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 323When fat color is measured, its composition should be kept in
mind, since its relation with fatty acids modifies its characteris-
tics, making it more brilliant or duller in appearance. The fat con-
tent of the conjunctive tissue must also be borne in mind, since
collagen may present a glassy appearance because, at acidic pH,
it is “swollen”, imparting a transparent aspect to the product.REDUCED NITRITE MEAT PRODUCTS
Health concerns relating to the use of nitrates and nitrites in cured
meats (cooked and dry cured) have led to a tendency toward
decreased usage to alleviate the potential risk of the formation
of carcinogenic, teratogenic, mutagenicN-nitroso compounds
(Karolyi 2003), cytotoxic effects of nitrosamines and by the toxic
effects of nitrite per se (metmyoglobinaemia and fall of blood
pressure). But it is well known that nitrate/nitrite is widely used
as a curing agent in the meat industry, although in recent years
its omission from meat processing has been proposed (Viuda-
Martos et al. 2009a).
Meat scientists have to take into account that any techno-
logical strategy (Perez-Alvarez 2008) or the use of other in- ́
gredients (meat, nonmeat, and functional ingredients) can mod-
ify color characteristics (Perez-Alvarez and Fern ́ andez-L ́ ́opez
2009a, S ́anchez-Zapata et al. 2009b).
As soon as nitrite is added in the meat formulation, it starts
to disappear (nitrite is reduced to nitric oxide (NO)) that reacts
with Mb to form NO-OMb and often can no longer be detected
analytically at a later time. The rate of depletion is dependent
on various factors, such as pH, initial nitrite concentration, pro-
cessing and storage temperatures, meat-to-water ratio, and the
presence of reductants (Perez-Alvarez et al. 1993). ́
According to Perez-Alvarez (2006), two-thirds of the Mb ́
present in the meat is transformed into NOMb, although it is
possible that only 50% of the Mb reacts. The rest corresponds
to the residual nitrite. Residual nitrite levels (10–20% of the
originally added sodium nitrite) correspond to nitrite that has
not reacted with Mb and it is available for other reactions in the
organism (Fern ́andez-L ́opez et al. 2007).
Recently, it has been found that plants and their extracts can be
used as indirect sources of nitrate (Shahid-Umar and Iqbal 2007,
Shahid-Umar et al. 2007, Parks et al. 2008) in the production of
meat products (Sebranek and Bacus 2007a, 2007b).
Six “technological” pathways exist for reducing the nitrite
present in the meat products:- Exposure toγradiation, as described by Wei et al. (2009).
- Reaction with compounds of a polyphenolic nature
(Garrote et al. 2004) derived basically from spices added
in the formulation of the meat products. Also, can react
with polyphenols, mainly hydroxycinnamic acids, like
caffeic or ferulic acid, or with glycosylated flavanones,
like hesperidin or narirutin, that are natural compounds of
citrus coproducts (Viuda-Martos et al. 2010a). - Reaction with reducing agents present in the formulation
or with endogenous substances. For example, when the pH
of the meat is less than six, the nitrite added or that aris-
ing from the microbial reduction of nitrates is transformed
into nitrous acid (relatively unstable). This, in turn, reacts
with endogenous (cysteine, reduced nicotinamide adenine
dinucleotide, cytochromes, and quinines) or exogenous
(ascorbic acid and its salts) reducing substances of the
meat and is transformed into NO, completing the dismuta-
tion reaction, as described by P ́erez-Alvarez (2006).- Action of bacteria with nitrite-reductase activity such as
Staphylococcus carnosus,Staphylococcus simulans,or
Staphylococcus saprophyticus(Gøtterup et al. 2007). The
action mechanism through which strains ofStaphylococcus
use nitrate/nitrite is thought to be related with its capacity
to act as alternative electron acceptor in the cell respiratory
chain (Gøtterup et al. 2008). The synthesis of nitrite reduc-
tases only occurs in anaerobic conditions and is induced by
the presence of nitrate or nitrite in the medium (Neubauer
and Gotz 1996). ̈ - Combined method, reducing the quantity of residual nitrite
by interaction with natural ingredients (tomato paste, an-
natto). Thus, Deba et al. (2007) reported that the addition
of tomato paste to frankfurters reduces the added nitrite
level from 150 to 100 mg/kg without any negative effect
on the processing and quality characteristics of the product
during storage. - Reaction with compounds present in citric coproducts
such as orange and lemon albedo (Aleson-Carbonell et al.
2003, Fernandez-Gin ́ ́es et al. 2004), orange dietary fiber
(Fern ́andez-Lopez et al. 2008b, 2009), citrus fiber wash- ́
ing water (Viuda-Martos et al. 2009b), orange fiber plus
essential oils (Viuda-Martos et al. 2010a, 2010b).
ALTERATIONS IN MUSCLE-BASED
FOOD COLORThe color of meat and meat products may be altered by several
factors, including exposure to light (source and intensity), mi-
crobial growth, rancidity, and exposure to oxygen. Despite the
different alterations in color that may take place, few have been
studied, including the pink color of boiled uncured products,
premature browning (PMB), and melanosis in crustaceans.Pink Color of Uncured Meat ProductsThe normal color of a meat product that has been heat treated but
not cured is “brown,” although it has recently been observed that
these products show an anomalous coloration (red or pink) (Hunt
and Kropf 1987). This problem is of great economic importance
in “grilled” products, since this type of color is not considered
desirable.
This defect may occur both in meats with a high hemoprotein
content such as beef and lamb (red) and in those with a low
concentration, including chicken and turkey (pink) (Conforth
et al. 1986).
One of the principal causes of this defect is the use of water
rich in nitrates, which are reduced to nitrites by nitrate-reducing
bacteria, which react with the Mb in meat to form NOMb (Nash
et al. 1985). The same defect may occur in meat products con-
taining paprika, which, according to Fernandez-L ́ opez (1998), ́