The color is to an extent indicator of physical, chemical and bacterial contamination. The microbes change the physiological environment by changing the pH and by producing amino acids and amines. They may also produce compounds which may react with the heme pigments to produce other colors. Catalase negative bacteria produce hydrogen peroxide that results in a green color. Microorganisms change the color also by producing pigments themselves.
Salt works as a prooxidant for heme pigment oxidation and thereby also influences the color.
Light can cause the dissociation of oxygen from the heme which may result in the fading of fresh meat color. Cooking causes protein denaturation and the browning reactions. During cooking the heme pigment protein denatures and the iron undergoes oxidation to the ferric state and ability of the pigment to complex oxygen is lost. Color shelf life extenders 1.Application of antioxidants like ascorbic acid, citric acid, alpha tocopherol etc. Application of nitrites and nitrates .