2009_Book_FoodChemistry

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 to Δ 5 -sterols, Δ 7 -sterols occur in
plant lipids; for example:
Table 3.53. Ratio of stigmasterol to campesterol in
various fats
Fat
Sterols (g/kg) % Stigmasterol
% Campesterol
Cocoa butter 1.8 2.8–3.5
Tenkawang a 2.15 0.42–0.55
Sal oil a 3 0.98
Illexao 30 − 90 b 1.15 − d
Palm oil 0.67 0.43
Palm seed oil 0.81 1.28
Choclin c 0.38
Kaobien c 0.56
Coconut oil 0.75 1.47
Peanut oil, hydrogenated 0.72
Coberine c 0.31–0.60
a Cocoa butter substitutes (cf. 14.3.2.2.3).
b Trade name for sheasterol.
c Trade name for cocoa butter substitutes from the middle
fraction of palm oil and shea butter.
d Contains no stigmasterol.
3.8.2.3.2 Methyl- and Dimethylsterols
Δ 7 -Avenasterol (3.109)
Sterols with α-oriented C-4 methyl groups occur
in oils of plant origin. The main compounds are:
(3.111)
Δ 7 -Stigmasterol (3.110)
Plant lipids contain 0.15–0.9% sterols, with sitosterol
as the main component (Table 3.52). In order
to identify blends of fats (oils), the data on
the predominant steroids are usually expressed
as a quotient. For example, the ratio of stigmasterol/campesterol
is determined in order to detect
adulteration of cocoa butter. As seen from Table
3.53, this ratio is significantly lower in a number
of cocoa butter substitutes than in pure cocoa
butter. The phytosterol fraction (e. g. sito- and
campesterol) has to be determined in order to detect
the presence of plant fats in animal fats.
4α,14α-Dimethyl-24-methylene-5α-cholest-8-
en-3β-ol (Obtusifoliol)
(3.112)
4α-Methyl-24-methylene-5α-cholest-7-en-3β-ol
(Gramisterol)