WHAT COLOR IS YOUR MEAT?
When you go to the market to buy fresh meat, what is the meat color that you look out for? Fresh meat food coloring is always denoted by the vivid red or pink color on its surface. This has always posed a challenge for meat manufacturers as many have been forced to sell meat at discounted prices because of the lack of red food coloring on the meat leads to poor sales.
WHY DOES MEAT CHANGE COLOR?
Oxidative rancidity and microbial spoilage are implied when the color of the meat is not red.
The natural food color of meat is determined by the heme protein called myoglobin. The amount of myoglobin present in a meat is dependent on various factors including age, sex, diet, genetics and environmental factors. Even within meat, the concentration of myoglobin per kilogram is dependent on the kind of meat it is – the highest concentration being in beef, followed by lamb, pork, and poultry.
The myoglobin in the meat takes three distinct forms. The bright red color that is associated with freshness of meat is when stable myoglobin is formed in an oxygen rich environment. This color is only present on the surface where the oxygen can reach. When the meat is cut into thicker pieces, the oxygen penetration is low and the myoglobin concentration is higher, the meat takes on a more purple color. The longer meat is left in the open, the more its chances of changing color to brown due to the oxidation of the heme iron. Meat that is brown in color is often perceived to not be fresh and gets rejected by customers. Food color manufacturers add synthetic food color to meat to make it fresher in appearance.
COLOR AFTER CURING OF MEAT
Meat is processed or cured by adding a combination of salt, sugar, nitrite and/or nitrate for the purposes of preservation, flavour and color. The reason for adding nitrate is because nitric oxide combines with the heme group of myoglobin to form a bright red and highly stable complex. The color brought on by curing is sustained even after heating – this is unlike uncured meat which will turn brown on contact with heat.
COLOR OF FROZEN MEAT
Frozen meat often loses its bright red color. This is because of the process of lipid oxidation of meat products and the Modified Atmosphere Packaging (MAP). Lipid oxidation without the presence of light generates a primary by product called hydroperoxide which degrades to form alkoxy radicals that go on to further form complex mixtures of secondary oxidative by products with different flavour and aroma which include molecules like alkanes, alkenes, aldehydes, ketones, alcohols, esters, lactones, epoxides, and acids.
This reaction is different from meat products that are displayed in refrigerated display cases. Susceptible to photo-oxidation due to a chemical reaction between light and fat lipids, the meats are prone to rancidity, which gives the meat a bad smell and a yellowish color. The higher the fat content in the meat, the faster it is for them to become rancid. This is why meats like bacons and sausages spoil much faster than other meats.
