive Index n : 1.489 - 1.494 20/20

20


D

Stability Data of Chocarom Pyrazine Chocarom Pyrazine was kept at 15°C for 55 days in order to measure changes in its physical parameters and odor profile. The color changed to 70 ΑΡΗ A (40 A P H A start point); no change was seen in other physical parameters and odor profile. In another experiment Chocarom Pyrazine was kept at 40°C for 22 days. The color changed to 70 A P H A (40 A P H A start point); no change in other physical parameters and odor profile. Analyses of Chocarom Pyrazine The structure and composition of Chocarome pyrazine was elucidated by a combination of G C , M S and N M R analyses (Figures 7 and 8 and tables III - VI). The substitution pattern of 3,5-dimethyl-2isobutylpyrazine and 3,6-dimethyl-2-isobutyl-pyrazine was elucidated by a combination of N M R methods, especially in mixtures by gradient selected H , N H M B C experiments at natural abundance level (II). Since the N - N M R spectrum of pyrazines was proven to be a powerful tool for their structural elucidation (12, 13) it is used to study these type of molecules. Tables V and V I details the N - N M R chemical shift of both nitrogen atoms of each isomer: !

1 5

l5

l5

Conclusion Chocarom Pyrazine is a remarkable pyrazine for flavors and fragrances. The diverse organoleptic characteristics of this outstanding pyrazine, having the warmth of cocoa and hazelnut. It is slightly musky-animalic in character, with patchouli and vétiver tones and a mentholic note, enabling its use as an important building block in perfumer and flavorist imaginations for preparing innovative formulations.



197

ï ο

S

ο

.1



sooooo

1oooooo

-I 5 0 0 0 0 0

300ΌΟΟΟ

250000O

3000000

3SOOOOO

4000000

4SOOOOO

soooooo

S500000

GOOOOOO

I 275

1 OO

t t

Ο

1 20

33 1 30

f

min): OHOG-F»YF*. Ο

Figure 8. MS of Dimethylisobutylpyrazine

Scan

I

Chocarom Pyrazine: A Remarkable Pyrazine for Flavors and

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