Color of Fresh and Processed Poultry Meat

The basic color differences between muscles are a result of the relative amounts of white and red muscle fibers. These fibers have different characteristics, and the most noticeable difference to the consumer is their color. Meat color is largely dependent on the amount of meat pigment-myoglobin present in these fibers. Chicken breast muscle is predominantly composed of white fibers, which have a low level and therefore their color is light. On the other hand, thigh meat is mainly composed of red fibers and shows a darker color. Different poultry species also vary in the inherited amount of pigment in their muscles (chicken vs duck). The myoglobin is a complex molecule consisting of two major parts: the protein portion (called globin) and the nonprotein portion (called heme). The latter is capable of binding different compounds and, by that, changing the color of the meat. When the myoglobin is bound to oxygen, chicken leg meat will appear bright pink (Fig. 2). When the same fresh meat is packaged under vacuum it will develop a brownish color (the result of oxidizing the myoglobin into metmyoglobin). On cooking, the protein part of the meat pigment is denatured (similar to denaturation of egg proteins during cooking, which also results in a color and textural change) and gives the meat its typical greyish cooked color. When nitrite is added to the meat, prior to cooking, as is the case in many cured meat products (eg, turkey ham), a typical light pink color will develop. The difference between cured and noncured meat products can be clearly

Table 4. Composition and Nutritional Value of Four Raw Poultry Meats

Source of meat

Species Meat Skin Water (%) Protein (%) Fat (%) Ash (%) Iron (mg) Calories (kcal)

Source: Ref. 6. Expressed on a 100-g portion of meat and skin.

Oxygen addition

Myoglobin -*- Oxymyoglobin

Oxygen removal

Oxygen removal

+ Nitrite

+ Nitrite

+ Nitrite

Nitrosomyoglobin (dark red)

Nitrosohemochrome (light pink)

+ Nitrite

Oxidation

Metmyoglobin (brown)

Denatured myoglobin (gray brown)

Figure 2. Colors of red poultry muscle (eg, chicken thigh meat).

illustrated when chicken leg meat is prepared at home (as a roast) resulting in a greyish color or when it is cured (as a turkey ham) in a processing plant resulting in the typical pink cured color.

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