Page 69 - Natural Antioxidants, Applications in Foods of Animal Origin

48 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir then low molecular volatile compounds such as aldehydes, ketones, carbox-

ylic acids, and short-chain alkanes and alkenes. In a study reported by Bhat-
nagar et al. (2009), it was found that the oxidative stability (OS) of oil blends
depended upon the PUFA and MUFA content of the oil blends. The higher
the PUFA and MUFA content, the lower would be the OS, while the RSA
of oil blends depended upon the total tocopherols’ content. The higher the
total tocopherols’ content the higher the DPPH scavenging activity would
be. Antioxidant decreases the frying oil oxidation, but the effectiveness of
antioxidant decreases with high frying temperature.
OS of stripped and crude seed oil was studied during 21 days under
accelerated oxidative conditions at 60 °C (Ramadan & Moersel, 2004).
Peroxide value (PV) and UV absorptivity were determined to monitor lipid
oxidation during the experiment. The crude oil had a much lower PV than
that of stripped oil over the entire storage period. PV in crude oil remained
increased at a low level over 21 days, whereas the peroxides accumulated
in the stripped oils to high levels. Absorption at 232 nm and 270 nm, due to
the formation of primary and secondary compounds of oxidation, showed a
pattern similar to that of the PV. The high content of conjugated oxidative
products is attributed to high PUFA content which is readily decomposed to
form conjugated hydroperoxides. It was concluded that the low OS of PUFA
rich oil could be partly explained by the fact that it has a high proportion of
PUFA. Aside from the fatty acid profile, factors such as oxygen concentra-
tion, metal contaminants, lipid hydroxy compounds, enzymes, and light may
also influence the OS of the oil (Ramadan, 2012).

2.7 VITAMIN E OR TOCOLS (TOCOPHEROLS AND
TOCOTRIENOLS)

Tocols (tocopherols and tocotrienols) constitute a series of benzopyranols
(or methyl tocols) that occur in plant tissues and vegetable oils and are
powerful lipid-soluble antioxidants. In the tocopherols, the C16 side chain
is saturated, and in the tocotrienols it contains three trans double bonds.
Together, these two groups are termed the tocochromanols. In essence,
the tocopherols have a 20-carbon phytyl tail (including the pyranol ring),
and the tocotrienols a 20-carbon geranyl tail with double bonds at the 3’,
7’, and 11’ positions, attached to the benzene ring. The side-chain methyl
groups have R,R,R stereochemistry. The four main constituents of the two
classes are termed—alpha (5,7,8-trimethyl), beta (5,8-dimethyl), gamma
(7,8-dimethyl), and delta (8-methyl) (Christie, 2013). The plant chloroplast