Printer Friendly

Composition of blackcurrant aroma isolated from leaves, buds, and berries of Ribes nigrum L/Mustsostra (Ribes nigrum L.) lehtede, pungade ja marjade aroomi keemiline koostis.

INTRODUCTION

Blackcurrant (Ribes nigrum L. (Saxifragacea)) is cultivated extensively in central and northern Europe. Its buds, berries, and also leaves have a very characteristic odour. Blackcurrant berries are used in many flavour applications of food and beverages, for jamming, and juice production. Blackcurrant buds are applied as a starting material for the preparation of the essential oil and absolutes, which are used as flavouring in cosmetics and food products. Leaves are used in canning some vegetables (cucumbers, tomatoes).

Numerous studies of the blackcurrant aroma were carried out by Anderson & von Sydow [1-4], Nursten & Williams [5], Latrasse and co-workers [6-9], Nijssen & Maarse [10], Kerslake & Menary [11], Marriott [12], Nishimura & Mihara [13], and Piry et al. [14]. A large number of components, of which the terpenoic hydrocarbons are quantitatively the most important, have been identified in the blackcurrant aroma. The compounds found in significant amounts are [alpha]- and [beta]-pinene, sabinene, 3-carene, [beta]-phellandrene, and terpinolene.

Different constituents, responsible for the characteristic "catty note" of black-currant, have been identified. Nishimura & Mihara [13] reported isolation of 3-hydroxy-2-methyl-butyronitriles and (Z)- and (E)-2-hydroxymethyl-2-butenenitriles from blackcurrant bud absolute as odour compounds. Latrasse and coworkers [6-8] identified 4-methoxy-2-methyl-2-butanethiol as a component with the characteristic catty note in blackcurrant buds. Non-sulphur containing aroma chemicals with blackcurrant odour (spiro-ethers) were studied by Van der Weerdt [15].

The aroma from R. nigrum growing in Estonia has not been studied earlier by capillary GC and we did not find any literature data about the use of the chiral capillary column for blackcurrant aroma analysis.

The aim of this work was to compare the composition of blackcurrant aroma extracts isolated by the simultaneous distillation/extraction (SDE) micromethod from berries, leaves, and buds of R. nigrum using nonpolar (OV-101), polar (PEG 20M), and chiral (CYDEX B) capillary columns and the GC/MS method. The blackcurrant oil yields from different materials and changes in the concentrations of aroma compounds during the ripening process were studied, and the enantiomeric ratio of some monoterpenoic compounds was determined.

EXPERIMENTAL

Materials

Buds, leaves, and berries were harvested from one blackcurrant bush growing in Estonia (near Rapla). A total of five samples were collected on different dates (Table 1).

Sample preparation

Aroma compounds were isolated from fresh blackcurrant material. SDE was performed in the micro-apparatus of Marcusson's type during 2 h using n-hexane as the solvent and n-tetradecane as the internal standard for yield determination. For the isolation procedure 100-140 g of fruits and about 20 g of leaves and buds were used.

Capillary gas chromatography

GC analyses were performed on a Chrom-5 gas chromatograph equipped with a flame ionization detector. Helium was used as the carrier gas with a splitting ratio 1 : 150. Fused silica capillary columns with stationary phases of different polarity were used. Table 2 specifies the columns used and the conditions of the analysis.

A Hewlett-Packard Model 3390A integrator was applied for data processing. Quantitation of peaks was expressed as a percentage of the total peak area. The yields (%) of aroma compounds were determined using the internal standard according to the formula

X = [K.sub.st]([A.sub.x]/[A.sub.st])%,

where [A.sub.x], [A.sub.st]--the total peak area of the aroma substances and the peak area of the internal standard, respectively

[K.sub.st]--% of the internal standard in the sample material

Component identification was based on the comparison of the temperature programming retention indices (RI) determined on different columns with authentic RI data either from our data bank or obtained from the literature [16-19]. The results obtained were confirmed by GC/MS.

Gas chromatography/mass spectrometry

Mass spectrometric analyses were carried out on a Hitachi M-80B gas chromatograph double-focusing mass spectrometer using a SPB-1 (30 m x 0.32 mm) fused silica capillary column. The temperature program was 3 min at 50[degrees]C, then 50-120[degrees]C at 5[degrees]C/min and 120-290[degrees]C at 8[degrees]C/min.

RESULTS AND DISCUSSION

The recoveries of essential oils from different fresh blackcurrant materials obtained applying the SDE micromethod with n-hexane as the solvent varied in the range 0.001-0.21% (Table 1). The yields of oil from blackcurrant berries from the three samples of different ripening stage were quite similar (0.001-0.003%) being the highest for fully ripe berries. A much higher yield of oil was obtained from blackcurrant leaves (0.04%) and especially from blackcurrant buds (0.21%). According to the literature data the oil yield from blackcurrant leaves is 0.08-0.74 mg/g [12] depending on the isolation method (distillation or extraction), from buds 2-5 mg/g [8], and from berries 10-13 ppm [3].

The complex nature of the blackcurrant aroma is demonstrated in the chromatogram (Fig. 1). Table 3 lists the compounds identified in the blackcurrant oils and their relative amounts (%) in the oils isolated from berries, buds, and leaves. The RI data in three stationary phases are also reported.

Altogether 63 compounds were identified in the blackcurrant oils studied. Perillaldehyde, decanoic acid, and palmitic acid have not been found in blackcurrant oil before. The monoterpenoic hydrocarbon fraction was the main part of the oil for all the parts of blackcurrant with its relative amounts varying from 55% to 67% of the oils (Table 3). The composition of the major monoterpenes was found to be in good agreement with the previous studies [1-14]. 3-Carene, [beta]-phellandrene, (Z)- and (E)-[beta]-ocimene, limonene, and terpinolene were identified in high quantities (0.9-26.9%).

Sesquiterpenes made up 7.5-15.7% of the blackcurrant oils. The major sesquiterpene in the oils was (E)-[beta]-caryophyllene (4.6-9.3%). The other sesquiterpenes made up less than 4.1% in all samples. Oxygenated terpenes were found in quantities 5.7-14.2% of oils. From the 20 oxygenated monoterpenes identified in the blackcurrant oils only [alpha]-terpineol and citronellyl acetate were found to form over 1%. The main oxygenated sesquiterpene was caryophyllene oxide (0.5-9.8%). The other groups of compounds in the oils were aromatic compounds, aliphatic aldehydes, alcohols and acids, and n-alkanes [C.sub.16]-[C.sub.21].

Generally the same substances although with quantitative differences were present in the oils of the different blackcurrant materials. Camphene and linalool were found in leaves and buds but not in berries. Some aliphatic oxygenated compounds (heptanal, decanal, 2-decanol, ethyl decanoate, palmitic acid, but also 1,8-cineole, myrtenal, 1-p-menthen-9-al, and perillaldehyde), not found in leaves, were identified in small quantities in buds and in the highest quantities in blackcurrant berries. The aromatic hydrocarbon p-cymenene was also found in small quantities in buds and leaves, but occurred in quantities up to 5% in berries. Compared with the other parts the blackcurrant buds contained more monoterpenes ([beta]-phellandrene, terpinolene, [alpha]-pinene, limonene) and n-alkanes. The aroma from blackcurrant leaves contained more [beta]-ocimene isomers and caryophyllene oxide than the oils from the other parts. The blackcurrant aroma isolated from berries was rich in aromatic and aliphatic compounds and oxygenated monoterpenes.

[FIGURE 1 OMITTED]

The aroma from fully ripe blackcurrant berries showed a higher yield and contained more monoterpenoic hydrocarbons and less oxygenated terpenes than the aroma of unripe and overripe berries.

The enantiomer ratios (the amount of one enantiomer expressed as percentage of the total amount of the pair of compounds) of some monoterpenoic compounds in the blackcurrant aroma samples are presented in Table 4. It was found that in the enantiomeric composition of the compounds studied the aroma from different blackcurrant parts and from berries of different ripening stage was quite similar.

In most cases a significant (+)-enantiomer excess was observed for the monoterpenes [alpha]- and [beta]-pinene (65-82%), but (-)-enantiomer excess (57-67%) was observed for oxygenated compounds (linalool, terpinen-4-ol, [alpha]-terpineol). In the case the content of linalool and [alpha]-terpineol in the oil of blackcurrant leaves was very low (< 0.1%), the enantiomeric distribution was not considerable. (-)-Limonene and (-)-[beta]-phellandrene were eluted with (Z)-[beta]-ocimene and (E)-[beta]-ocimene (Table 3) and therefore the enantiomeric distribution of their enantiomers could not be determined.

ACKNOWLEDGEMENT

Financial support for the work reported here was provided by the Estonian Science Foundation (grant No. 4028).

Received 10 July 2002, in revised form 8 October 2002

REFERENCES

[1.] Andersson, J. & von Sydow, E. The aroma of black currants I. Higher boiling compounds. Acta Chem. Scand., 1964, 18, 1105-1114.

[2.] Andersson, J. & von Sydow, E. The aroma of black currants II. Lower boiling compounds. Acta Chem. Scand., 1966, 20, 522-528.

[3.] Andersson, J. & von Sydow, E. The aroma of black currants III. Chemical characterization of different varieties and stages of ripneness by gas chromatography. Acta Chem. Scand., 1966, 20, 529-535.

[4.] Andersson, J., Bosvik, R. & von Sydow, E. The composition of the essential oil of the black currant leaves (Ribes nigrum L.). J. Sci. Food Agric., 1963, 14, 834-840.

[5.] Nursten, H. E. & Williams, A. A. Volatile constituents of the black currant (Ribes nigrum L.). II. The fresh fruit. J. Sci. Food Agric., 1969, 20, 613-619.

[6.] Latrasse, A., Rigaud, J. & Sarris, J. L'arome du cassis (Ribes nigrum L.) odeur principale et notes secondaries. Sci. Aliments, 1982, 2, 145-162.

[7.] Rigaud, J., Etievant, P., Henry, R. & Latrasse, A. 4-Methoxy-2-methyl-2-mercapto-butane, a major constituent of the aroma of the blackcurrant bud (Ribes nigrum L.). Sci. Aliments, 1986, 6, 213-220.

[8.] Le Quere, J.-L. & Latrasse, A. Composition of the essential oils of blackcurrant buds (Ribes nigrum L.). J. Agric. Food Chem., 1990, 38, 3-10.

[9.] Le Quere, J.-L. & Latrasse, A. Identification of (+)spathylenol in the essential oil of blackcurrant buds (Ribes nigrum L.). Sci. Aliments, 1986, 6, 47-59.

[10.] Nijssen, L. M. & Maarse, H. Volatile compounds in black currant products. An additional factor in authenticity control of fruit juices. Flav. Fragr. J., 1986, 1, 143-148.

[11.] Kerslake, M. F. & Menary, R. C. Aroma constituents of black currant buds (Ribes nigrum L.). Perfum. Flavor., 1985, 9, 13-24.

[12.] Marriott, R. J. Isolation and analysis of blackcurrant (Ribes nigrum L.) leaf oil. In Flavors and Fragrances: A World Perspective (Lawrence, B. M., Mookherjee, B. D. & Willis, B. J., eds.). Proceedings of the 10th International Congress of Essential Oils, Fragrances and Flavors, Washington, DC, U.S.A., 16-20 November 1986. Elsivier Science Publishers B.V., Amsterdam, 1988, 387-403.

[13.] Nishimura, O. & Mihara, S. Aroma constituents of blackcurrant buds (Ribes nigrum L.). In Flavors and Fragrances: A World Perspective (Lawrence, B. M., Mookherjee, B. D. & Willis, B. J., eds.). Proceedings of the 10th International Congress of Essential Oils, Fragrances and Flavors, Washington, DC, U.S.A., 16-20 November 1986. Elsevier Science Publishers B.V., Amsterdam, 1988, 375-386.

[14.] Piry, J., Pribela, A., Durcanska, J. & Farkas, P. Fractionation of volatiles from blackcurrant (Ribes nigrum L.) by different extractive methods. Food Chem., 1995, 54, 73-77.

[15.] Van der Weerdt, A. J. A. Non-sulphur containing aroma chemicals with blackcurrant odor. In Flavors and Fragrances: A World Perspective (Lawrence, B. M., Mookherjee, B. D. & Willis, B. J., eds.). Proceedings of the 10th International Congress of Essential Oils, Fragrances and Flavors, Washington, DC, U.S.A., 16-20 November 1986. Elsevier Science Publishers B.V., Amsterdam, 1988, 405-423.

[16.] Davies, N. W. Gas chromatographic retention indices of monoterpenes and sesquiterpenes on methyl silicone and Carbowax 20M phases. J. Chromatogr., 1990, 503, 1-24.

[17.] Zenkevich, I. G. Analytical parameters of components of essential oils for their GC and GC/MS identification. Mono- and sesquiterpenic hydrocarbons. Rastit. resur., 1996, 32, 48-58 (in Russian).

[18.] Zenkevich, I. G. Analytical parameters of components of essential oils for their GC and GC/MS identification. Oxygen containing derivatives of mono- and sesquiterpenic hydrocarbons. Rastit. resur., 1997, 33, 16-28 (in Russian).

[19.] Zenkevich, I. G. Analytical parameters of components of essential oils for their GC and GC/MS identification. Acetates of terpenic alcohols. Rastit. resur., 1999, 35, 30-37 (in Russian).

Anne Orav *, Tiiu Kailas, and Mati Muurisepp

Institute of Chemistry, Tallinn Technical University, Akadeemia tee 15, 12618 Tallinn, Estonia

* Corresponding author, aorav@chemnet.ee
Table 1. Time of collection and characterization of blackcurrant
samples

Sample Material Date of harvest Ripening stage Oil yield,
 No. %

1 Buds May 2000 0.21
2 Berries 4 July 2000 Unripe 0.002
3 Berries 17 July 2000 Fully ripe 0.003
4 Berries 16 August 2000 Overripe 0.001
5 Leaves August 2000 0.04

Table 2. Capillary columns and operating conditions

 Parameter Stationary phase

 OV-101 SW-10 CYDEX B

Column length, m 50 60 50
Column internal diameter, mm 0.20 0.32 0.22
Stationary phase film 0.50 0.25 0.25
 thickness, [micro]m
Plate number for n-decane 145 000 300 000 170 000
 at 90[degrees]C
Helium flow rate, cm/sec 17-25 17-25 30-35
Injector temperature, [degrees]C 160 260 160
Column temperature, [degrees]C 50-250 70-220 60-220
Programming rate, [degrees]C/min 2 2 2

Table 3. Retention indices (RI) and composition of the essential
oils of blackcurrant buds, berries, and leaves. The components
identified in the highest yields are in bold

 Compound RI

 OV-101 SW-10 CYDEX B

[alpha]-Thujene (MS) 923 1029 954
(-)-[alpha]-Pinene (MS) 930 1029 985
(+)-[alpha]-Pinene (MS) 930 1029 990
n-Heptanal 879 1000
(+)-Camphene 940 1074 1010
Sabinene (MS) 963 1125 1024
Myrcene (MS) 980 1161 1026
(+)-[beta]-Pinene (MS) 967 1116 1035
(-)-[beta]-Pinene (MS) 967 1116 1039
(+)(-)-3-Carene (MS) 1002 1148 1045
[alpha]-Phellandrene (MS) 993 1167 1046
[alpha]-Terpinene (MS) 1007 1180 1055
(Z)-[beta]-Ocimene (MS) 1026 1232 1069
(-)-Limonene (MS) 1020 1204 1069
(+)-Limonene (MS) 1020 1204 1072
p-Cymene (MS) 1010 1273 1079
(E)-[beta]-Ocimene (MS) 1037 1250 1083
(-)-[beta]-Phellandrene 1019 1213 1083
(+)-[beta]-Phellandrene (MS) 1019 1213 1086
[gamma]-Terpinene (MS) 1047 1246 1100
1,8-Cineole (MS) 1020 1211 1114
Terpinolene (MS) 1078 1282 1124
p-Cymenene (MS) 1072 1428 1157
1-Octen-3-ol (MS) 970 1450 1142
Oxygenated mono- 1055 1431 1167
 terpene [C.sub.10]
 [H.sub.18]O
(-)-Fenchone 1066 1397 1205
Methyl benzoate 1068 1205
trans-Linalool oxide 1072 1451 1210
(-)-Linalool (MS) 1085 1547 1238
(+)-Linalool (MS) 1085 1547 1240
Methyl chavicol 1175 1660 1300
n-Decanal 1185 1311
(-)-Terpinen-4-ol (MS) 1160 1593 1321
(+)-Terpinen-4-ol (MS) 1160 1593 1324
2-Decanol 1197 1335
(+)-Myrtenal 1166 1348
1-p-Menthen-9-al (MS) 1166 1352
(+)-[alpha]-Terpineol (MS) 1172 1690 1360
(-)-[alpha]-Terpineol (MS) 1172 1690 1363
Isoborneol 1146 1370
Borneol 1150 1693 1376
Bornyl acetate 1268 1574 1381
Nerol 1213 1800 1389
Citronellyl acetate (MS) 1334 1671 1432
(-)-Perillaldehyde a a 1243 1774 1441
Ethyl decanoate 1375 1457
Geranyl acetate (MS) 1365 1755 1474
(+)(-)-(E)-[betaa]-Caryo- 1412 1586 1476
 phyllene (MS)
[gamma]-Elemene (MS) 1423 1494
[alpha]-Humulene (MS) 1443 1653 1511
Germacrene D 1470 1690 1541
Bicyclogermacrene (MS) 1482 1716 1563
[delta]-Cadinene (MS) 1509 1749 1572
n-Hexadecane 1600 1600 1600
Germacrene B (MS) 1547 1805 1615
Decanoic acid 1368 2270 1652
n-Heptadecane 1700 1700 1700
(+)(-)-Caryophyllene 1564 1960 1728
 oxide (MS)
n-Octadecane 1800 1800 1800
n-Butyl cinnamate (MS) 1850
n-Nonadecane 1900 1900 1900
n-Eicosane (MS) 2000 2000 2000
n-Heneicosane (MS) 2100 2100 2100
Palmitic acid 1945 2217

COMPONENT GROUPS:
 Monoterpenes
 Oxygenated
 monoterpenes
 Sesquiterpenes
 Oxygenated
 sesquiterpenes
 Aliphatic
 compounds

 Total %

 Compound Concentration *, %

 Buds Berries Leaves

 1 2 3 4 5

[alpha]-Thujene (MS) 0.2 tr. 0.1 tr. 0.1
(-)-[alpha]-Pinene (MS) 0.6 0.3 0.4 0.4 0.3
(+)-[alpha]-Pinene (MS) 2.3 1.2 1.8 1.6 1.2
n-Heptanal tr. 0.3 0.4 0.7 --
(+)-Camphene 0.2 -- -- -- 0.1
Sabinene (MS) 2.4 1.3 1.6 1.3 1.9
Myrcene (MS) 0.8 0.3 0.4 0.4 0.6
(+)-[beta]-Pinene (MS) 0.3 0.3 0.4 0.2 0.8
(-)-[beta]-Pinene (MS) 0.1 0.1 0.2 0.1 0.2
(+)(-)-3-Carene (MS) 20.2 21.2 26.9 20.2 25.4
[alpha]-Phellandrene (MS) 0.7 0.7 0.8 0.8 0.3
[alpha]-Terpinene (MS) 1.1 2.2 2.5 1.9 0.7
(Z)-[beta]-Ocimene (MS) 6.7 2.7 5.5 2.1 11.3
(-)-Limonene (MS) {
(+)-Limonene (MS) 4.9 3.4 3.2 3.9 2.3
p-Cymene (MS) 0.1 0.9 0.8 0.4 0.6
(E)-[beta]-Ocimene (MS) 2.4 2.0 1.5 0.9 7.7
(-)-[beta]-Phellandrene {
(+)-[beta]-Phellandrene (MS) 11.3 5.4 6.7 6.1 2.6
[gamma]-Terpinene (MS) 0.3 0.8 0.7 0.4 0.3
1,8-Cineole (MS) tr. 0.6 0.3 0.4 --
Terpinolene (MS) 10.2 8.7 8.7 6.8 7.7
p-Cymenene (MS) 0.2 3.5 4.8 4.0 0.3
1-Octen-3-ol (MS) 0.1 0.2 0.5 0.1 0.2
Oxygenated mono- 0.1 0.4 0.5 1.0 --
 terpene [C.sub.10]
 [H.sub.18]O
(-)-Fenchone 0.1 0.4 0.3 0.4 0.2
Methyl benzoate
trans-Linalool oxide 0.1 0.3 0.3 0.2 --
(-)-Linalool (MS) 0.1 -- -- -- 0.3
(+)-Linalool (MS) 0.1 -- -- -- 0.3
Methyl chavicol -- 0.7 0.3 1.2 --
n-Decanal -- 0.3 0.4 0.3 0.1
(-)-Terpinen-4-ol (MS) 0.2 0.5 0.2 0.6 0.2
(+)-Terpinen-4-ol (MS) 0.1 0.2 0.2 0.4 0.1
2-Decanol 0.1 0.4 0.4 0.6 --
(+)-Myrtenal tr. 0.5 0.4 0.3 --
1-p-Menthen-9-al (MS) 0.1 1.4 0.7 0.6 --
(+)-[alpha]-Terpineol (MS) 0.1 1.0 0.7 1.0 0.3
(-)-[alpha]-Terpineol (MS) 0.1 1.6 1.1 1.6 0.3
Isoborneol 0.1 0.6 0.8 0.6 0.2
Borneol 0.2 0.2 0.4 0.4 0.3
Bornyl acetate 0.4 0.2 0.2 0.3 0.5
Nerol 0.1 0.6 0.7 0.9 0.3
Citronellyl acetate (MS) 0.7 1.0 1.1 0.8 0.4
(-)-Perillaldehyde a a 0.1 0.5 0.5 0.4 --
Ethyl decanoate 0.2 0.7 0.4 0.6 --
Geranyl acetate (MS) 0.4 0.5 0.7 0.7 0.3
(+)(-)-(E)-[betaa]-Caryo- 8.3 9.3 5.2 4.6 4.7
 phyllene (MS)
[gamma]-Elemene (MS) 0.2 1.4 1.1 3.8 0.4
[alpha]-Humulene (MS) 0.7 0.8 0.3 1 0.8
Germacrene D 0.2 0.2 0.2 0.2 0.2
Bicyclogermacrene (MS) 0.1 0.8 0.4 2 0.1
[delta]-Cadinene (MS) 0.2 0.2 0.2 0.1 0.5
n-Hexadecane 0.1 0.5 0.2 0.7 0.1
Germacrene B (MS) 4.1 3.0 1.6 1.6 0.8
Decanoic acid 0.2 0.5 0.3 0.2 0.1
n-Heptadecane 0.2 1.0 0.5 1.9 0.3
(+)(-)-Caryophyllene 2.4 1.0 0.5 0.6 9.8
 oxide (MS)
n-Octadecane 0.2 0.8 0.5 tr. 0.2
n-Butyl cinnamate (MS) 0.2 1.0 0.8 0.9 0.7
n-Nonadecane 0.3 1.0 0.8 1.1 0.5
n-Eicosane (MS) tr. 0.4 tr. 0.3 0.1
n-Heneicosane (MS) -- 0.5 0.2 1.8 --
Palmitic acid 0.1 2.1 2.2 2.9 0.4

COMPONENT GROUPS:
 Monoterpenes 65.0 55.0 67.0 51.4 64.4
 Oxygenated 3.3 12.2 10.3 12.7 4.4
 monoterpenes
 Sesquiterpenes 13.8 15.7 9.0 13.3 7.5
 Oxygenated 2.4 1.0 0.5 0.6 9.8
 sesquiterpenes
 Aliphatic 1.5 8.7 6.8 11.2 1.8
 compounds

 Total % 86.0 92.6 93.6 89.2 87.9

MS--determined on GC/MS

*--determined on CYDEX B

tr.--traces (< 0.05%)

Table 4. Enantiomeric distribution of some monoterpenoic
Compounds in blackcurrant aroma

Compound Enantiomeric distribution, %

 Buds Berries Leaves

 1 2 3 4 5

(-)-[alpha]-Pinene 19.9 20.3 19.1 18.8 22.5
(+)-[alpha]-Pinene 80.1 79.7 80.9 81.2 77.5

(+)-[beta]-Pinene 75.0 65.1 67.3 69.7 81.7
(-)-[beta]-Pinene 25.0 34.9 32.6 30.3 18.3

(-)-Linalool 61.5 -- -- -- 54.8
(+)-Linalool 38.5 -- -- -- 45.2

(-)-Terpinen-4-ol 61.3 67.2 58.8 60.0 57.6
(+)-Terpinen-4-ol 38.7 32.8 41.2 40.0 42.4

(+)-[alpha]-Terpineol 42.8 39.5 37.2 39.0 48.3
(-)-[alpha]-Terpineol 57.1 60.5 62.8 61.0 51.7

--not detected
COPYRIGHT 2002 Estonian Academy Publishers
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2002 Gale, Cengage Learning. All rights reserved.

 Reader Opinion

Title:

Comment:



 

Article Details
Printer friendly Cite/link Email Feedback
Author:Orav, Anne; Kailas, Tiiu; Muurisepp, Mati
Publication:Estonian Academy of Sciences: Chemistry
Date:Dec 1, 2002
Words:3429
Previous Article:Isobaric vapour-liquid equilibria of the ternary system toluene + p-xylene + 1,2-dichloroethane/Kolmiksusteemi tolueen + p-ksuleen + 1,2-dikloroetaan...
Next Article:Ultrasonic acceleration of ester hydrolysis in ethanol--water and 1,4-dioxane--water binary solvents/Estri hudroluusi kiirendamine ultraheliga...


Related Articles
Good enough to eat.

Terms of use | Copyright © 2015 Farlex, Inc. | Feedback | For webmasters