Food Chemistry

3.8 Unsaponifiable Constituents 231

Δ^5 -Avenasterol is a sitosterol derivative:

Δ
5
-Avenasterol (3.108)

Steroids which, like the avenasterols, contain an
ethylidene group have antioxidative activity at the
temperatures used in deep frying because under
these conditions, a peroxyl radical can abstract an
H-atom from this group.
In addition toΔ^5 -sterols, Δ^7 -sterols occur in
plant lipids; for example:

Δ^7 -Avenasterol (3.109)

Δ^7 -Stigmasterol (3.110)

Plant lipids contain 0.15–0.9% sterols, with sitos-
terol as the main component (Table 3.52). In or-
der to identify blends of fats (oils), the data on
the predominant steroids are usually expressed
as a quotient. For example, the ratio of stigmas-
terol/campesterol is determined in order to detect
adulteration of cocoa butter. As seen from Ta-
ble 3.53, this ratio is significantly lower in a num-
ber of cocoa butter substitutes than in pure co-
coa butter. The phytosterol fraction (e. g. sito- and
campesterol) has to be determined in order to de-
tect the presence of plant fats in animal fats.

Table 3.53.Ratio of stigmasterol to campesterol in

various fats

Fat Sterols (g/kg) % Stigmasterol

% Campesterol

Cocoa butter 1. 82 .8–3. 5

Tenkawanga 2. 15 0 .42–0. 55

Sal oila 30. 98

Illexao 30− 90 b 1. 15 −d

Palm oil 0. 67 0. 43

Palm seed oil 0. 81 1. 28

Choclinc 0. 38

Kaobienc 0. 56

Coconut oil 0. 75 1. 47

Peanut oil, hydrogenated 0. 72

Coberinec 0 .31–0. 60

aCocoa butter substitutes (cf. 14.3.2.2.3).

bTrade name for sheasterol.

cTrade name for cocoa butter substitutes from the mid-

dle fraction of palm oil and shea butter.

dContains no stigmasterol.

3.8.2.3.2 Methyl-andDimethylsterols..............................

Sterols withα-oriented C-4 methyl groups occur

in oils of plant origin. The main compounds are:

(3.111)

4 α, 14 α-Dimethyl-24-methylene-5α-cholest-8-

en-3β-ol (Obtusifoliol)

(3.112)

4 α-Methyl-24-methylene-5α-cholest-7-en-3β-ol

(Gramisterol)