Metals and food oxidation - Oxidation in Foods and Beverages and Antioxidant Applications - page 51

oxidation and autoxidation, and are affected by a wide spectrum of active
oxygen species and metal ions, such as O 2 ·ÿ , H 2 O 2 , HO · , HOCl, NO 2 · , lipid
oxy-radicals, ferrous/O 2 and ferryl.
Several authors have postulated that oxymyoglobin oxidation and lipid per-
oxidation in muscle tissue are interrelated (Greene, 1969; Lin and Hultin, 1977;
Yin and Faustman, 1993). Free radicals generated during lipid peroxidation
promote the accumulation of metmyoglobin (Kanner, 1994). The use of hemi-
chrome accumulation from the oxidation of hemeproteins has been recom-
mended as a method for the evaluation of tissue oxidation and autoxidation in
vivo (Tappel, 1999). We have developed a model system containing oxymyo-
globin and muscle membranes oxidized by an iron redox cycle to elucidate the
mechanism of oxymyoglobin oxidation (Gorelik and Kanner, 2001a, 2001b).
The model system demonstrated that MbO 2 oxidation is a process that is
affected by two pathways; the first pathway generates active oxygen species
such as O 2 ·ÿ and H 2 O 2 ; the second generates lipid peroxides and lipid free
radicals. Maximum inhibition was achieved only by introducing inhibitors of
both pathways, such as SOD, catalase, conalbumin (chelator) and catechin, into
the system. The membrane lipid peroxidation in this model was affected mainly
by iron `redox cycle'. In order to elucidate the interrelated effects of MbO 2
oxidation and lipid peroxidation in in-situ muscle tissues, a study was developed
to examine the effects of high PUFA and vitamin E supplementation in the feed
on calf muscle lipid peroxidation and fresh muscle color retention, following
NaCl addition and storage at 4ëC.
Meat tissue from calves fed a ration rich in PUFA was significantly more
susceptible to lipid peroxidation and MbO 2 oxidation following salting.
However, vitamin E supplementation in the diet prevented these changes, and
the fresh meat retained its high sensory properties (color, flavor) and nutritive
value (vitamin E) (Granit et al., 2001). In raw muscle tissue Mb acts mostly as a
pseudo-peroxidase and inhibit lipid peroxidation and propagation of color loss,
(Harel and Kanner, 1985b; Kanner et al., 1991c; Ahn et al., 1995; Gorelik and
Kanner, 2001a).
2.7.2 Muscle food flavor
The term `warmed-over flavor' was first introduced (Tims and Watts, 1958), to
describe the rapid onset of rancidity in cooked meat during storage. Heating
could affect many factors involved in lipid peroxidation of muscle foods. The
level of `free' iron in muscle tissue greatly increases during cooking (Kanner et
al., 1988a, 1991a, 1991b) and the iron `redox cycle' is more pronounced and
propagation of lipid peroxidation increases. This pro-oxidant effect is inhibited
by relatively low concentration of EDTA, which indicate that most of the metal
catalyzed lipid peroxidation in cooked muscle tissues is affected by `free' iron
redox cycle (Kanner et al., 1988a). Heating inactivates many antioxidant
enzymes, myoglobin release hemin (Grunwald and Richards, 2006) and loses its
solubility and antioxidant effect. Heating of muscle food very much disturbs the