Color, pigments hemoglobin

Copper ions in the (I) and (II) oxidation state are biologically important. These ions appear to stabilize walls of certain blood vessels including the aorta and the sheath around the spinal cord. They are involved in the body s production of the color pigments of the skin, hair, and eyes, and in the in vivo synthesis of hemoglobin (232, 250). 

The yellow color of urine is due to uro-chromes, which are related to the bile pigments produced by hemoglobin degradation (see p. 194). If urine is left to stand long enough, oxidation of the urochromes may lead to a darkening in color. 

Under physiological conditions, CSF is clear and colorless. It may be pink or red if many red blood cells (RBCs) are present, and cloudy if more than 400 elements/mm are present, white blood cells (WBCs) are present, or the protein content is especially high. When blood has been present in the CSF for more than four hours, xanthochromia may occur owing to the presence of hemoglobin pigment from lysed red blood cells. Also, high protein levels (>1.5 g L ) may produce a yellowish color that can simulate xanthochromia of red blood cell origin. 

Love and Pearson (6) have described a model meat system in which bovine muscle was ground and extracted with distilled, deionized water at 4°C until it was devoid of color, indicating the removal of all meat pigments, i.e., myoglobin and hemoglobin. Other water-soluble components would also be partially or completely extracted by this procedure. The remaining extracted muscle was then used as a model system to which purified myoglobin, ferrous iron and ferric iron were added back to ascertain their role in WOF. 

A potential source of red and brown heme pigments is animal blood and its dehydrated protein extracts, which mainly consist of hemoglobin and may be used as red and brown colorings to meat products. However, in most countries their usage as a food coloring agent is not permitted. 

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