2009_Book_FoodChemistry

244 3 Lipids
(3.143)
3.8.4.5 Use of Carotenoids in Food Processing
Carotenoids are utilized as food pigments to color
margarine, ice creams, various cheese products,
beverages, sauces, meat, and confectionery and
bakery products. Plant extracts and/or individual
compounds are used.
3.8.4.5.1 Plant Extracts
Annato is a yellow oil or aqueous alkaline
extract of fruit pulp of Raku or Orleans shrubs or
brushwood (Bixa orellana). The major pigments
of annato are bixin (XVIII) and norbixin, both of
which give dicarboxylic acids upon hydrolysis.
Oleoresin from paprika is a red, oil extract
containing about 50 different pigments. The
aqueous extract of saffron (more accurately,
from the pistils of the flower Crocus sativus)
contains crocin (XVII) as its main constituent.
It is used for coloring beverages and bakery
products.
Raw, unrefined palm oil contains 0.05–0.2%
carotenoids with α- andβ-carotenes, in a ratio
of 2:3, as the main constituents. It is of particular
use as a colorant for margarine.
3.8.4.5.2 Individual Compounds
β-Carotene (VII), canthaxanthin (XII), β-
apo-8 ′ -carotenal (XIX) and the carboxylic
acid ethyl ester derived from the latter are
synthesized for use as colorants for edible
fats and oils. These carotenoids, in
combination with surface-active agents, are
available as micro-emulsions (cf. 8.15.1) for
coloring foods with a high moisture content.
3.8.4.6 Analysis
The total lipids are first extracted from food
with ispropanol/petroleum ether (3:1 v/v) or
with acetone. Alkaline hydrolysis follows,
removing the extracted acyl-lipids and the
carotenoids from the unsaponifiable fraction.
This is the usual procedure when alkalistable
carotenoids are analyzed. Although
carotenoids are generally alkali stable, there
are exceptions. When alkali-labile carotenoids
are present, the acyl lipids are removed
instead by a saponification method using
column chromatography as the separation
technique.
A preliminary separation of the lipids into classes
of carotenoids is carried out when a complex
mixture of carotenoids is present. For example,
column chromatography is used with Al 2 O 3 as
an adsorbent (Table 3.60). Additional separation
into classes or individual compounds is achieved
Table 3.60. Separation of carotenoids into classes by
column chromatography using neutral aluminum oxide
(6% moisture) as an adsorbent P: Petroleum ether,
D: diethyl ether
Elution with
Carotenoids in effluent
100% P Carotenes
5% D in P Carotene-epoxides
20–59% D in P Monohydroxy-carotenoids
100% D Dihydroxy-carotenoids
5% Ethanol in D Dihydroxy-epoxy-carotenoids