Page 47 - Natural Antioxidants, Applications in Foods of Animal Origin

26 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir muscle foods, ferrylmyoglobin is able to initiate lipid oxidation (Hogg et

al., 1994). However, under the conditions found in fresh meat (pH 5.5–5.8),
ferrylmyoglobin autoreduces rapidly to metmyoglobin. Nevertheless, under
physiological conditions (pH 7.4), ferrylmyoglobin is a strong prooxidant,
which is able to abstract a hydrogen atom from fatty acids with subsequent
stereospecific addition of oxygen (Rao et al., 1994). The prooxidative
activity of ferrylmyoglobin is independent of pH and of lipid concentration
(Baron & Andersen, 2002). Therefore, ferrylmyoglobin is expected to be
an effective prooxidant under the conditions found in muscle food, as well
as under physiological conditions. However, ferrylmyoglobin formation in
muscle tissues is determined by hydrogen peroxide and lipid hydroperoxide
production. Its potential to oxidize lipids depends on the concentration of
reducing agents and their compartmentalization in the muscle cells (Baron
& Andersen, 2002).
The interrelationship between myoglobin oxidation, lipid oxidation,
and discoloration in oxeye scad fish during ice storage has been reported
by Wongwichian et al. (2015). The myoglobin autoxidation rate, hydrogen
peroxide, and ferrylmyoglobin concentrations increased with increasing
storage time. The CD and PV of oxeye scad lipids tended to stabilize during
the initial phase of storage, increased in the differentiation phase and had
declined at the end of storage. However, TBARS increased markedly.
Overall, lipid and myoglobin oxidations in oxeye scad occurred in a concur-
rent manner and each process appeared to enhance the other.
Heme, hematin and hemin are normally used interchangeably to describe
the existence of non-protein bound heme-iron (or “free heme iron”). Heme
in solution is mainly found as hematin (ferriprotoporphyrin hydroxide).
Hemin is ferriprotoporphyrin chloride which readily converts to hematin
in aqueous solution and accordingly the term hematin should be used for
non-protein bound heme-iron (Carlsen et al., 2005). Grunwald and Richards
(2006b) suggested that sperm whale myoglobin having a more rapid hemin
loss rate possessed a more effective prooxidative activity than did modified
myoglobin with high hemin affinity. It was found that hemin concentrations
in mackerel light muscle increased around 3-fold during ice storage (Decker
& Hultin, 1990). Following release of hemin from the globin, hemin is
proposed to intercalate within phospholipids membranes due to hydrophobic
attractions. Also the propionate groups of hemin can bind with phospho-
lipid headgroup amines by electrostatic interactions (Cannon et al., 1984).
Hemin can react with lipid hydroperoxide to form alkoxyl radical and ferryl-
hydroxo complex (Dix & Marnett, 1985). Ferryl-hydroxo complex can react