BLBS102-c17 BLBS102-Simpson March 21, 2012 11:52 Trim: 276mm X 219mm Printer Name: Yet to Come
17 Chemical and Biochemical Aspects of Color in Muscle-Based Foods 325free ions of these two metals interact, they reduce the action of
certain agents, such as cysteine, ascorbate andα-tocopherol, ox-
idizing them and significantly reducing the antioxidant capacity
in muscle (Zanardi et al. 1998).
The iron in meat is 90% heme iron (HI), which is several
times more absorbable than nonheme iron (NHI) present in other
foods (Fernandez-L ́ opez et al. 2008a). Although the mechanism ́
for heme iron release in meat has not been determined, oxidation
of the porphyrin ring and denaturation of Mb (Kristensen and
Purslow 2001) are probably involved.
Harel et al. (1988) reported that the interaction of MMb
with H 2 O 2 or lipid hydroperoxide results in the release of
free ionic iron. Free ionic iron can serve as a catalyst in the
production ofaOH from H ̇ 2 O 2 as well as in the degradation of
lipid hydroperoxides to produce peroxyl and alkoxyl radicals,
which can initiate lipid oxidation and/or be self-degraded to
the secondary products of lipid oxidation (Min and Ahn 2005).
However, reducing compounds are essential to convert ferric to
ferrous ion, a catalyst for Fenton reaction.
Lee et al. (1998) reported that during refrigerated storage of
meat, there is a release of iron from the heme group, with a
consequent increase in NHI, which speeds up lipid oxidation.
Also, the heme molecule can break down during cooking or
storage (Gomez-Basauri and Regenstein 1992a, 1992b, Miller ́
et al. 1994a, 1994b) and can generate NHI. The increase of NHI
in meats and fish is considered to be a reflection of the decrease
of HI and is linked to the oxidative deterioration (Schricker and
Miller 1983).
Nonheme iron is considered the most important oxidation
promoter in meat systems, and therefore, knowledge of the pro-
portions of the chemical forms of iron is of great importance
(Kanner et al. 1991). An increase in the amount of NHI as a
result of thermal processes on meat systems has been demon-
strated by several authors (Schricker et al. 1982, Lombardi-
Boccia et al. 2002). Gomez-Basauri and Regenstein (1992a,
1992b), suggested cooking is not as important as the subsequent
refrigerated storage of cooked meats for the release of NHI from
Mb.
The relationship between oxidative processes and the release
of iron from Mb and the effect of these chemical changes on color
characteristics of cooked products is still not well understood.
The increase of NHI could have some important con-
sequences, affecting both the nutritional and technological
properties of liver pate. The degradation of heme iron would
reduce the nutritional value of the pates in terms of bioavail-
ability of iron, since HI is more available than NHI (Hunt and
Roughead 2000). Furthermore, iron achieves enhanced ability
for promoting oxidation processes when it is released from the
heme molecule (Kanner et al. 1991), and therefore, pates with
increasing amounts of NHI might also have increased oxidative
susceptibility.
From a nutritional point of view, Ahn and Kim (1998) reported
that the status of ionic iron is more important than the amount
of iron.
Traditionally, researchers have determined the discoloration
of meat using as criterion the brown color of the product, cal-
culated as percent of MMb (Mancini et al. 2003). These authorsdemonstrated that in the estimation of the shelf life of beef or
veal (considered as discoloration of the product), the diminution
in the percent of OMb is a better tool than the increase in percent
of MMb.
Occasionally, when the meat cut contains bone (especially in
pork and beef), the haemopigments (mainly Hb) present in the
medulla lose color because the erythrocytes are broken during
cutting and accumulate on the surface of the bone Hb. When
exposed to light and air, the color of the Hb changes from bright
red (OHb) characteristic of blood to brown (MHb) and even
black (Gill 1996). This discoloration basically takes place during
long periods of storage and especially during shelf life display
(Mancini et al. 2004). This characteristic is aggravated if the
product is kept in a modified atmosphere rich in oxygen (Lanari
et al. 1995). These authors also point out that the effect of bone
marrow discoloration is minimized by the effect of bacterial
growth in modified atmosphere packaging.
As in the case of fresh meat, the shelf life of meat products is
limited by discoloration (Mancini et al. 2004). This phenomenon
is important in this type of product because they are normally
displayed in illuminated cabinets. Consequently, the possibility
of nitrosated pigments photo-oxidation of (NOMb) needs to be
taken into account. During this process, the molecule is activated
because it absorbs light; this may subsequently deactivate the
NOMb and give the free electrons to the oxygen to generate
MMb and free nitrite.
In model systems of NOMb photo-oxidation, this effect can be
diminished by adding solutions of dextrose, which is a very im-
portant component of the salts used for curing cooked products
and in meat emulsions.
When a meat product is exposed to light or is stored in dark-
ness, the use of ascorbic acid or its salts may help stabilize the
product’s color. Such behavior has been described both in model
systems of NOMb (Walsh and Rose 1956) and in dry-cured
meat products (e.g., “longanizas” and Spanish dry-fermented
sausage). However, when sodium isoascorbate or erythorbate is
used in “longaniza” production, color stability is much reduced
during the retail process (Ru ́ız-Peluffo et al. 1994).
The discoloration of white meats like turkey is characterized
by a color changes, which go from pink/yellow to yellow/brown,
while in veal/beef the changes go from purple to grayish/brown.
In turkey, it has been demonstrated that the presence or absence
of lipid oxidation depends on, among other things, the concen-
tration of vitamin E in the tissues. The color and lipid oxidation
are interrelated, since it has been seen that lipid oxidation in red
and white muscle depends on the predominant form of catalyz-
ing iron, Mb, or free iron (Mercier et al. 1998).
Compared with red meat, tuna flesh tends to undergo more
rapid discoloration during refrigerated storage. Discoloration
due to oxidation of Mb in red fish presented a problem, even
at low temperature. This low color stability might be related to
the lower activity or poorer stability of MMb reductase in tuna
flesh (Ching et al. 2000). One of the reasons of this behavior
is that aldehydes known to be produced during lipid oxidation
can accelerate tuna OMb oxidation in vitro (Lee et al. 2003).
Also, tuna flesh could be immersed in MMb reductase solution
that could extend the color stability of tuna fish. Also, the use