2009_Book_FoodChemistry

240 3 Lipids
Bixin (XVIII) (3.138)
Bixin is the main pigment of annato extract.
Annato originates from the West Indies and
the pigment is isolated from the seed pulp of
the tropical bush Bixa orellana. Bixin is the
monomethyl ester of norbixin, a dicarboxylic
acid homologous to crocetin.
3.8.4.2 Physical Properties
Carotenoids are very soluble in apolar solvents,
including edible fats and oils, but they are
not soluble in water. Hence, they are denoted
“lipochromes”. Carotenoids are readily extracted
β-apo-8 ′ -carotenal * (XIX) (3.139)
Carotenoids are, as a rule, present in plants as
a complex mixture. For example, the orange has
more than 50 well characterized compounds, of
which only those that exceed 5% of the total
carotenoids are presented in Table 3.57.
Hydroxy-carotinoids are often present as esters of
fatty acids; e. g., orange juice contains 3-hydroxyβ-carotene
(cryptoxanthin) esterified with lauric,
myristic and palmitic acid. The quantitative
analysis of this ester fraction is used as proof of an
adulteration of orange juice with mandarin juice.
from plant sources with petroleum ether, ether or
benzene. Ethanol and acetone are also suitable
solvents.
The color of carotenoids is the result of the
presence of a conjugated double bond system in
the molecules. The electron excitation spectra of
such systems are of interest for elucidation of
their structure and for qualitative and quantitative
analyses.
Carotenoids show three distinct maxima in the
visible spectrum, with wavelength positions
dependent on the number of conjugated double
Table 3.57. Major carotenoid components in orange
juice
Carotenoid
Phytoene (I) 13
ξ -Carotene (III) 5.4
Cryptoxanthin 5.3
(3-Hydroxy-β-carotene)
Antheraxanthin 5.8
(5,6-Epoxyzeaxanthin)
Mutatoxanthin (XVI) 6.2
Violaxanthin (XIII) 7.4
Luteoxanthin (XIV) 17.0
Auroxanthin (XV) 12.0
As percent of
total carotenoids
c The prefix “apo” indicates a compound derived from
a carotenoid by removing part of its structure.
Table 3.58. Absorption wavelength maxima for some
carotenoids
Compound Conjugated Wavelength, nm
double bonds (petroleum ether)
A. Effect of the number of conjugated double bonds
Phytoene (I) 3 275 285 296
Phytofluene (II) 5 331 348 367
ξ -Carotene (III) 7 378 400 425
Neurosporene 9 416 440 470
Lycopene (IV) 11 446 472 505
B. Effect of the ring structure
γ-Carotene (V) 11 431 462 495
β-Carotene (VII) 11 425 a 451 483
a Maximum absorption wavelength is not unequivocal
(cf. Fig. 3.47).