“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.
“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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Ingredient suppliers offer numerous solutions to assist with stabilizing desirable color in meat and poultry. There are conventional generally recognized as safe (GRAS) additives and clean-label ingredients with color-stabilizing properties.
“Color or appearance is one of the most important indicators of freshness to the consumer, therefore processors really can’t afford to chance it,” says Amanda King, technical sales manager – proteins, Kemin Food Technologies, Des Moines, Iowa. “There are many things that can help delay color loss, including processing techniques, storage conditions and ingredient inclusions.”
Color loss is an issue for any meat and poultry product stored under lighted conditions. Because shoppers like to see food, opaque or fully printed packaging is not usually an option.
“A key attribute in color bloom is pH. In cured meats, a low pH is best while in fresh, non-cured meats, a higher pH is desired,” says Jim Anderson, regional market segment lead North America – meat, poultry, seafood, ICL Food Specialties, St. Louis. “Ingredients that offer pH control typically do so with significant flavor impact; they impart unpleasant taste. Specialty phosphates are the exception. Selection and application of the proper phosphate can provide a desired pH target in post-processed meat. They are particularly desirable due to their extremely low addition rates, no more than 0.5 percent, while resulting in a bright and clean flavor profile with no flavor masking. In many instances an increased flavor potentiation can result.”
When it comes to developing and preserving desirable cured pink color in bacon, ham and select processed meats, nitrite is most efficacious in acidic conditions, according to Anderson.
“Carefully targeting low pH is best, but it is critical not to become too acidic, which will cause the gassing off of nitrates,” Anderson says. “This could be dangerous to the plant personnel processing the meat. Also, uncured hot pockets may develop in the meat.
“An ancillary benefit of lower pH is that it facilitates color accelerators like sodium erythorbates. If it’s too alkaline, this effect is retarded,” Anderson says. “Again, the precise pH control offered by phosphates is imperative and will result in rapid and stable cured color development.”
Phosphates are also included in meats to retain moisture. They help to retain optimum flavor, juiciness, texture and color.
“The main functional property of phosphates is to help meat and poultry maintain juiciness, and bind added marinades containing flavors and seasonings,” Herrera says. “The phosphates also prevent free water residue, or purge, in packages, which may cause undesirable early spoilage.
“Neutral pH during processing accelerates the reaction between sodium nitrite and sodium erythorbate, increasing the rate of production of nitric oxide and nitrous acid, which in turn come together with myoglobin to form nitric oxide myoglobin,” Herrera says. “During thermal processing, nitrosylhemochrome is formed, which gives the characteristic pink pigment in cured meat products. Addition of the right phosphate may give this final color more stability because the phosphate can act as a pro-antioxidant. This behavior in combination, with vacuum packaging and other ingredients, reduces oxidation induced by light and oxygen.”
Innophos also has specialty systems that contain both phosphates and antioxidants such as lemon juice solids. These systems may further delay oxidation of lipids and stabilize colors.
In applications where sodium reduction is desired, often a potassium phosphate will be substituted in part or in whole for sodium phosphate. This reduces sodium content while adding potassium, a nutrient lacking in many diets.
“Potassium is an essential nutrient and may provide a nutrient label declaration,” Herrera says. “The newly updated Nutrition Facts requires the listing of potassium on the label.”
A number of “natural flavorings” serve as clean-label options for preserving color, as they function as antioxidants. The US Dept. of Agriculture defines natural flavorings as: spices (e.g., black pepper, basil and ginger), spice extracts, essential oils, oleoresins, onion powder, garlic powder, celery powder, onion juice and garlic juice. They may be declared by individual name or generically as “natural flavor,” “flavor” or “flavoring.”
“Incorporating antioxidants to stabilize color in meat products improves the processors’ position with their retailers, and ultimately the consumer, as their purchasing decisions are primarily influenced by product color,” says Austin Lowder, applications scientist, DuPont Nutrition & Health, St. Louis. “The shelf life of a meat product, whether fresh or cooked, can be extended by delaying discoloration, thereby reducing the number of markdowns, consumer complaints and product returns to the processor.
“Lipid oxidation actually affects more than just color, as it can lead to foul odors and off flavors,” Lowder says. “Texture can also be impacted, as oxidation will cause physical crosslinking of proteins that eventually makes the meat tougher to cut and chew. As both of these factors can lead to a negative sensory experience for the consumer, utilizing antioxidant ingredients protects sensory quality and improves shelf life through multiple avenues.”
Select plant-based extracts such as rosemary, green tea and acerola cherry powder function as antioxidants and assist with color stabilization.
“Rosemary and green tea extracts are rich sources of phenolic compounds, while acerola cherry powder contains both phenolic compounds and ascorbic acid, otherwise known as vitamin C,” Lowder says. “Phenolic compounds can perform a number of antioxidant functions, most notably quenching destructive free radical compounds and chelating metal ions that will initiate oxidation reactions and the production of free radicals.
“Ascorbic acid can also act as a metal chelator but more importantly, it can directly reduce formation of the oxidized metmyoglobin pigment responsible for the brown discoloration of fresh red meats, and allow it to rebind oxygen and bloom cherry red again,” Lowder says. “Using these compounds together can allow for a more effective one-two punch.”