Food Biochemistry and Food Processing (2 edition)

BLBS102-c17 BLBS102-Simpson March 21, 2012 11:52 Trim: 276mm X 219mm Printer Name: Yet to Come

324 Part 3: Meat, Poultry and Seafoods

contains nitrates that, once incorporated in the product, may be

similarly reduced by the microorganisms. Conforth et al. (1991)

mentions that several nitrogen oxides may be generated in gas

and electric ovens used for cooked ham and that these will react

with the Mb to generate nitrosohemopigments. Also produced in

ovens is CO, which reacts with Mb during thermal treatment to

form a pink-colored pigment, carboxyhemochrome. It has also

been described how the use of adhesives formed from starchy

substances produces the same undesirable color in cooked prod-

ucts (Scriven et al. 1987).

The same anomalous color may be generated when the pH

of the meat is high (because of the addition of egg albumin

to the ingredients) (Froning et al. 1968) and when the cooking

temperature during processing is too low. These conditions favor

the development of a reducing environment that maintains the

iron of the Mb in its ferrous form, imparting a reddish/pink color

(as a function of the concentration of hemopigments) instead of

the typical grayish-brown color of heat-treated uncured meat

products.

Cooking uncured meat products, such as roast beef, at low

temperatures (less than 60◦C) may produce a reddish color in-

side the product, which some consumers may like. This internal

coloring is not related with the formation of nitrosopigments, but

results from the formation of OMb, a phenomenon that occurs

because MMb-reducing enzymatic systems exist in the muscle

that are activated at temperatures below 60◦C (Osborn et al.

2003).

Microbial growth may also cause the formation of a pink

color in cooked meats, since these reduce the oxido-reduction

potential of the product during their growth. This is important

when the microorganisms that develop in the medium are anaer-

obes, since they may generate reducing substances that reduce

the heme iron. When extracts ofPseudomonascultures are ap-

plied, the MMb may be reduced to Mb (Faustman et al. 1990).

Recently, Gallego-Restrepo et al. (2010) reported that microor-

ganism can play an important role in the color of uncured meat

products during its elaboration process. These authors recom-

mended the use of microbiological starter culture with a higher

metabolic action at refrigeration conditions to obtain excellent

color characteristics on this type of products.

Melanosis

Melanosis or blackspot, involving the appearance of a dark, even

black, color, may develop post mortem in certain shellfish during

chilled and frozen storage (Slattery et al. 1995). Melanosis is of

huge economic importance, since the coloration may suggest

a priori in the eyes of the consumer that the product is in bad

condition, despite the fact that the formation of the pigments

responsible involves no health risk.

Melanosis is an objectionable surface discoloration of high

valuable shellfish as lobsters caused by enzymic formation of

precursors of phenolic pigments. Blackspot is a process regu-

lated by a complex biochemical mechanism, whereby the phe-

nols present in a food are oxidized to quinones in a series of

enzymatic reactions caused by polyphenoloxidase (PO) (Ogawa

et al. 1984). This is followed by a polymerization reaction, which

produces pigments of a high molecular weight and dark in color.

Melanosis is produced in the exoskeleton of crustaceans, first

in the head and gradually spreading toward the tail. Melanosis

of shell and hyperdermal tissue in some shellfish as lobsters

was related to stage of molt. The molting fluid is considered

as the source of the natural activator(s) of pro-PO. Polyphenol

oxidase (catechol oxidase) can be isolated from shellfish cuti-

cle (Ali et al. 1994) and still active during iced or refrigerated

storage. The process can be controlled by using sulfites (Ferrer

et al. 1989), although their use is prohibited in many countries.

Also ficin (Taoukis et al. 1990), 4-hexylresorcinol, functioned

as a blackspot inhibitor, alone and in combination withl-lactic

acid (Benner et al. 1994). Recently, Encarnacion et al. (2010) re-

ported that dietary supplementation of theFlammulina velutipes

mushroom extract in shrimp could be a promising approach to

control postmortem development of melanosis and lipid oxida-

tioninshrimpmuscles.

Premature Browning

Hard-to-cook patties show persistent internal red color and are

associated with high pH (>6) raw meat. Pigment concentration

affects red color intensity after cooking (residual undenatured

Mb), so this phenomenon is often linked to high pH dark-cutting

meat from older animals. PMB is a condition in which ground

beef (mince) looks well done at lower than expected temperature

(Warren et al. 1996).

PMB of beef mince is a condition in which Mb denatura-

tion appears to occur on cooking at temperature lower than

expected and, therefore, may indicate falsely that an appropriate

internal core temperature of 71◦C has been achieved (Suman

et al. 2004). The relationship between cooked color and inter-

nal temperature of beef muscle is inconsistent and depends on

pH and animal maturity. Increasing the pH may be of benefit

in preventing PMB but may increase incidence of red color in

well-cooked meat (cooked over internal temperature of 71.1◦C)

(Berry 1997). When PSE meat is used in patties processing and

those containing OMb easily exhibited PMB. One of the reasons

of this behavior is that percentage of Mb denaturation increased

as cooking temperature increased (Lien et al. 2002). Recently,

Mancini et al. (2010) reported that the use of several additives

such as lactate improved raw color stability, but did not minimize

PMB.

COLOR AND SHELF LIFE OF

MUSCLE-BASED FOODS

Meat and meat products are susceptible to degradation during

storage and throughout the retail process. In this respect, color

is one of the most important quality attributes for indicating the

state of preservation in meat.

Any energy received by food can initiate its degradation, the

rate of any reactions depending on the exact composition of

the product (Jensen et al. 1998), environmental factors (light,

temperature, presence of oxygen), or the presence of additives.

Transition metals, such as copper or iron, are very impor-

tant in the oxidative/antioxidative balance of meat. When the