On food and cooking the science and lore of the kitchen ( PDFDrive ) 261

unloaded oxygen into our cells.) And when oxygen manages to rob the iron atom of an electron and then escape, the iron atom loses its ability to hold oxygen at all, has to settle for a water molecule, and the myoglobin becomes brown White and red muscle fibers Fast muscle cells are thicker than slow cells, contain little oxygen-storing myoglobin pigment and few fat-burning mitochondria The thinness of slow, red muscle fibers speeds the diffusion of oxygen from the external blood supply to the center of the fibers Each of these myoglobins — the red, the purple, and the brown — is present in red meat Their relative proportions, and so the meat’s appearance, are determined by several factors: the amount of oxygen available, the activity of oxygen-consuming enzymes in the muscle tissue, and the activity of enzymes that can resupply brown myoglobin with an electron, which turns it purple again Acidity, temperature, and salt concentration also matter; if any is high enough to destabilize the attached protein, myoglobin is more likely to lose an electron and turn brown Generally, fresh red meat with active enzyme systems will be red on the surface, where oxygen is abundant, and purple inside, where the little oxygen that diffuses through is consumed by enzymes When we cut into raw meat or into a rare steak, the initially purple interior quickly “blooms,” or reddens, thanks to its direct exposure to the air Similarly, vacuum-packed meat appears purple due to the absence of oxygen, and reddens only when removed from the package The pink color of salt-cured meats comes from yet another alteration of the myoglobin molecule (p 148)  ...activity of oxygen-consuming enzymes in the muscle tissue, and the activity of enzymes that can resupply brown myoglobin with an electron, which turns it purple again Acidity, temperature, and salt concentration also... exposure to the air Similarly, vacuum-packed meat appears purple due to the absence of oxygen, and reddens only when removed from the package The pink color of salt-cured meats comes from yet another alteration of the myoglobin... will be red on the surface, where oxygen is abundant, and purple inside, where the little oxygen that diffuses through is consumed by enzymes When we cut into raw meat or into a rare steak, the initially purple interior quickly