Page 190 - Natural Antioxidants, Applications in Foods of Animal Origin

Natural Antioxidants in Poultry Products 169
VetBooks.ir Fe + ROOH Fe + RO + OH – (5.4)

–
+++
++
and Fe can be regenerated as follows:
++
Fe + ROOH ROO + Fe + H + (5.5)
–
+++
++
Oxygen (O ) also reduces ferric iron to ferrous and cupric copper to
2
cuprous in vivo, allowing a redox cycle in which the transition metal ion is
used several times:

O + Fe Fe + O 2
+++
++
2
O + Cu Cu + O
++
+
2 2
Other strong reductants such as ascorbic acid (AA) and parquet also
reduce Fe to Fe . Both ROO and RO can initiate further reactions (3)
++
–
+++
–
and the following:
RO + RH ROH + R (5.6)
–
The RO can also undergo β-scission and degrade to alkyl radicals
–
(R– CH ) and a range of aldehydes (R–CHO) depending on the particular
2-
hydroperoxide present.
RO – R–CH + R–CHO (5.7)
–
(R–CH ) can initiate further chain reactions resulting in the formation
2–
of ethane and pentane, while the aldehydes, including hexanal, malondial-
dehyde, and 4-hydroxynonenal, can react readily with e-amino groups of
proteins to yield Maillard-type complexes.

5.2.2 FACTORS PREDISPOSING LIPID OXIDATION

The propensity of meats and meat products to undergo oxidation depends
on several factors including pre-slaughter events such as stress and post-
slaughter events such as early post-mortem pH, carcass temperature, cold
shortening, and techniques such as electrical stimulation. Oxidation can
also be accelerated due to disruption of the integrity of muscle membranes
by mechanical deboning, grinding, restructuring, or cooking which alters
cellular compartmentalization and releases the catalytic metal ions.