J Sci Food Agric 1996,72,104-110

Volatile ComDonents of Aaueous Liauid Smokes from Vitis vikyera L Shoot; and Fagis sylvatica L

- -

Wood Maria D Guillh* and Maria L Ibargoitia

Tecnologia de 10s Alimentos, Facultad de Farmacia, Universidad del Pais Vasco, Consejo Superior de Investigaciones Cientificas, Paseo Marquks de Urquijo s/n, 1006 Vitoria, Spain

(Received 16 November 1995; revised version received 5 March 1996; accepted 12 April 1996)

Abstract: Vitis uinfera L shoots and Fagus sylvatica L wood were used to obtain aqueous smoke flavouring preparations. Both flavourings have a gold colour and pleasant odour. The flavour components of both samples are extracted with dichloromethane. The identification and quantitation of the components of the extracts are carried out by means of gas chromatographyJmass spectrometry, and gas chromatography with flame ionisation detection. In both preparations carbonyl derivatives are in higher concentrations than phenol derivatives. Com- pounds that confer sweet, burnt and pungent flavours are in higher concentra- tions in the Vitis vinfera L shoots smoke flavouring, and compounds that give smoky flavours are in higher concentrations in the Fagus syluatica L wood smoke flavouring. Ratios between the concentrations of the main components are proposed as parameters in order to characterise smoke and smoke flavour- ings, manufactured under specific conditions, from a specific wood. Finally, the yield of some components from a fixed amount of wood is also given.

Key words: liquid smoke, composition, Vitis oinfera L shoots, Fagus syluatica L wood.

INTRODUCTION

The acceptability of smoked foods is increasing, even in countries without a tradition of these commodities. Nowadays the smoking of food has become a technique for conferring flavour to food instead of a preserving technique. In addition, the importance of the health of consumers is leading the food industry to the use of smoke flavourings which are known to be free of poly- cyclic aromatic hydrocarbons (Gomaa et al 1993; Yabiku et a1 1993). Furthermore, increasing interest in the conservation of forests, for ecological reasons, might suggest the use of smoke flavouring preparations obtained from wood otherwise wasted annually, such as the prunings of fruit trees.

* To whom correspondence should be addressed.

We have previously studied the composition of several commercial smoke flavouring preparations, both solid and liquid, with very different appearances and used nowadays in the Spanish food industry (GuillCn et a1 1995; GuillCn and Manzanos 1996a). The composi- tion of commercial smoke flavouring preparations is very varied. Other authors using different method- ologies have also studied some commercial smoke fla- vouring preparations (Fiddler et a1 1970a,b; Fujimaki et al 1974; Kim et a1 1974; Radecki et a1 1976; Radecki et a1 1977; Baltes et a1 1981; Radecki and Grzybowski 1981 ; Wittkowski et a1 1981 ; Wittkowski et a1 1990).

The odour, composition and antimicrobial activity of the smoke is recognized to be highly dependent on the nature of the wood (Fujimaki et a1 1974; Sofos and Maga 1987; Boyle et al 1988; Sofos et al 1988; Asita and Campbell 1990; Girard 1991). Some studies have

104 J Sci Food Agric 0022-5142/96/$09.00 0 1996 SCI. Printed in Great Britain

Volatile components from Vitis vinifera and Fagus sylvatica 105

recognised beech and oak woods as those which tioned in the centre of the sawdust charge. The smoke produce wood smoke with the best sensory properties resulting from 100 g of sawdust was filtered and col- (Tilgner 1958; Pallu 1971; Maga 1988). In some Medi- lected in 150 ml of distilled water. terranean countries (Spain) several culinary prep- arations such as lamb or sardines grilled over fires of vine shoots are highly appreciated by the consumers, due to their excellent sensory properties. With these ideas in mind the production of liquid smoke prep-

Determination of the acidity and extraction of the flavouring components of the liquid smokes

arations from vine (Vitis uinifera L) shoots and beech (Fagus syluatica L) wood was carried out. In relation to vine shoots smoke, to the best of our knowledge only the sensory properties of foods smoked using this kind of wood have been described (Pallu 1971), but neither are there references to the obtaining of flavouring prep- arations nor are there data for the composition of vine shoots smoke. However, beech wood smoke has received more attention, though quantitative data of its components and studies of smoke flavouring prep- arations from this wood are few (Toth 1980a,b; Toth and Potthast 1984).

In this paper the preparation of aqueous liquid smoke flavourings derived from vine shoots and beech wood, and the characterisation of their components are reported. The characterisation was carried out by means of gas chromatography/mass spectrometry (GC/ MS), and gas chromatography (GC) with flame ionisa- tion detection (FID). The composition of these flavour- ing preparations is compared with others previously studied.

MATERIALS AND METHODS

Materials

The vine (Vitis uinifera L) shoots from the annual pruning were collected in the winter of 1993. They were air dried for 6 months and ground in a Restch DR 15/40 mill. Beech (Fagus syluatica L) sawdust of white colour was available commercially.

Smoke generation and collection

Smoke generation was carried out in a laboratory round-bottomed flask smoke-generator made of quartz; only sawdust particles smaller than 2 mmz were used. The pyrolytic process was started with the use of a rheostat-controlled heating mantle and the maximum reaction temperature was between 450 and 500°C. At this temperature the pyrolysis of the three wood com- ponents is fairly complete (Maga 1988). All the other parameters that influence the smoke generation process were kept constant in the several runs. The temperature was measured with a Crison thermometer 639K posi-

The acidity of the smoke flavouring preparations was determined by titration with 0.01 M NaOH. In order to isolate the flavouring fractions a sample of 30 ml of each aqueous liquid smoke was extracted with 35 ml of dichloromethane by liquid-liquid extraction as in pre- vious studies (Guillen et a1 1995; Guillen and Manzanos 1996a,b). This organic solvent was selected for its low boiling point and its high effectiveness in extracting polycyclic aromatic compounds (Guillen et a1 1991 ; Guilltn 1994) and aromatic compounds (Guillen and Manzanos 1994; Guillen and Ibargoitia 1995) in general. The volume of the extract was reduced to 10 ml and kept in a refrigerator.

Identification and quantitation of the components

The identification of some of the smoke components was carried out by GC/MS using a Hewlett-Packard chromatograph, model 5890 series 11, equipped with a Mass Spectrometer Selective Detector 5971, and a Hewlett-Packard Vectra 486/66U computer. A fused- silica capillary column (30 m long and 0.25 mm diameter), coated with a non-polar stationary phase (Hewlett Packard-5 cross-linked (5%) phenyl- methylsilicone) was used. The temperature pro- gramme began at 50°C (0.5 min) and increased at 2°C min-' to 280°C (15 min); He was used as gas carrier. Injector and detector temperatures were 250°C and 280"C, respectively. The injection technique used was splitless. The injection volume was of 1 pl. Mass spectra were recorded at an ionisation energy of 70 eV. Components were identified by comparing their mass spectra with those in a commercial library (Wiley138k, Mass Spectral Database, 1990), and in many cases using standards, as in previous studies (Guillen et a1 1995; Guilltn and Manzanos 1996a,b). All compounds aster- isked in Table 1 were used as standard compounds for identification ; they were available from Aldrich, Fluka and Sigma.

The quantitation of the components was carried out using a Hewlett-Packard gas chromatograph model 5890 series 11, equipped with a flame ionisation detector (FID) and a Hewlett-Packard 3395 integrator. A fused- silica capillary column (30 m long, 0.32 mm id), coated with a non-polar stationary phase (Hewlett-Packard-5, cross-linked (5%) phenylmethylsilicone) was used. The gas chromatographic conditions were the same as in the

106 M D Guilltn, M L Ibargoitia

TABLE 1 Compounds identified in the volatile fraction of the extract in dichloromethane of the vine shoots (VSLS) and beech (BLS) wood liquid smokes and their concentration in the preparation in mg litre-'

Compound" VSLS SD BLS SD

Total aldehydes Ethanal* Propanal* 3-Methylbutanal* 2-Ethylbutanal*

Total common ketones Propan-2-one* Butan-2-one* 3-Methyl-butan-2-one* Pentan-2-one* 4-Methyl-pentan-2-one* 2-Methyl-pentan-3-one* 3-Methyl-pentan-2-one* Hexan-3-one* Cyclopentanone* 4-Hydroxy-4-methyl-pentan-2-one* 1-Acetoxy-propan-2-one 2-Methyl-2-cyclopenten-l-one* A dimethyl-2-cyclopenten-1-one (structural isomer) 3- Methyl- 2-cy clopenten- 1 -one* A dimethyl-2-cyclopenten-1-one (structural isomer) 3,4,5-Trimethyl-2-cyclopenten-l-one A dimethyl-2-cyclopenten-1-one (structural isomer) A phenylethanone* Nonan-2-one*

Total diketones 3-Methyl-cyclopentane- 1,2-dione(cyclotene)* 3,5-Dimethyl-cyclopentane-1,2-dione A dimethyl-cyclopentane-1,2-dione (structural isomer) 3-Ethyl-cyclopentane-l,2-dione* 5-Ethyl-3-methyl-cyclopentane-1 ,2-dione

2-Furancarboxaldehyde(furfural)* 2-Furanmethanol* 5-Methyl-2(3H)-furanone* 1-(2-furanyl)-ethanone* 2(5H)-Furanone(y-crotonolactone)* Dihydro-2(3H)-furanone 5-Methyl-2(5H)-furanone 5-Methyl-2-furancarboxaldehydeC 3-Methyl-2(5H)-furanone* 3-Hydroxy-5-methyl-2(5H)-furanone 3-Hydroxy-2-methyl-4H-pyran-4-one(maltol)* 5-Hydroxymethyl-2-furancarboxaldehyde*

Total common esters Methyl propionate* Ethyl propionate* Ethyl butyrate* Butyl acetate* Methyl pentanoate' Ethyleneglycol monoacetate* Ethyl pentanoate* Ethyleneglycol diacetatel

Total common furan and pyran derivatives

1035.2 88.5

658-4 10.3

278.0

2428.1 80.3

114.8 241.5 248.7 48.3 12.6 11.8 70.2

203.3 83.6

929.6 221.2 73.0

207.1 110.0 151.0 29.2 12.2 23.5

641.3 424.3

18.4 29.6

152.0 17.0

5141.2 1937.7

nq 175.1 132.5

1680.3 270.6 25.3

128.9 26.1

591.1 119.8 53.8

396.5 36.1 38.8 14.0

22.7 110.1 23.9

150.9

-

22.7 2.4

10.5 3.5 6.3

59-5 3.6 3.9 6.1 5-7 1 *3 0.5 0.8 2.3 5.2 3.1

15.4 4.8 1 45 7-3 3.1 3 *O 1.2 2.3 1.5

21.4 10.2 1 *6 2.3 4.1 3 *2

120.4 36.2 nq 5.1 4.1

43-8 4.4 2.5 5.3 2.8 6.7 7.1 2.4

24.0 3 a4 2.9 1.5

3.1 6.2 2.5 4.4

-

563.0 52.1

285.3 37.2

188.4

1264.5

nq 191.0

33.2 0.9

26.7 52.9 96.7 33.4

304.0 130.6 56.3

122.3 50-2 96.6 47.7

5.2 16.8

685.0 425.6 33.0 40.2 98.2 88-0

4388.3 1741.1 149.6 42.9 73.9

1131.7 432-9 26.4

220.8 92.6

410.9 15249 62.2

327.3 14-1 86.7 10.7 31.6 33.3 63.5 15.3

103.7

nqb

-

14.8 1.7 7.3 1 *2 4.6

46.3 nq nq 4.8

2.3 0.4 1 *2 2.1 2.9 1 *4 8.1 4.2 2-5 5.0 1.4 3.5 3.1 1 *o 2.4

20.0 9.8 2.7 1.8 3.7 2.0

98.2 22.9 4.5 1.9 2.3

30.1 5.6 3.2 6.1 4.6 9.3 3.6 4.1

30.2 2.1 4.2 2-3 3.4 2.9 5.1 5.4 8.2

-

Volatile components from Vitis vinifera and Fagus sylvatica

TABLE 1. (continued)

107

Compound" VSLS SD BLS SD

Total common acids Acetic acid* Propionic acid* Butyric acid* Pentanoic acid* Hexanoic acid* 4-Oxopentanoic acid* Heptanoic acid* Octanoic acid* Nonanoic acid*

Phenol derivatives Phenol* 2-Methylphenol* 3-Methylphenol* and 4-methylphenol* 2,6-Dimethylphenol* 2-Ethylphenol* 2,4-Dimethylphenol* and 2,5-Dimethylphenol* 4-Ethylphenol* 2,3-Dimethylphenol*

Guaiacol derivatives 2-Methoxyphenol(guaiacol)* 4-Methyl-2-methoxyphenol* 4-Ethyl-2-methoxyphenol* 4-Vinyl-2-methoxyphenol* 4-(2-Propenyl)-2-methoxyphenol(eugenol)* 4-Propyl-2-methoxyphenol* 4-Hydroxy-3-methoxybenzaldehyde(vanillin)* 4-( 1 -Propenyl)-2-methoxyphenol(trans-isoeugenol)* 44 1 -Propenyl)-2-methoxyphenol(cis-isoeugenol)* 1 -(4-Hydroxy-3-methoxyphenyl)ethanone* 1 -(4-Hydroxy-3-methoxyphenyl)-propan-2-one

2,6-Dimethoxyphenol (syringol)* 4-Methyl-2,6-dimethoxyphenol* 4-Ethyl-2,6-dimethoxyphenol 4-(2-Propenyl)-2,6-dimethoxyphenol* 4-Propyl-2,6-dimethoxyphenol 44 l-trans-Propenyl)-2,6-dimethoxyphenol 4-Hydroxy-3,5-dimethoxybenzaldehyde* 4-( 1 -cis-Propenyl)-2,6-dimethoxyphenol l-(4-Hydroxy-3,5-dimethoxyphenyl)ethanone* 1 -(4-Hydroxy-3,5-dimethoxyphenyl)-propan-2-one 1 -(4-Hydroxy-3,5-dimethoxyphenyl)propanal Pyrocatechol* 3-Methoxypyrocatechol*

Syringol derivatives

129.2 2921.0

7.0 26.1 6-9

14.5 47.6 12.1 1.8

15.0

14.0 60.4 3.0 1-2 0.7 2.2 3.9 1 .o 1.2 2.0

1280.1 38.8 363.5 6.2 303.4 7-5 336.2 4.8 42.9 5.1 36.8 2,8

101.8 5.1 42.2 3 .O 53.3 4,3

1282.1 37.9 662.7 9-1 179-4 4.6 126.7 5.1 96.9 3.2 35.5 3.4 13.0 1.3 18.7 2.5 25.9 1.4 58.6 2.9 20.6 1.2 44.1 3.2

890.7 36.9 512.9 6.1 101-8 4.3 73.7 4.6 20.5 3.8 12.9 1.6 11.5 1.9 14.1 2.5 27.2 3.1 29.0 4.2 76.7 3.6 10.4 1.2 30.1 4.1

354.7 6.4

Miscellaneous 1,4-Dimethoxybenzene* 23.0 3.2 2,6-Dimethoxytoluene 10.9 1.9

Total common carbonyl derivatives 9245.8 224.0 Total common esters 396.5 24.0 Total common acids 129.2 14.0 Total common phenol derivatives 3837.7 124-1

Asterisked compounds were used as standard for identification and quantitation. nq, not quantified.

427.5 nq 15.6

276.5 14.9 22.4 64.4 12.5

21.2

856.6 181.1 213.9 240-6 32.6 27.5 55.1 32.8 73.0

1340.0 456.4 252-8 116.2 95.0 55-0 25.2 89.4 49.8 78.6 49.3 72.3

1489.0 589.5 239-2 103.9 50.0 27.7 21.5 64.2 37.7

114.2 183.6 51.5 8.3

294.3

-

19.6 23.4

6900.8 327.3 427.5

3988.2

18.2 nq 2.5 4-6 1.4 2.5 1.6 2.5

3.1

28.8 4.1 6.4 5.1 4.2 4.3 4.3 2.8 1.9

50.4 6.3 8-2 2.9 4.9 2-5 2.5 7.6 4.3 3.5 3.6 4.1

49.0 9.2 6.1 3.2 4.1 2.9 3.2 4.4 3 -6 5.1 4.3 2.9 2.8 7.1

-

2.6 3.4

179.3 30.2 18.2

138.1

108 M D Guilldn, M L Ibargoitia

GC/MS study. The quantitation was carried out using external standards. To this aim response factors of all compounds asterisked in Table 1 were determined as in previous studies (Blanco et a1 1992). For the quantitat- ion of compounds not available commercially, response factors of compounds of similar nature were used.

Each step of the total process, that is smoke gener- ation, acidity determination, extraction of aliquot parts of the liquid smoke and chromatographic study was carried out three times with each starting material.

RESULTS AND DISCUSSION

In the pyrolytic processes 184 ml and 181 ml of vine shoots (VSLS) and of beech wood (BLS) liquid smoke, respectively, were obtained. Both preparations are gold in colour, with a reddish shade in the case of the vine shoots product. The odour of both preparations has been judged as pleasant but distinctive. The acidity of BLS is higher than of VSLS (VSLS: 358 meq acid litre-'; BLS: 394 meq acid litre-').

The preparations were extracted with dichloro- methane and the identification of the components in the extract was carried out by GC/MS and using standards. The identified compounds are given in Table 1 together with their concentrations (mg litre-') in the flavouring preparation and the standard deviations of the means of several analyses. Those compounds whose separation was not good enough were not quantified (nq in Table 1). Methanal was not found in any of the dichloro- methane extracts.

As can be expected from cellulose and hemicellulose thermal degradation, carbonyl derivatives such as esters, aldehydes, ketones, diketones, furan and pyran derivatives, as well as acids are formed (Fengel and Wegener 1983; Shafizadeh 1984). Carbonyl derivatives have been detected as major components in both liquid smokes. These compounds have been attributed in general with caramel or burnt sugar aromas (Fiddler et al 1970b). Main components are 2-furancarboxaldehyde fsweet, bread-like, caramel-like), 2(5H)-furanone, 1- acetoxy-propan-Zone and 3-methyl-cyclopentane-1,2- dione (brandy or caramel, an odour and taste such as hydrolysed vegetable protein, smoked ham, cloves) (Toth and Potthast 1984; Potthast and Eigner 1988; Potthast et al 1988). Other compounds in smaller con- centrations contribute with similar flavour notes, such as 3-methyl-2(5H)-furanone (sweet, like burnt caramel), 3-methyl-2-cyclopenten-l-one (somewhat sweet, grassy) (Kim et al 1974) or 3-hydroxy-2-methyl-4H-pyran-4-one (caramel, butterscotch) (Anon 1994). The concentration of carbonyl derivatives overall is higher in VSLS than in BLS. Ketones are more concentrated in VSLS than in BLS, however diketones are in similar concentration in both preparations. In the group of furan and pyran derivatives, 2-furancarboxaldehyde and 2(5H)-furanone

are in higher concentrations in VSLS than in BLS, but their derivatives are more concentrated in BLS.

Chromatographic results for the concentration of acids in both preparations are in agreement with the titration results, showing again that BLS has a higher acidity than VSLS.

Phenol derivatives are formed from the thermal deg- radation of lignin (Fengel and Wegener 1983; Shafiza- deh 1984). Phenol (pungent), alkylphenol derivatives (pungent and cresolic flavour), guaiacol (sweet, smoky, somewhat pungent), alkylguaiacol derivatives (sweet, smoky, woody), syringol (smoky), alkylsyringol deriv- atives (mild, heavy, burnt) (Kim et a1 1974), together with carbonyl derivatives of guaiacol and syringol, con- stitute the main components of the phenolic fraction. Concentrations of phenol, alkylphenol derivatives and guaiacol are higher in VSLS than in BLS, however syr- ingol, and alkyl and carbonyl derivatives from guaiacol and syringol, are more concentrated in BLS than in VSLS.

These results show that both preparations should have differences in their sensory properties. The propor- tion of carbonyl derivatives is higher in both flavourings than the proportion of phenol derivatives, but the sweet, caramel, burnt and pungent notes will be more intense in VSLS and the smoky notes in BLS.

It must be pointed out that in spite of the large number of hydrocarbons present in the smoke, these were absent in both smoke flavourings. An important proportion of these compounds was retained on a filter, whereas others passed through the water and after- wards were retained on another carrier (Guillen and Ibargoitia unpublished).

The composition of the wood determines the com- position of the smoke and therefore its sensory proper- ties, provided that the pyrolytic process is run keeping constant all factors that influence the smoke generation. This assumption should be true if the temperature of the process is near 500"C, at which the pyrolysis of wood is fairly complete. It can be observed that the components of both smoke flavouring preparations are the same and that the difference is basically in the con- centration of each one of the components. For these reasons, the ratios of the concentrations of some of the main components could be considered as characteristic parameters of the smoke, and of the smoke flavouring preparation, obtained from a specific wood under fixed conditions for smoke generation and manufacture. Ratios of the concentrations of some of the main com- ponents in both flavourings are given in Table 2. These parameters clearly indicate great differences in the com- position of both preparations. However, more data are necessary in order to make a generalization from these parameters. Other authors give data for proportions of some components in hardwood (and softwood) smoke (Baltes et al 1981). With these data, ratios have been calculated for phenol/guaiacol = 0.5(0.4), phenol/

Volatile components @om Vitis vinifera and Fagus sylvatica 109

TABLE 2 Ratio between concentrations of some components of VSLS and BLS"

~

Ratio VSLS BLS Ratio VSLS BLS

ap/cyclo tene 2.2 0.7 ap/furfural 0.5 0.2 ap/croto 0.5 0.3 Cyclotene/croto 0.2 0-4 Furfural/croto 1.1 1.5 Phenol/2mp 1.2 0.8 Phenol/guaiacol 0.5 0.3 Phenol/syringol 0.7 0.3 Guaiacol/4mg 3.7 1.8 Guaiacoll4eg 5.2 3.9 Guaiacol/syringol 1.3 0.8 Syringol/4ms 5.0 2.5 Syringoll4es 7-0 5.7 Syringol/3mpy 1 -4 2.0

a ap, 1-acetoxy-propan-2-one; croto, 2(5H)-furanone; 2mp, 2-methylphenol; 4mg, 4-methyl-2-methoxyphenol; 4eg, 4-ethyl-2-methoxyphenol; 4ms, 4- methyl-2,6-dimethoxyphenol; 4es, 4-ethyl-2,6-dimethoxyphenol; 3mpy, 3- methoxypyrocatechol.

syringol = 0.3(1.3) and guaiacol/syringol = 0.7(3-3). The BLS data in Table 2 are in agreement with those corre- sponding to hardwood smoke and the VSLS sample shows values intermediate between hardwood and soft- wood smokes.

Finally, from the data in Table 1, and taking into account the volume obtained for both preparations, it is possible to calculate the amount (mg kg-') of each compound produced from sawdust. These data can only be partially contrasted because there are no such detailed results in the literature of smoke flavouring preparations. Some authors (Toth 1980a,b) have found that when the smoke generation temperature is between 450 and 500"C, as in this study, the amount of phenol derivatives obtained from sawdust of beech wood is about 8 g kg-'. Data calculated from values in Table 1 (VSLS: 7-06 g kg-' and BLS: 7.22 g kg-') are in good agreement with this previous result. Also data for the amount of some phenol derivatives obtained from beech wood sawdust are given at 450 and 550°C (phenol: 200 and 300; guaiacol 400 and 600; syringol 850 and 1500 mg kg-') (T6th 1980b). These data agree with the results of our study, especially with BLS (VSLS: phenol 670, guaiacol 1220 and syringol 940, BLS: phenol 330, guaiacol830 and syringol 1070 mg kg-I).

The yield in flavour compounds, under the conditions in which the smoke generation was carried out, is slight- ly higher from vine shoots than from beech wood. Com- paring the composition of both smoke flavouring preparations with commercial flavourings (Baltes and Sochtig 1979; Guillh et a1 1995; GuillCn and Man- zanos 1996a) it can be concluded that both are ade- quate for the food industry. The choice will be a function of the sensory properties required for the food.

ACKNOWLEDGEMENT

This work has been supported by the Comision Inter- ministerial de Ciencia y Tecnologia (CICYT, ALI94- 0989).

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