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12 Carotenoids A Source of Flavor and Aroma W. W. Weeks Department of Crop Science, North Carolina State University, Raleigh, NC 27695-7620 Over four hundred carotenoids have been found in nature of which α - , β , γ carotene and lycopene are encountered most frequently. β-Carotene, a direct precusor to Vitamin A, is the most widely known tetraterpene in plants. The polyene chain of the carotenes is readily oxidized, giving rise to cyclic and acyclic compounds often having an oxygen-containing functional group on a trimethylcyclo hexane ring, or an oxygen containing functional group on the allylic side chain. In plants used for food, improved nutrition and palatibility are often associated with high carotene levels. Higher concentrations of carotenes in flue-cured tobacco have resulted in a wider variety of carotenoid derivatives some in increased concentration, in the tobacco leaf and in the smoke. -
-
The yellow carotenoid pigments are tetraterpenes of which over 400 occur in higher plants (1), algae and bacteria, and in some animals that depend on plants for their existence (2). The carotenoid color from plants is a precursor for pigmentation in marine animals, egg yolks and fat globules and serves as a source for Vitamin A for mammals. Carotenoids are synthesized from pro ducts of acyclic C40H56 polyene lycopenes by hydrogenation, dehydrogenation, cyclization, methyl-migrâtion, and chain elongation (2). They are companion pigments to chlorophyll in plants and their sensitivity to light and oxygen is demonstrated by xanthophylls and other pigments containing hydroxyl, carboxyl, carbonyl and esters as terminal groups. These oxygenated pigments are associated with yellow colors so very prominent in the fall. Figure 1 illustrates examples of acyclic, monocyclic, bicyclic, and oxygenated tetraterpenes. The four most common tetraterpenes in nature are lycopene, α- β-, and γ-carotene. β-Carotene is the most widely recog nized member of the group because of its association with Vitamin A. Carotenoid levels in mature cells of leaves and fruits remain relatively constant until the onset of senescence. In the case of seed plants, senescence occurs following flowering; in fruits J. 0097-6156/86/0317-0157$06.00/ 0 © 1986 American Chemical Society In Biogeneration of Aromas; Parliment, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
158
BIOGENERATION OF AROMAS
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12.
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Pk.
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14
15
18
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Carotenoids:
A Source
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Darftascenone
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4-hydroxy-5-ionol
Dehydro-G-ionone
Figure 6. Compounds i d e n t i f i e d as carotenoid derivatives in flue cured tobacco.
In Biogeneration of Aromas; Parliment, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
166
BIOGENERATION OF AROMAS
Acknowledgment This chapter is Paper No. 10088 of the Journal Series of North Carolina Agricultural Research Service, Raleigh, NC 27695. The use of trade names in this publication does not imply endorsement by the North Carolina Research Service of the products named, nor criticism of similar ones not mentioned.
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Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.
Bauernfeind, J. C. "Carotenes as Colorants and Vitamin A Precur sors; Academic Press, New York and London. 1981, p. xiii. Goodwin, T. W. "The Biochemistry of the Carotenoids"; Vol. 1. Plants 2nd edition, Chapman and Hall, London and New York, 1980, 1, 77-90. Goodwin, T. W.; Mercer E. I. "Introduction to Plant Biochem istry"; 2nd. edit Pergaman Press, Oxford, New York, Toronto, Paus and Frankfort, 1983, 304-306. Enzell, C. R. Recent Advances in Tobacco Science 1976, 2, 32-66. Ohloff, G. Flavour Industry. 1972, 3, 501-508. Theimer, Ε. T. "Fragrance Chemistry The Science of the Sense of Smell"; Academic Press, New York and London, 1972, 301-308. Apt, C. "Flavor: Its Chemical, Behavioral and Commercial Aspects"; Proceedings of the Arthur D. Little Inc. Flavor Symposium, 1977, 12-29. Leffingwell, J. H.; Young H.; Bernasek E. "Tobacco Flavoring for Smoking Products"; R. J. Reynolds Tobacco Company, WinstonSalem, N.C., 1972. Guenther, E. "The Essential Oils"; Vol. 2, D. Van Nostrand Co., Inc. Toronto, New York and London, 1949, 348-349. Sanderson, G.; Graham H. N. Journal of Agriculture and Food Chemistry, 1973, 21, 576=584. Kaneko, H. Koryo. 1980, 128, 23-33. Beatson, R.A.; Wernsman Ε. Α.; Long R. C. Crop Science, 1984, 24, 67-71.
RECEIVED February 18, 1986
In Biogeneration of Aromas; Parliment, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
