Page 165 - Natural Antioxidants, Applications in Foods of Animal Origin

144 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir 4.2 OXIDATION IN FISH PRODUCTS

Oxidation in fish and fish products possess a high risk of quality loss leading
to rancid taste, off-flavor, and development of many different compounds
which have adverse effect to human health (Ames et al., 1993). Oxidation

limits storage time and this affects marketing and distribution of fish and
fish products. Oxidation is high in fish because of presence of omega-3
PUFAs susceptible to peroxidation and results in restriction to storage and
processing possibilities (Gray et al., 1996). Products of peroxidation-alde-

hydes, react with specific amino acids to form carbonyls and protein aggre-
gates which causes additional nutritional loss (Uchida & Stadtman, 1993);

for instance, in red fish such as salmon, oxidation not only deteriorates
the lipids but also affects the color, thus affecting visual consumer accept-
ability of fish products (Scaife et al., 2000). Two forms of oxidation occur

in fish products—lipid and protein oxidation and they are discussed in the
following subsections. While lipid oxidation leads to formation of unhealthy
compounds and off-flavors such as rancid, protein oxidation affects the
functional properties, including texture, and may potentially affect the taste
of fish products. Lipid and protein oxidation occur as a result of the pres-
ence of reactive oxygen species (ROS) which include oxygen radicals such
as superoxide anion (O ), hydroxyl (HO ), peroxy (ROO ), alkoxy (RO ),
−
−
−
−
2
and hydroperoxy (HOO) radicals. Non-radical derivates of oxygen such as
hydrogen peroxide (H O ), ozone (O ), and singlet oxygen ( O ) are also
−
1
2
2
2
3
ROS(Choe & Min, 2009).

The thiobarbituric acid reactive substances (TBARS) as reported by
Botsoglou et al. (1994) are naturally present in biological specimens and

composed of lipid hydroperoxides (HPOs) and aldehydes which increase in
concentration as a response to oxidative stress. The sensitivity of measuring
TBARS has made this assay the method of choice for screening and moni-
toring lipid peroxidation which is a major indicator of oxidative stress.
TBARS assay values are usually reported in malonaldehyde (MDA) equiva-
lents, which is a compound that results from the decomposition of PUFA
lipid peroxides. This assay is well recognized and an established method for
quantifying lipid peroxides.
4.2.1 LIPID OXIDATION
Lipids are one of the important functional and structural components of
foods. They provide energy and essential nutrients such as EPA, DHA,