Tequilas: Charm Analysis of Blanco, Reposado, and Anejo Tequilas

Chapter 6

Tequilas: Charm Analysis of Blanco, Reposado, and Anejo Tequilas 1

Mercedes G. López and Jean Pierre Dufour

2

Downloaded by UNIV OF ARIZONA on December 21, 2012 | http://pubs.acs.org Publication Date: March 1, 2001 | doi: 10.1021/bk-2001-0782.ch006

1

Unidad de Biotecnología e Ingeniería Genética de Plantas, Centro de Investigación y de Estudios Avanzados del IPN, Unidad Irapuato, Apartado Postal 629, Irapuato, Gto. 36500, México Food Science, Otago University, Dunedin, New Zealand 2

Tequila is a Mexican alcoholic beverage obtained from Agave tequilana Weber var. azul that requires from 8 to 12 years to mature. Traditionally, raw agave pines are cooked, fermented, and double distilled to produce Blanco, Reposado, and Añejo tequilas. Recently, some important tequila flavor components have been published. The main aims of this study were to establish the differences among the three tequila types and to determine the most potent odorants in each type by gas chromatography-olfactometry. Tequila extracts were obtained by liquid-liquid extraction with dichloromethane. Fifth dilution series was used to determine the charm values. Qualitative and quantitative differences were observed in all tequilas. The most potent odorants were phenylethanol and phenylethyl acetate in Blanco tequila; phenylethanol, phenylethyl acetate, and vanillin in Reposado tequila; and phenylethanol, vanillin, and an unknown in Añejo tequila. A good correlation was found between flavor compounds and the aging process of tequilas in white oak casks.

Introduction Agave plants are cultivated in Mexico for production of different alcoholic beverages such as Mezcal, Pulque, Bacanora, and Tequila, to mention some. However, Agave tequilana var. azul is the most cultivated variety of Agave spp. since it is the main raw material used for the production of Tequila. A. tequilana is cultivated in Mexico mainly in the states of Jalisco, Guanajuato, Tamaulipas, Michoacân, and Nayarit. A large percentage of the tequila production is exported and 65% of this amount is exported to the Unites States,

62

© 2001 American Chemical Society In Gas Chromatography-Olfactometry; Leland, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2001.

63


Traditionally, A. tequilana plants are harvested between 8 and 12 years, and the pines (cores) are cooked in brick ovens for at least 32 hours at 100 °C, the agave juice is then fermented for 24 hours and Anally, a double distillation is performed to produce Blanco (white) or Plata (silver) tequila (Figure 1) (1). Tequila Blanco can then be matured in large wood tanks from two to six months to produce Reposado type or in white oak barrels from six to 24 months to generate Aflejo class. Tequila production is regulated by the Official Norm NOM006-SCFI-1993. After aging most tequilas are diluted with demineralized water to adjust the proof entry to 110 or 40 proof. Very few studies have been carried out on tequila flavor and aroma. Benn and Peppard (2) found the most potent odorants in some tequilas by instrumental and sensory analysis. In 1999, Lopez (3) published some of the main volatiles involved in Tequila aroma.

Objectives Therefore, the main objectives of this study were to determine the most potent odorants in Blanco, Reposado, and Aflejo tequilas from the same batch and to establish the main differences among these three tequilas.

Materials Tequila samples were a gift from one of the largest and well known Tequila Companies. Blanco tequila was only distilled, Reposado tequila was distilled and rested for three months and Aflejo tequila was distilled and aged for a year.

Experimental Figure 2 shows the methodology employed to obtain the extracts from all the tequilas samples. One hundred mL of tequila samples (Blanco, Reposado, and Aflejo) were diluted with 100 mL of distilled water and then extracted three times with SO mL CH2CI2. The extracts were combined and dried over anhydrous Na2S04 column. The extracts were concentrated in a Kuderna-Danish apparatus with a nitrogen flow (10 mL/min) to a 100 |iL volume. A gas chromatography coupled to olfactometry (GC-O) was used to generate the charm for the characterization of the compounds present in each of the extracts. The chromatographic conditions used were: a Nukoi (25 m X 0.25 mm) column with an oven temperature of 45 °C, for 5 min, at a rate 1 of 20 7min to 100 °C for 1 min and rate 2 of 3 °C/min to 190 °C for 40 min. The injector and detector temperatures were 200 and 220, respectively. The Kovats indeces were calculated using a hydrocarbon series (C8-C26)fromAldrich. Fifth dilution serial (1/5, 1/25, 1/125,1/625, and 1/3125) was used to establish the charm values of the most potent odorants in each tequila. The characterization of all active compounds was performed in a GC-MS under the same chromatographic conditions as above, except for the length of the column which was 60 m long in this case.

In Gas Chromatography-Olfactometry; Leland, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2001.


Milling

Agave plant

Fermentation

Jima

Distillation

Cooking



Blanco Tequila Figure 1. Tequila process.

Maturation


Tequilas

OS in

66 EXT. UQ-LIQ • C H A (3X50mL) SHAKE

TEQUILA 100 mL

CONC KUDERNA-DANISH s

GC-FID

I

N FLOW 10 mL/mliV

GC-0

REDISOLVE 50 μ ί CHjCI,


CHARM

GC-MS Figure 2. Diagram of the methodology used to prepare the Tequila extracts.

Results and Discussion The main differences among the analyzed tequilas were essentially quantitative more than qualitative. Figure 3 shows a typical aromagram/chromatogram profiles of a Blanco tequila extract.

ι JiljLiiII _J

ι

[==]

Figure 3. Analysis of Blanco tequila extract by GC-0 (aromagram) and GCF (chromatogram). On the other hand, Figure 4 shows the original aromagrams of all tequilas. It is important to mention than the main differences are observed at the beginning of the aromagrams, therefore, more highly volatiles compounds are present in Reposado and Aflejo tequila classes that in the non aged tequila. However, many odorants are common to all samples. Table I lists most of the volatiles that were completely characterized in all the tequila extracts.


67

REPOSADO


fUICllV

j a i l l i lui.

I

1

iTJil, ni il l.Jjll 1 JllJl Jl I 1 n i 1

Figure 4. Aromagrams of the original tequila extracts. On the other hand, the dilutions are shown in Figures 5 (Blanco), 6 (Reposado), and 7 (Aflejo). In spite of the large similarity of odorants in all tequilas, it is clearly seen that the most potent odorants in each tequila are quite different not only in number but also in intensity. Three active odors were present in the last dilution series (1/3125) of Blanco tequila. On the other hand, reposado tequila presented six potent odorants responsible of its flavor and Aflejo tequila only displayed two very relevant odorants. From this data, it can be said that the Reposado tequila has a more complex overall aroma than the other two classes, in spite of the large difference in aging time between Reposado (two months) and Aflejo (she months).

1

™

Il

150

I •

I

^llllynil

iluJiJ i.H.i.lm... I

il ι. I.I 11 ι

J li

H i

••

ιΐίιι

150 80

LU

40

Figure 5. Dilution series of tequila Blanco. It is worthwhile to mention that the three most potent odorants in Blanco tequilas are also very important in the Reposado class but not so much in the Aflejo. However, one of the two most potent odors in Aflejo tequila is also potent in the Reposado class.


68 Table I. Main Volatiles in the Three Classes of Tequila


Group Compounds ALCOHOLS (21) Butanol, 3-metbyl 4-Penten-l-ol 2-Heptanol Pentanol, 4-methyl Hexanol 4-Heptanol Propanol, 3-ethoxy 4-Hexen-l-ol 3-Octanol Cyclohexanol Pentanol, 3,4-Dimethyl Hexanol, 2-ethyl 2-Nonanol Octanol Undecanol Benzyl alcohol Phenylethyl alcohol ESTERS (40) Propanoic acid EE Hexanoic acid EE Ethyl lactate Octanoic acid EE Pentanoic acid 4-oxo EE Butanoic acid 2-hydroxy Decanoic acid EE Ethyl succinate Formic acid 2-phenyl EE Acetic acid 2-phenyl EE Dodecanoic acid EE Tetradecanoic acid EE Hexadecanoic acid EE Ethyl 9-hexadecanoate Octadecanoic acid EE Ethyl oleate Linoleic acid EE Octanoic acid phenyl EE ACIDS (13) Propanoic acid 2-methyl Acetic acid Propanoic acid Butanoic acid

KI 1197 1282 1293 1298 1335 1351 1363 1373 1379 1394 1412 1480 1509 1549 1747 1872 1904 1175 1217 1330 1421 1601 1605 1622 1667 1773 1799 1824 2029 2235 2259 2354 2442 2486 2597 1179 1468 1553 1639

Blanco

Reposado

Aflejo

X X

X X X

X X X

X X X X X X X X X X X X

X X X X X X X X X X

X X X

X

X

X X

X X X X X

X X X X X

X X X X X

X X

X X X X X X X X X X X X X X X

X X X X X X

X X X X

X X X X


X X X X

X X X X X X X X X

69


Table I. (Continued) Blanco

Reposado

Aflejo

1747 1852 2065 2276 2471

X X X X X

X X X X

X X X X

1628

X

X

X

X

X

X X

X X

X X X X X X X X X X X X X X

X X X

X X X X

Group Compounds

KI

Pentanoic acid Hexanoic acid Octanoic acid Decanoic acid Dodecanoic acid Pentanoic acid 4-hydroxy 4-methyl-Y-lactone Octanoic acid 4-hydroxy γ-lactone TERPENOIDS (24) Linalool Terpin-4-ol Ocimene Linalyl propanoate Neral t-Linalool oxide Menth-2-en-7-ol Citronellol Nerol 2-Hydrocineole t-Geraniol Nerolidol Cymen-9-oI Eugenol Guaiol Farnesol acetate Farnesol FURANS (12) Furan Furfural 2-Acetylfuran 5-Methyl-2-furfural 2-Acetyl-2,5-Dime-furan 2-Furanmethanol 2-Acetyl, 5-mefuran KETONES (7) 3-Heptanone, 2,4-Dime 3-Hexen-2-one, 5-Me 3-Hexanone-2-methyl 2-Heptanone, 5-methyl Cyclohexanone 2-Hepten-4-one, 2-Me 4-Heptanone, 3-ethyl

1940 1540 1590 1653 1686 1720 1728 1743 1757 1839 1845 2004 2027 2094 2157 2198 2244 2340 1456 1468 1504 1570 1573 1662 1856 1456 1484 1504 1570 1573 2010 2023

X

X X X X X X X X X X

X

X X X X

X X X X X X X

X X X X X X X

X X X X

X

X X X

X X

X X

X

X X X X

Continued on next page.


70 Table I. (Continued)


Group Compounds PHENOLS (9) Phenol, 4-methyl Tymol Phenol, 4-ethyl Carvacrol Cresol Phenol OTHERS (50) Propanal, 3-ethoxy Benzaldebyde Vainillin Syringaldehyde Ethyl vanillate Vainillin derivative Thiazole, 2-ethoxy Thiopene, 2-methyl

KI

Blanco

Reposado

Aflejo

2087 2173 2181 2189 2206 2263

X X X X X

X X X X X

X

1175 1516 2561 2650 2661 2674 1667 1890

X X X

X X X X

X X

X X

X

X X X X X

X

X

NOTE: KI stands for Kovats index; EE for ethyl ester; Me for methyl; Dime for dimethyl. Figure 8 presents the Charm chromatograms of the three tequilas. Here, the differences among all tequilas are based on the integration of all the dilution series. It is obvious that Reposado and Aflejo tequilas have a more complex aroma profile than Blanco tequila. This is certainly due to the resting and aging processes. Again, there are many common aromas in all samples, however, the intensity (Charm values) of many odorants are superior for Reposado and Aflejo. L ι. . . . J u l . . . 1S0

.

1 5 0

Lu. L

. I .. • III •

ι

.. J

.I.J • .J

ι i l l

i » -

I

ι

ι

eo

j

I I II

60

ι

LJJ

ι

.

Figure 6. Dilution series of tequila Reposado.


..

71

-1 -*

I I I I I ι ι llml

(25) (125)

Lu

J i l I JilJl.Ji ι I . J ι

J

' -- J_Li

(625)

i l l

J

(3125) Downloaded by UNIV OF ARIZONA on December 21, 2012 | http://pubs.acs.org Publication Date: March 1, 2001 | doi: 10.1021/bk-2001-0782.ch006

I I

, 1 ι

Figure 7. Dilution series of tequila Aflejo.

BLANCO

J JLJU-

REPOSADO

Π

ANEJO

A,,U

J.

Figure 8. Charm response chromatograms of Blanco, Reposado, and Aflejo T series. Finally, Table II lists the most potent odorants in all tequilas along with the Kovat indeces and the descriptors given to each odorant. Based exclusively on the Charm values of the odorants listed in Table Π, it is very clear that the aroma compounds present in the Aflejo class have much higher odor values.

Conclusion It can be concluded that the Aflejo class has a more complex overall aroma. Most of these odorants must be generated during the aging process in white oak barrels. However, it is also important to mention at this point, that three of these potent compounds are still unknown, therefore, it is crucial to carry out more experiments using larger tequila volumes to be able to charcaterized these compounds by GC-MS.


72

Table Π. Most Potent Odorants in all Tequilas KI

Compounds

Descriptor

Charm values Reposado

Aflejo

Solvent 748 Alcohol, vinous 2407

845 2065

2842 6515

Fatty 267 Tepache, floral 1564 Medicinal 880 Sweet, floral 6083 Plastic Medicinal, sweet 941 Chicken 1259 Fatty Vainilla, sweet 1959

400 2415 1501 4560 1644 1498 2241 411 3641

357 3035 2221 7771 16956 2403 4733 2102 5510

Blanco


1030 1200 1659 1809 1862 1906 1953 2166 2201 2266 2555

Unknown Butanol, 3-methyl Decanoic acid ethyl ester Phenylethyl acetate Unknown Phenlylethyl alcohol Unknown Eugenol Terpenoid Decanoic acid Vainillin

References

1. Cedeño, M. Crit. Rev. Biotechnol. 1995, 15, 1-11. 2. Benn, S.M.; Peppard, T.L.J.Agric. Food Chem. 1996, 44, 557-566. 3. López, M.G. Flavor Chemistry of Ethnic Foods ; Shahidi, F.; Ho, J.C., Eds.; Plenum Publishing Co., 1999; pp 211-217.


Tequilas: Charm Analysis of Blanco, Reposado, and Anejo Tequilas

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