Food Chemistry

228 3 Lipids

Table 3.49.Cholesterol content of some food

Food Amount (mg/100 g)

Calf brain 2000
Egg yolka 1010
Pork kidney 410
Pork liver 340
Butter 215–330
Pork meat, lean 70
Beef, lean 60
Fish (Halibut;
Hypoglossus vulgaris)50

aEgg white is devoid of cholesterol.

peroxy radicals, proceeds through the inter-
mediary 3β-hydroxycholest-5-en-7α-and7β-
hydroperoxides, of which the 7β-epimer is more
stable because of its quasi-equatorial conforma-
tion and, hence, is formed predominantly. Unlike
autoxidation, the photosensitized oxidation (reac-
tion with a singlet oxygen) of cholesterol yields
3 β-hydroxycholest-6-en-5α-hydroperoxide.
Among the many derivatives obtained by the
further degradation of the hydroperoxides,
cholest-5-en-3β,7α-diol, cholest-5en-3β,7β-diol,
3 β-hydroxycholest-5-en-7-one, 5,6β-epoxy-5β-
cholestan-3β-ol and 5α-cholestan-3β,5,6β-triol
have been identified as major products. These
so-called “oxycholesterols” have been detected
as side components in some food items (dried
egg yolk, whole milk powder, butter oil and
heated meat). It is difficult to quantify these
oxidation products because significant losses can
occur in the clean-up of the analyte, e. g., in the
case of polar cholestantriol. In addition, artifacts
are easily formed. For this reason, quantitative
values found in the literature are frequently only
approximations.
In the animal organism, cholesterol is the start-
ing point for the synthesis of other steroids,
such as sex hormones and bile acids. In fact,
GC-MS analyses and radio immunoassays show
that among the sex hormones, progesterone
(I in Formula 3.102) appears most often in
animal food. It is enriched in the fat phase,
leading to relatively high concentrations in butter
(Table 3.50). Traces of this steroid also occur in
plant foods. Testosterone (II in Formula 3.102),
3,17-estradiol (III) and 17-estrone (IV) are other
sex hormones which have been identified as

Table 3.50.Progesterone in foods

Food Progesterone

(μg/kg)

Beef, malea 0 .01–5

Beef, femalea 0 .5–40

Pork (muscle) 1 .1–1. 8

Chicken 0. 24

Turkey 8. 18

Chicken egg 12 .5–43. 6

Skim milk (0.1% fat) 1 .3–4. 6

Whole milk (3.5% fat) 9.5–12. 5

Cream (32% fat) 42–73

Butter (82% fat) 133–300

Cheese (Gouda, 29% fat) 44

Potatoes 5. 1

Wheat 0 .6–2. 9

Corn germ oil 0. 3

Safflower oil 0. 7

aedible parts.

natural trace components of meat, milk and their

products.

(3.102)

Products of cholesterol metabolism include

C 19 -sterols which produce the specific smell

of boar in boar meat. Five aroma components

(Table 3.51) were identified; 5α-androst-16-en-

3 α-ol (Formula 3.103) has also been detected in

truffels (cf. 17.1.2.6.1).

(3.103)