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Volatile constituents of Coccolobo uvifera
Phytochemistry, Vol. 31, No. 10,pp. 3495-3497,1992 Printed m Great Britain.
0031 9422/92S5.00+ 0.00 Pergamon Press Ltd
VOLATILE CONSTITUENTS OF COCCOLOBO UVZFERA PHILIP USDA
E. SHAW, MANUEL
G. MOSHONAS
and
ELIZABETH
A.
BALDWIN
Citrus and Subtropical Products Laboratory, *600 Avenue S, NW (Post Office Box 1909), Winter Haven, FL 33883-1909, U.S.A. (Received 28 February 1992)
Key Word Index-Cocc&ba
uvijhra; Polygonaceae; sea grape.; volatiles; cyclopentylacetic acid; organic acids.
Abstract-Sea grape pulp was extracted and the extract analysed by gas chromatography-mass spectrometry, resulting in identification of 34 volatile pulp components; these included 20 carboxylic acids, and only two esters and three aldehydes. One volatile component, cyclopentylacetic acid had not been reported earlier as a food component or food flavouring. Components quantified in sea grape pulp were fructose, glucose, sucrose, and ascorbic acid as well as total acid content.
INTRODUCTION
The sea grape (Coccoloba uoi@a) originated on the American continent and its use by Indians and early settlers was documented as early as 1578 [l]. The tree is not usually cultivated commercially, and the wild trees that grow along the Florida coast are protected by a state law forbidding commercial harvest of the fruit. One processor currently producing sea grape jelly in Florida (Palmetto Canning Co., Palmetto, Florida) must rely on imported fruit for the raw material. Little information has been reported on the composition of sea grape. The general composition has been reported [2], but the amounts of individual sugars or the volatile flavour components has not been documented. In the current study, the quantities of sugars, total acids and ascorbic acid in sea grape as well as identification of 34 volatile components are reported. RESULTS AND DISCUSSION
Gas chromatographic separation of a dichloromethane extract from sea grape pulp afforded the 34 identified volatile pulp components, plus the extraction solvent (Table 1). The profile of volatile components is very different from that found in most fruits. The majority of the 34 components is carboxylic acids (20 identified), a class of compounds not usually associated with fresh fruit flavours [3]. Berger [4] pointed out that Schreier et al. [S] had reported acids as one of the major classes of compounds in grapes (Vitis uinifera L.) but did not consider them important to grape flavour. In some fruits they are considered major precursors for more flavourful compounds such as esters and aldehydes [4]. Aldehydes and esters are two classes of compounds usually important to fruit flavours, but only three aldehydes and two esters were identified from sea grape extract.
*South Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture.
One of the aldehydes, benzaldehyde, is important in cherry and bitter almond flavors [6J One component, 2methyl-2,3-epoxybutane, was to our knowledge reported only once earlier as a food component [7], A possible precursor, 2-methyl-2-butene, was also found in this study. The three components apparently not reported earlier as food components were cyclopentylacetic acid, cyclohexylacetic acid and cyclohexylcarboxylic acid. The latter two cyclohexane derivatives have been used in food flavorings, however [6, 8-j. Because of this unusual profile of volatile components in sea grape, two separate samples of fruit from different locations harvested in different years were extracted and analysed. The same profile of volatile components was found in both samples. Sea grape is noted to have a mild flavour, and its primary use is in sea grape jelly where, even when cooked, it has an unusually mild fruit flavour. This study showing the composition of sea grape volatiles as lacking in components with strong, fruity flavours, helps explain the mild flavour observed in the fresh fruit and in products as well. Other components important to flavour and nutrition of sea grape were also measured in this study. The indiviudal sugars present in sea grape were fructose, 8.8%; glucose 7.2%; and sucrose 0.1% (total, 16.1%). The total acid content was 0.47% and the ascorbic acid content was 6.6 mg/lOO g. Previous reported values were 18% carbohydrate and 17 mg/lOO g ascorbic acid [2]. EXPERIMENTAL Ripe. sea grapes (red to purple in colour) were harvested from wild trees on the west coast of Central Florida on 1 October 1990, and on the east coast of South Florida on 18 September 1989. A 266.2 g sample of fruit alforded 146.7 g of pulp and 103.4 g of seeds. The pulp was blended with 295 ml of type 1 deionized H,O (1: 2 dilution) in a Waring blendor for l-2 min, and the mixture filtered to yield 185 ml of filtrate. A 50-ml portion was used for the determination of total acids (9). A 5-ml portion was filtered through a 0.45 pm tilter and analysed for sugars on a Waters Sugar-Pak column at 90” with a mobile
3495
P. E. SHAW et al.
3496
Table
1. Volatile
constituents
in sea grape
Component
Component*
2. 3. 4. 5. 6. I. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
identified
Acetonet 2-Methyl-2-butenet Methylene chloride: Acetic acid? Ethyl acetate? 2-Methyl-2,3-epoxybutane$ 3-Hydroxy-2-butanonet Butanoic acid? Hexanalt 2-Methylbutanoic acidt trans-2-Hexenalt trans-2-Hexen-1-olt Pentanoic acid7 2-Methylpcntanoic acidt 2-(2-Methoxyethoxy)ethanolII Hexanoic acid? Benzaldehydet 3-Hexenoic acid?
19. 20. 21. 22. 23. 24. 25. 26. 21. 28. 29. 30. 31. 32. 33. 34. 35.
*Listed in order of increasing retention times on nonpolar tPreviously reported in food 1123. SExtracted solvent. §Reported in roasted chicken fat [7]. 11 Reported in guava fruit [ 133 BReported as food flavouring [S]. **Reported as food flavouring [6]. TtReported in grilled and smoked foods [14]. $fGC retention time 58.6 min.
phase of 0.0001 M CaEDTA at a flow rate of 0.5 ml mm-’ [lo]. The bulk of the filtrate was extracted with 3 x 100 ml of dry CH,Cl, (Burdick and Jackson Capillary GC/GC-MS grade solvent). The combined extracts were dried over Na,SO, and coned to small vol. (to.5 ml) under red. pres. This coned extract was used for analyses by GC and GC-MS. A sample of sea grape for ascorbic acid analysis was prepared by blending 56.6 g of pulp with 114ml of 6% metaphosphoric acid and filtering through filter aid. Ascorbic acid determinations were carried out by a standard titration procedure [9]. Synthesis of 2-methyl-2,3-epoxybutane. A solution of 1 ml (9.5 mmol) of 2-methyl-Zbutene (99+ %, Aldrich) in 5 ml CH,Cl, was treated dropwise over a 10 min period with stirring with a solution of 3.29 g (9.5 mmol) of 50% 3chloroperoxyben zoic acid (Aldrich) in 30ml CH,CI, at room temp. [ll]. The resulting mixture was stirred for 30 min and washed with 5% NaHCO, soln, H,O, satd NaCI, dried and filtered. The filtrate was used for GC-MS analysis described below to authenticate the presence of 2-methyl-2,3-epoxybutane in sea grape extract. GC and GC-MS analyses. The coned CH,Cl, extract of sea grape above was used for these analyses. GC determinations were carried out with a Hewlett-Packard 5880A GC equipped with a 0.32 mm i.d. x 50 m capillary fused silica cross-linked 5% phenylmethyl silicon column (Hewlett-Packard, Avondale, PA) and a capillary inlet system fitted with a 100: 1 splitter and using 1.0 4 injections, Helium flow was 1.5 mlmin-’ and injection port and injector were at 275”. The column was held initially at 60” for 4 min, then increased to 200” at 6” min-’ and held for 30 min. A Hewlett-Packard Model 5970B, MSD, GC-MS was used with the same capillary GC column described above. Initial
tmns-2-Hexenoic acid? Heptanoic acid? Cyclopentylacetic acid 2Ethylhexanoic acid? Cyclohexylcarboxylic acid7 Octanoic acid5 Benzoic acid? Phenylethyl alcoholt Cyclohexylacetic acid** 2-(2-Butoxyethoxy)-ethanol$ Nonanoic acid? Phthalic acidt Decanoic acidt Undecanoic acid? Diethyl phthalatet Dodecanoic acidt Anthraquinonett$$
GC column.
oven temperature of 55” was held for 9 min, then the oven was programmed at 7.5” min- ’ to 220” and held for 30 min. Injection port and ionizing source were kept at 280” and mass units were monitored from 25 to 350 at 70 eV. Compound identifications were made by comparison of MS and R,s with those of authentic compounds.
REFERENCES
1. Boza, F. V. and de Velez, G. V. (1990) Edible Plants of Venezuela, p. 221. Bigott Foundation, La Salle Society of Natural Sciences, Caracas, Venezuela. 2. Leung, W.-T. W. and Flares, M. (1966) Food Composition Tables for use in Latin America, p. 64. Benjamin Burton Panamerican Health Organization, Washington, D.C. 3. Maarse, H. (ed.) (1991) Volatile Compounds in Food and Beverages. Marcel De.kker, New York. 4. Berger, R. G. (1991) in Volatile Compounds in Food and Beoerages (Maarse, H., ed.), p. 283. Marcel Dekker, New York. 5. Schreier, P., Drawert, F. and Junker, A. (1976) .I. Agric. Food Chem. 24,331.
6. Arctander, S. (1969) Perfvne and Flavor Chemicals, Vols I and II, S. Arctander, Montclair, New Jersey. 7. Noleau, I. and Toulemonde, B. (1987) Lebensm.-Wiss. Technol. 20, 31. 8. Oser, B. L. and Ford, R. A. (1978) Food Technol. 32, 60.
Volatile constituents of sea grape 9. Redd, J. B., Hendrix, C. M., Jr. and Hendrix, D. L. (1986) Quality Control Manual for Citrus Processing Plants, Vol. I, pp. 9,45. Intercit, Safety Harbor, Florida. 10. Baldwin, E. A., Nisperos-Carriedo, M. O., Baker, R. A. and Scott, J. W. (1991) J. Agric. Food Chem. 39, 1135. 11. Fieser, L. F. and Fieser, M. (1967) Reagents for Organic Synthesis, VoL 1, p. 136. Wiley, New York. 12 Maarse, H. and Visscher, C. A. (Eds) (1989). Volatile
Compounds
3491 in Food-Qualitative
and Quantitative
Data,
Vols 1 and 2, TNO-CIVO Food Analysis Institute, Zeist, The Netherlands. 13. Nishimura, O., Yamaguchi, K., Mihara, S. and Shibamoto, T. (1989) J. Agric. Food. Chem. 37, 139. 14. Larsson, B. K., Eyysalo, H. and Sauri, M. (1988) Z. Lebensm.Vnters. Forsch. 187,546.
0031 9422/92S5.00+ 0.00 Pergamon Press Ltd
VOLATILE CONSTITUENTS OF COCCOLOBO UVZFERA PHILIP USDA
E. SHAW, MANUEL
G. MOSHONAS
and
ELIZABETH
A.
BALDWIN
Citrus and Subtropical Products Laboratory, *600 Avenue S, NW (Post Office Box 1909), Winter Haven, FL 33883-1909, U.S.A. (Received 28 February 1992)
Key Word Index-Cocc&ba
uvijhra; Polygonaceae; sea grape.; volatiles; cyclopentylacetic acid; organic acids.
Abstract-Sea grape pulp was extracted and the extract analysed by gas chromatography-mass spectrometry, resulting in identification of 34 volatile pulp components; these included 20 carboxylic acids, and only two esters and three aldehydes. One volatile component, cyclopentylacetic acid had not been reported earlier as a food component or food flavouring. Components quantified in sea grape pulp were fructose, glucose, sucrose, and ascorbic acid as well as total acid content.
INTRODUCTION
The sea grape (Coccoloba uoi@a) originated on the American continent and its use by Indians and early settlers was documented as early as 1578 [l]. The tree is not usually cultivated commercially, and the wild trees that grow along the Florida coast are protected by a state law forbidding commercial harvest of the fruit. One processor currently producing sea grape jelly in Florida (Palmetto Canning Co., Palmetto, Florida) must rely on imported fruit for the raw material. Little information has been reported on the composition of sea grape. The general composition has been reported [2], but the amounts of individual sugars or the volatile flavour components has not been documented. In the current study, the quantities of sugars, total acids and ascorbic acid in sea grape as well as identification of 34 volatile components are reported. RESULTS AND DISCUSSION
Gas chromatographic separation of a dichloromethane extract from sea grape pulp afforded the 34 identified volatile pulp components, plus the extraction solvent (Table 1). The profile of volatile components is very different from that found in most fruits. The majority of the 34 components is carboxylic acids (20 identified), a class of compounds not usually associated with fresh fruit flavours [3]. Berger [4] pointed out that Schreier et al. [S] had reported acids as one of the major classes of compounds in grapes (Vitis uinifera L.) but did not consider them important to grape flavour. In some fruits they are considered major precursors for more flavourful compounds such as esters and aldehydes [4]. Aldehydes and esters are two classes of compounds usually important to fruit flavours, but only three aldehydes and two esters were identified from sea grape extract.
*South Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture.
One of the aldehydes, benzaldehyde, is important in cherry and bitter almond flavors [6J One component, 2methyl-2,3-epoxybutane, was to our knowledge reported only once earlier as a food component [7], A possible precursor, 2-methyl-2-butene, was also found in this study. The three components apparently not reported earlier as food components were cyclopentylacetic acid, cyclohexylacetic acid and cyclohexylcarboxylic acid. The latter two cyclohexane derivatives have been used in food flavorings, however [6, 8-j. Because of this unusual profile of volatile components in sea grape, two separate samples of fruit from different locations harvested in different years were extracted and analysed. The same profile of volatile components was found in both samples. Sea grape is noted to have a mild flavour, and its primary use is in sea grape jelly where, even when cooked, it has an unusually mild fruit flavour. This study showing the composition of sea grape volatiles as lacking in components with strong, fruity flavours, helps explain the mild flavour observed in the fresh fruit and in products as well. Other components important to flavour and nutrition of sea grape were also measured in this study. The indiviudal sugars present in sea grape were fructose, 8.8%; glucose 7.2%; and sucrose 0.1% (total, 16.1%). The total acid content was 0.47% and the ascorbic acid content was 6.6 mg/lOO g. Previous reported values were 18% carbohydrate and 17 mg/lOO g ascorbic acid [2]. EXPERIMENTAL Ripe. sea grapes (red to purple in colour) were harvested from wild trees on the west coast of Central Florida on 1 October 1990, and on the east coast of South Florida on 18 September 1989. A 266.2 g sample of fruit alforded 146.7 g of pulp and 103.4 g of seeds. The pulp was blended with 295 ml of type 1 deionized H,O (1: 2 dilution) in a Waring blendor for l-2 min, and the mixture filtered to yield 185 ml of filtrate. A 50-ml portion was used for the determination of total acids (9). A 5-ml portion was filtered through a 0.45 pm tilter and analysed for sugars on a Waters Sugar-Pak column at 90” with a mobile
3495
P. E. SHAW et al.
3496
Table
1. Volatile
constituents
in sea grape
Component
Component*
2. 3. 4. 5. 6. I. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
identified
Acetonet 2-Methyl-2-butenet Methylene chloride: Acetic acid? Ethyl acetate? 2-Methyl-2,3-epoxybutane$ 3-Hydroxy-2-butanonet Butanoic acid? Hexanalt 2-Methylbutanoic acidt trans-2-Hexenalt trans-2-Hexen-1-olt Pentanoic acid7 2-Methylpcntanoic acidt 2-(2-Methoxyethoxy)ethanolII Hexanoic acid? Benzaldehydet 3-Hexenoic acid?
19. 20. 21. 22. 23. 24. 25. 26. 21. 28. 29. 30. 31. 32. 33. 34. 35.
*Listed in order of increasing retention times on nonpolar tPreviously reported in food 1123. SExtracted solvent. §Reported in roasted chicken fat [7]. 11 Reported in guava fruit [ 133 BReported as food flavouring [S]. **Reported as food flavouring [6]. TtReported in grilled and smoked foods [14]. $fGC retention time 58.6 min.
phase of 0.0001 M CaEDTA at a flow rate of 0.5 ml mm-’ [lo]. The bulk of the filtrate was extracted with 3 x 100 ml of dry CH,Cl, (Burdick and Jackson Capillary GC/GC-MS grade solvent). The combined extracts were dried over Na,SO, and coned to small vol. (to.5 ml) under red. pres. This coned extract was used for analyses by GC and GC-MS. A sample of sea grape for ascorbic acid analysis was prepared by blending 56.6 g of pulp with 114ml of 6% metaphosphoric acid and filtering through filter aid. Ascorbic acid determinations were carried out by a standard titration procedure [9]. Synthesis of 2-methyl-2,3-epoxybutane. A solution of 1 ml (9.5 mmol) of 2-methyl-Zbutene (99+ %, Aldrich) in 5 ml CH,Cl, was treated dropwise over a 10 min period with stirring with a solution of 3.29 g (9.5 mmol) of 50% 3chloroperoxyben zoic acid (Aldrich) in 30ml CH,CI, at room temp. [ll]. The resulting mixture was stirred for 30 min and washed with 5% NaHCO, soln, H,O, satd NaCI, dried and filtered. The filtrate was used for GC-MS analysis described below to authenticate the presence of 2-methyl-2,3-epoxybutane in sea grape extract. GC and GC-MS analyses. The coned CH,Cl, extract of sea grape above was used for these analyses. GC determinations were carried out with a Hewlett-Packard 5880A GC equipped with a 0.32 mm i.d. x 50 m capillary fused silica cross-linked 5% phenylmethyl silicon column (Hewlett-Packard, Avondale, PA) and a capillary inlet system fitted with a 100: 1 splitter and using 1.0 4 injections, Helium flow was 1.5 mlmin-’ and injection port and injector were at 275”. The column was held initially at 60” for 4 min, then increased to 200” at 6” min-’ and held for 30 min. A Hewlett-Packard Model 5970B, MSD, GC-MS was used with the same capillary GC column described above. Initial
tmns-2-Hexenoic acid? Heptanoic acid? Cyclopentylacetic acid 2Ethylhexanoic acid? Cyclohexylcarboxylic acid7 Octanoic acid5 Benzoic acid? Phenylethyl alcoholt Cyclohexylacetic acid** 2-(2-Butoxyethoxy)-ethanol$ Nonanoic acid? Phthalic acidt Decanoic acidt Undecanoic acid? Diethyl phthalatet Dodecanoic acidt Anthraquinonett$$
GC column.
oven temperature of 55” was held for 9 min, then the oven was programmed at 7.5” min- ’ to 220” and held for 30 min. Injection port and ionizing source were kept at 280” and mass units were monitored from 25 to 350 at 70 eV. Compound identifications were made by comparison of MS and R,s with those of authentic compounds.
REFERENCES
1. Boza, F. V. and de Velez, G. V. (1990) Edible Plants of Venezuela, p. 221. Bigott Foundation, La Salle Society of Natural Sciences, Caracas, Venezuela. 2. Leung, W.-T. W. and Flares, M. (1966) Food Composition Tables for use in Latin America, p. 64. Benjamin Burton Panamerican Health Organization, Washington, D.C. 3. Maarse, H. (ed.) (1991) Volatile Compounds in Food and Beverages. Marcel De.kker, New York. 4. Berger, R. G. (1991) in Volatile Compounds in Food and Beoerages (Maarse, H., ed.), p. 283. Marcel Dekker, New York. 5. Schreier, P., Drawert, F. and Junker, A. (1976) .I. Agric. Food Chem. 24,331.
6. Arctander, S. (1969) Perfvne and Flavor Chemicals, Vols I and II, S. Arctander, Montclair, New Jersey. 7. Noleau, I. and Toulemonde, B. (1987) Lebensm.-Wiss. Technol. 20, 31. 8. Oser, B. L. and Ford, R. A. (1978) Food Technol. 32, 60.
Volatile constituents of sea grape 9. Redd, J. B., Hendrix, C. M., Jr. and Hendrix, D. L. (1986) Quality Control Manual for Citrus Processing Plants, Vol. I, pp. 9,45. Intercit, Safety Harbor, Florida. 10. Baldwin, E. A., Nisperos-Carriedo, M. O., Baker, R. A. and Scott, J. W. (1991) J. Agric. Food Chem. 39, 1135. 11. Fieser, L. F. and Fieser, M. (1967) Reagents for Organic Synthesis, VoL 1, p. 136. Wiley, New York. 12 Maarse, H. and Visscher, C. A. (Eds) (1989). Volatile
Compounds
3491 in Food-Qualitative
and Quantitative
Data,
Vols 1 and 2, TNO-CIVO Food Analysis Institute, Zeist, The Netherlands. 13. Nishimura, O., Yamaguchi, K., Mihara, S. and Shibamoto, T. (1989) J. Agric. Food. Chem. 37, 139. 14. Larsson, B. K., Eyysalo, H. and Sauri, M. (1988) Z. Lebensm.Vnters. Forsch. 187,546.