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Natural Antioxidants in Poultry Products 167
VetBooks.ir stability of foods and act as a site for oxidative process initiation. Further, the

fatty acids mostly exist in unsaturated state which makes them more prone to
oxidation. Lipid oxidation is influenced by the composition of phospholipids,
polyunsaturated fatty acids (PUFA), metal ions, oxygen, heme pigments,
and addition of salt and processing approaches. It is one of the major factors
affecting the quality of animal foods; however, in cured meat, due to forma-
tion of stable pink color by ferrous form of pigment, there is less oxidation as
compared to cooked uncured meat. This oxidation is initiated when PUFA react
with molecular oxygen via free radical chain mechanism form peroxides and
accomplished with discoloration and production of malodorous compounds.
These compounds not only give rancid odors but significantly affect human
health. Color and flavor are the first stimuli for the consumers to purchase
meat and meat products, and in this regard, lipid oxidation is the main limiting
factor (Gray et al., 1996). Further, the low oxidative stability of fresh meat,
precooked and restructured meat products is a problem for all those involved
in the meat production chain, including the primary producers, processors,
distributors, and retailers, and a major challenge for meat scientists. The
scientific literature pertaining to propensity of lipid oxidation in animal foods
including poultry products and other biological systems is vast and suggests
various remedies to combat this problem; however, before adopting the solu-
tion there is a need to understand the concept of lipid oxidation.

5.2 LIPID OXIDATION

Lipid oxidation is often the decisive factor in determining the useful storage
life of food products, even when their fat content is as low as 0.5–1%. Oxida-
tive rancidity is initiated by the so called “reactive oxygen species” (ROS)
(Evans & Halliwell, 2001). The ROS in-turn combines various free radicals
which not only include oxygen-centered free radicals but also non-radical
derivatives of oxygen. Free radicals contain one or more unpaired electrons
and are capable of independent existence. Lipid oxidation in muscle foods is
initiated in the highly unsaturated phospholipid fraction of subcellular bio-
membranes; unsaturated portions of fatty acid esters react with molecular
oxygen to form peroxides, hydroperoxides, and carbonyl compounds. The
lipid hydroperoxides formed during the propagation of the per-oxidation
processes are unstable and are reductively cleaved in the presence of trace
elements to give a range of new free radicals and non-radical compounds
including aldehydes, ketones, alcohols, and acids that cause the off-odor,
off-color, change in nutritive value, and safety of muscle foods. Besides