The eye test

by Donna Berry
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Ingredient Issues 
Consumers look to color to communicate freshness and quality of meat.
Without eye appeal, many foods get rejected by shoppers. This is particularly true with meat and poultry products, for which consumers have specific color expectations.

“Consumers shop based on perception of quality and freshness, especially meat and poultry products,” says Vanessa Herrera, technical service and applications – meat, poultry and seafood, Innophos Inc., Cranbury, New Jersey.

“Traditionally cured products, such as ham, should have a pink coloration, while uncured pork should be white,” she says. “They [consumers] expect beef products to be cherry-red as an optimum surface color, as this cherry-red means fresh or good quality.”

This characteristic color is formed when myoglobin in the meat is exposed to oxygen. This converts the myoglobin (blue) to oxymyoglobin (red). Think how enclosed veins are blue and exposed blood is red. Different species of meat have different concentrations of myoglobin in their blood, which is why there are varying intensities of red in meat. For example, beef has about four times as much myoglobin as pork.

“Fresh beef and pork products are prone to color changes that result from the formation of metmyoglobin from oxymyoglobin,” says Tom Rourke, director of business development, Corbion, Lenexa, Kansas. “This creates a harmless, yet unappealing brown color.”

Metmyoglobin is the oxidized form of oxymyoglobin. Ingredients can assist with preventing this undesirable transformation in beef and pork.

Raw whole-muscle poultry color expectations are different and can be quite varied, from bluish-white to yellow. Color depends on the bird’s age, breed, diet and even slaughter and post-slaughter conditions. With ground poultry, color variations are typically due to the amount of white and dark meat in the mixture. White meat is virtually void of myoglobin while dark meat gets its name because of its myoglobin content.

Color of whole-muscle poultry depends on the bird's age, breed, diet and even slaughter and post-slaughter conditions.

“A higher amount of dark meat translates into a darker pink, while a higher inclusion of white meat or skin gives it a lighter tone,” Herrera says. “With frozen and refrigerated poultry products, if the pH of the product is not balanced properly by the processor, the consumer may follow the cooking instructions at home and still get a pink appearance, alarming the consumer; and although in some instances the product may be cooked to the right internal temperature, most likely the consumer will continue to overcook and eventually discard the product. By overcooking, the juiciness will be lost resulting in an impression of poor quality for the product.”

Poulson Joseph, principal scientist and team leader–meat and poultry, Kalsec, Kalamazoo, Michigan, says, “Color deterioration is more noticeable in dark meats such as beef, followed by pork, turkey, and to a lesser extent in chicken, which corresponds to the level of natural myoglobin in these meats.

“The grinding process acts as a stress factor,” Joseph says. “Storage and retail display are additional stress factors that compromise oxidative stability of these meats. The result is discoloration – metmyoglobin formation – along with lack of fresh flavor.”

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