Leffingwell Reports, Vol. 2 (No. 3), October, 2002
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Carotenoids as Flavor & Fragrance Precursors
A Review by John C. Leffingwell. Ph.D.
This is the introduction to our series on aroma materials produced by
carotenoid degradation.
Carotenoids are the pigments responsible for the colors of many plants, fruits and
flowers. They serve as Light Harvesting Complexes (with proteins) in
photosynthesis. Carotenoids are important in human nutrition as a source of
Vitamin A (e.g., from beta-carotene) and as a prevention agent for cancer and heart
disease (e.g. lycopene). In addition, carotenoids add color to foods and beverages
(e.g. orange juice). And in addition, carotenoids are the precursors of many
important chemicals responsible for the flavor of foods and the fragrance of flowers.
Carotenoids are a class of hydrocarbons (carotenes) and their oxygenated derivatives
(xanthophylls). About 600 carotenoids have been isolated from natural sources.
Where are Carotenoids Found in Nature
For us, the most important source for carotenoids are plants, where often the brilliant
colors of the carotenoids are masked by the green chlorophyllic pigments (i.e. in green
vegetables and leaves). In a number of cases, as plants mature, the chlorophyll content
decreases leaving the carotenoids responsible for the beautiful colors of most fruits
(pineapple, oranges, lemons, grapefruit, strawberry, tomatoes, paprika, rose hips) and
many flowers (Eschscholtzia, Narcissus). Carotenoids are also responsible for the colors of
some birds (flamingo, canary), certain insects, and marine animals (shrimp, lobster and
salmon).
Health Aspects of Carotenoids
Carotenoids are important factors in human health and essential for vision. The role of
beta-carotene and other carotenoids as the main dietary source of vitamin A has been
known for the better part of this century. More recently, protective effects of carotenoids
against serious disorders such as cancer, heart disease and degenerative eye disease have
been recognized, and have stimulated intensive research into the role of carotenoids as
antioxidants and as regulators of the immune response system.
Lycopene, a carotenoid found in tomato products, prevents oxidation of low density
lipoprotein (LDL) cholesterol and reduces the risk of developing atherosclerosis and
coronary heart disease according to a recent study published in the October 1998 issue of
Lipids (Agarwal, S., and Rao A.V.; Tomato lycopene and low-density lipoprotein
oxidation: a human dietary intervention study. Lipids, 33, 981-984 (1998). This study
showed that daily consumption of tomato products providing at least 40 mg of lycopene
was enough to substantially reduce low density lipoprotein (LDL) oxidation. High LDL
Leffingwell Reports, Vol. 2 (No. 3), October, 2002
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oxidation is associated with increased risk of atherosclerosis and coronary heart disease.
This lycopene level can be achieved by drinking just two glasses of tomato juice a day.
Research shows that lycopene in tomatoes can be absorbed more efficiently by the body if
processed into tomato juice, sauce, paste and ketchup. The bound chemical form of
lycopene found in tomatoes is converted by the temperature changes involved in
processing to make it more easily absorbed by the body. Ongoing research suggests that
lycopene can reduce the risk of prostate cancer and cancers of the lung, bladder, cervix
and skin.
What do Tea, Rose, Osmanthus flowers, Tobacco, Grapes and Saffron all
have in common?
The answer: flavor & aroma constituents derived from carotenoids!
In the discussion of chemical constituents derived from carotenoids in the linked
pages we will explore some of the important materials which contribute to the
flavor/aroma.
As plants mature, or die, the chlorophyllic pigments rapidly decrease and virtually
disappear (one of the normal catabolic changes during plant senescence). The yellow -
orange carotenoid pigments of plants also decrease during the senescence or the death
phase of plants, but do not always decrease to the point of near extinction as do the
chlorophyllic pigments. Thus for plant parts such as the stigma of saffron an intense
yellow color (due to carotenoids) remains...and in the green citrus "orange", the fruit
turns yellow-orange with maturity.
Below you will see four (of the more than 600) common carotenoid structures found in
plants and flowers.
C13
C12
C11
C10
C9
beta-CAROTENE
VIOLAXANTHIN
O
O
OH
HO
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LUTEIN
NEOXANTHIN
The primary odor constituents derived from carotenoids are C13 - C11 - C10 - and C9
derivatives formed via enzymatic oxidation and photo-oxidation of the various
carotenoids found in plants, flowers and fruits. While other aroma constituents such as
esters, terpenes, pyrazines, etc. are usually also present, these C9 to C13 compounds
often are essential to the odor profile. Above you will see a common oxidative
fragmentation pattern (shown for beta-Carotene).
Examples of aroma compounds produced in nature are shown below:
C13 ��..
O
O
O
Beta-Ionone
Beta-Damascenone
Alpha-Ionone
C11��..
O
CHO
C10��..
CHO
C9��..
O
O
Isophorone-4-acetaldehyde
Safranal
4-Ketoisophorone
HO
OH
O
OH
OH
HO
H
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Common Carotenoid Degradation Products Found in
Plants
Name
Structure
Examples of Occurrence
beta-Ionone
Osmanthus, Rose, Black Tea, Tomato,
Blackberries, Raspberries, Passion
fruit,Carrots, Tobacco, Apricot, Carambola,
Cherries, Mango, Bell Pepper, Plum
alpha-Ionone
Black currant, Osmanthus, Black Tea,
Blackberries, Raspberries,Carrots, Tobacco,
Banana, Cherries, Plum, Celery, Peach,
Popcorn, Tomato
beta-Damascone
Rose, Osmanthus, Black tea, Mountain
papaya, Rum, Tobacco
beta-Damascenone
Apricot, Rose, Beer, Carambola, Grape,
Kiwi, Mango, Tomato, Wine, Rum,
Raspberries, Passion fruit, Blackberries
Oxo-Edulan I
Purple Passionfruit, Osmanthus, Burley
tobacco, Virginia tobacco
Oxo-Edulan II
Purple Passionfruit, Osmanthus, Burley
tobacco, Virginia tobacco
Theaspirone
Yellow Passionfruit, Black Tea, Burley
tobacco
4-Oxo-beta-ionone
Red Fox, Black Tea, Osmanthus, Burley
tobacco, Freesia flower, Boronia
3-Oxo-alpha-Ionone
Osmanthus, Virginia tobacco,
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Dihydroactinodiolide
Osmanthus, Black Tea, Tomato, Cassia,
Cassie, Ambergris, Tobacco
4-Oxoisophorone
Osmanthus, Black tea, Saffron
Safranal
Saffron, Osmanthus, Black tea, Grapefruit
juice, Mate, Paprika
beta-Cyclocitral
Roasted Mate, Rum, Tea, Tomato,
Cantaloupe, Paprika, Peas, Apricot, Brocolli,
Melon
