Food Biochemistry and Food Processing (2 edition)

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17 Chemical and Biochemical Aspects of Color in Muscle-Based Foods 323

When 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:

1. Exposure toγradiation, as described by Wei et al. (2009).


2. 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).


3. 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).

4. 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). ̈


5. 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.


6. 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 COLOR

The 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 Products

The 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), ́